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Sample records for tetrahymena meiotic nuclear

  1. Nuclear localization signal targeting to macronucleus and micronucleus in binucleated ciliate Tetrahymena thermophila.

    Science.gov (United States)

    Iwamoto, Masaaki; Mori, Chie; Osakada, Hiroko; Koujin, Takako; Hiraoka, Yasushi; Haraguchi, Tokuko

    2018-06-08

    Ciliated protozoa possess two morphologically and functionally distinct nuclei: a macronucleus (MAC) and a micronucleus (MIC). The MAC is transcriptionally active and functions in all cellular events. The MIC is transcriptionally inactive during cell growth, but functions in meiotic events to produce progeny nuclei. Thus, these two nuclei must be distinguished by the nuclear proteins required for their distinct functions during cellular events such as cell proliferation and meiosis. To understand the mechanism of the nuclear transport specific to either MAC or MIC, we identified specific nuclear localization signals (NLSs) in two MAC- and MIC-specific nuclear proteins, macronuclear histone H1 and micronuclear linker histone-like protein (Mlh1), respectively. By expressing GFP-fused fragments of these proteins in Tetrahymena thermophila cells, two distinct regions in macronuclear histone H1 protein were assigned as independent MAC-specific NLSs and two distinct regions in Mlh1 protein were assigned as independent MIC-specific NLSs. These NLSs contain several essential lysine residues responsible for the MAC- and MIC-specific nuclear transport, but neither contains any consensus sequence with known monopartite or bipartite NLSs in other model organisms. Our findings contribute to understanding how specific nuclear targeting is achieved to perform distinct nuclear functions in binucleated ciliates. © 2018 The Authors. Genes to Cells published by Molecular Biology Society of Japan and John Wiley & Sons Australia, Ltd.

  2. Role of apoptosis-inducing factor (AIF in programmed nuclear death during conjugation in Tetrahymena thermophila

    Directory of Open Access Journals (Sweden)

    Endoh Hiroshi

    2010-02-01

    Full Text Available Abstract Background Programmed nuclear death (PND, which is also referred to as nuclear apoptosis, is a remarkable process that occurs in ciliates during sexual reproduction (conjugation. In Tetrahymena thermophila, when the new macronucleus differentiates, the parental macronucleus is selectively eliminated from the cytoplasm of the progeny, concomitant with apoptotic nuclear events. However, the molecular mechanisms underlying these events are not well understood. The parental macronucleus is engulfed by a large autophagosome, which contains numerous mitochondria that have lost their membrane potential. In animals, mitochondrial depolarization precedes apoptotic cell death, which involves DNA fragmentation and subsequent nuclear degradation. Results We focused on the role of mitochondrial apoptosis-inducing factor (AIF during PND in Tetrahymena. The disruption of AIF delays the normal progression of PND, specifically, nuclear condensation and kilobase-size DNA fragmentation. AIF is localized in Tetrahymena mitochondria and is released into the macronucleus prior to nuclear condensation. In addition, AIF associates and co-operates with the mitochondrial DNase to facilitate the degradation of kilobase-size DNA, which is followed by oligonucleosome-size DNA laddering. Conclusions Our results suggest that Tetrahymena AIF plays an important role in the degradation of DNA at an early stage of PND, which supports the notion that the mitochondrion-initiated apoptotic DNA degradation pathway is widely conserved among eukaryotes.

  3. Structural and functional adaptations of the mammalian nuclear envelope to meet the meiotic requirements.

    Science.gov (United States)

    Link, Jana; Jahn, Daniel; Alsheimer, Manfred

    2015-01-01

    Numerous studies in the past years provided definite evidence that the nuclear envelope is much more than just a simple barrier. It rather constitutes a multifunctional platform combining structural and dynamic features to fulfill many fundamental functions such as chromatin organization, regulation of transcription, signaling, but also structural duties like maintaining general nuclear architecture and shape. One additional and, without doubt, highly impressive aspect is the recently identified key function of selected nuclear envelope components in driving meiotic chromosome dynamics, which in turn is essential for accurate recombination and segregation of the homologous chromosomes. Here, we summarize the recent work identifying new key players in meiotic telomere attachment and movement and discuss the latest advances in our understanding of the actual function of the meiotic nuclear envelope.

  4. Spliceosomal small nuclear RNAs of Tetrahymena thermophila and some possible snRNA-snRNA base-pairing interactions

    DEFF Research Database (Denmark)

    Orum, H; Nielsen, Henrik; Engberg, J

    1991-01-01

    We have identified and characterized the full set of spliceosomal small nuclear RNAs (snRNAs; U1, U2, U4, U5 and U6) from the ciliated protozoan Tetrahymena thermophila. With the exception of U4 snRNA, the sizes of the T. thermophila snRNAs are closely similar to their metazoan homologues. The T....... thermophila snRNAs all have unique 5' ends, which start with an adenine residue. In contrast, with the exception of U6, their 3' ends show some size heterogeneity. The primary sequences of the T. thermophila snRNAs contain the sequence motifs shown, or proposed, to be of functional importance in other...

  5. A novel mitochondrial nuclease-associated protein: a major executor of the programmed nuclear death in Tetrahymena thermophila.

    Science.gov (United States)

    Osada, Eriko; Akematsu, Takahiko; Asano, Tomoya; Endoh, Hiroshi

    2014-03-01

    Programmed nuclear death (PND) in the ciliate Tetrahymena is an apoptosis-like phenomenon that occurs in a restricted space of cytoplasm during conjugation. In the process, only the parental macronucleus is selectively eliminated from the progeny cytoplasm, in conjunction with differentiation of new macronuclei for the next generation. For the last decade, mitochondria have been elucidated to be a crucial executioner like apoptosis: apoptosis-inducing factor and yet-unidentified nucleases localised in mitochondria are major factors for PND. To identify such nucleases, we performed a DNase assay in a PAGE (SDS-DNA-PAGE) using total mitochondrial proteins. Some proteins showed DNase activity, but particularly a 17 kDa protein exhibited the highest and predominant activity. Mass spectrometric analysis revealed a novel mitochondrial nuclease, named TMN1, whose homologue has been discovered only in the ciliate Paramecium tetraurelia, but not in other eukaryotes. Gene disruption of TMN1 led to a drastic reduction of mitochondrial nuclease activity and blocked nuclear degradation during conjugation, but did not affect accumulation of autophagic and lysosomal machinery around the parental macronucleus. These observations strongly suggest that the mitochondrial nuclease-associated protein plays a key role in PND as a major executor. Taking the novel protein specific to ciliates in consideration, Tetrahymena would have diverted a different protein from common apoptotic factors shared in eukaryotes to PND in the course of ciliate evolution. © 2014 Société Française des Microscopies and Société de Biologie Cellulaire de France. Published by John Wiley & Sons Ltd.

  6. Transient and Partial Nuclear Lamina Disruption Promotes Chromosome Movement in Early Meiotic Prophase.

    Science.gov (United States)

    Link, Jana; Paouneskou, Dimitra; Velkova, Maria; Daryabeigi, Anahita; Laos, Triin; Labella, Sara; Barroso, Consuelo; Pacheco Piñol, Sarai; Montoya, Alex; Kramer, Holger; Woglar, Alexander; Baudrimont, Antoine; Markert, Sebastian Mathias; Stigloher, Christian; Martinez-Perez, Enrique; Dammermann, Alexander; Alsheimer, Manfred; Zetka, Monique; Jantsch, Verena

    2018-04-23

    Meiotic chromosome movement is important for the pairwise alignment of homologous chromosomes, which is required for correct chromosome segregation. Movement is driven by cytoplasmic forces, transmitted to chromosome ends by nuclear membrane-spanning proteins. In animal cells, lamins form a prominent scaffold at the nuclear periphery, yet the role lamins play in meiotic chromosome movement is unclear. We show that chromosome movement correlates with reduced lamin association with the nuclear rim, which requires lamin phosphorylation at sites analogous to those that open lamina network crosslinks in mitosis. Failure to remodel the lamina results in delayed meiotic entry, altered chromatin organization, unpaired or interlocked chromosomes, and slowed chromosome movement. The remodeling kinases are delivered to lamins via chromosome ends coupled to the nuclear envelope, potentially enabling crosstalk between the lamina and chromosomal events. Thus, opening the lamina network plays a role in modulating contacts between chromosomes and the nuclear periphery during meiosis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  7. The Nuclear Cap-Binding Complex Mediates Meiotic Silencing by Unpaired DNA

    Directory of Open Access Journals (Sweden)

    Logan M. Decker

    2017-04-01

    Full Text Available In the filamentous fungus Neurospora crassa, cross walls between individual cells are normally incomplete, making the entire fungal network vulnerable to attack by viruses and selfish DNAs. Accordingly, several genome surveillance mechanisms are maintained to help the fungus combat these repetitive elements. One of these defense mechanisms is called meiotic silencing by unpaired DNA (MSUD, which identifies and silences unpaired genes during meiosis. Utilizing common RNA interference (RNAi proteins, such as Dicer and Argonaute, MSUD targets mRNAs homologous to the unpaired sequence to achieve silencing. In this study, we have identified an additional silencing component, namely the cap-binding complex (CBC. Made up of cap-binding proteins CBP20 and CBP80, CBC associates with the 5′ cap of mRNA transcripts in eukaryotes. The loss of CBC leads to a deficiency in MSUD activity, suggesting its role in mediating silencing. As confirmed in this study, CBC is predominantly nuclear, although it is known to travel in and out of the nucleus to facilitate RNA transport. As seen in animals but not in plants, CBP20’s robust nuclear import depends on CBP80 in Neurospora. CBC interacts with a component (Argonaute of the perinuclear meiotic silencing complex (MSC, directly linking the two cellular factors.

  8. Viable calves produced by somatic cell nuclear transfer using meiotic-blocked oocytes.

    Science.gov (United States)

    De Bem, Tiago H C; Chiaratti, Marcos R; Rochetti, Raquel; Bressan, Fabiana F; Sangalli, Juliano R; Miranda, Moysés S; Pires, Pedro R L; Schwartz, Kátia R L; Sampaio, Rafael V; Fantinato-Neto, Paulo; Pimentel, José R V; Perecin, Felipe; Smith, Lawrence C; Meirelles, Flávio V; Adona, Paulo R; Leal, Cláudia L V

    2011-10-01

    Somatic cell nuclear transfer (SCNT) has had an enormous impact on our understanding of biology and remains a unique tool for multiplying valuable laboratory and domestic animals. However, the complexity of the procedure and its poor efficiency are factors that limit a wider application of SCNT. In this context, oocyte meiotic arrest is an important option to make SCNT more flexible and increase the number of cloned embryos produced. Herein, we show that the use of butyrolactone I in association with brain-derived neurotrophic factor (BDNF) to arrest the meiotic division for 24 h prior to in vitro maturation provides bovine (Bos indicus) oocytes capable of supporting development of blastocysts and full-term cloned calves at least as efficiently as nonarrested oocytes. Furthermore, the procedure resulted in cloned blastocysts with an 1.5- and twofold increase of POU5F1 and IFNT2 expression, respectively, which are well-known markers of embryonic viability. Mitochondrial DNA (mtDNA) copy number was diminished by prematuration in immature oocytes (718,585±34,775 vs. 595,579±31,922, respectively, control and treated groups) but was unchanged in mature oocytes (522,179±45,617 vs. 498,771±33,231) and blastocysts (816,627±40,235 vs. 765,332±51,104). To our knowledge, this is the first report of cloned offspring born to prematured oocytes, indicating that meiotic arrest could have significant implications for laboratories working with SCNT and in vitro embryo production.

  9. Cyc17, a meiosis-specific cyclin, is essential for anaphase initiation and chromosome segregation in Tetrahymena thermophila.

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    Yan, Guan-Xiong; Dang, Huai; Tian, Miao; Zhang, Jing; Shodhan, Anura; Ning, Ying-Zhi; Xiong, Jie; Miao, Wei

    2016-07-17

    Although the role of cyclins in controlling nuclear division is well established, their function in ciliate meiosis remains unknown. In ciliates, the cyclin family has undergone massive expansion which suggests that diverse cell cycle systems exist, and this warrants further investigation. A screen for cyclins in the model ciliate Tetrahymena thermophila showed that there are 34 cyclins in this organism. Only 1 cyclin, Cyc17, contains the complete cyclin core and is specifically expressed during meiosis. Deletion of CYC17 led to meiotic arrest at the diakinesis-like metaphase I stage. Expression of genes involved in DNA metabolism and chromosome organization (chromatin remodeling and basic chromosomal structure) was repressed in cyc17 knockout matings. Further investigation suggested that Cyc17 is involved in regulating spindle pole attachment, and is thus essential for chromosome segregation at meiosis. These findings suggest a simple model in which chromosome segregation is influenced by Cyc17.

  10. Dynein light chain family in Tetrahymena thermophila.

    Science.gov (United States)

    Wilkes, David E; Rajagopalan, Vidyalakshmi; Chan, Clarence W C; Kniazeva, Ekaterina; Wiedeman, Alice E; Asai, David J

    2007-02-01

    Dyneins are large protein complexes that produce directed movement on microtubules. In situ, dyneins comprise combinations of heavy, intermediate, light-intermediate, and light chains. The light chains regulate the locations and activities of dyneins but their functions are not completely understood. We have searched the recently sequenced Tetrahymena thermophila macronuclear genome to describe the entire family of dynein light chains expressed in this organism. We identified fourteen genes encoding putative dynein light chains and seven genes encoding light chain-like proteins. RNA-directed PCR revealed that all 21 genes were expressed. Quantitative real time reverse transcription PCR showed that many of these genes were upregulated after deciliation, indicating that these proteins are present in cilia. Using the nomenclature developed in Chlamydomonas, Tetrahymena expresses two isoforms each of LC2, LC4, LC7, and Tctex1, three isoforms of p28, and six LC8/LC8-like isoforms. Tetrahymena also expresses two LC3-like genes. No Tetrahymena orthologue was found for Chlamydomonas LC5 or LC6. This study provides a complete description of the different genes and isoforms of the dynein light chains that are expressed in Tetrahymena, a model organism in which the targeted manipulation of genes is straightforward. (c) 2006 Wiley-Liss, Inc.

  11. Purification, characterization and molecular cloning of TGP1, a novel G-DNA binding protein from Tetrahymena thermophila.

    OpenAIRE

    Lu, Q; Schierer, T; Kang, S G; Henderson, E

    1998-01-01

    G-DNA, a polymorphic family of four-stranded DNA structures, has been proposed to play roles in a variety of biological processes including telomere function, meiotic recombination and gene regulation. Here we report the purification and cloning of TGP1, a G-DNA specific binding protein from Tetrahymena thermophila. TGP1 was purified by three-column chromatographies, including a G-DNA affinity column. Two major proteins (approximately 80 and approximately 40 kDa) were present in the most high...

  12. Nuclear vlimata and aneuploidy in embryonic cells is caused by meiosis. Behaviour and properties of meiotic cells

    OpenAIRE

    Logothetou-Rella, H.

    1995-01-01

    This study demonstrates that human embryonic cells divide by meiosis. The use of trophoblastic tissue cells (early embryo) and amniotic cells (late embryo) exhibited the following characteristic events of meiosis: nuclear (NVs) and nucleolar (NuVs) vlimata formation; NV invasion in host cells; extrusion of chromosomes; nuclear fusion; metaphase fusion; hybrid cell formation; nuclear, nucleolar and cytoplasmic bridges, chromosomal transfer, variablesized nuc...

  13. Biomechanics of Tetrahymena escaping from dead ends

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    Ishikawa, Takuji; Kikuchi, Kenji

    2017-11-01

    Behaviors of swimming microorganisms in complex environments are important in understanding cells' distribution in nature and in industries. Although cell's swimming and spreading in an infinite fluid has been intensively investigated, that in a narrow region bounded by walls is still unclear. Thus, in this study, we used Tetrahymena thermophila as a model microorganism, and experimentally investigated its behavior between flat plates with an angle. The results showed that the cells tended to escape from the narrow region, and the swimming velocity and the radius of curvature of the trajectories decreased as they swam narrower region. We then developed a computational model of swimming Tetrahymena. The results showed that the escaping behavior could be well explained by fluid mechanics. The obtained knowledge is useful in understanding cells' behaviors in complex environments, such as in porous media and in a granular matter. This research was supported by JSPS KAKENHI Grants, numbers 25000008 and 17H00853.

  14. Tetrahymena metallothioneins fall into two discrete subfamilies.

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    Silvia Díaz

    2007-03-01

    Full Text Available Metallothioneins are ubiquitous small, cysteine-rich, multifunctional proteins which can bind heavy metals.We report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5. Sequence alignments of all known Tetrahymena metallothioneins have allowed us to rationalize the structure of these proteins. We now formally subdivide the known metallothioneins from the ciliate genus Tetrahymena into two well defined subfamilies, 7a and 7b, based on phylogenetic analysis, on the pattern of clustering of Cys residues, and on the pattern of inducibility by the heavy metals Cd and Cu. Sequence alignment also reveals a remarkably regular, conserved and hierarchical modular structure of all five subfamily 7a MTs, which include MTT3 and MTT5. The former has three modules, while the latter has only two. Induction levels of the three T. thermophila genes were determined using quantitative real time RT-PCR. Various stressors (including heavy metals brought about dramatically different fold-inductions for each gene; MTT5 showed the highest fold-induction. Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs. EST evidence for alternative splicing in the 3' UTR of the MTT5 mRNA with potential regulatory activity is reported.The small number and remarkably regular structure of Tetrahymena MTs, coupled with the experimental tractability of this model organism for studies of in vivo function, make it an attractive system for the experimental dissection of the roles, structure/function relationships, regulation of gene expression, and adaptive evolution of these proteins, as well as for the development of biotechnological applications for the environmental monitoring of toxic substances.

  15. The key role of CYC2 during meiosis in Tetrahymena thermophila.

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    Xu, Qianlan; Wang, Ruoyu; Ghanam, A R; Yan, Guanxiong; Miao, Wei; Song, Xiaoyuan

    2016-04-01

    Meiotic recombination is carried out through a specialized pathway for the formation and repair of DNA double-strand breaks (DSBs) made by the Spo11 protein. The present study shed light on the functional role of cyclin, CYC2, in Tetrahymena thermophila which has transcriptionally high expression level during meiosis process. Knocking out the CYC2 gene results in arrest of meiotic conjugation process at 2.5-3.5 h after conjugation initiation, before the meiosis division starts, and in company with the absence of DSBs. To investigate the underlying mechanism of this phenomenon, a complete transcriptome profile was performed between wild-type strain and CYC2 knock-out strain. Functional analysis of RNA-Seq results identifies related differentially expressed genes (DEGs) including SPO11 and these DEGs are enriched in DNA repair/mismatch repair (MMR) terms in homologous recombination (HR), which indicates that CYC2 could play a crucial role in meiosis by regulating SPO11 and participating in HR.

  16. J-GLOBAL MeSH Dictionary: Tetrahymena pyriformis [MeCab user dictionary for science technology term[Archive

    Lifescience Database Archive (English)

    Full Text Available MeCab user dictionary for science technology term Tetrahymena pyriformis 名詞 一般 * * * * Tetrahymena... pyriformis ... MeSH D013769 200906097287118996 C LS07 UNKNOWN_2 Tetrahymena pyriformis

  17. J-GLOBAL MeSH Dictionary: Tetrahymena thermophila [MeCab user dictionary for science technology term[Archive

    Lifescience Database Archive (English)

    Full Text Available MeCab user dictionary for science technology term Tetrahymena thermophila 名詞 一般 * * * * Tetrahymena... thermophila ... MeSH D016808 200906086486381246 C LS07 UNKNOWN_2 Tetrahymena thermophila

  18. Regulation of Meiotic Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Gregory p. Copenhaver

    2011-11-09

    Meiotic recombination results in the heritable rearrangement of DNA, primarily through reciprocal exchange between homologous chromosome or gene conversion. In plants these events are critical for ensuring proper chromosome segregation, facilitating DNA repair and providing a basis for genetic diversity. Understanding this fundamental biological mechanism will directly facilitate trait mapping, conventional plant breeding, and development of genetic engineering techniques that will help support the responsible production and conversion of renewable resources for fuels, chemicals, and the conservation of energy (1-3). Substantial progress has been made in understanding the basal recombination machinery, much of which is conserved in organisms as diverse as yeast, plants and mammals (4, 5). Significantly less is known about the factors that regulate how often and where that basal machinery acts on higher eukaryotic chromosomes. One important mechanism for regulating the frequency and distribution of meiotic recombination is crossover interference - or the ability of one recombination event to influence nearby events. The MUS81 gene is thought to play an important role in regulating the influence of interference on crossing over. The immediate goals of this project are to use reverse genetics to identify mutants in two putative MUS81 homologs in the model plant Arabidopsis thaliana, characterize those mutants and initiate a novel forward genetic screen for additional regulators of meiotic recombination. The long-term goal of the project is to understand how meiotic recombination is regulated in higher eukaryotes with an emphasis on the molecular basis of crossover interference. The ability to monitor recombination in all four meiotic products (tetrad analysis) has been a powerful tool in the arsenal of yeast geneticists. Previously, the qrt mutant of Arabidopsis, which causes the four pollen products of male meiosis to remain attached, was developed as a facile system

  19. A Link between Meiotic Prophase Progression and CrossoverControl

    Energy Technology Data Exchange (ETDEWEB)

    Carlton, Peter M.; Farruggio, Alfonso P.; Dernburg, Abby F.

    2005-07-06

    During meiosis, most organisms ensure that homologous chromosomes undergo at least one exchange of DNA, or crossover, to link chromosomes together and accomplish proper segregation. How each chromosome receives a minimum of one crossover is unknown. During early meiosis in Caenorhabditis elegans and many other species, chromosomes adopt a polarized organization within the nucleus, which normally disappears upon completion of homolog synapsis. Mutations that impair synapsis even between a single pair of chromosomes in C. elegans delay this nuclear reorganization. We quantified this delay by developing a classification scheme for discrete stages of meiosis. Immunofluorescence localization of RAD-51 protein revealed that delayed meiotic cells also contained persistent recombination intermediates. Through genetic analysis, we found that this cytological delay in meiotic progression requires double-strand breaks and the function of the crossover-promoting heteroduplex HIM-14 (Msh4) and MSH-5. Failure of X chromosome synapsis also resulted in impaired crossover control on autosomes, which may result from greater numbers and persistence of recombination intermediates in the delayed nuclei. We conclude that maturation of recombination events on chromosomes promotes meiotic progression, and is coupled to the regulation of crossover number and placement. Our results have broad implications for the interpretation of meiotic mutants, as we have shown that asynapsis of a single chromosome pair can exert global effects on meiotic progression and recombination frequency.

  20. Galvanotactic behavior of Tetrahymena pyriformis under electric fields

    International Nuclear Information System (INIS)

    Kim, Dal Hyung; Kim, Paul Seung Soo; Kim, Min Jun; Lee, Kyoungwoo; Kim, JinSeok

    2013-01-01

    Tetrahymena pyriformis, a eukaryotic ciliate, swims toward a cathode in straight or cross-shaped microchannels under an applied electric field, a behavioral response called cathodal galvanotaxis. In straight channel experiments, a one-dimensional electric field was applied, and the galvanotactic swimming behavior of Tetrahymena pyriformis was observed and described in detail while the polarity of this field is switched. In most individual cases, the cell would immediately switch its direction toward the cathode; however, exceptional cases have been observed where cells exhibit a turning delay or do not turn after a polarity switch. In cross-channel experiments, feedback control using vision-based tracking was used to steer a cell in the microchannel intersection using a two-dimensional electric field generated by four electrodes placed at four ends of the cross channel. The motivation for this work is to study the swimming behavior of Tetrahymena pyriformis as a microrobot under the control of electric fields. (paper)

  1. Binding and internalization of 3H-epinephrine in Tetrahymena

    International Nuclear Information System (INIS)

    Csaba, G.; Sudar, F.; Pados, R.

    1980-01-01

    Exposure of Tetrahymena to exogenous epinephrine is followed by appearance of the hormone in the cell membrane, intracytoplasmic vacuoles and nucleus. The intranuclear localization is always heterochromatic. Only a minor proportion of the epinephrine applied gains access to the nucleus, while the bulk of it attaches to the membrane. (author)

  2. Inhibition of Tetrahymena pyriformis growth by Aliphatic Alcohols ...

    African Journals Online (AJOL)

    A Quantitative Structure- Activity Relationship (QSAR) study was undertaken to evaluate the relative toxicity of a mixed series of 21 (linear and branched-chain) alcohols and 9 normal aliphatic amines in term of the 50% inhibitory growth concentration (IGC50) of Tetrahymena pyriformis. The applied simple linear regression ...

  3. Localization and roles of Ski8p protein in Sordaria meiosis and delineation of three mechanistically distinct steps of meiotic homolog juxtaposition.

    Science.gov (United States)

    Tessé, Sophie; Storlazzi, Aurora; Kleckner, Nancy; Gargano, Silvana; Zickler, Denise

    2003-10-28

    Ski8p is implicated in degradation of non-poly(A) and double-stranded RNA, and in meiotic DNA recombination. We have identified the Sordaria macrospora SKI8 gene. Ski8p is cytoplasmically localized in all vegetative and sexual cycle cells, and is nuclear localized, specifically in early-mid-meiotic prophase, in temporal correlation with Spo11p, the meiotic double-strand break (DSB) transesterase. Localizations of Ski8p and Spo11p are mutually interdependent. ski8 mutants exhibit defects in vegetative growth, entry into the sexual program, and sporulation. Diverse meiotic defects, also seen in spo11 mutants, are diagnostic of DSB absence, and they are restored by exogenous DSBs. These results suggest that Ski8p promotes meiotic DSB formation by acting directly within meiotic prophase chromosomes. Mutant phenotypes also divide meiotic homolog juxtaposition into three successive, mechanistically distinct steps; recognition, presynaptic alignment, and synapsis, which are distinguished by their differential dependence on DSBs.

  4. Genetics and Epigenetics of Mating Type Determination in Paramecium and Tetrahymena.

    Science.gov (United States)

    Orias, Eduardo; Singh, Deepankar Pratap; Meyer, Eric

    2017-09-08

    While sex is an ancient and highly conserved eukaryotic invention, self-incompatibility systems such as mating types or sexes appear to be derived limitations that show considerable evolutionary plasticity. Within a single class of ciliates, Paramecium and Tetrahymena species have long been known to present a wide variety of mating type numbers and modes of inheritance, but only recently have the genes involved been identified. Although similar transmembrane proteins mediate self/nonself recognition in both ciliates, the mechanisms of mating type determination differ widely, ranging from Mendelian systems to developmental nuclear differentiation, either stochastic or maternally inherited. The non-Mendelian systems rely on programmed editing of the germline genome that occurs during differentiation of the somatic nucleus, and they have co-opted different DNA recombination mechanisms-some previously unknown. Here we review the recent molecular advances and some remaining unsolved questions and discuss the possible implications of these diverse mechanisms for inbreeding/outbreeding balance regulation.

  5. The conjugation-specific Die5 protein is required for development of the somatic nucleus in both Paramecium and Tetrahymena.

    Science.gov (United States)

    Matsuda, Atsushi; Shieh, Annie Wan-Yi; Chalker, Douglas L; Forney, James D

    2010-07-01

    Development in ciliated protozoa involves extensive genome reorganization within differentiating macronuclei, which shapes the somatic genome of the next vegetative generation. Major events of macronuclear differentiation include excision of internal eliminated sequences (IESs), chromosome fragmentation, and genome amplification. Proteins required for these events include those with homology throughout eukaryotes as well as proteins apparently unique to ciliates. In this study, we identified the ciliate-specific Defective in IES Excision 5 (DIE5) genes of Paramecium tetraurelia (PtDIE5) and Tetrahymena thermophila (TtDIE5) as orthologs that encode nuclear proteins expressed exclusively during development. Abrogation of PtDie5 protein (PtDie5p) function by RNA interference (RNAi)-mediated silencing or TtDie5p by gene disruption resulted in the failure of developing macronuclei to differentiate into new somatic nuclei. Tetrahymena DeltaDIE5 cells arrested late in development and failed to complete genome amplification, whereas RNAi-treated Paramecium cells highly amplified new macronuclear DNA before the failure in differentiation, findings that highlight clear differences in the biology of these distantly related species. Nevertheless, IES excision and chromosome fragmentation failed to occur in either ciliate, which strongly supports that Die5p is a critical player in these processes. In Tetrahymena, loss of zygotic expression during development was sufficient to block nuclear differentiation. This observation, together with the finding that knockdown of Die5p in Paramecium still allows genome amplification, indicates that this protein acts late in macronuclear development. Even though DNA rearrangements in these two ciliates look to be quite distinct, analysis of DIE5 establishes the action of a conserved mechanism within the genome reorganization pathway.

  6. Comparative Proteome Bioinformatics: Identification of Phosphotyrosine Signaling Proteins in the Unicellular Protozoan Ciliate Tetrahymena

    DEFF Research Database (Denmark)

    Gammeltoft, Steen; Christensen, Søren Tvorup; Joachimiak, Marcin

    2005-01-01

    Tetrahymena, bioinformatics, cilia, evolution, signaling, TtPTK1, PTK, Grb2, SH-PTP 2, Plcy, Src, PTP, PI3K, SH2, SH3, PH......Tetrahymena, bioinformatics, cilia, evolution, signaling, TtPTK1, PTK, Grb2, SH-PTP 2, Plcy, Src, PTP, PI3K, SH2, SH3, PH...

  7. The fission yeast MTREC and EJC orthologs ensure the maturation of meiotic transcripts during meiosis.

    Science.gov (United States)

    Marayati, Bahjat Fadi; Hoskins, Victoria; Boger, Robert W; Tucker, James F; Fishman, Emily S; Bray, Andrew S; Zhang, Ke

    2016-09-01

    Meiosis is a highly regulated process by which genetic information is transmitted through sexual reproduction. It encompasses unique mechanisms that do not occur in vegetative cells, producing a distinct, well-regulated meiotic transcriptome. During vegetative growth, many meiotic genes are constitutively transcribed, but most of the resulting mRNAs are rapidly eliminated by the Mmi1-MTREC (Mtl1-Red1 core) complex. While Mmi1-MTREC targets premature meiotic RNAs for degradation by the nuclear 3'-5' exoribonuclease exosome during mitotic growth, its role in meiotic gene expression during meiosis is not known. Here, we report that Red5, an essential MTREC component, interacts with pFal1, an ortholog of eukaryotic translation initiation factor eIF4aIII in the fission yeast Schizosaccharomyces pombe In mammals, together with MAGO (Mnh1), Rnps1, and Y14, elF4AIII (pFal1) forms the core of the exon junction complex (EJC), which is essential for transcriptional surveillance and localization of mature mRNAs. In fission yeast, two EJC orthologs, pFal1 and Mnh1, are functionally connected with MTREC, specifically in the process of meiotic gene expression during meiosis. Although pFal1 interacts with Mnh1, Y14, and Rnps1, its association with Mnh1 is not disrupted upon loss of Y14 or Rnps1. Mutations of Red1, Red5, pFal1, or Mnh1 produce severe meiotic defects; the abundance of meiotic transcripts during meiosis decreases; and mRNA maturation processes such as splicing are impaired. Since studying meiosis in mammalian germline cells is difficult, our findings in fission yeast may help to define the general mechanisms involved in accurate meiotic gene expression in higher eukaryotes. © 2016 Marayati et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  8. Characteristics of bovine oocytes with different meiotic competence in terms of their mitochondrial status and expression of nuclear-encoded factors

    Czech Academy of Sciences Publication Activity Database

    Machatková, M.; Jeseta, M.; Hulínská, P.; Knitlová, D.; Němcová, Lucie; Kaňka, Jiří

    2012-01-01

    Roč. 47, č. 5 (2012), s. 806-814 ISSN 0936-6768 R&D Projects: GA MZe QI91A018 Grant - others:GA ČR(CZ) GD523/08/H064 Program:GD Institutional research plan: CEZ:AV0Z50450515 Keywords : bovine oocytes * mitochondrial status * nuclear-encoded factors Subject RIV: GI - Animal Husbandry ; Breeding Impact factor: 1.392, year: 2012

  9. Meiotic recombination in human oocytes.

    Directory of Open Access Journals (Sweden)

    Edith Y Cheng

    2009-09-01

    Full Text Available Studies of human trisomies indicate a remarkable relationship between abnormal meiotic recombination and subsequent nondisjunction at maternal meiosis I or II. Specifically, failure to recombine or recombination events located either too near to or too far from the centromere have been linked to the origin of human trisomies. It should be possible to identify these abnormal crossover configurations by using immunofluorescence methodology to directly examine the meiotic recombination process in the human female. Accordingly, we initiated studies of crossover-associated proteins (e.g., MLH1 in human fetal oocytes to analyze their number and distribution on nondisjunction-prone human chromosomes and, more generally, to characterize genome-wide levels of recombination in the human female. Our analyses indicate that the number of MLH1 foci is lower than predicted from genetic linkage analysis, but its localization pattern conforms to that expected for a crossover-associated protein. In studies of individual chromosomes, our observations provide evidence for the presence of "vulnerable" crossover configurations in the fetal oocyte, consistent with the idea that these are subsequently translated into nondisjunctional events in the adult oocyte.

  10. Variations in survival and ''petite'' mutagenesis induced by ultraviolet light during the meiotic cycle of Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Hottinguer-de Margerie, Helene; Moustacchi, Ethel

    1975-01-01

    Cyclic variations in sensitivity to killing and cytoplasmic ''petite'' rho induction by ultraviolet light occur during the meiosis of Saccharomyces cerevisiae. Maximal sensitivity to killing coincides with the period of meiotic nuclear DNA synthesis. Cyclic fluctuations in ''petite'' induction could not be correlated with known meiotic events and the pattern could vary temporarily from batch to batch. A dark liquid holding of irradiated cells aided the repair of lethal lesions but on the other hand an enhancement of ''petite'' induction was observed at all meiotic stages [fr

  11. Low Base-Substitution Mutation Rate in the Germline Genome of the Ciliate Tetrahymena thermophila

    Science.gov (United States)

    2016-09-15

    Tetrahymena thermophila, a model eukaryote. PLoS Biol. 4:e286. Farlow A, et al. 2015. The spontaneous mutation rate in the fission yeast Schizosaccharomyces...spontane- ous mutations in yeast . Proc Natl Acad Sci U S A. 105:9272–9277. Lynn DH, Doerder FP. 2012. The life and times of Tetrahymena. Methods Cell...Low Base-Substitution Mutation Rate in the Germline Genome of the Ciliate Tetrahymena thermophila Hongan Long1,2,y, David J. Winter3,*,y, Allan Y.-C

  12. Rapid biotransformation of arsenic by a model protozoan Tetrahymena thermophila

    Energy Technology Data Exchange (ETDEWEB)

    Yin Xixiang [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); State Key Lab of Urban and Regional Ecology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China); Zhang Yongyu; Yang Jun [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Zhu Yongguan, E-mail: ygzhu@rcees.ac.cn [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); State Key Lab of Urban and Regional Ecology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China)

    2011-04-15

    Arsenic biomethylation and biovolatilization are thought to be two important metabolic pathways in aquatic and soil environments. Tetrahymena thermophila is a genus of free-living ciliated protozoan that is widely distributed in freshwater environments around the world. In this study, we studied arsenic accumulation, speciation, efflux, methylation and volatilization in this unicellular eukaryote exposed to various concentrations of arsenate. Our results show that T. thermophila accumulated 187 mg.kg{sup -1} dry weight of arsenic when exposed to 40 {mu}M for 48 h, with MMAs(V) (monomethylarsenate) and DMAs(V) (dimethylarsenate) as the dominant species, accounting for 66% of the total arsenic. Meanwhile, arsenate, arsenite, MMAs(V) and DMAs(V) were detected in the culture medium; the last three were released by the cells. The production of volatile arsenic increased with increasing external As(V) concentrations and exposure time. To our knowledge, this is the first study on arsenic metabolism, particularly biomethylation and biovolatilization, in protozoa. - Tetrahymena thermophila can rapidly methylate arsenic, and produce volatile arsenicals.

  13. Regulation of meiotic gene expression in plants

    Directory of Open Access Journals (Sweden)

    Adele eZhou

    2014-08-01

    Full Text Available With the recent advances in genomics and sequencing technologies, databases of transcriptomes representing many cellular processes have been built. Meiotic transcriptomes in plants have been studied in Arabidopsis thaliana, rice (Oryza sativa, wheat (Triticum aestivum, petunia (Petunia hybrida, sunflower (Helianthus annuus, and maize (Zea mays. Studies in all organisms, but particularly in plants, indicate that a very large number of genes are expressed during meiosis, though relatively few of them seem to be required for the completion of meiosis. In this review, we focus on gene expression at the RNA level and analyze the meiotic transcriptome datasets and explore expression patterns of known meiotic genes to elucidate how gene expression could be regulated during meiosis. We also discuss mechanisms, such as chromatin organization and non-coding RNAs, that might be involved in the regulation of meiotic transcription patterns.

  14. Spermatogenesis-specific features of the meiotic program in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Diane C Shakes

    2009-08-01

    Full Text Available In most sexually reproducing organisms, the fundamental process of meiosis is implemented concurrently with two differentiation programs that occur at different rates and generate distinct cell types, sperm and oocytes. However, little is known about how the meiotic program is influenced by such contrasting developmental programs. Here we present a detailed timeline of late meiotic prophase during spermatogenesis in Caenorhabditis elegans using cytological and molecular landmarks to interrelate changes in chromosome dynamics with germ cell cellularization, spindle formation, and cell cycle transitions. This analysis expands our understanding C. elegans spermatogenesis, as it identifies multiple spermatogenesis-specific features of the meiotic program and provides a framework for comparative studies. Post-pachytene chromatin of spermatocytes is distinct from that of oocytes in both composition and morphology. Strikingly, C. elegans spermatogenesis includes a previously undescribed karyosome stage, a common but poorly understood feature of meiosis in many organisms. We find that karyosome formation, in which chromosomes form a constricted mass within an intact nuclear envelope, follows desynapsis, involves a global down-regulation of transcription, and may support the sequential activation of multiple kinases that prepare spermatocytes for meiotic divisions. In spermatocytes, the presence of centrioles alters both the relative timing of meiotic spindle assembly and its ultimate structure. These microtubule differences are accompanied by differences in kinetochores, which connect microtubules to chromosomes. The sperm-specific features of meiosis revealed here illuminate how the underlying molecular machinery required for meiosis is differentially regulated in each sex.

  15. HIM-8 binds to the X chromosome pairing center and mediates chromosome-specific meiotic synapsis.

    Science.gov (United States)

    Phillips, Carolyn M; Wong, Chihunt; Bhalla, Needhi; Carlton, Peter M; Weiser, Pinky; Meneely, Philip M; Dernburg, Abby F

    2005-12-16

    The him-8 gene is essential for proper meiotic segregation of the X chromosomes in C. elegans. Here we show that loss of him-8 function causes profound X chromosome-specific defects in homolog pairing and synapsis. him-8 encodes a C2H2 zinc-finger protein that is expressed during meiosis and concentrates at a site on the X chromosome known as the meiotic pairing center (PC). A role for HIM-8 in PC function is supported by genetic interactions between PC lesions and him-8 mutations. HIM-8 bound chromosome sites associate with the nuclear envelope (NE) throughout meiotic prophase. Surprisingly, a point mutation in him-8 that retains both chromosome binding and NE localization fails to stabilize pairing or promote synapsis. These observations indicate that stabilization of homolog pairing is an active process in which the tethering of chromosome sites to the NE may be necessary but is not sufficient.

  16. Female meiotic sex chromosome inactivation in chicken.

    Directory of Open Access Journals (Sweden)

    Sam Schoenmakers

    2009-05-01

    Full Text Available During meiotic prophase in male mammals, the heterologous X and Y chromosomes remain largely unsynapsed, and meiotic sex chromosome inactivation (MSCI leads to formation of the transcriptionally silenced XY body. In birds, the heterogametic sex is female, carrying Z and W chromosomes (ZW, whereas males have the homogametic ZZ constitution. During chicken oogenesis, the heterologous ZW pair reaches a state of complete heterologous synapsis, and this might enable maintenance of transcription of Z- and W chromosomal genes during meiotic prophase. Herein, we show that the ZW pair is transiently silenced, from early pachytene to early diplotene using immunocytochemistry and gene expression analyses. We propose that ZW inactivation is most likely achieved via spreading of heterochromatin from the W on the Z chromosome. Also, persistent meiotic DNA double-strand breaks (DSBs may contribute to silencing of Z. Surprisingly, gammaH2AX, a marker of DSBs, and also the earliest histone modification that is associated with XY body formation in mammalian and marsupial spermatocytes, does not cover the ZW during the synapsed stage. However, when the ZW pair starts to desynapse, a second wave of gammaH2AX accumulates on the unsynapsed regions of Z, which also show a reappearance of the DSB repair protein RAD51. This indicates that repair of meiotic DSBs on the heterologous part of Z is postponed until late pachytene/diplotene, possibly to avoid recombination with regions on the heterologously synapsed W chromosome. Two days after entering diplotene, the Z looses gammaH2AX and shows reactivation. This is the first report of meiotic sex chromosome inactivation in a species with female heterogamety, providing evidence that this mechanism is not specific to spermatogenesis. It also indicates the presence of an evolutionary force that drives meiotic sex chromosome inactivation independent of the final achievement of synapsis.

  17. Meiotic behaviour of tetraploid wheats (Triticum turgidum L.) and ...

    Indian Academy of Sciences (India)

    cause for the meiotic instability (Oettler 2005). Meiotic in- stability in triticale seems to have another molecular cause. Rye chromosomes generally .... economic yield is the product of sexual reproduction (Saini. 1997). Global warming is now ...

  18. Initiation of Meiotic Recombination in Mammals

    Directory of Open Access Journals (Sweden)

    Rajeev Kumar

    2010-12-01

    Full Text Available Meiotic recombination is initiated by the induction of programmed DNA double strand breaks (DSBs. DSB repair promotes homologous interactions and pairing and leads to the formation of crossovers (COs, which are required for the proper reductional segregation at the first meiotic division. In mammals, several hundred DSBs are generated at the beginning of meiotic prophase by the catalytic activity of SPO11. Currently it is not well understood how the frequency and timing of DSB formation and their localization are regulated. Several approaches in humans and mice have provided an extensive description of the localization of initiation events based on CO mapping, leading to the identification and characterization of preferred sites (hotspots of initiation. This review presents the current knowledge about the proteins known to be involved in this process, the sites where initiation takes place, and the factors that control hotspot localization.

  19. Meiotic behaviour of tetraploid wheats (Triticum turgidum L.)

    Indian Academy of Sciences (India)

    Meiotic behaviour of plant chromosomes is influenced by both genetic and environmental factors. In this study, the meiotic behaviour of cereal crops was investigated, which includes tetraploid wheat genotypes (with and without the meiotic restitution trait) and their derivates (synthetic hexaploid wheats and a doubled ...

  20. JST Thesaurus Headwords and Synonyms: Tetrahymena [MeCab user dictionary for science technology term[Archive

    Lifescience Database Archive (English)

    Full Text Available MeCab user dictionary for science technology term Tetrahymena 名詞 一般 * * * * テトラヒメナ属... テトラヒメナゾク テトラヒメナゾク Thesaurus2015 200906089871776382 C LS07 UNKNOWN_1 Tetrahymena

  1. Polyploidization increases meiotic recombination frequency in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Rehmsmeier Marc

    2011-04-01

    Full Text Available Abstract Background Polyploidization is the multiplication of the whole chromosome complement and has occurred frequently in vascular plants. Maintenance of stable polyploid state over generations requires special mechanisms to control pairing and distribution of more than two homologous chromosomes during meiosis. Since a minimal number of crossover events is essential for correct chromosome segregation, we investigated whether polyploidy has an influence on the frequency of meiotic recombination. Results Using two genetically linked transgenes providing seed-specific fluorescence, we compared a high number of progeny from diploid and tetraploid Arabidopsis plants. We show that rates of meiotic recombination in reciprocal crosses of genetically identical diploid and autotetraploid Arabidopsis plants were significantly higher in tetraploids compared to diploids. Although male and female gametogenesis differ substantially in meiotic recombination frequency, both rates were equally increased in tetraploids. To investigate whether multivalent formation in autotetraploids was responsible for the increased recombination rates, we also performed corresponding experiments with allotetraploid plants showing strict bivalent pairing. We found similarly increased rates in auto- and allotetraploids, suggesting that the ploidy effect is independent of chromosome pairing configurations. Conclusions The evolutionary success of polyploid plants in nature and under domestication has been attributed to buffering of mutations and sub- and neo-functionalization of duplicated genes. Should the data described here be representative for polyploid plants, enhanced meiotic recombination, and the resulting rapid creation of genetic diversity, could have also contributed to their prevalence.

  2. Meiotic recombination hotspots - a comparative view.

    Science.gov (United States)

    Choi, Kyuha; Henderson, Ian R

    2015-07-01

    During meiosis homologous chromosomes pair and undergo reciprocal genetic exchange, termed crossover. Meiotic recombination has a profound effect on patterns of genetic variation and is an important tool during crop breeding. Crossovers initiate from programmed DNA double-stranded breaks that are processed to form single-stranded DNA, which can invade a homologous chromosome. Strand invasion events mature into double Holliday junctions that can be resolved as crossovers. Extensive variation in the frequency of meiotic recombination occurs along chromosomes and is typically focused in narrow hotspots, observed both at the level of DNA breaks and final crossovers. We review methodologies to profile hotspots at different steps of the meiotic recombination pathway that have been used in different eukaryote species. We then discuss what these studies have revealed concerning specification of hotspot locations and activity and the contributions of both genetic and epigenetic factors. Understanding hotspots is important for interpreting patterns of genetic variation in populations and how eukaryotic genomes evolve. In addition, manipulation of hotspots will allow us to accelerate crop breeding, where meiotic recombination distributions can be limiting. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  3. Highly divergent mitochondrial ATP synthase complexes in Tetrahymena thermophila.

    Directory of Open Access Journals (Sweden)

    Praveen Balabaskaran Nina

    2010-07-01

    Full Text Available The F-type ATP synthase complex is a rotary nano-motor driven by proton motive force to synthesize ATP. Its F(1 sector catalyzes ATP synthesis, whereas the F(o sector conducts the protons and provides a stator for the rotary action of the complex. Components of both F(1 and F(o sectors are highly conserved across prokaryotes and eukaryotes. Therefore, it was a surprise that genes encoding the a and b subunits as well as other components of the F(o sector were undetectable in the sequenced genomes of a variety of apicomplexan parasites. While the parasitic existence of these organisms could explain the apparent incomplete nature of ATP synthase in Apicomplexa, genes for these essential components were absent even in Tetrahymena thermophila, a free-living ciliate belonging to a sister clade of Apicomplexa, which demonstrates robust oxidative phosphorylation. This observation raises the possibility that the entire clade of Alveolata may have invented novel means to operate ATP synthase complexes. To assess this remarkable possibility, we have carried out an investigation of the ATP synthase from T. thermophila. Blue native polyacrylamide gel electrophoresis (BN-PAGE revealed the ATP synthase to be present as a large complex. Structural study based on single particle electron microscopy analysis suggested the complex to be a dimer with several unique structures including an unusually large domain on the intermembrane side of the ATP synthase and novel domains flanking the c subunit rings. The two monomers were in a parallel configuration rather than the angled configuration previously observed in other organisms. Proteomic analyses of well-resolved ATP synthase complexes from 2-D BN/BN-PAGE identified orthologs of seven canonical ATP synthase subunits, and at least 13 novel proteins that constitute subunits apparently limited to the ciliate lineage. A mitochondrially encoded protein, Ymf66, with predicted eight transmembrane domains could be a

  4. Cell death in Tetrahymena thermophila: new observations on culture conditions.

    Science.gov (United States)

    Christensen, S T; Sørensen, H; Beyer, N H; Kristiansen, K; Rasmussen, L; Rasmussen, M I

    2001-01-01

    We previously suggested that the cell fate of the protozoan ciliate, Tetrahymena thermophila, effectively relates to a quorum-sensing mechanism where cell-released factors support cell survival and proliferation. The cells have to be present above a critical initial density in a chemically defined nutrient medium in order to release a sufficient level of these factors to allow a new colony to flourish. At a relatively high rate of metabolism and/or macromolecular synthesis and below this critical density, cells began to die abruptly within 30 min of inoculation, and this death took the form of an explosive disintegration lasting less than 50 milliseconds. The cells died at any location in the culture, and the frequency of cell death was always lower in well-filled vials than those with medium/air interface. Cell death was inhibited by the addition of Actinomycin D or through modifications of the culture conditions either by reducing the oxygen tension or by decreasing the temperature of the growth medium. In addition, plastic caps in well-filled vials release substances, which promote cell survival. The fate of low-density cultures is related to certain 'physical' conditions, in addition to the availability of oxygen within closed culture systems. Copyright 2001 Academic Press.

  5. Evaluation of guppy (Poecilia reticulata Peters) immunization against Tetrahymena sp. by enzyme-linked immunosorbent assay (ELISA).

    Science.gov (United States)

    Sharon, Galit; Nath, Pulak R; Isakov, Noah; Zilberg, Dina

    2014-09-15

    Analysis of the effectiveness of guppy (Poecilia reticulata Peters) immunization based on measurements of antibody (Ab) titers suffers from a shortage of reagents that can detect guppy antibodies (Abs). To overcome this problem, we immunized mice with different preparations of guppy immunoglobulins (Igs) and used the mouse antisera to develop a quantitative enzyme-linked immunosorbent assay (ELISA). The most efficient immunogen for mouse immunization was guppy Igs adsorbed on protein A/G beads. Antisera from mice boosted with this immunoglobulin (Ig) preparation were highly specific and contained high Ab titers. They immunoreacted in a Western blot with Ig heavy and light chains from guppy serum, and Ig heavy chain from guppy whole-body homogenate. The mouse anti-guppy Ig was applied in an ELISA aimed at comparing the efficiency of different routes of guppy immunization against Tetrahymena: (i) anal intubation with sonicated Tetrahymena (40,000 Tetrahymena/fish in a total volume of 10 μL) mixed with domperidon, deoxycholic acid and free amino acids (valine, leucine, isoleucine, phenylalanine and tryptophan), or (ii) intraperitoneal (i.p.) injection of sonicated Tetrahymena in complete Freund's adjuvant (15,000 Tetrahymena/fish in total a volume of 20 μL). Negative control fish were anally intubated with the intubation mixture without Tetrahymena, or untreated. ELISA measurement of anti-Tetrahymena Ab titer revealed a significantly higher level of Abs in i.p.-immunized guppies, compared to the anally intubated and control fish. In addition, the efficiency of immunization was tested by monitoring guppy mortality following (i) i.p. challenge with Tetrahymena (900 Tetrahymena/fish) or (ii) cold stress followed by immersion in water containing 10,000 Tetrahymena/mL. Fish mortality on day 14 post-Tetrahymena infection by i.p. injection exceeded 50% in the control and anally intubated fish, compared to 31% in i.p.-immunized fish. Immunization did not protect from

  6. Experimental identification and analysis of macronuclear non-coding RNAs from the ciliate Tetrahymena thermophila

    DEFF Research Database (Denmark)

    Andersen, Kasper Langebjerg; Nielsen, Henrik

    2012-01-01

    expressed during vegetative growth or sexual reorganization. In order to get an overview of medium-sized (40-500¿nt) RNAs expressed from the Tetrahymena genome, we created a size-fractionated cDNA library from macronuclear RNA and analyzed 80 RNAs, most of which were previously unknown. The most abundant...... class was small nucleolar RNAs (snoRNAs), many of which are formed by an unusual maturation pathway. The modifications guided by the snoRNAs were analyzed bioinformatically and experimentally and many Tetrahymena-specific modifications were found, including several in an essential, but not conserved...

  7. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    International Nuclear Information System (INIS)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J.

    2014-01-01

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed

  8. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J., E-mail: m.neale@sussex.ac.uk

    2014-11-15

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed.

  9. Many functions of the meiotic cohesin.

    Science.gov (United States)

    Bardhan, Amit

    2010-12-01

    Sister chromatids are held together from the time of their formation in S phase until they segregate in anaphase by the cohesin complex. In meiosis of most organisms, the mitotic Mcd1/Scc1/Rad21 subunit of the cohesin complex is largely replaced by its paralog named Rec8. This article reviews the specialized functions of Rec8 that are crucial for diverse aspects of chromosome dynamics in meiosis, and presents some speculations relating to meiotic chromosome organization.

  10. The effect of extracellular environment on the sensitivity of two strains of Tetrahymena to gamma rays

    International Nuclear Information System (INIS)

    Gebicki, J.M.; Darlington, J.L.; Baumgartner, S.

    1980-01-01

    The radiosensitivity of two strains of Tetrahymena pyriformis to gamma radiation was studied. Irradiation of mass suspensions of Tetrahymena in their normal growth medium confirmed earlier reports of their very high resistance to gamma rays. However this resistance was lowered when the cells were irradiated singly. Using mass and single cell cultures of Tetrahymena, it was shown that the mass cultures were not protected by anoxia from the effects of gamma radiation. However when lysates of Tetrahymena suspensions were added to single cell isolates just before irradiation, the cells were protected. Thus the high resistance of cells in mass culture might lie in the release of protective substances by other cells lysing spontaneously, or as a result of radiation damage. The absence of proteose-peptone-yeast in the growth medium markedly increased the lethality of the gamma rays for both strains. The most likely explanation appeared to lie in the protection of cells from indirect effects of radiation by organic materials in the external medium. The results of the present study emphasise the role of the indirect component of radiation damage in cell death. It is likely that much of this damage occurs in cell membranes. (U.K.)

  11. HIM-8 binds to the X chromosome pairing center and mediates chromosome-specific meiotic synapsis

    International Nuclear Information System (INIS)

    Phillips, Carolyn M.; Wong, Chihunt; Bhalla, Needhi; Carlton, Peter M.; Weiser, Pinky; Meneely, Philip M.; Dernburg, Abby F.

    2005-01-01

    The him-8 gene is essential for proper meiotic segregation of the X chromosomes in C. elegans. Here we show that loss of him-8 function causes profound X-chromosome-specific defects in homolog pairing and synapsis.him-8 encodes a C2H2 zinc finger protein that is expressed during meiosis and concentrates at a site on the X chromosome known as themeiotic Pairing Center (PC). A role for HIM-8 in PC function is supported by genetic interactions between PC lesions and him-8 mutations. HIM-8-bound chromosome sites associate with the nuclear envelope (NE)throughout meiotic prophase. Surprisingly, a point mutation in him-8 that retains both chromosome binding and NE localization fails to stabilize pairing or promote synapsis. These observations indicate that stabilization of homolog pairing is an active process in which the tethering of chromosome sites to the NE may be necessary but is not sufficient

  12. Combinatorial QSAR modeling of chemical toxicants tested against Tetrahymena pyriformis.

    Science.gov (United States)

    Zhu, Hao; Tropsha, Alexander; Fourches, Denis; Varnek, Alexandre; Papa, Ester; Gramatica, Paola; Oberg, Tomas; Dao, Phuong; Cherkasov, Artem; Tetko, Igor V

    2008-04-01

    Selecting most rigorous quantitative structure-activity relationship (QSAR) approaches is of great importance in the development of robust and predictive models of chemical toxicity. To address this issue in a systematic way, we have formed an international virtual collaboratory consisting of six independent groups with shared interests in computational chemical toxicology. We have compiled an aqueous toxicity data set containing 983 unique compounds tested in the same laboratory over a decade against Tetrahymena pyriformis. A modeling set including 644 compounds was selected randomly from the original set and distributed to all groups that used their own QSAR tools for model development. The remaining 339 compounds in the original set (external set I) as well as 110 additional compounds (external set II) published recently by the same laboratory (after this computational study was already in progress) were used as two independent validation sets to assess the external predictive power of individual models. In total, our virtual collaboratory has developed 15 different types of QSAR models of aquatic toxicity for the training set. The internal prediction accuracy for the modeling set ranged from 0.76 to 0.93 as measured by the leave-one-out cross-validation correlation coefficient ( Q abs2). The prediction accuracy for the external validation sets I and II ranged from 0.71 to 0.85 (linear regression coefficient R absI2) and from 0.38 to 0.83 (linear regression coefficient R absII2), respectively. The use of an applicability domain threshold implemented in most models generally improved the external prediction accuracy but at the same time led to a decrease in chemical space coverage. Finally, several consensus models were developed by averaging the predicted aquatic toxicity for every compound using all 15 models, with or without taking into account their respective applicability domains. We find that consensus models afford higher prediction accuracy for the

  13. Meiotic behaviour in three interspecific three-way hybrids between ...

    Indian Academy of Sciences (India)

    In H17, abnormalities were more frequent from anaphase II, when many laggard chromosomes appeared, suggesting that each genome presented a different genetic control for meiotic phase timing. Despite the phylogenetic proximity among these two species, these three hybrids presented a high frequency of meiotic ...

  14. Meiotic chromosome behaviour and sexual sterility in two Nigerian ...

    African Journals Online (AJOL)

    The behaviour of meiotic chromosomes and the subsequent behaviour of the meiotic products were investigated in two Nigerian species of Aloe, namely Aloe keayi and Aloe macrocarpa var major with a view to uncovering the cause of their inability to reproduce sexually. The two plant materials used in this study were ...

  15. The inhibition of polo kinase by matrimony maintains G2 arrest in the meiotic cell cycle.

    Directory of Open Access Journals (Sweden)

    Youbin Xiang

    2007-12-01

    Full Text Available Many meiotic systems in female animals include a lengthy arrest in G2 that separates the end of pachytene from nuclear envelope breakdown (NEB. However, the mechanisms by which a meiotic cell can arrest for long periods of time (decades in human females have remained a mystery. The Drosophila Matrimony (Mtrm protein is expressed from the end of pachytene until the completion of meiosis I. Loss-of-function mtrm mutants result in precocious NEB. Coimmunoprecipitation experiments reveal that Mtrm physically interacts with Polo kinase (Polo in vivo, and multidimensional protein identification technology mass spectrometry analysis reveals that Mtrm binds to Polo with an approximate stoichiometry of 1:1. Mutation of a Polo-Box Domain (PBD binding site in Mtrm ablates the function of Mtrm and the physical interaction of Mtrm with Polo. The meiotic defects observed in mtrm/+ heterozygotes are fully suppressed by reducing the dose of polo+, demonstrating that Mtrm acts as an inhibitor of Polo. Mtrm acts as a negative regulator of Polo during the later stages of G2 arrest. Indeed, both the repression of Polo expression until stage 11 and the inactivation of newly synthesized Polo by Mtrm until stage 13 play critical roles in maintaining and properly terminating G2 arrest. Our data suggest a model in which the eventual activation of Cdc25 by an excess of Polo at stage 13 triggers NEB and entry into prometaphase.

  16. Eccentric localization of catalase to protect chromosomes from oxidative damages during meiotic maturation in mouse oocytes.

    Science.gov (United States)

    Park, Yong Seok; You, Seung Yeop; Cho, Sungrae; Jeon, Hyuk-Joon; Lee, Sukchan; Cho, Dong-Hyung; Kim, Jae-Sung; Oh, Jeong Su

    2016-09-01

    The maintenance of genomic integrity and stability is essential for the survival of every organism. Unfortunately, DNA is vulnerable to attack by a variety of damaging agents. Oxidative stress is a major cause of DNA damage because reactive oxygen species (ROS) are produced as by-products of normal cellular metabolism. Cells have developed eloquent antioxidant defense systems to protect themselves from oxidative damage along with aerobic metabolism. Here, we show that catalase (CAT) is present in mouse oocytes to protect the genome from oxidative damage during meiotic maturation. CAT was expressed in the nucleus to form unique vesicular structures. However, after nuclear envelope breakdown, CAT was redistributed in the cytoplasm with particular focus at the chromosomes. Inhibition of CAT activity increased endogenous ROS levels, but did not perturb meiotic maturation. In addition, CAT inhibition produced chromosomal defects, including chromosome misalignment and DNA damage. Therefore, our data suggest that CAT is required not only to scavenge ROS, but also to protect DNA from oxidative damage during meiotic maturation in mouse oocytes.

  17. QSAR studies for the acute toxicity of nitrobenzenes to the Tetrahymena pyriformis

    Directory of Open Access Journals (Sweden)

    Wang Dan-Dan

    2014-01-01

    Full Text Available Quantitative structure-activity relationship (QSAR models play a key role in finding the relationship between molecular structures and the toxicity of nitrobenzenes to Tetrahymena pyriformis. In this work, genetic algorithm, along with partial least square (GA-PLS was employed to select optimal subset of descriptors that have significant contribution to the toxicity of nitrobenzenes to Tetrahymena pyriformis. A set of five descriptors, namely G2, HOMT, G(Cl…Cl, Mor03v and MAXDP, was used for the prediction of the toxicity of 45 nitrobenzene derivatives and then were used to build the model by multiple linear regression (MLR method. It turned out that the built model, whose stability was confirmed using the leave-one-out validation and external validation test, showed high statistical significance (R2=0.963, Q2LOO=0.944. Moreover, Y-scrambling test indicated there was no chance correlation in this model.

  18. Thyrotropin (TSH) regulates triiodothyronine (T3) production in the unicellular Tetrahymena.

    Science.gov (United States)

    Csaba, G; Pállinger, Eva

    2011-09-01

    The aim of the experiments was to study the regulation of triiodothyronine (T3) production in the unicellular Tetrahymena. Untreated and troph-hormone treated specimen were prepared and in different timepoints T3 content was measured and compared by immunocytochemical flow cytometry. 0.1 or 0.001 IU TSH in tryptone-yeast medium stimulated T3 synthesis at 10, 20, 30 min, but does not stimulate after 1 h. The overlapping gonadotropic hormone (GTH) also did it, however only at 10 min. In Losina salt solution (physiological for Tetrahymena) the effect was weaker, however outer amino acid source was not absolutely needed for the production of the hormone. The results show that the TSH regulation of thyroid hormone synthesis (storage, secretion) and troph-hormone overlap can be deduced to a unicellular level. This may allow the hypothesis that the endocrine mechanisms proved at a low level of phylogeny are preserved for the higher ranked organisms.

  19. Comparative study of infection with Tetrahymena of different ornamental fish species

    DEFF Research Database (Denmark)

    Sharon, G.; Leibowitz, M. Pimenta; Chettri, Jiwan Kumar

    2014-01-01

    different super orders. The species examined were platy (Xiphophorus), molly (Poecilia sphenops) and angelfish (Pterophyllum scalare) of the Acanthopterygii super order (which also includes guppies) and goldfish (Carassius auratus auratus) and koi carp (Cyprinus carpio) of the Ostariophysi super order....... These two super orders are phylogenetically distant from each other. Infection with Tetrahymena resulted in parasite invasion of internal organs, skin and muscle in all fish species. A relatively strong inflammatory response was observed in infected goldfish and koi, with negligible response in fish species...... of the Acanthopterygii super order. Guppies were the most susceptible to Tetrahymena infection, exhibiting a mortality rate of 87% and 100% in two separate experiments. A high mortality rate was also observed in platy (77%), while that of molly and angelfish was significantly lower (23% and 33%, respectively). Goldfish...

  20. Macronuclear genome sequence of the ciliate Tetrahymena thermophila, a model eukaryote.

    Directory of Open Access Journals (Sweden)

    Jonathan A Eisen

    2006-09-01

    Full Text Available The ciliate Tetrahymena thermophila is a model organism for molecular and cellular biology. Like other ciliates, this species has separate germline and soma functions that are embodied by distinct nuclei within a single cell. The germline-like micronucleus (MIC has its genome held in reserve for sexual reproduction. The soma-like macronucleus (MAC, which possesses a genome processed from that of the MIC, is the center of gene expression and does not directly contribute DNA to sexual progeny. We report here the shotgun sequencing, assembly, and analysis of the MAC genome of T. thermophila, which is approximately 104 Mb in length and composed of approximately 225 chromosomes. Overall, the gene set is robust, with more than 27,000 predicted protein-coding genes, 15,000 of which have strong matches to genes in other organisms. The functional diversity encoded by these genes is substantial and reflects the complexity of processes required for a free-living, predatory, single-celled organism. This is highlighted by the abundance of lineage-specific duplications of genes with predicted roles in sensing and responding to environmental conditions (e.g., kinases, using diverse resources (e.g., proteases and transporters, and generating structural complexity (e.g., kinesins and dyneins. In contrast to the other lineages of alveolates (apicomplexans and dinoflagellates, no compelling evidence could be found for plastid-derived genes in the genome. UGA, the only T. thermophila stop codon, is used in some genes to encode selenocysteine, thus making this organism the first known with the potential to translate all 64 codons in nuclear genes into amino acids. We present genomic evidence supporting the hypothesis that the excision of DNA from the MIC to generate the MAC specifically targets foreign DNA as a form of genome self-defense. The combination of the genome sequence, the functional diversity encoded therein, and the presence of some pathways missing from

  1. Involvement of a putative intercellular signal-recognizing G protein-coupled receptor in the engulfment of Salmonella by the protozoan Tetrahymena

    Directory of Open Access Journals (Sweden)

    P.N. Agbedanu

    2013-07-01

    Full Text Available In an effort to investigate the molecular basis of protozoa engulfment-mediated hypervirulence of Salmonella in cattle, we evaluated protozoan G protein-coupled receptors (GPCRs as transducers of Salmonella engulfment by the model protozoan Tetrahymena. Our laboratory previously demonstrated that non-pathogenic protozoa (including Tetrahymena engulf Salmonella and then exacerbate its virulence in cattle, but the mechanistic details of the phenomenon are not fully understood. GPCRs were investigated since these receptors facilitate phagocytosis of particulates by Tetrahymena, and a GPCR apparently modulates bacterial engulfment for the pathogenic protozoan Entamoeba histolytica. A database search identified three putative Tetrahymena GPCRs, based on sequence homologies and predicted transmembrane domains, that were the focus of this study. Salmonella engulfment by Tetrahymena was assessed in the presence of suramin, a non-specific GPCR inhibitor. Salmonella engulfment was also assessed in Tetrahymena in which expression of putative GPCRs was knocked-down using RNAi. A candidate GPCR was then expressed in a heterologous yeast expression system for further characterization. Our results revealed that Tetrahymena were less efficient at engulfing Salmonella in the presence of suramin. Engulfment was reduced concordantly with a reduction in the density of protozoa. RNAi-based studies revealed that knock-down of one the Tetrahymena GPCRs caused diminished engulfment of Salmonella. Tetrahymena lysates activated this receptor in the heterologous expression system. These data demonstrate that the Tetrahymena receptor is a putative GPCR that facilitates bacterial engulfment by Tetrahymena. Activation of the putative GPCR seemed to be related to protozoan cell density, suggesting that its cognate ligand is an intercellular signaling molecule.

  2. Two-dimensional gravitactic bioconvection in a protozoan (tetrahymena pyriformis) culture

    OpenAIRE

    Nguyen-Quang, Tri; Nguyen, The Hung; Guichard, Frederic; Nicolau, Ana; Szatmari, George; LePalec, Georges; Dusser, Martine; Lafossee, Josee; Bonnet, Jean Louis; Bohatier, Jacques

    2009-01-01

    Gravitactic bioconvective patterns created by Tetrahymena pyriformis in a Hele-Shaw apparatus were realized and compared with theoretical results. There were found to be two thresholds for bioconvection development: the first indicates the transition from the diffusion to the steady convection state; the second corresponds to the transition from the steady to the unsteady convection state. The results showed that the Hele-Shaw apparatus may be used as a physical analogy of poro...

  3. Meiotic recombination, synapsis, meiotic inactivation and sperm aneuploidy in a chromosome 1 inversion carrier.

    Science.gov (United States)

    Kirkpatrick, Gordon; Chow, Victor; Ma, Sai

    2012-01-01

    Disrupted meiotic behaviour of inversion carriers may be responsible for suboptimal sperm parameters in these carriers. This study investigated meiotic recombination, synapsis, transcriptional silencing and chromosome segregation effects in a pericentric inv(1) carrier. Recombination (MLH1), synapsis (SYCP1, SYCP3) and transcriptional inactivation (γH2AX, BRCA1) were examined by fluorescence immunostaining. Chromosome specific rates of recombination were determined by fluorescence in-situ hybridization. Furthermore, testicular sperm was examined for aneuploidy and segregation of the inv(1). Our findings showed that global recombination rates were similar to controls. Recombination on the inv(1) and the sex chromosomes were reduced. The inv(1) associated with the XY body in 43.4% of cells, in which XY recombination was disproportionately absent, and 94.3% of cells displayed asynapsed regions which displayed meiotic silencing regardless of their association with the XY body. Furthermore, a low frequency of chromosomal imbalance was observed in spermatozoa (3.4%). Our results suggest that certain inversion carriers may display unimpaired global recombination and impaired recombination on the involved and the sex chromosomes during meiosis. Asynapsis or inversion-loop formation in the inverted region may be responsible for impaired spermatogenesis and may prevent sperm-chromosome imbalance. Copyright © 2011 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  4. Origin of meiotic nondisjunction in Drosophila females

    International Nuclear Information System (INIS)

    Grell, R.F.

    1978-01-01

    Meiotic nondisjunction can be induced by external agents, such as heat, radiation, and chemicals, and by internal genotypic alterations, namely, point mutations and chromosomal rearrangements. In many cases nondisjunction arises from a reduction or elimination of crossing-over, leading to the production of homologous univalents which fail to co-orient on the metaphase plate and to disjoin properly. In some organisms, e.g., Drosophila and perhaps man, distributive pairing [i.e., a post-exchange, size-dependent pairing] ensures the regular segregation of such homologous univalents. When a nonhomologous univalent is present, which falls within a size range permitting nonhomologous recognition and pairing, distributive nondisjunction of the homologues may follow. Examples of nondisjunction induced by inversion heterozygosity, translocation heterozygosity, chromosome fragments, radiation, heat, and recombination-defective mutants are presented

  5. RNAi and heterochromatin repress centromeric meiotic recombination

    DEFF Research Database (Denmark)

    Ellermeier, Chad; Higuchi, Emily C; Phadnis, Naina

    2010-01-01

    During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes, is essen......During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes....... Surprisingly, one mutant derepressed for recombination in the heterochromatic mating-type region during meiosis and several mutants derepressed for centromeric gene expression during mitotic growth are not derepressed for centromeric recombination during meiosis. These results reveal a complex relation between...... types of repression by heterochromatin. Our results also reveal a previously undemonstrated role for RNAi and heterochromatin in the repression of meiotic centromeric recombination and, potentially, in the prevention of birth defects by maintenance of proper chromosome segregation during meiosis....

  6. Analysis of meiosis in SUN1 deficient mice reveals a distinct role of SUN2 in mammalian meiotic LINC complex formation and function.

    Directory of Open Access Journals (Sweden)

    Jana Link

    2014-02-01

    Full Text Available LINC complexes are evolutionarily conserved nuclear envelope bridges, composed of SUN (Sad-1/UNC-84 and KASH (Klarsicht/ANC-1/Syne/homology domain proteins. They are crucial for nuclear positioning and nuclear shape determination, and also mediate nuclear envelope (NE attachment of meiotic telomeres, essential for driving homolog synapsis and recombination. In mice, SUN1 and SUN2 are the only SUN domain proteins expressed during meiosis, sharing their localization with meiosis-specific KASH5. Recent studies have shown that loss of SUN1 severely interferes with meiotic processes. Absence of SUN1 provokes defective telomere attachment and causes infertility. Here, we report that meiotic telomere attachment is not entirely lost in mice deficient for SUN1, but numerous telomeres are still attached to the NE through SUN2/KASH5-LINC complexes. In Sun1(-/- meiocytes attached telomeres retained the capacity to form bouquet-like clusters. Furthermore, we could detect significant numbers of late meiotic recombination events in Sun1(-/- mice. Together, this indicates that even in the absence of SUN1 telomere attachment and their movement within the nuclear envelope per se can be functional.

  7. Chromosome numbers and meiotic behavior of some Paspalum accessions

    Directory of Open Access Journals (Sweden)

    Eleniza de Victor Adamowski

    2005-12-01

    Full Text Available Chromosome number and meiotic behavior were evaluated in 36 Brazilian accessions of the grass Paspalum (which had never previously been analyzed to determinate which accessions might be useful in interspecific hybridizations. The analysis showed that one accession of Paspalum coryphaeum was diploid (2n = 2x = 20 and one accession of Paspalum conspersum hexaploid (2n = 6x = 60, the remaining 34 accessions being tetraploid (2n = 4x = 40. The pairing configuration was typical for the ploidy level i.e. in the diploid, chromosomes paired as 10 bivalents, in tetraploids as bi-, tri- and quadrivalents, and in hexaploid as 30 bivalents. A low frequency of meiotic abnormalities (less than 10% was observed in the diploid, hexaploid and some tetraploid accessions, although the majority of tetraploid accessions showed a high frequency of meiotic irregularities. The use of accessions with a low frequency of meiotic abnormalities in breeding programs is discussed.

  8. Magic with moulds: Meiotic and mitotic crossing over in Neurospora ...

    Indian Academy of Sciences (India)

    2006-02-16

    Feb 16, 2006 ... Home; Journals; Journal of Biosciences; Volume 31; Issue 1. Commentary: Magic with moulds: Meiotic and mitotic crossing over in Neurospora inversions and duplications. Durgadas P Kasbekar. Volume 31 Issue 1 March 2006 pp 3-4 ...

  9. wtf genes are prolific dual poison-antidote meiotic drivers.

    Science.gov (United States)

    Nuckolls, Nicole L; Bravo Núñez, María Angélica; Eickbush, Michael T; Young, Janet M; Lange, Jeffrey J; Yu, Jonathan S; Smith, Gerald R; Jaspersen, Sue L; Malik, Harmit S; Zanders, Sarah E

    2017-06-20

    Meiotic drivers are selfish genes that bias their transmission into gametes, defying Mendelian inheritance. Despite the significant impact of these genomic parasites on evolution and infertility, few meiotic drive loci have been identified or mechanistically characterized. Here, we demonstrate a complex landscape of meiotic drive genes on chromosome 3 of the fission yeasts Schizosaccharomyces kambucha and S. pombe . We identify S. kambucha wtf4 as one of these genes that acts to kill gametes (known as spores in yeast) that do not inherit the gene from heterozygotes. wtf4 utilizes dual, overlapping transcripts to encode both a gamete-killing poison and an antidote to the poison. To enact drive, all gametes are poisoned, whereas only those that inherit wtf4 are rescued by the antidote. Our work suggests that the wtf multigene family proliferated due to meiotic drive and highlights the power of selfish genes to shape genomes, even while imposing tremendous costs to fertility.

  10. Meiotic behaviour in three interspecific three-way hybrids between ...

    Indian Academy of Sciences (India)

    The meiotic behaviour of three three-way interspecific promising hybrids (H17, H27, and H34) was evaluated. ... Arrangement of parental genomes in distinct ... vanna due to its physiological tolerance to low fertility acid ... nomic evaluations.

  11. Cytological techniques to study human female meiotic prophase.

    Science.gov (United States)

    Roig, Ignasi; Garcia-Caldés, Montserrat

    2009-01-01

    Most of the human aneuploidies have a maternal origin. This feature makes the study of human female meiosis a fundamental topic to understand the reasons leading to this important social problem. Unfortunately, due to sample collection difficulties, not many studies have been performed on human female meiotic prophase. In this chapter we present a comprehensive collection of protocols that allows the study of human female meiotic prophase through different technical approaches using both spread and structurally preserved oocytes.

  12. Nuclear dualism.

    Science.gov (United States)

    Karrer, Kathleen M

    2012-01-01

    Nuclear dualism is a characteristic feature of the ciliated protozoa. Tetrahymena have two different nuclei in each cell. The larger, polyploid, somatic macronucleus (MAC) is the site of transcriptional activity in the vegetatively growing cell. The smaller, diploid micronucleus (MIC) is transcriptionally inactive in vegetative cells, but is transcriptionally active in mating cells and responsible for the genetic continuity during sexual reproduction. Although the MICs and MACs develop from mitotic products of a common progenitor and reside in a common cytoplasm, they are different from one another in almost every respect. Copyright © 2012 Elsevier Inc. All rights reserved.

  13. Protein Determinants of Meiotic DNA Break Hotspots

    Science.gov (United States)

    Fowler, Kyle R.; Gutiérrez-Velasco, Susana

    2013-01-01

    SUMMARY Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to hundreds of times more frequently at special sites, called hotspots, than in other regions of the genome. What distinguishes hotspots from cold regions is an unsolved problem, although transcription factors determine some hotspots. We report the discovery that three coiled-coil proteins – Rec25, Rec27, and Mug20 – bind essentially all hotspots with unprecedented specificity even without DSB formation. These small proteins are components of linear elements, are related to synaptonemal complex proteins, and are essential for nearly all DSBs at most hotspots. Our results indicate these hotspot determinants activate or stabilize the DSB-forming protein Rec12 (Spo11 homolog) rather than promote its binding to hotspots. We propose a new paradigm for hotspot determination and crossover control by linear element proteins. PMID:23395004

  14. Meiotic transmission of Drosophila pseudoobscura chromosomal arrangements.

    Directory of Open Access Journals (Sweden)

    Richard P Meisel

    Full Text Available Drosophila pseudoobscura harbors a rich gene arrangement polymorphism on the third chromosome generated by a series of overlapping paracentric inversions. The arrangements suppress recombination in heterokaryotypic individuals, which allows for the selective maintenance of coadapted gene complexes. Previous mapping experiments used to determine the degree to which recombination is suppressed in gene arrangement heterozygotes produced non-recombinant progeny in non-Mendelian ratios. The deviations from Mendelian expectations could be the result of viability differences between wild and mutant chromosomes, meiotic drive because of achiasmate pairing of homologues in heterokaryotypic females during meiosis, or a combination of both mechanisms. The possibility that the frequencies of the chromosomal arrangements in natural populations are affected by mechanisms other than adaptive selection led us to consider these hypotheses. We performed reciprocal crosses involving both heterozygous males and females to determine if the frequency of the non-recombinant progeny deviates significantly from Mendelian expectations and if the frequencies deviate between reciprocal crosses. We failed to observe non-Mendelian ratios in multiple crosses, and the frequency of the non-recombinant classes differed in only one of five pairs of reciprocal crosses despite sufficient power to detect these differences in all crosses. Our results indicate that deviations from Mendelian expectations in recombination experiments involving the D. pseudoobscura inversion system are most likely due to fitness differences of gene arrangement karyotypes in different environments.

  15. Biochanin a and Daidzein Influence Meiotic Maturation of Pig Oocytes in a Different Manner

    Directory of Open Access Journals (Sweden)

    Hošková K.

    2014-09-01

    Full Text Available The aim of the study was to determine the influence of different concentrations of phytoestrogens biochanin A (BIO A; 20, 40, 50μg ml-1 and daidzein (DAI; 10, 20, 40, 50μg ml-1 on the course of meiotic maturation of pig oocytes. After a 24-hour cultivation, a stage of nuclear maturation was achieved and the areas of cumulus-oocyte complexes (COCs, as an indicator of cumulus expansion, were evaluated. The effects of both contaminants on oocytes were mani - fested from the lowest concentration used. Nuclear maturation was inhibited in a dose-dependent manner in the case of BIO A. Effects of DAI reached a plateau at a concentration of 20μg ml-1.Possible relationship to limited solubility of DAI was excluded because limits of DAI solubility in culture medium were confirmed at 50 μg ml-1.The cumulus expansion was also influenced in a different manner - reduction of the COC’s area by BIO A was dose-dependent, whereas DAI had the strongest effect on CCs in the lowest and highest concentrations used. Both phytoestrogens negatively influence the meiotic maturation of porcine oocytes but there are significant differences in their concrete effects which could relate to the diverse mechanisms of their acting on target cells.

  16. Meiotic recombination breakpoints are associated with open chromatin and enriched with repetitive DNA elements in potato

    Science.gov (United States)

    Meiotic recombination provides the framework for the genetic variation in natural and artificial populations of eukaryotes through the creation of novel haplotypes. Thus, determining the molecular characteristics of meiotic recombination remains essential for future plant breeding efforts, which hea...

  17. The fidelity of synaptonemal complex assembly is regulated by a signaling mechanism that controls early meiotic progression.

    Science.gov (United States)

    Silva, Nicola; Ferrandiz, Nuria; Barroso, Consuelo; Tognetti, Silvia; Lightfoot, James; Telecan, Oana; Encheva, Vesela; Faull, Peter; Hanni, Simon; Furger, Andre; Snijders, Ambrosius P; Speck, Christian; Martinez-Perez, Enrique

    2014-11-24

    Proper chromosome segregation during meiosis requires the assembly of the synaptonemal complex (SC) between homologous chromosomes. However, the SC structure itself is indifferent to homology, and poorly understood mechanisms that depend on conserved HORMA-domain proteins prevent ectopic SC assembly. Although HORMA-domain proteins are thought to regulate SC assembly as intrinsic components of meiotic chromosomes, here we uncover a key role for nuclear soluble HORMA-domain protein HTP-1 in the quality control of SC assembly. We show that a mutant form of HTP-1 impaired in chromosome loading provides functionality of an HTP-1-dependent checkpoint that delays exit from homology search-competent stages until all homolog pairs are linked by the SC. Bypassing of this regulatory mechanism results in premature meiotic progression and licensing of homology-independent SC assembly. These findings identify nuclear soluble HTP-1 as a regulator of early meiotic progression, suggesting parallels with the mode of action of Mad2 in the spindle assembly checkpoint. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. RESULTS OF IN VITRO MATURATION OF MEIOTICALLY IMMATURE HUMAN OOCYTES IN A SIMPLE MEDIUM

    Directory of Open Access Journals (Sweden)

    Borut Kovačič

    2002-12-01

    Full Text Available Background. Among oocytes obtained during aspiration of preovulatory ovarian follicles in hormonally stimulated cycles, we ascertained the percentage of immature oocytes with the nucleus in the metaphase (M I oocytes or even in the prophase (GV oocytes of the first meiotic division and their capacity to mature in vitro in a simple medium without hormonal supplements.Methods. In 818 women, stimulated by gonadotropin releasing hormone agonist (GnRHa and gonadotropins, aspiration of preovulatory size follicles yielded 4972 oocytes. From these we denuded cells of cumulus oophorus and corona, meiotic maturity was evaluated under a microscope. Cells in the metaphase of the second meiotic division (M II oocytes and those maturing after 5 hours were used clinically in the intracytoplasmic sperm injection (ICSI procedure. Immature cells were left in the simple medium. The degree of their nuclear maturity was evaluated after one and after two days of culture. In vitro maturation was clinically used also in 14 cycles with no mature oocytes.Results. Among 4731 oocytes with denuded corona and cumulus, 4199 (88.8% were mature M II oocytes, 295 (6.2% immature M I oocytes and 237 (5% immature GV oocytes. Under in vitro conditions, 68.7% (90/131 GV oocytes attained maturity. Among M I oocytes, 63.6% (136/214 cells matured already after 5 hours and 26.6% (57/214 until the next day. In all 14 women with only immature oocytes, the embryos for embryotransfer were obtained after in vitro maturation and ICSI procedure. The result was four pregnancies and two deliveries.Conclusions. Immature oocytes, obtained in hormonally stimulated cycles, may become clinically applicable if left to mature in vitro in a simple medium without supplementation of growth factors and hormones.

  19. Meiotic analysis in induced tetraploids of Brachiaria decumbens Stapf

    Directory of Open Access Journals (Sweden)

    Carine Simioni

    2011-01-01

    Full Text Available The meiotic behavior of three tetraploid plants (2n=4x=36 originated from somatic chromosome duplication ofsexually reproducing diploid plants of Brachiaria decumbens was evaluated. All the analyzed plants presented abnormalities relatedto polyploidy, such as irregular chromosome segregation, leading to precocious chromosome migration to the poles and micronucleiduring both meiotic divisions. However, the abnormalities observed did not compromise the meiotic products which were characterizedby regular tetrads and satisfactory pollen fertility varying from 61.36 to 64.86%. Chromosomes paired mostly as bivalents indiakinesis but univalents to tetravalents were also observed. These studies contributed to the choice of compatible fertile sexualgenitors to be crossed to natural tetraploid apomicts in the B. decumbens by identifying abnormalities and verifying pollen fertility.Intraespecific crosses should reduce sterility in the hybrids produced in the breeding program of Brachiaria, a problem observedwith the interspecific hybrids produced so far.

  20. The role of meiotic drive in hybrid male sterility.

    Science.gov (United States)

    McDermott, Shannon R; Noor, Mohamed A F

    2010-04-27

    Meiotic drive causes the distortion of allelic segregation away from Mendelian expected ratios, often also reducing fecundity and favouring the evolution of drive suppressors. If different species evolve distinct drive-suppressor systems, then hybrid progeny may be sterile as a result of negative interactions of these systems' components. Although the hypothesis that meiotic drive may contribute to hybrid sterility, and thus species formation, fell out of favour early in the 1990s, recent results showing an association between drive and sterility have resurrected this previously controversial idea. Here, we review the different forms of meiotic drive and their possible roles in speciation. We discuss the recent empirical evidence for a link between drive and hybrid male sterility, also suggesting a possible mechanistic explanation for this link in the context of chromatin remodelling. Finally, we revisit the population genetics of drive that allow it to contribute to speciation.

  1. Effects of protein kinase C activators and staurosporine on protein kinase activity, cell survival, and proliferation in Tetrahymena thermophila

    DEFF Research Database (Denmark)

    Straarup, EM; Schousboe, P; Hansen, HQ

    1997-01-01

    Autocrine factors prevent cell death in the ciliate Tetrahymena thermophila, a unicellular eukaryote, in a chemically defined medium. At certain growth conditions these factors are released at a sufficient concentration by > 500 cells ml-1 to support cell survival and proliferation. The protein...

  2. Phylogenetic evidence for the acquisition of ribosomal RNA introns subsequent to the divergence of some of the major Tetrahymena groups

    DEFF Research Database (Denmark)

    Sogin, M L; Ingold, A; Karlok, M

    1986-01-01

    . In an attempt to evaluate the evolutionary origins of the intervening sequences, we have now determined complete small subunit ribosomal RNA gene sequences from 13 species of Tetrahymena and the absolute number of nucleotide differences between the sequences was used to construct a phylogenetic tree...

  3. Chromosome numbers and meiotic analysis in the pre-breeding of ...

    Indian Academy of Sciences (India)

    Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness ...

  4. ATR acts stage specifically to regulate multiple aspects of mammalian meiotic silencing

    NARCIS (Netherlands)

    Royo, Hélène; Prosser, Haydn; Ruzankina, Yaroslava; Mahadevaiah, Shantha K.; Cloutier, Jeffrey M.; Baumann, Marek; Fukuda, Tomoyuki; Höög, Christer; Tóth, Attila; de Rooij, Dirk G.; Bradley, Allan; Brown, Eric J.; Turner, James M. A.

    2013-01-01

    In mammals, homologs that fail to synapse during meiosis are transcriptionally inactivated. This process, meiotic silencing, drives inactivation of the heterologous XY bivalent in male germ cells (meiotic sex chromosome inactivation [MSCI]) and is thought to act as a meiotic surveillance mechanism.

  5. Selecting one of several mating types through gene segment joining and deletion in Tetrahymena thermophila.

    Directory of Open Access Journals (Sweden)

    Marcella D Cervantes

    Full Text Available The unicellular eukaryote Tetrahymena thermophila has seven mating types. Cells can mate only when they recognize cells of a different mating type as non-self. As a ciliate, Tetrahymena separates its germline and soma into two nuclei. During growth the somatic nucleus is responsible for all gene transcription while the germline nucleus remains silent. During mating, a new somatic nucleus is differentiated from a germline nucleus and mating type is decided by a stochastic process. We report here that the somatic mating type locus contains a pair of genes arranged head-to-head. Each gene encodes a mating type-specific segment and a transmembrane domain that is shared by all mating types. Somatic gene knockouts showed both genes are required for efficient non-self recognition and successful mating, as assessed by pair formation and progeny production. The germline mating type locus consists of a tandem array of incomplete gene pairs representing each potential mating type. During mating, a complete new gene pair is assembled at the somatic mating type locus; the incomplete genes of one gene pair are completed by joining to gene segments at each end of germline array. All other germline gene pairs are deleted in the process. These programmed DNA rearrangements make this a fascinating system of mating type determination.

  6. Ultraviolet light photobiology of the protozoan Tetrahymena pyriformis and chemical reactivation of DNA damage

    International Nuclear Information System (INIS)

    Wheeler, J.S.

    1988-01-01

    The tunable dye laser was developed in order to perform UV-B and UV-C (254-320 nm) action spectra studies on several different organisms. Using the laser, action spectra studies have been performed for Escherichia coli, Saccharomyces, Chlamydomonas, Caenorhabditis elegans, Paramecium, and Tetrahymena pyriformis. Studies generally indicate increasing LD 50 values with increasing wavelength. Two notable findings were made: (1) The action spectra does not follow the DNA absorption spectra at 280, 290 and 295 nm; (2) The repair competent/repair defective sensitization factor does not remain constant throughout the wavelength region. In addition it was found that the repair defective strain of E. coli, Bs-1, showed an increase in survival with increasing UV irradiation, at certain dose levels. Further experiments were designed to better characterize the reactivation. Tetrahymena were exposed to UV-C and reactivated with methyl methanesulfonate (MMS) and 4-nitro quinoline oxide (4-NQO). In both cases survival was seen to increase after chemical exposure. Likewise, UV-C was found to reactivate chemical damage (MMS)

  7. Selective inhibition of precursor incorporation into ribosomal RNA in gamma-irradiated Tetrahymena pyriformis

    International Nuclear Information System (INIS)

    Ernst, S.G.; Oleinick, N.L.; Rustad, R.C.; Greenblatt, R.M.

    1979-01-01

    Sublethal doses of γ radiation are known to inhibit total RNA synthesis in the ciliate protozoan Tetrahymena. To determine if the synthesis of a particular class of RNA is preferentially inhibited, pulse-labeled RNA was isolated from normal exponentially growing cells, irradiated cells, and cells in which total RNA synthesis had recovered to the pre-irradiation level. The RNAs were analyzed by SDS-polyacrylamide gel electrphoresis and oligo(dT)-cellulose column chromatography. Inhibition of RNA synthesis primarily involves ribosomal RNA. However, radiation does not cause a delay in the processing of precursor rRNA or a preferential loss of either of the mature rRNAs. Following irradiation, poly(A)-containing RNA [poly(A+)RNA] is synthesized at a rate up to three times greater than the control rate. The elevated poly(A+)RNA synthesis occurs during the period of depressed rRNA synthesis and even after rRNA synthesis has recovered to its pre-irradiation rate. While the sizes of the total cellular ribonucleoside triphosphate pools are depressed in the irradiated cells, these pools probably do not represent the actual compartments containing the precursors for RNA synthesis, and the observed changes cannot explain the modifications in macromolecular synthesis in irradiated Tetrahymena. (Auth.)

  8. Tetrahymena thermophila acidic ribosomal protein L37 contains an archaebacterial type of C-terminus

    DEFF Research Database (Denmark)

    Hansen, T S; Andreasen, P H; Dreisig, H

    1991-01-01

    We have cloned and characterized a Tetrahymena thermophila macronuclear gene (L37) encoding the acidic ribosomal protein (A-protein) L37. The gene contains a single intron located in the 3'-part of the coding region. Two major and three minor transcription start points (tsp) were mapped 39 to 63 ...... by protein sequencing. The T. thermophila L37 clearly belongs to the P1-type family of eukaryotic A-proteins, but the C-terminal region has the hallmarks of archaebacterial A-proteins.......We have cloned and characterized a Tetrahymena thermophila macronuclear gene (L37) encoding the acidic ribosomal protein (A-protein) L37. The gene contains a single intron located in the 3'-part of the coding region. Two major and three minor transcription start points (tsp) were mapped 39 to 63...... nucleotides upstream from the translational start codon. The uppermost tsp mapped to the first T in a putative T. thermophila RNA polymerase II initiator element, TATAA. The coding region of L37 predicts a protein of 109 amino acid (aa) residues. A substantial part of the deduced aa sequence was verified...

  9. How applicable is the general adaptation syndrome to the unicellular Tetrahymena?

    Science.gov (United States)

    Csaba, György; Pállinger, Eva

    2009-01-01

    Hormone receptors, hormones and signal transduction pathways characteristic of higher vertebrates can be observed also in the unicellular Tetrahymena. Previous work showed that stress conditions (starvation, high temperature, high salt concentration, formaldehyde or alcohol treatment) elevated the intracellular level of four hormones (ACTH, endorphin, serotonin and T(3)). Here, the effect of other stressors (CuSO4 poisoning, tryptophan hydroxylase inhibitor parachlorophenylalanine (PCPA) treatment) on the same and other hormones (epinephrine, insulin, histamine) was studied, using immunocytochemistry and flow cytometric analysis. It was found, that each effect increased the intracellular hormone contents, but some hormones (histamine, T(3)) were less reactive. Insulin--which is a life-saving factor for Tetrahymena--itself provoked elevation of hormone amounts in association with a stressor, further increased the level of hormones. It was concluded that the ancestor of Selye's General Adaptation Syndrome (GAS) can be found already at unicellular level, and this possibly has a life saving function. Copyright 2008 John Wiley & Sons, Ltd.

  10. [Identification of the meiotic events in grasshopper spermatogenesis].

    Science.gov (United States)

    Liu, Meng-Hao; Zhao, Kai-Qiang; Wang, Ya-Dong; Yang, Meng-Ping; Zhao, Ning-Ning; Yang, Da-Xiang

    2012-12-01

    The grasshoppers are ideal materials to study various meiotic stages of spermatogenesis due to their easy availability, fairly large chromosomes, and fewer numbers of chromosomes. It is easy to make temporary squash preparation of grasshopper testes; however, it is usually difficult for the beginners to differentiate between stages of meiosis. In view of this, we demonstrated the method of identification of meiotic stages by chromosome number and chromosome conformation, taking spermatogonial meiosis of Locusta migratoria manilensis as an example. We described briefly the mitosis of spermatogonia and the spermatogenesis of this species as well.

  11. Distinct toxicological characteristics and mechanisms of Hg2+ and MeHg in Tetrahymena under low concentration exposure.

    Science.gov (United States)

    Liu, Cheng-Bin; Qu, Guang-Bo; Cao, Meng-Xi; Liang, Yong; Hu, Li-Gang; Shi, Jian-Bo; Cai, Yong; Jiang, Gui-Bin

    2017-12-01

    Inorganic divalent mercury complexes (Hg 2+ ) and monomethylmercury complexes (MeHg) are the main mercury species in aquatic systems and their toxicity to aquatic organisms is of great concern. Tetrahymena is a type of unicellular eukaryotic protozoa located at the bottom of food chain that plays a fundamental role in the biomagnification of mercury. In this work, the dynamic accumulation properties, toxicological characteristics and mechanisms of Hg 2+ and MeHg in five Tetrahymena species were evaluated in detail. The results showed that both Hg 2+ and MeHg were ingested and exhibited inhibitory effects on the proliferation or survival of Tetrahymena species. However, the ingestion rate of MeHg was significantly higher than that of Hg 2+ . The mechanisms responsible for the toxicity of MeHg and Hg 2+ were different, although both chemicals altered mitochondrial membrane potential (MMP). MeHg disrupted the integrity of membranes while Hg 2+ had detrimental effects on Tetrahymena as a result of the increased generation of reactive oxygen species (ROS). In addition, the five Tetrahymena species showed different capacities in accumulating Hg 2+ and MeHg, with T. corlissi exhibiting the highest accumulations. The study also found significant growth-promoting effect on T. corlissi under low concentration exposure (0.003 and 0.01μg Hg/mL (15 and 50nM)), suggesting different effect and mechanism that should be more closely examined when assessing the bioaccumulation and toxicity of mercury in aquatic ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Positive Feedback of NDT80 Expression Ensures Irreversible Meiotic Commitment in Budding Yeast

    Science.gov (United States)

    Tsuchiya, Dai; Yang, Yang; Lacefield, Soni

    2014-01-01

    In budding yeast, meiotic commitment is the irreversible continuation of the developmental path of meiosis. After reaching meiotic commitment, cells finish meiosis and gametogenesis, even in the absence of the meiosis-inducing signal. In contrast, if the meiosis-inducing signal is removed and the mitosis-inducing signal is provided prior to reaching meiotic commitment, cells exit meiosis and return to mitosis. Previous work has shown that cells commit to meiosis after prophase I but before entering the meiotic divisions. Since the Ndt80 transcription factor induces expression of middle meiosis genes necessary for the meiotic divisions, we examined the role of the NDT80 transcriptional network in meiotic commitment. Using a microfluidic approach to analyze single cells, we found that cells commit to meiosis in prometaphase I, after the induction of the Ndt80-dependent genes. Our results showed that high-level expression of NDT80 is important for the timing and irreversibility of meiotic commitment. A modest reduction in NDT80 levels delayed meiotic commitment based on meiotic stages, although the timing of each meiotic stage was similar to that of wildtype cells. A further reduction of NDT80 resulted in the surprising finding of inappropriately uncommitted cells: withdrawal of the meiosis-inducing signal and addition of the mitosis-inducing signal to cells at stages beyond metaphase I caused return to mitosis, leading to multi-nucleate cells. Since Ndt80 enhances its own transcription through positive feedback, we tested whether positive feedback ensured the irreversibility of meiotic commitment. Ablating positive feedback in NDT80 expression resulted in a complete loss of meiotic commitment. These findings suggest that irreversibility of meiotic commitment is a consequence of the NDT80 transcriptional positive feedback loop, which provides the high-level of Ndt80 required for the developmental switch of meiotic commitment. These results also illustrate the

  13. The Phosphatase Dusp7 Drives Meiotic Resumption and Chromosome Alignment in Mouse Oocytes

    Directory of Open Access Journals (Sweden)

    Thomas Tischer

    2016-10-01

    Full Text Available Mammalian oocytes are stored in the ovary, where they are arrested in prophase for prolonged periods. The mechanisms that abrogate the prophase arrest in mammalian oocytes and reinitiate meiosis are not well understood. Here, we identify and characterize an essential pathway for the resumption of meiosis that relies on the protein phosphatase DUSP7. DUSP7-depleted oocytes either fail to resume meiosis or resume meiosis with a significant delay. In the absence of DUSP7, Cdk1/CycB activity drops below the critical level required to reinitiate meiosis, precluding or delaying nuclear envelope breakdown. Our data suggest that DUSP7 drives meiotic resumption by dephosphorylating and thereby inactivating cPKC isoforms. In addition to controlling meiotic resumption, DUSP7 has a second function in chromosome segregation: DUSP7-depleted oocytes that enter meiosis show severe chromosome alignment defects and progress into anaphase prematurely. Altogether, these findings establish the phosphatase DUSP7 as an essential regulator of multiple steps in oocyte meiosis.

  14. RPA homologs and ssDNA processing during meiotic recombination.

    Science.gov (United States)

    Ribeiro, Jonathan; Abby, Emilie; Livera, Gabriel; Martini, Emmanuelle

    2016-06-01

    Meiotic homologous recombination is a specialized process that involves homologous chromosome pairing and strand exchange to guarantee proper chromosome segregation and genetic diversity. The formation and repair of DNA double-strand breaks (DSBs) during meiotic recombination differs from those during mitotic recombination in that the homologous chromosome rather than the sister chromatid is the preferred repair template. The processing of single-stranded DNA (ssDNA) formed on intermediate recombination structures is central to driving the specific outcomes of DSB repair during meiosis. Replication protein A (RPA) is the main ssDNA-binding protein complex involved in DNA metabolism. However, the existence of RPA orthologs in plants and the recent discovery of meiosis specific with OB domains (MEIOB), a widely conserved meiosis-specific RPA1 paralog, strongly suggest that multiple RPA complexes evolved and specialized to subdivide their roles during DNA metabolism. Here we review ssDNA formation and maturation during mitotic and meiotic recombination underlying the meiotic specific features. We describe and discuss the existence and properties of MEIOB and multiple RPA subunits in plants and highlight how they can provide meiosis-specific fates to ssDNA processing during homologous recombination. Understanding the functions of these RPA homologs and how they interact with the canonical RPA subunits is of major interest in the fields of meiosis and DNA repair.

  15. Meiotic faults as a major cause of offspring inviability

    DEFF Research Database (Denmark)

    Levitis, Daniel; Zimmerman, Kolea; Pringle, Anne

    2014-01-01

    , this result demonstrates that failures associated with meiosis are a major cause of offspring inviability not only for meiotic parthenogenesis, but for sexual reproducers such as humans. Meiosis is necessary for genetic recombination in eukaryotes, but is vestigial, and costly, in parthenogens. The question...... range of organisms....

  16. INDUCTION OF ARTIFICIAL MEIOTIC GY~OGENESIS WITH ...

    African Journals Online (AJOL)

    BSN

    INDUCTION OF ARTIFICIAL MEIOTIC GY~OGENESIS WITH. ULTRAVIOLET RAYS IN THE AFRICA:" CATFISH, CI.ARIAS. ANGUILLARIS. ABSTRACT. P.O. ALUKO. National Institute for Freshwater Fisheries. Research, P.M.B. 6006, New Bussa. Artificial gynogenesis was induced in Clarias a11gw aris ) fenilizing the eggs ...

  17. Highlights of meiotic genes in Arabidopsis thaliana | Consiglio ...

    African Journals Online (AJOL)

    Meiosis is a fascinating and complex phenomenon and, despite its central role in sexual plant reproduction, little is known on the molecular mechanisms involved in this process. We review the progress made in recent years using Arabidopsis thaliana mutants for isolating meiotic genes. In particular, emphasis is given on ...

  18. Transcriptome analysis of the model protozoan, Tetrahymena thermophila, using Deep RNA sequencing.

    Directory of Open Access Journals (Sweden)

    Jie Xiong

    Full Text Available BACKGROUND: The ciliated protozoan Tetrahymena thermophila is a well-studied single-celled eukaryote model organism for cellular and molecular biology. However, the lack of extensive T. thermophila cDNA libraries or a large expressed sequence tag (EST database limited the quality of the original genome annotation. METHODOLOGY/PRINCIPAL FINDINGS: This RNA-seq study describes the first deep sequencing analysis of the T. thermophila transcriptome during the three major stages of the life cycle: growth, starvation and conjugation. Uniquely mapped reads covered more than 96% of the 24,725 predicted gene models in the somatic genome. More than 1,000 new transcribed regions were identified. The great dynamic range of RNA-seq allowed detection of a nearly six order-of-magnitude range of measurable gene expression orchestrated by this cell. RNA-seq also allowed the first prediction of transcript untranslated regions (UTRs and an updated (larger size estimate of the T. thermophila transcriptome: 57 Mb, or about 55% of the somatic genome. Our study identified nearly 1,500 alternative splicing (AS events distributed over 5.2% of T. thermophila genes. This percentage represents a two order-of-magnitude increase over previous EST-based estimates in Tetrahymena. Evidence of stage-specific regulation of alternative splicing was also obtained. Finally, our study allowed us to completely confirm about 26.8% of the genes originally predicted by the gene finder, to correct coding sequence boundaries and intron-exon junctions for about a third, and to reassign microarray probes and correct earlier microarray data. CONCLUSIONS/SIGNIFICANCE: RNA-seq data significantly improve the genome annotation and provide a fully comprehensive view of the global transcriptome of T. thermophila. To our knowledge, 5.2% of T. thermophila genes with AS is the highest percentage of genes showing AS reported in a unicellular eukaryote. Tetrahymena thus becomes an excellent unicellular

  19. A community model of ciliate Tetrahymena and bacteria E. coli. Part 1: Individual-based models of Tetrahymena and E. coli populations

    Energy Technology Data Exchange (ETDEWEB)

    Jaworska, J.S.; Hallam, T.G.; Schultz, T.W. [Univ. of Tennessee, Knoxville, TN (United States)

    1996-03-01

    The dynamics of a microbial community consisting of a eucaryotic ciliate Tetrahymena pyriformis and procaryotic. Escherichia coli in a batch culture is explored by employing an individual-based approach. In this portion of the article, Part 1, population models are presented. Because both models are individual-based, models of individual organisms are developed prior to construction of the population models. The individual models use an energy budget method in which growth depends on energy gain from feeding and energy sinks such as maintenance and reproduction. These models are not limited by simplifying assumptions about constant yield, constant energy sinks and Monod growth kinetics as are traditional models of microbial organisms. Population models are generated from individual models by creating distinct individual types and assigning to each type the number of real individuals they represent. A population is a compilation of individual types that vary in a phase of cell cycle and physiological parameters such as filtering rate for ciliates and maximum anabolic rate for bacteria. An advantage of the developed models is that they realistically describe the growth of the individual cells feeding on resource which varies in density and composition. Part 2, the core of the project, integrates models into a dynamic microbial community and provides model analysis based upon available data.

  20. Meiotic Consequences of Genetic Divergence Across the Murine Pseudoautosomal Region.

    Science.gov (United States)

    Dumont, Beth L

    2017-03-01

    The production of haploid gametes during meiosis is dependent on the homology-driven processes of pairing, synapsis, and recombination. On the mammalian heterogametic sex chromosomes, these key meiotic activities are confined to the pseudoautosomal region (PAR), a short region of near-perfect sequence homology between the X and Y chromosomes. Despite its established importance for meiosis, the PAR is rapidly evolving, raising the question of how proper X / Y segregation is buffered against the accumulation of homology-disrupting mutations. Here, I investigate the interplay of PAR evolution and function in two interfertile house mouse subspecies characterized by structurally divergent PARs, Mus musculus domesticus and M. m. castaneus Using cytogenetic methods to visualize the sex chromosomes at meiosis, I show that intersubspecific F 1 hybrids harbor an increased frequency of pachytene spermatocytes with unsynapsed sex chromosomes. This high rate of asynapsis is due, in part, to the premature release of synaptic associations prior to completion of prophase I. Further, I show that when sex chromosomes do synapse in intersubspecific hybrids, recombination is reduced across the paired region. Together, these meiotic defects afflict ∼50% of spermatocytes from F 1 hybrids and lead to increased apoptosis in meiotically dividing cells. Despite flagrant disruption of the meiotic program, a subset of spermatocytes complete meiosis and intersubspecific F 1 males remain fertile. These findings cast light on the meiotic constraints that shape sex chromosome evolution and offer initial clues to resolve the paradox raised by the rapid evolution of this functionally significant locus. Copyright © 2017 by the Genetics Society of America.

  1. Product analysis illuminates the final steps of IES deletion in Tetrahymena thermophila.

    Science.gov (United States)

    Saveliev, S V; Cox, M M

    2001-06-15

    DNA sequences (IES elements) eliminated from the developing macronucleus in the ciliate Tetrahymena thermophila are released as linear fragments, which have now been detected and isolated. A PCR-mediated examination of fragment end structures reveals three types of strand scission events, reflecting three steps in the deletion process. New evidence is provided for two steps proposed previously: an initiating double-stranded cleavage, and strand transfer to create a branched deletion intermediate. The fragment ends provide evidence for a previously uncharacterized third step: the branched DNA strand is cleaved at one of several defined sites located within 15-16 nucleotides of the IES boundary, liberating the deleted DNA in a linear form.

  2. Tetrahymena thermophila acidic ribosomal protein L37 contains an archaebacterial type of C-terminus.

    Science.gov (United States)

    Hansen, T S; Andreasen, P H; Dreisig, H; Højrup, P; Nielsen, H; Engberg, J; Kristiansen, K

    1991-09-15

    We have cloned and characterized a Tetrahymena thermophila macronuclear gene (L37) encoding the acidic ribosomal protein (A-protein) L37. The gene contains a single intron located in the 3'-part of the coding region. Two major and three minor transcription start points (tsp) were mapped 39 to 63 nucleotides upstream from the translational start codon. The uppermost tsp mapped to the first T in a putative T. thermophila RNA polymerase II initiator element, TATAA. The coding region of L37 predicts a protein of 109 amino acid (aa) residues. A substantial part of the deduced aa sequence was verified by protein sequencing. The T. thermophila L37 clearly belongs to the P1-type family of eukaryotic A-proteins, but the C-terminal region has the hallmarks of archaebacterial A-proteins.

  3. H3-THYMIDINE DERIVATIVE POOLS IN RELATION TO MACRONUCLEAR DNA SYNTHESIS IN TETRAHYMENA PYRIFORMIS

    Science.gov (United States)

    Stone, G. E.; Miller, O. L.; Prescott, D. M.

    1965-01-01

    The formation of a soluble H3-thymidine derivative pool has been examined in Tetrahymena pyriformis as a function of macronuclear DNA synthesis during the cell life cycle. An autoradiographic technique which allows the detection of water-soluble materials within a cell has shown that these cells do not take up and retain exogenous H3-thymidine during G1 or G2. Uptake of H3-thymidine is restricted to the S period of the cell cycle. Additional autoradiographic experiments show, however, that a soluble pool of H3-thymidine derivatives persists from the end of one DNA synthesis period to the beginning of the next synthesis period in the subsequent cell cycle. Since this persisting pool cannot be labeled with H3-thymidine, the pool does not turn over during non-S periods. PMID:19866660

  4. The effects of temperature upon the electrophysiological properties of Tetrahymena pyriformis-NT1.

    Science.gov (United States)

    Connolly, J G; Brown, I D; Lee, A G; Kerkut, G A

    1985-01-01

    Cells of Tetrahymena pyriformis--NT1 were cultured at 38 degrees C (Tg 38 degrees C) and 20 degrees C (Tg 20 degrees C) and their properties investigated over the range 0-40 degrees C. Tg 20 degrees C cells were viable in the range 3-33 degrees C and changes in their properties were readily reversible between 10 degrees C and 30 degrees C. Tg 38 degrees cells were viable in the range 40-10 degrees C and their property changes were immediately reversible in the range 40-23 degrees C. The I-V relations of Tg 38 degrees C cells showed increased excitability as the cells were cooled from 40 degrees C. At 10 degrees C there was a considerable loss of excitability and slope resistance. Cooling Tg 20 degrees C cells from 20 degrees C gave a similar pattern, although over a narrower temperature range. Warming Tg 20 degrees C Tetrahymena above 20 degrees C led to a progressive loss of excitability and the cells were markedly less viable above 35 degrees C. Within physiological limits the regenerative spike magnitude, repolarization time, time to peak and input resistance increased as temperature was lowered, whereas resting potential was diminished. When compared at their growth temperatures and most intermediate temperatures, the value of the various parameters monitored were generally different for the two cultures. The Q10 value for resting potential changes of Tg 20 degrees C cells about 20 degrees C was 1.20. As in T. vorax this was significantly (P less than 0.01) greater than that predicted for a diffusion potential and suggested that T. pyriformis--NT1 may have an electrogenic pump component in its membrane potential.

  5. Uptake, localization and clearance of quantum dots in ciliated protozoa Tetrahymena thermophila

    International Nuclear Information System (INIS)

    Mortimer, Monika; Kahru, Anne; Slaveykova, Vera I.

    2014-01-01

    Protozoa as phagocytizing cells have been shown to integrate engineered nanoparticles (NPs), while the mechanism, dynamics and extent of such uptake are unclear. Here our fluorescence microscopy data showed that CdSe/ZnS quantum dots (QDs) with primary size of 12 nm were readily phagocytized into the food vacuoles of Tetrahymena thermophila in a time- and dose-dependent manner. Twenty hours after the exposure to QDs in sublethal concentration the clearance of the QDs from the cells was incomplete suggesting that phagocytosis of QDs into food vacuoles was not the only pathway of uptake by T. thermophila. This was further proven by the results that the inhibition of phagocytosis did not block the internalization of QDs into protozoans. This study provides a new insight into uptake and cellular trafficking of subtoxic concentrations of nanoparticles that may, due to prolonged retention times in the cells, pose risks by potentially becoming available to higher trophic levels. - Highlights: • Tetrahymena thermophila internalized QDs in a dose- and time-dependent manner. • The egested QDs were not significantly biodegraded in the food vacuoles. • In addition to phagocytosis QDs entered protozoa by alternative uptake pathways. • The clearance of the QDs from the cells was incomplete after 20 h in fresh medium. • The prolonged retention time of nontoxic NPs in protozoa could increase their transfer in food chain. - In addition to phagocytosis, quantum dots (QDs) entered protozoans by alternative pathways which did not lead to complete clearance of the QDs from the cells

  6. Repression of meiotic genes by antisense transcription and by Fkh2 transcription factor in Schizosaccharomyces pombe.

    Science.gov (United States)

    Chen, Huei-Mei; Rosebrock, Adam P; Khan, Sohail R; Futcher, Bruce; Leatherwood, Janet K

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s) of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the "unspliced" signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression.

  7. Repression of Meiotic Genes by Antisense Transcription and by Fkh2 Transcription Factor in Schizosaccharomyces pombe

    Science.gov (United States)

    Chen, Huei-Mei; Rosebrock, Adam P.; Khan, Sohail R.; Futcher, Bruce; Leatherwood, Janet K.

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s) of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the “unspliced” signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression. PMID:22238674

  8. Repression of meiotic genes by antisense transcription and by Fkh2 transcription factor in Schizosaccharomyces pombe.

    Directory of Open Access Journals (Sweden)

    Huei-Mei Chen

    Full Text Available In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the "unspliced" signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression.

  9. JST Thesaurus Headwords and Synonyms: Tetrahymena pyriformis [MeCab user dictionary for science technology term[Archive

    Lifescience Database Archive (English)

    Full Text Available MeCab user dictionary for science technology term Tetrahymena pyriformis 名詞 一般 * * ...* * Tetrahymena pyriformis Tetrahymena pyriformis ティーイーティーアールエイエイチワイエムイーエヌエイ ピーワイアールアイエフオーアールエムアイエス Thesaurus2015 200906097287118996 C LS07 UNKNOWN_2 Tetrahymena pyriformis

  10. JST Thesaurus Headwords and Synonyms: Tetrahymena thermophila [MeCab user dictionary for science technology term[Archive

    Lifescience Database Archive (English)

    Full Text Available MeCab user dictionary for science technology term Tetrahymena thermophila 名詞 一般 * *... * * Tetrahymena thermophila Tetrahymena thermophila ティーイーティーアールエイエイチワイエムイーエヌエイ ティーエイチイーアールエムオーピーエイチアイエルエイ Thesaurus2015 200906086486381246 C LS07 UNKNOWN_2 Tetrahymena thermophila

  11. Different polyamine pathways from bacteria have replaced eukaryotic spermidine biosynthesis in ciliates Tetrahymena thermophila and Paramecium tetaurelia.

    Science.gov (United States)

    Li, Bin; Kim, Sok Ho; Zhang, Yang; Hanfrey, Colin C; Elliott, Katherine A; Ealick, Steven E; Michael, Anthony J

    2015-09-01

    The polyamine spermidine is absolutely required for growth and cell proliferation in eukaryotes, due to its role in post-translational modification of essential translation elongation factor eIF5A, mediated by deoxyhypusine synthase. We have found that free-living ciliates Tetrahymena and Paramecium lost the eukaryotic genes encoding spermidine biosynthesis: S-adenosylmethionine decarboxylase (AdoMetDC) and spermidine synthase (SpdSyn). In Tetrahymena, they were replaced by a gene encoding a fusion protein of bacterial AdoMetDC and SpdSyn, present as three copies. In Paramecium, a bacterial homospermidine synthase replaced the eukaryotic genes. Individual AdoMetDC-SpdSyn fusion protein paralogues from Tetrahymena exhibit undetectable AdoMetDC activity; however, when two paralogous fusion proteins are mixed, AdoMetDC activity is restored and spermidine is synthesized. Structural modelling indicates a functional active site is reconstituted by sharing critical residues from two defective protomers across the heteromer interface. Paramecium was found to accumulate homospermidine, suggesting it replaces spermidine for growth. To test this concept, a budding yeast spermidine auxotrophic strain was found to grow almost normally with homospermidine instead of spermidine. Biosynthesis of spermidine analogue aminopropylcadaverine, but not exogenously provided norspermidine, correlated with some growth. Finally, we found that diverse single-celled eukaryotic parasites and multicellular metazoan Schistosoma worms have lost the spermidine biosynthetic pathway but retain deoxyhypusine synthase. © 2015 John Wiley & Sons Ltd.

  12. Meiotic Consequences of Genetic Divergence Across the Murine Pseudoautosomal Region

    OpenAIRE

    Dumont, Beth L.

    2017-01-01

    The production of haploid gametes during meiosis is dependent on the homology-driven processes of pairing, synapsis, and recombination. On the mammalian heterogametic sex chromosomes, these key meiotic activities are confined to the pseudoautosomal region (PAR), a short region of near-perfect sequence homology between the X and Y chromosomes. Despite its established importance for meiosis, the PAR is rapidly evolving, raising the question of how proper X/Y segregation is buffered against the ...

  13. Meiotic delay of translocation carrying spermatocytes responsible for reduced transmission

    International Nuclear Information System (INIS)

    Buul, P.P.W. van

    1991-01-01

    Using in vivo pulse labelling of spermatocytes from mice irradiated with different doses of X-rays (6 and 7 Gy). The authors demonstrated that cells having translocations derived from irradiated stem cells tend to spend longer time at the meiotic prophase than normal cells. At the 2 Gy level this effect is much less pronounced. The recorded delay forms a good explanation for the reduced transmission of translocations to the next generation observed by others. (author)

  14. Repression of Meiotic Genes by Antisense Transcription and by Fkh2 Transcription Factor in Schizosaccharomyces pombe

    OpenAIRE

    Chen, Huei-Mei; Rosebrock, Adam P.; Khan, Sohail R.; Futcher, Bruce; Leatherwood, Janet K.

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription ...

  15. Meiotic and post-meiotic studies in the male mouse exposed to X-rays and their human implications

    International Nuclear Information System (INIS)

    Szemere, G.

    1977-01-01

    Cytological studies were carried out on the meiotic process of control and irradiated male mice in order to provide direct means of estimating the non-disjunction rate for autosomes and sex chromosomes. Analysis of second meiotic divisions showed that while spontaneous rates of anaphase I non-disjunctions were extremely low, they could be enhanced by X-ray treatment of prophase spermatocytes. Irradiation at pre-leptotene resulted in a higher rate of anaphase I non-disjunction than did irradiation at pachytene, while early spermatogonia were relatively insensitive. In the present experiments, a relatively high proportion of chromosomally abnormal fetuses (including triploidy, X monosomy, autosomal trisomy and several mosaicisms) have been found amoung the progeny of males irradiated at pre-leptotene. The human implications of these findings with respect to the radiation hazards are discussed

  16. A knockout mutation of a constitutive GPCR in Tetrahymena decreases both G-protein activity and chemoattraction.

    Directory of Open Access Journals (Sweden)

    Thomas J Lampert

    Full Text Available Although G-protein coupled receptors (GPCRs are a common element in many chemosensory transduction pathways in eukaryotic cells, no GPCR or regulated G-protein activity has yet been shown in any ciliate. To study the possible role for a GPCR in the chemoresponses of the ciliate Tetrahymena, we have generated a number of macronuclear gene knockouts of putative GPCRs found in the Tetrahymena Genome database. One of these knockout mutants, called G6, is a complete knockout of a gene that we call GPCR6 (TTHERM_00925490. Based on sequence comparisons, the Gpcr6p protein belongs to the Rhodopsin Family of GPCRs. Notably, Gpcr6p shares highest amino acid sequence homologies to GPCRs from Paramecium and several plants. One of the phenotypes of the G6 mutant is a decreased responsiveness to the depolarizing ions Ba²⁺ and K⁺, suggesting a decrease in basal excitability (decrease in Ca²⁺ channel activity. The other major phenotype of G6 is a loss of chemoattraction to lysophosphatidic acid (LPA and proteose peptone (PP, two known chemoattractants in Tetrahymena. Using microsomal [³⁵S]GTPγS binding assays, we found that wild-type (CU427 have a prominent basal G-protein activity. This activity is decreased to the same level by pertussis toxin (a G-protein inhibitor, addition of chemoattractants, or the G6 mutant. Since the basal G-protein activity is decreased by the GPCR6 knockout, it is likely that this gene codes for a constitutively active GPCR in Tetrahymena. We propose that chemoattractants like LPA and PP cause attraction in Tetrahymena by decreasing the basal G-protein stimulating activity of Gpcr6p. This leads to decreased excitability in wild-type and longer runs of smooth forward swimming (less interrupted by direction changes towards the attractant. Therefore, these attractants may work as inverse agonists through the constitutively active Gpcr6p coupled to a pertussis-sensitive G-protein.

  17. Molecular and biochemical analysis of conjugation and adolescence in Tetrahymena thermophila

    International Nuclear Information System (INIS)

    Rogers, M.B.

    1986-01-01

    A previously unrecognized stage in the development of sexual maturity in Tetrahymena thermophila, adolescence, has been described. When the progeny of successfully mated cells are grown logarithmically, they are unable to form mating pairs for about 65 generations. This period is known as immaturity. During the next stage, adolescence, the progeny pair with mature cells but not with other adolescent cells despite the presence of complementary mating types. Adolescence persists for 20-25 generations before the cells attain maturity (the ability to mate with any cell of different mating type). Once paired with mature cells, adolescents successfully complete conjugation was shown genetically. Mating pairs formed between adolescent and mature cells are indistinguishable from those formed between mature cells by the criteria of cytology and two-dimensional gel electrophoresis of proteins extracted from mating pairs pulse-labelled with [ 35 S]methionine. An analysis of proteins induced during the first ten hours of conjugation was carried out using two-dimensional gel electrophoresis. The protein patterns obtained from all controls were similar. The synthesis of numerous large and basic proteins were induced during conjugation. The majority of the proteins were detected during meiosis and none were mating type specific. A library of micronuclear DNA was constructed in the plasmic PUC18. The library was screened by differential colony hybridization using cDNA complementary to polyA + RNA isolated from conjugating and control cells. Eight recombinant clones were isolated which contain sequences transcriptionally induced in conjugating cells

  18. Effect of salt and urban water samples on bacterivory by the ciliate, Tetrahymena thermophila

    Energy Technology Data Exchange (ETDEWEB)

    St Denis, C.H.; Pinheiro, M.D.O.; Power, M.E. [Department of Biology, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1 (Canada); Bols, Niels C., E-mail: ncbols@uwaterloo.c [Department of Biology, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1 (Canada)

    2010-02-15

    The effect of road salt on the eating of bacteria or bacterivory by the ciliate, Tetrahymena thermophila, was followed in non-nutrient Osterhout's solution with Escherichia coli expressing green fluorescent protein. Bacterivory was impaired at between 0.025 and 0.050% w/v but the ciliates appeared to have normal morphologies and motilities, whereas at above 0.1%, bacterivory was blocked and many ciliates died. By contrast, E. coli remained viable, suggesting salt could alter predator-prey relationships in microbial communities. In nutrient medium, salt was not toxic and the ciliates grew. After growth in salt, ciliates consumed bacteria in 0.2% salt, indicating the salt acclimation of bacterivory. Bacteria and ciliates were added to urban creek samples to compare their capacity to support exogenous bacterivory. Even though samples were collected weekly for a year and be expected to have fluctuating salt levels as a result of deicing, all creek samples supported a similar level of bacterivory. - Road salt at some concentrations inhibits bacterivory by ciliates, and thus potentially could alter the microbial food web.

  19. The fate of deleted DNA produced during programmed genomic deletion events in Tetrahymena thermophila.

    Science.gov (United States)

    Saveliev, S V; Cox, M M

    1994-01-01

    Thousands of DNA deletion events occur during macronuclear development in the ciliate Tetrahymena thermophila. In two deleted genomic regions, designated M and R, the eliminated sequences form circles that can be detected by PCR. However, the circles are not normal products of the reaction pathway. The circular forms occur at very low levels in conjugating cells, but are stable. Sequencing analysis showed that many of the circles (as many as 50% of those examined) reflected a precise deletion in the M and R regions. The remaining circles were either smaller or larger and contained varying lengths of sequences derived from the chromosomal DNA surrounding the eliminated region. The chromosomal junctions left behind after deletion were more precise, although deletions in either the M or R regions can generate any of several alternative junctions (1). Some new chromosomal junctions were detected in the present study. The results suggest that the deleted segment is released as a linear DNA species that is degraded rapidly. The species is only rarely converted to the stable circles we detect. The deletion mechanism is different from those proposed for deletion events in hypotrichous ciliates (2-4), and does not reflect a conservative site-specific recombination process such as that promoted by the bacteriophage lambda integrase (5). Images PMID:7838724

  20. Developmentally programmed DNA deletion in Tetrahymena thermophila by a transposition-like reaction pathway.

    Science.gov (United States)

    Saveliev, S V; Cox, M M

    1996-01-01

    We provide a molecular description of key intermediates in the deletion of two internal eliminated sequences (IES elements), the M and R regions, during macronuclear development in Tetrahymena thermophila. Using a variety of PCR-based methods in vivo, double-strand breaks are detected that are generated by hydrolytic cleavage and correspond closely to the observed chromosomal junctions left behind in the macronuclei. The breaks exhibit a temporal and structural relationship to the deletion reaction that provides strong evidence that they are intermediates in the deletion pathway. Breaks in the individual strands are staggered by 4 bp, producing a four nucleotide 5' extension. Evidence is presented that breaks do not occur simultaneously at both ends. The results are most consistent with a deletion mechanism featuring initiation by double-strand cleavage at one end of the deleted element, followed by transesterification to generate the macronuclear junction on one DNA strand. An adenosine residue is found at all the nucleophilic 3' ends used in the postulated transesterification step. Evidence for the transesterification step is provided by detection of a 3' hydroxyl that would be liberated by such a step at a deletion boundary where no other DNA strand ends are detected. Images PMID:8654384

  1. Induced tubulin synthesis is caused by induced gene transcription in Tetrahymena

    International Nuclear Information System (INIS)

    Seyfert, H.M.; Kohle, D.; Jenovai, S.

    1987-01-01

    Tubulin synthesis and tubulin mRNA concentrations increase to variable extents during ciliary regeneration in the ciliate Tetrahymena. Experiments described here were carried out to determine whether the increased tubulin mRNa concentrations are due to induced transcription of tubulin genes or to stabilization of tubulin mRNA. In vivo labeling experiments with [ 3 H]uridine and in vitro transcription assays suggest that under conditions of increased protein and tubulin synthesis the rate of transcription is enhanced. Hybridization assays of in vitro transcribed RNA also demonstrate qualitatively that the tubulin genes are transcribed at higher rates when tubulin synthesis is stimulated during ciliary regeneration. This observation is supported by measurements of the half-life of tubulin mRNA molecules in nondeciliated cells: This is approximately 2 h. Since the concentration of tubulin mRNA in cells engaged in cilia regeneration increases from 5 to 19-fold during the first hour of the regeneration period, even a complete stabilization of the tubulin mRNA molecules could not account for an increase in tubulin mRNA concentration of this magnitude

  2. Effect of salt and urban water samples on bacterivory by the ciliate, Tetrahymena thermophila

    International Nuclear Information System (INIS)

    St Denis, C.H.; Pinheiro, M.D.O.; Power, M.E.; Bols, Niels C.

    2010-01-01

    The effect of road salt on the eating of bacteria or bacterivory by the ciliate, Tetrahymena thermophila, was followed in non-nutrient Osterhout's solution with Escherichia coli expressing green fluorescent protein. Bacterivory was impaired at between 0.025 and 0.050% w/v but the ciliates appeared to have normal morphologies and motilities, whereas at above 0.1%, bacterivory was blocked and many ciliates died. By contrast, E. coli remained viable, suggesting salt could alter predator-prey relationships in microbial communities. In nutrient medium, salt was not toxic and the ciliates grew. After growth in salt, ciliates consumed bacteria in 0.2% salt, indicating the salt acclimation of bacterivory. Bacteria and ciliates were added to urban creek samples to compare their capacity to support exogenous bacterivory. Even though samples were collected weekly for a year and be expected to have fluctuating salt levels as a result of deicing, all creek samples supported a similar level of bacterivory. - Road salt at some concentrations inhibits bacterivory by ciliates, and thus potentially could alter the microbial food web.

  3. A new seed-based assay for meiotic recombination in Arabidopsis thaliana.

    NARCIS (Netherlands)

    Melamed-Bessudo, C.; Yehuda, E.; Stuitje, A.R.; Levy, A.A.

    2005-01-01

    Meiotic recombination is a fundamental biological process that plays a central role in the evolution and breeding of plants. We have developed a new seed-based assay for meiotic recombination in Arabidopsis. The assay is based on the transformation of green and red fluorescent markers expressed

  4. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum, Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable meiotic process and ...

  5. Genetically enhanced asynapsis of autosomal chromatin promotes transcriptional dysregulation and meiotic failure

    Czech Academy of Sciences Publication Activity Database

    Homolka, David; Jansa, Petr; Forejt, Jiří

    2012-01-01

    Roč. 121, č. 1 (2012), s. 91-104 ISSN 0009-5915 R&D Projects: GA MŠk(CZ) LD11079 Institutional research plan: CEZ:AV0Z50520514 Keywords : meiotic silencing of unsynapsed chromatin * meiotic sex chromosome inactivation * autosomal translocation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.340, year: 2012

  6. Meiotic Clade AAA ATPases: Protein Polymer Disassembly Machines.

    Science.gov (United States)

    Monroe, Nicole; Hill, Christopher P

    2016-05-08

    Meiotic clade AAA ATPases (ATPases associated with diverse cellular activities), which were initially grouped on the basis of phylogenetic classification of their AAA ATPase cassette, include four relatively well characterized family members, Vps4, spastin, katanin and fidgetin. These enzymes all function to disassemble specific polymeric protein structures, with Vps4 disassembling the ESCRT-III polymers that are central to the many membrane-remodeling activities of the ESCRT (endosomal sorting complexes required for transport) pathway and spastin, katanin p60 and fidgetin affecting multiple aspects of cellular dynamics by severing microtubules. They share a common domain architecture that features an N-terminal MIT (microtubule interacting and trafficking) domain followed by a single AAA ATPase cassette. Meiotic clade AAA ATPases function as hexamers that can cycle between the active assembly and inactive monomers/dimers in a regulated process, and they appear to disassemble their polymeric substrates by translocating subunits through the central pore of their hexameric ring. Recent studies with Vps4 have shown that nucleotide-induced asymmetry is a requirement for substrate binding to the pore loops and that recruitment to the protein lattice via MIT domains also relieves autoinhibition and primes the AAA ATPase cassettes for substrate binding. The most striking, unifying feature of meiotic clade AAA ATPases may be their MIT domain, which is a module that is found in a wide variety of proteins that localize to ESCRT-III polymers. Spastin also displays an adjacent microtubule binding sequence, and the presence of both ESCRT-III and microtubule binding elements may underlie the recent findings that the ESCRT-III disassembly function of Vps4 and the microtubule-severing function of spastin, as well as potentially katanin and fidgetin, are highly coordinated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Prevention of DNA Rereplication Through a Meiotic Recombination Checkpoint Response

    Directory of Open Access Journals (Sweden)

    Nicole A. Najor

    2016-12-01

    Full Text Available In the budding yeast Saccharomyces cerevisiae, unnatural stabilization of the cyclin-dependent kinase inhibitor Sic1 during meiosis can trigger extra rounds of DNA replication. When programmed DNA double-strand breaks (DSBs are generated but not repaired due to absence of DMC1, a pathway involving the checkpoint gene RAD17 prevents this DNA rereplication. Further genetic analysis has now revealed that prevention of DNA rereplication also requires MEC1, which encodes a protein kinase that serves as a central checkpoint regulator in several pathways including the meiotic recombination checkpoint response. Downstream of MEC1, MEK1 is required through its function to inhibit repair between sister chromatids. By contrast, meiotic recombination checkpoint effectors that regulate gene expression and cyclin-dependent kinase activity are not necessary. Phosphorylation of histone H2A, which is catalyzed by Mec1 and the related Tel1 protein kinase in response to DSBs, and can help coordinate activation of the Rad53 checkpoint protein kinase in the mitotic cell cycle, is required for the full checkpoint response. Phosphorylation sites that are targeted by Rad53 in a mitotic S phase checkpoint response are also involved, based on the behavior of cells containing mutations in the DBF4 and SLD3 DNA replication genes. However, RAD53 does not appear to be required, nor does RAD9, which encodes a mediator of Rad53, consistent with their lack of function in the recombination checkpoint pathway that prevents meiotic progression. While this response is similar to a checkpoint mechanism that inhibits initiation of DNA replication in the mitotic cell cycle, the evidence points to a new variation on DNA replication control.

  8. REC-1 and HIM-5 distribute meiotic crossovers and function redundantly in meiotic double-strand break formation in Caenorhabditis elegans.

    Science.gov (United States)

    Chung, George; Rose, Ann M; Petalcorin, Mark I R; Martin, Julie S; Kessler, Zebulin; Sanchez-Pulido, Luis; Ponting, Chris P; Yanowitz, Judith L; Boulton, Simon J

    2015-09-15

    The Caenorhabditis elegans gene rec-1 was the first genetic locus identified in metazoa to affect the distribution of meiotic crossovers along the chromosome. We report that rec-1 encodes a distant paralog of HIM-5, which was discovered by whole-genome sequencing and confirmed by multiple genome-edited alleles. REC-1 is phosphorylated by cyclin-dependent kinase (CDK) in vitro, and mutation of the CDK consensus sites in REC-1 compromises meiotic crossover distribution in vivo. Unexpectedly, rec-1; him-5 double mutants are synthetic-lethal due to a defect in meiotic double-strand break formation. Thus, we uncovered an unexpected robustness to meiotic DSB formation and crossover positioning that is executed by HIM-5 and REC-1 and regulated by phosphorylation. © 2015 Chung et al.; Published by Cold Spring Harbor Laboratory Press.

  9. Chromosomal rearrangement interferes with meiotic X chromosome inactivation

    Czech Academy of Sciences Publication Activity Database

    Homolka, David; Ivánek, Robert; Čapková, Jana; Jansa, Petr; Forejt, Jiří

    2007-01-01

    Roč. 17, č. 10 (2007), s. 1431-1437 ISSN 1088-9051 R&D Projects: GA MŠk(CZ) 1M0520; GA ČR GA301/06/1334; GA ČR GA301/07/1383 Grant - others:Howard Hughes Medical Institute(US) HHMI 55000306 Institutional research plan: CEZ:AV0Z50520514 Keywords : chromosomal translocations * meiotic X chromosome inactivation * spermatogenesis Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 11.224, year: 2007

  10. Meiotic behavior of wild Caricaceae species potentially suitable for papaya improvement

    Directory of Open Access Journals (Sweden)

    Emanuelli Narducci da Silva

    2012-01-01

    Full Text Available The purpose of this study was to evaluate the meiotic behavior and determine the meiotic index and pollen viability of representative plants of the wild species V. goudotiana, V. quercifolia and J. spinosa. Meiotic analysis confirmed that the species are diploid and have 18 chromosomes. Meiosis was partially normal, since some abnormalities, e.g, sticky and lagging chromosomes, precocious segregation, lack of synchrony, and disturbances in the spindle fibers were observed. These abnormalities resulted in post-meiotic products (monads, dyads, triads, and polyads that probably contributed to the meiotic index of 85.7 % (V. goudotiana to 95.9 % (J. spinosa; significant variation was observed in the species V. goudotiana. The pollen viability of 68.0% (V. goudotiana to 96.0 % (J. spinosa was reasonably good in these wild species. Crossings in breeding programs involving V. goudotiana should therefore be carefully planned, since part of the gametes of this species is unviable.

  11. Genetic analysis of variation in human meiotic recombination.

    Directory of Open Access Journals (Sweden)

    Reshmi Chowdhury

    2009-09-01

    Full Text Available The number of recombination events per meiosis varies extensively among individuals. This recombination phenotype differs between female and male, and also among individuals of each gender. In this study, we used high-density SNP genotypes of over 2,300 individuals and their offspring in two datasets to characterize recombination landscape and to map the genetic variants that contribute to variation in recombination phenotypes. We found six genetic loci that are associated with recombination phenotypes. Two of these (RNF212 and an inversion on chromosome 17q21.31 were previously reported in the Icelandic population, and this is the first replication in any other population. Of the four newly identified loci (KIAA1462, PDZK1, UGCG, NUB1, results from expression studies provide support for their roles in meiosis. Each of the variants that we identified explains only a small fraction of the individual variation in recombination. Notably, we found different sequence variants associated with female and male recombination phenotypes, suggesting that they are regulated by different genes. Characterization of genetic variants that influence natural variation in meiotic recombination will lead to a better understanding of normal meiotic events as well as of non-disjunction, the primary cause of pregnancy loss.

  12. Meiotically stable natural epialleles of Sadhu, a novel Arabidopsis retroposon.

    Directory of Open Access Journals (Sweden)

    Sanjida H Rangwala

    2006-03-01

    Full Text Available Epigenetic variation is a potential source of genomic and phenotypic variation among different individuals in a population, and among different varieties within a species. We used a two-tiered approach to identify naturally occurring epigenetic alleles in the flowering plant Arabidopsis: a primary screen for transcript level polymorphisms among three strains (Col, Cvi, Ler, followed by a secondary screen for epigenetic alleles. Here, we describe the identification of stable, meiotically transmissible epigenetic alleles that correspond to one member of a previously uncharacterized non-LTR retroposon family, which we have designated Sadhu. The pericentromeric At2g10410 element is highly expressed in strain Col, but silenced in Ler and 18 other strains surveyed. Transcription of this locus is inversely correlated with cytosine methylation and both the expression and DNA methylation states map in a Mendelian manner to stable cis-acting variation. The silent Ler allele can be converted by the epigenetic modifier mutation ddm1 to a meiotically stable expressing allele with an identical primary nucleotide sequence, demonstrating that the variation responsible for transcript level polymorphism among Arabidopsis strains is epigenetic. We extended our characterization of the Sadhu family members and show that different elements are subject to both genetic and epigenetic variation in natural populations. These findings support the view that an important component of natural variation in retroelements is epigenetic.

  13. X-ray induction of mitotic and meiotic chromosome aberrations

    International Nuclear Information System (INIS)

    Yao, K.T.S.

    1980-01-01

    In 1964 six pairs of rat kangaroo (Potorous tridactylis) were obtained from Australia. The tissues of these animals were used to initiate cell lines. Since this species has a low chromosome number of six pairs, each pair with its own distinctive morphology, it is particularly favorable for cytogenetic research. In cell cultures derived from the corneal endothelial tissues of one animal there emerged a number of haploid cells. The number of haploid cells in the cultures reached as high as 20% of the total mitotic configurations. The in vitro diploid and haploid mixture cell cultures could be a resemblance or a coincidence to the mixture existence of the diploid primary spermatocytes and the haploid secondary spermatocytes (gametes) in the in vivo testicular tissues of the male animals. It would be interesting to compare reactions of the haploid and diploid cell mixture, either in the cultures or in the testes, to x-ray exposure. Two other studies involving x-ray effects on Chinese hamster oocyte maturation and meiotic chromosomes and the x-ray induction of Chinese hamster spermatocyte meiotic chromosome aberrations have been done in this laboratory. A review of these three studies involving diploid and haploid chromosomes may lead to further research in the x-ray induction of chromosome aberrations

  14. Autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast.

    Science.gov (United States)

    Matsuhara, Hirotada; Yamamoto, Ayumu

    2016-01-01

    Autophagy is a conserved intracellular degradation system, which contributes to development and differentiation of various organisms. Yeast cells undergo meiosis under nitrogen-starved conditions and require autophagy for meiosis initiation. However, the precise roles of autophagy in meiosis remain unclear. Here, we show that autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast. Autophagy-defective strains bearing a mutation in the autophagy core factor gene atg1, atg7, or atg14 exhibit deformed nuclear structures during meiosis. These mutant cells require an extracellular nitrogen supply for meiosis progression following their entry into meiosis and show delayed meiosis progression even with a nitrogen supply. In addition, they show frequent chromosome dissociation from the spindle together with spindle overextension, forming extra nuclei. Furthermore, Aurora kinase, which regulates chromosome segregation and spindle elongation, is significantly increased at the centromere and spindle in the mutant cells. Aurora kinase down-regulation eliminated delayed initiation of meiosis I and II, chromosome dissociation, and spindle overextension, indicating that increased Aurora kinase activity may cause these aberrances in the mutant cells. Our findings show a hitherto unrecognized relationship of autophagy with the nuclear structure, regulation of cell cycle progression, and chromosome segregation in meiosis. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

  15. Maize histone H2B-mCherry: a new fluorescent chromatin marker for somatic and meiotic chromosome research.

    Science.gov (United States)

    Howe, Elizabeth S; Clemente, Thomas E; Bass, Hank W

    2012-06-01

    Cytological studies of fluorescent proteins are rapidly yielding insights into chromatin structure and dynamics. Here we describe the production and cytological characterization of new transgenic maize lines expressing a fluorescent histone fusion protein, H2B-mCherry. The transgene is expressed under the control of the maize ubiquitin1 promoter, including its first exon and intron. Polymerase chain reaction-based genotyping and root-tip microscopy showed that most of the lines carrying the transgene also expressed it, producing bright uniform staining of nuclei. Further, plants showing expression in root tips at the seedling stage also showed expression during meiosis, late in the life cycle. Detailed high-resolution three-dimensional imaging of cells and nuclei from various somatic and meiotic cell types showed that H2B-mCherry produced remarkably clear images of chromatin and chromosome fiber morphology, as seen in somatic, male meiotic prophase, and early microgametophyte cells. H2B-mCherry also yielded distinct nucleolus staining and was shown to be compatible with fluorescence in situ hybridization. We found several instances where H2B-mCherry was superior to DAPI as a generalized chromatin stain. Our study establishes these histone H2B-mCherry lines as new biological reagents for visualizing chromatin structure, chromosome morphology, and nuclear dynamics in fixed and living cells in a model plant genetic system.

  16. RNA precursor pool metabolism and RNA synthesis in X-irradiated Tetrahymena

    International Nuclear Information System (INIS)

    Stephens, R.E.; Paul, I.J.; Zimmerman, A.M.

    1976-01-01

    The incorporation of a radioactive RNA precursor ( 3 H-uridine) has been used in many studies as an index for measuring the synthesis of RNA, yet there is a distinct possibility that the results so obtained were significantly influenced by radiation-induced effects on the metabolism of this precursor into UTP (the primary immediate precursor of RNA) before its incorporation into RNA. A direct examination was therefore undertaken of the effects of X-irradiation on the metabolism of 3 H-uridine and its relationship to RNA synthesis as determined by incorporation. X-irradiation of logarithmically growing Tetrahymena pyriformis caused a dose-dependent depression of total cellular RNA synthesis. Ribosomal RNA (which comprises about 80 per cent of total cellular RNA) synthesis was also depressed by X-irradiation in a dose-dependent manner. Measurements of the levels of radioactivity present in the UTP precursor pool of both irradiated and unirradiated cells were obtained by means of DEAE-cellulose column chromatography of the extracted free nucleotides. Metabolism of 3 H-uridine into UMP, UDP and UTP was depressed by 40%, 26% and 27% respectively, whereas incorporation of 3 H-uridine into RNA was depressed by 77%. The results show that about one-third of the observed (apparent) depression in RNA synthesis was due to radiation-induced effects on the precursor pool, and the remaining two-thirds due to some definite effect of radiation at the transcription level leading to depressed synthesis of RNA. (U.K.)

  17. The C. elegans DSB-2 protein reveals a regulatory network that controls competence for meiotic DSB formation and promotes crossover assurance.

    Directory of Open Access Journals (Sweden)

    Simona Rosu

    Full Text Available For most organisms, chromosome segregation during meiosis relies on deliberate induction of DNA double-strand breaks (DSBs and repair of a subset of these DSBs as inter-homolog crossovers (COs. However, timing and levels of DSB formation must be tightly controlled to avoid jeopardizing genome integrity. Here we identify the DSB-2 protein, which is required for efficient DSB formation during C. elegans meiosis but is dispensable for later steps of meiotic recombination. DSB-2 localizes to chromatin during the time of DSB formation, and its disappearance coincides with a decline in RAD-51 foci marking early recombination intermediates and precedes appearance of COSA-1 foci marking CO-designated sites. These and other data suggest that DSB-2 and its paralog DSB-1 promote competence for DSB formation. Further, immunofluorescence analyses of wild-type gonads and various meiotic mutants reveal that association of DSB-2 with chromatin is coordinated with multiple distinct aspects of the meiotic program, including the phosphorylation state of nuclear envelope protein SUN-1 and dependence on RAD-50 to load the RAD-51 recombinase at DSB sites. Moreover, association of DSB-2 with chromatin is prolonged in mutants impaired for either DSB formation or formation of downstream CO intermediates. These and other data suggest that association of DSB-2 with chromatin is an indicator of competence for DSB formation, and that cells respond to a deficit of CO-competent recombination intermediates by prolonging the DSB-competent state. In the context of this model, we propose that formation of sufficient CO-competent intermediates engages a negative feedback response that leads to cessation of DSB formation as part of a major coordinated transition in meiotic prophase progression. The proposed negative feedback regulation of DSB formation simultaneously (1 ensures that sufficient DSBs are made to guarantee CO formation and (2 prevents excessive DSB levels that could

  18. Comparison of primary and secondary 26S rRNA structures in two Tetrahymena species: evidence for a strong evolutionary and structural constraint in expansion segments

    DEFF Research Database (Denmark)

    Engberg, J; Nielsen, Henrik; Lenaers, G

    1990-01-01

    We have determined the nucleotide sequence of the 26S large subunit (LSU) rRNA genes for two Tetrahymena species, T. thermophila and T. pyriformis. The inferred rRNA sequences are presented in their most probable secondary structures based on compensatory mutations, energy, and conservation crite...

  19. A simple model for the influence of meiotic conversion tracts on GC content.

    Directory of Open Access Journals (Sweden)

    Marie-Claude Marsolier-Kergoat

    Full Text Available A strong correlation between GC content and recombination rate is observed in many eukaryotes, which is thought to be due to conversion events linked to the repair of meiotic double-strand breaks. In several organisms, the length of conversion tracts has been shown to decrease exponentially with increasing distance from the sites of meiotic double-strand breaks. I show here that this behavior leads to a simple analytical model for the evolution and the equilibrium state of the GC content of sequences devoid of meiotic double-strand break sites. In the yeast Saccharomyces cerevisiae, meiotic double-strand breaks are practically excluded from protein-coding sequences. A good fit was observed between the predictions of the model and the variations of the average GC content of the third codon position (GC3 of S. cerevisiae genes. Moreover, recombination parameters that can be extracted by fitting the data to the model coincide with experimentally determined values. These results thus indicate that meiotic recombination plays an important part in determining the fluctuations of GC content in yeast coding sequences. The model also accounted for the different patterns of GC variations observed in the genes of Candida species that exhibit a variety of sexual lifestyles, and hence a wide range of meiotic recombination rates. Finally, the variations of the average GC3 content of human and chicken coding sequences could also be fitted by the model. These results suggest the existence of a widespread pattern of GC variation in eukaryotic genes due to meiotic recombination, which would imply the generality of two features of meiotic recombination: its association with GC-biased gene conversion and the quasi-exclusion of meiotic double-strand breaks from coding sequences. Moreover, the model points out to specific constraints on protein fragments encoded by exon terminal sequences, which are the most affected by the GC bias.

  20. Rapid detection of predation of Escherichia coli O157:H7 and sorting of bacterivorous Tetrahymena by flow cytometry

    Directory of Open Access Journals (Sweden)

    Bradley J. Hernlem

    2014-05-01

    Full Text Available Protozoa are known to harbor bacterial pathogens, alter their survival in the environment and make them hypervirulent. Rapid non-culture based detection methods are required to determine the environmental survival and transport of enteric pathogens from point sources such as dairies and feedlots to food crops grown in proximity. Grazing studies were performed on a soil isolate of Tetrahymena fed green fluorescent protein (GFP expressing Escherichia coli O157:H7 to determine the suitability of the use of such fluorescent prey bacteria to locate and sort bacterivorous protozoa by flow cytometry. In order to overcome autofluorescence of the target organism and to clearly discern Tetrahymena with ingested prey versus those without, a ratio of prey to host of at least 100:1 was determined to be preferable. Under these conditions, we successfully sorted the two populations using short 5 to 45 min exposures of the prey and verified the internalization of E. coli O157:H7 cells in protozoa by confocal microscopy. This technique can be easily adopted for environmental monitoring of rates of enteric pathogen destruction versus protection in protozoa.

  1. Using Micromanipulation to Analyze Control of Vertebrate Meiotic Spindle Size

    Directory of Open Access Journals (Sweden)

    Jun Takagi

    2013-10-01

    Full Text Available The polymerization/depolymerization dynamics of microtubules (MTs have been reported to contribute to control of the size and shape of spindles, but quantitative analysis of how the size and shape correlate with the amount and density of MTs in the spindle remains incomplete. Here, we measured these parameters using 3D microscopy of meiotic spindles that self-organized in Xenopus egg extracts and presented a simple equation describing the relationship among these parameters. To examine the validity of the equation, we cut the spindle into two fragments along the pole-to-pole axis by micromanipulation techniques that rapidly decrease the amount of MTs. The spheroidal shape spontaneously recovered within 5 min, but the size of each fragment remained small. The equation we obtained quantitatively describes how the spindle size correlates with the amount of MTs while maintaining the shape and the MT density.

  2. Aberrant meiotic behavior in Agave tequilana Weber var. azul.

    Science.gov (United States)

    Ruvalcaba-Ruiz, Domingo; Rodríguez-Garay, Benjamin

    2002-10-23

    Agave tequilana Weber var. azul, is the only one variety permitted by federal law in México to be used for tequila production which is the most popular contemporary alcoholic beverage made from agave and recognized worldwide. Despite the economic, genetic, and ornamental value of the plant, it has not been subjected to detailed cytogenetic research, which could lead to a better understanding of its reproduction for future genetic improvement. The objective of this work was to study the meiotic behavior in pollen mother cells and its implications on the pollen viability in Agave tequilana Weber var. azul. The analysis of Pollen Mother Cells in anaphase I (A-I) showed 82.56% of cells with a normal anaphase and, 17.44% with an irregular anaphase. In which 5.28% corresponded to cells with side arm bridges (SAB); 3.68% cells with one bridge and one fragment; 2.58% of irregular anaphase showed cells with one or two lagging chromosomes and 2.95% showed one acentric fragment; cells with two bridges and cells with two bridges and one acentric fragment were observed in frequencies of 1.60% and 1.35% respectively. In anaphase II some cells showed bridges and fragments too. Aberrant A-I cells had many shrunken or empty pollen grains (42.00%) and 58.00 % viable pollen. The observed meiotic irregularities suggest that structural chromosome aberrations have occurred, such as heterozygous inversions, sister chromatid exchanges, deletions and duplications which in turn are reflected in a low pollen viability.

  3. Aberrant meiotic behavior in Agave tequilana Weber var. azul

    Directory of Open Access Journals (Sweden)

    Rodríguez-Garay Benjamin

    2002-10-01

    Full Text Available Abstract Background Agave tequilana Weber var. azul, is the only one variety permitted by federal law in México to be used for tequila production which is the most popular contemporary alcoholic beverage made from agave and recognized worldwide. Despite the economic, genetic, and ornamental value of the plant, it has not been subjected to detailed cytogenetic research, which could lead to a better understanding of its reproduction for future genetic improvement. The objective of this work was to study the meiotic behavior in pollen mother cells and its implications on the pollen viability in Agave tequilana Weber var. azul. Results The analysis of Pollen Mother Cells in anaphase I (A-I showed 82.56% of cells with a normal anaphase and, 17.44% with an irregular anaphase. In which 5.28% corresponded to cells with side arm bridges (SAB; 3.68% cells with one bridge and one fragment; 2.58% of irregular anaphase showed cells with one or two lagging chromosomes and 2.95% showed one acentric fragment; cells with two bridges and cells with two bridges and one acentric fragment were observed in frequencies of 1.60% and 1.35% respectively. In anaphase II some cells showed bridges and fragments too. Aberrant A-I cells had many shrunken or empty pollen grains (42.00% and 58.00 % viable pollen. Conclusion The observed meiotic irregularities suggest that structural chromosome aberrations have occurred, such as heterozygous inversions, sister chromatid exchanges, deletions and duplications which in turn are reflected in a low pollen viability.

  4. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    KAUST Repository

    Fučí ková , Karolina; Pažoutová , Marie; Rindi, Fabio

    2015-01-01

    being the only partial exceptions (only four genes present). The evidence of sex provided by the meiotic genes is phylogenetically widespread in the class and indicates that sexual reproduction is not associated with any particular morphological

  5. The temporal response of recombination events to gamma radiation of meiotic cells in Sordaria brevicollis.

    Science.gov (United States)

    Lewis, L A

    1982-01-01

    The temporal frequencies of different stages of prophase I were determined cytologically in Sordaria brevicollis (Olive and Fantini) as the basis for ascertaining the degree of synchrony in meiosis in this ascomycete. Croziers, karyogamy-zygotene and pachytene asci were shown to be in significant majorities at three distinct periods of the meiotic cycle. The response of recombination frequency to ionizing radiation was examined for the entire meiotic cycle. Three radiosensitive periods were determined. This response, which correlated temporally with each of the three peaks in ascal frequency, is interpreted as showing that the meiotic cycle of this organism is divided into periods of recombination commitment (radiation reduced frequencies) during the pre-meiotic S phase and recombination consummation (radiation induced frequencies) during zygotene and pachytene. The results are discussed in the context of the time at which recombination is consummated in eukaryotes such as yeast and Drosophila.

  6. Meiotic behavior of Adesmia DC. (Leguminosae-Faboideae species native to Rio Grande do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    Coelho Liliana Gressler May

    1998-01-01

    Full Text Available Meiotic behavior in Adesmia DC. is described for the first time. The study encompassed twelve populations of seven Adesmia DC. species native to Rio Grande do Sul, Brazil. Populations with 2n = 2x = 20 are A. securigerifolia 9615, A. riograndensis 9590 (subnudae, A. latifolia 1568, 1775, 15025, A. bicolor JB-UFSM, A. incana var. incana 9636, 10288, A. punctata var. hilariana 6885, 10812, and A. tristis 10757. A. incana var. incana 9637 is a tetraploid with 2n = 4x = 40. The material was stained with 1% acetic orcein. The meiotic behavior of the populations studied was considered normal. The meiotic index (MI and the estimates of pollen grain viability were above 95%, except for A. latifolia 1568 (MI = 89%. The present data indicate that these plants are meiotically stable and potentially fertile, apparently with no problems for use in programs of selection, crossing and viable seed production.

  7. Hybrid Sterility Locus on Chromosome X Controls Meiotic Recombination Rate in Mouse.

    Directory of Open Access Journals (Sweden)

    Maria Balcova

    2016-04-01

    Full Text Available Meiotic recombination safeguards proper segregation of homologous chromosomes into gametes, affects genetic variation within species, and contributes to meiotic chromosome recognition, pairing and synapsis. The Prdm9 gene has a dual role, it controls meiotic recombination by determining the genomic position of crossover hotspots and, in infertile hybrids of house mouse subspecies Mus m. musculus (Mmm and Mus m. domesticus (Mmd, it further functions as the major hybrid sterility gene. In the latter role Prdm9 interacts with the hybrid sterility X 2 (Hstx2 genomic locus on Chromosome X (Chr X by a still unknown mechanism. Here we investigated the meiotic recombination rate at the genome-wide level and its possible relation to hybrid sterility. Using immunofluorescence microscopy we quantified the foci of MLH1 DNA mismatch repair protein, the cytological counterparts of reciprocal crossovers, in a panel of inter-subspecific chromosome substitution strains. Two autosomes, Chr 7 and Chr 11, significantly modified the meiotic recombination rate, yet the strongest modifier, designated meiotic recombination 1, Meir1, emerged in the 4.7 Mb Hstx2 genomic locus on Chr X. The male-limited transgressive effect of Meir1 on recombination rate parallels the male-limited transgressive role of Hstx2 in hybrid male sterility. Thus, both genetic factors, the Prdm9 gene and the Hstx2/Meir1 genomic locus, indicate a link between meiotic recombination and hybrid sterility. A strong female-specific modifier of meiotic recombination rate with the effect opposite to Meir1 was localized on Chr X, distally to Meir1. Mapping Meir1 to a narrow candidate interval on Chr X is an important first step towards positional cloning of the respective gene(s responsible for variation in the global recombination rate between closely related mouse subspecies.

  8. Radiation-induced mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Parry, J.M.; Sharp, D.; Tippins, R.S.; Parry, E.M.

    1979-01-01

    A number of genetic systems are described which in yeast may be used to monitor the induction of chromosome aneuploidy during both mitotic and meiotic cell division. Using these systems the authors have been able to demonstrate the induction of both monosomic and trisomic cells in mitotically dividing cells and disomic spores in meiotically dividing cells after both UV light and X-ray exposure. (Auth.)

  9. Meiotic behaviour and spermatogenesis in male mice heterozygous for translocation types also occurring in man

    International Nuclear Information System (INIS)

    Nijhoff, J.H.

    1981-01-01

    In this thesis a start was made with meiotic observations of mouse translocation types - a Robertsonian translocation and a translocation between a metacentric and an acrocentric chromosome - which also occur in man. As an exogeneous factor of possible influence, the meiotic effects of two types of radiation (fission neutrons and X-rays) administered at relatively low doses 2 and 3 hours before prometaphase-metaphase II (probably during metaphase-anaphase I), were determined in Rb4Bnr/+-males. (Auth.)

  10. Hybrid Sterility Locus on Chromosome X Controls Meiotic Recombination Rate in Mouse.

    Science.gov (United States)

    Balcova, Maria; Faltusova, Barbora; Gergelits, Vaclav; Bhattacharyya, Tanmoy; Mihola, Ondrej; Trachtulec, Zdenek; Knopf, Corinna; Fotopulosova, Vladana; Chvatalova, Irena; Gregorova, Sona; Forejt, Jiri

    2016-04-01

    Meiotic recombination safeguards proper segregation of homologous chromosomes into gametes, affects genetic variation within species, and contributes to meiotic chromosome recognition, pairing and synapsis. The Prdm9 gene has a dual role, it controls meiotic recombination by determining the genomic position of crossover hotspots and, in infertile hybrids of house mouse subspecies Mus m. musculus (Mmm) and Mus m. domesticus (Mmd), it further functions as the major hybrid sterility gene. In the latter role Prdm9 interacts with the hybrid sterility X 2 (Hstx2) genomic locus on Chromosome X (Chr X) by a still unknown mechanism. Here we investigated the meiotic recombination rate at the genome-wide level and its possible relation to hybrid sterility. Using immunofluorescence microscopy we quantified the foci of MLH1 DNA mismatch repair protein, the cytological counterparts of reciprocal crossovers, in a panel of inter-subspecific chromosome substitution strains. Two autosomes, Chr 7 and Chr 11, significantly modified the meiotic recombination rate, yet the strongest modifier, designated meiotic recombination 1, Meir1, emerged in the 4.7 Mb Hstx2 genomic locus on Chr X. The male-limited transgressive effect of Meir1 on recombination rate parallels the male-limited transgressive role of Hstx2 in hybrid male sterility. Thus, both genetic factors, the Prdm9 gene and the Hstx2/Meir1 genomic locus, indicate a link between meiotic recombination and hybrid sterility. A strong female-specific modifier of meiotic recombination rate with the effect opposite to Meir1 was localized on Chr X, distally to Meir1. Mapping Meir1 to a narrow candidate interval on Chr X is an important first step towards positional cloning of the respective gene(s) responsible for variation in the global recombination rate between closely related mouse subspecies.

  11. Colocalization of somatic and meiotic double strand breaks near the Myc oncogene on mouse chromosome 15.

    Science.gov (United States)

    Ng, Siemon H; Maas, Sarah A; Petkov, Petko M; Mills, Kevin D; Paigen, Kenneth

    2009-10-01

    Both somatic and meiotic recombinations involve the repair of DNA double strand breaks (DSBs) that occur at preferred locations in the genome. Improper repair of DSBs during either mitosis or meiosis can lead to mutations, chromosomal aberration such as translocations, cancer, and/or cell death. Currently, no model exists that explains the locations of either spontaneous somatic DSBs or programmed meiotic DSBs or relates them to each other. One common class of tumorigenic translocations arising from DSBs is chromosomal rearrangements near the Myc oncogene. Myc translocations have been associated with Burkitt lymphoma in humans, plasmacytoma in mice, and immunocytoma in rats. Comparing the locations of somatic and meiotic DSBs near the mouse Myc oncogene, we demonstrated that the placement of these DSBs is not random and that both events clustered in the same short discrete region of the genome. Our work shows that both somatic and meiotic DSBs tend to occur in proximity to each other within the Myc region, suggesting that they share common originating features. It is likely that some regions of the genome are more susceptible to both somatic and meiotic DSBs, and the locations of meiotic hotspots may be an indicator of genomic regions more susceptible to DNA damage. (c) 2009 Wiley-Liss, Inc.

  12. Conditional genomic rearrangement by designed meiotic recombination using VDE (PI-SceI) in yeast.

    Science.gov (United States)

    Fukuda, Tomoyuki; Ohya, Yoshikazu; Ohta, Kunihiro

    2007-10-01

    Meiotic recombination plays critical roles in the acquisition of genetic diversity and has been utilized for conventional breeding of livestock and crops. The frequency of meiotic recombination is normally low, and is extremely low in regions called "recombination cold domains". Here, we describe a new and highly efficient method to modulate yeast meiotic gene rearrangements using VDE (PI-SceI), an intein-encoded endonuclease that causes an efficient unidirectional meiotic gene conversion at its recognition sequence (VRS). We designed universal targeting vectors, by use of which the strain that inserts the VRS at a desired site is acquired. Meiotic induction of the strains provided unidirectional gene conversions and frequent genetic rearrangements of flanking genes with little impact on cell viability. This system thus opens the way for the designed modulation of meiotic gene rearrangements, regardless of recombinational activity of chromosomal domains. Finally, the VDE-VRS system enabled us to conduct meiosis-specific conditional knockout of genes where VDE-initiated gene conversion disrupts the target gene during meiosis, serving as a novel approach to examine the functions of genes during germination of resultant spores.

  13. An evolutionarily conserved phosphatidate phosphatase maintains lipid droplet number and endoplasmic reticulum morphology but not nuclear morphology

    Directory of Open Access Journals (Sweden)

    Anoop Narayana Pillai

    2017-11-01

    Full Text Available Phosphatidic acid phosphatases are involved in the biosynthesis of phospholipids and triacylglycerol, and also act as transcriptional regulators. Studies to ascertain their role in lipid metabolism and membrane biogenesis are restricted to Opisthokonta and Archaeplastida. Here, we report the role of phosphatidate phosphatase (PAH in Tetrahymena thermophila, belonging to the Alveolata clade. We identified two PAH homologs in Tetrahymena, TtPAH1 and TtPAH2. Loss of function of TtPAH1 results in reduced lipid droplet number and an increase in endoplasmic reticulum (ER content. It also results in more ER sheet structure as compared to wild-type Tetrahymena. Surprisingly, we did not observe a visible defect in the nuclear morphology of the ΔTtpah1 mutant. TtPAH1 rescued all known defects in the yeast pah1Δ strain and is conserved functionally between Tetrahymena and yeast. The homologous gene derived from Trypanosoma also rescued the defects of the yeast pah1Δ strain. Our results indicate that PAH, previously known to be conserved among Opisthokonts, is also present in a set of distant lineages. Thus, a phosphatase cascade is evolutionarily conserved and is functionally interchangeable across eukaryotic lineages.

  14. Building up a QSAR model for toxicity toward Tetrahymena pyriformis by the Monte Carlo method: A case of benzene derivatives.

    Science.gov (United States)

    Toropova, Alla P; Schultz, Terry W; Toropov, Andrey A

    2016-03-01

    Data on toxicity toward Tetrahymena pyriformis is indicator of applicability of a substance in ecologic and pharmaceutical aspects. Quantitative structure-activity relationships (QSARs) between the molecular structure of benzene derivatives and toxicity toward T. pyriformis (expressed as the negative logarithms of the population growth inhibition dose, mmol/L) are established. The available data were randomly distributed three times into the visible training and calibration sets, and invisible validation sets. The statistical characteristics for the validation set are the following: r(2)=0.8179 and s=0.338 (first distribution); r(2)=0.8682 and s=0.341 (second distribution); r(2)=0.8435 and s=0.323 (third distribution). These models are built up using only information on the molecular structure: no data on physicochemical parameters, 3D features of the molecular structure and quantum mechanics descriptors are involved in the modeling process. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Selective Regulation of Oocyte Meiotic Events Enhances Progress in Fertility Preservation Methods

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    Onder Celik

    2015-01-01

    Full Text Available Following early embryonic germ cell migration, oocytes are surrounded by somatic cells and remain arrested at diplotene stage until luteinizing hormone (LH surge. Strict regulation of both meiotic arrest and meiotic resumption during dormant stage are critical for future fertility. Intercellular signaling system between the somatic compartment and oocyte regulates these meiotic events and determines the follicle quality. As well as the collected number of eggs, their qualities are also important for in vitro fertilization (IVF outcome. In spontaneous and IVF cycles, germinal vesicle (GV–stage oocytes, premature GV breakdown, and persistence of first meiotic arrest limit the reproductive performance. Likewise, both women with premature ovarian aging and young cancer women are undergoing chemoradiotherapy under the risk of follicle loss because of unregulated meiotic events. Understanding of oocyte meiotic events is therefore critical for the prevention of functional ovarian reserve. High levels of cyclic guanosine monophophate (cGMP, cyclic adenosine monophophate (cAMP and low phosphodiesterase (PDE 3A enzyme activity inside the oocyte are responsible for maintaining of meiotic arrest before the LH surge. cGMP is produced in the somatic compartment, and natriuretic peptide precursor C (Nppc and natriuretic peptide receptor 2 (Npr2 regulate its production. cGMP diffuses into the oocyte and reduces the PDE3A activity, which inhibits the conversion of cAMP to the 5′AMP, and cAMP levels are enhanced. In addition, oocyte itself has the ability to produce cAMP. Taken together, accumulation of cAMP inside the oocyte induces protein kinase activity, which leads to the inhibition of maturation-promoting factor and meiotic arrest also continues. By stimulating the expression of epidermal growth factor, LH inhibits the Nppc/Npr2 system, blocks cGMP synthesis, and initiates meiotic resumption. Oocytes lacking the functional of this pathway may lead to

  16. Nuclear Architecture of Mouse Spermatocytes: Chromosome Topology, Heterochromatin, and Nucleolus.

    Science.gov (United States)

    Berrios, Soledad

    2017-01-01

    The nuclear organization of spermatocytes in meiotic prophase I is primarily determined by the synaptic organization of the bivalents that are bound by their telomeres to the nuclear envelope and described as arc-shaped trajectories through the 3D nuclear space. However, over this basic meiotic organization, a spermatocyte nuclear architecture arises that is based on higher-ordered patterns of spatial associations among chromosomal domains from different bivalents that are conditioned by the individual characteristics of chromosomes and the opportunity for interactions between their domains. Consequently, the nuclear architecture is species-specific and prone to modification by chromosomal rearrangements. This model is valid for the localization of any chromosomal domain in the meiotic prophase nucleus. However, constitutive heterochromatin plays a leading role in shaping nuclear territories. Thus, the nuclear localization of nucleoli depends on the position of NORs in nucleolar bivalents, but the association among nucleolar chromosomes mainly depends on the presence of constitutive heterochromatin that does not affect the expression of the ribosomal genes. Constitutive heterochromatin and nucleoli form complex nuclear territories whose distribution in the nuclear space is nonrandom, supporting the hypothesis regarding the existence of a species-specific nuclear architecture in first meiotic prophase spermatocytes. © 2017 S. Karger AG, Basel.

  17. Induction of congenital malformations in the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages

    International Nuclear Information System (INIS)

    Kirk, K.M.; Lyon, M.F.

    1984-01-01

    The induction of congenital malformations among the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages has been studied in two experiments. Firstly, animals were exposed to varying doses of X-rays and mated at various time intervals, so as to sample spermatozoa, spermatids and spermatogonial stem cells. In the second experiment, only treated spermatogonial stem cells were sampled. One group of males was given a single dose, a second group a fractionated dose and a third group was left unexposed. In the first experiment, induced post-implantation dominant lethality increased with dose, and was highest in week 3, in line with the known greater radiosensitivity of the early spermatid stage. Preimplantation loss also increased with dose and was highest in week 3. There was no clear induction of either pre-implantation or post-implantation loss at spermatogonial stem cell stages. There was a clear induction of congenital malformations at post-meiotic stages. At the two highest doses the early spermatids (15-21 days) appeared more sensitive than spermatozoa, and at this stage the incidence of malformations increased with dose. Expt. 2 showed a statistically significant induction of malformations at both dose levels. The relative sensitivities of male stem cells, post-meiotic stages and mature oocytes to the induction of congenital malformations were reasonably similar to their sensitivities for specific-locus mutations, except that the expected enhancing effect of the fractionation regime used was not seen. (Auth.)

  18. Induction of congenital malformations in the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, K.M.; Lyon, M.F. (Medical Research Council, Harwell (UK). Radiobiological Research Unit)

    1984-01-01

    The induction of congenital malformations among the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages has been studied in two experiments. Firstly, animals were exposed to varying doses of X-rays and mated at various time intervals, so as to sample spermatozoa, spermatids and spermatogonial stem cells. In the second experiment, only treated spermatogonial stem cells were sampled. One group of males was given a single dose, a second group a fractionated dose and a third group was left unexposed. In the first experiment, induced post-implantation dominant lethality increased with dose, and was highest in week 3, in line with the known greater radiosensitivity of the early spermatid stage. Preimplantation loss also increased with dose and was highest in week 3. There was no clear induction of either pre-implantation or post-implantation loss at spermatogonial stem cell stages. There was a clear induction of congenital malformations at post-meiotic stages. At the two highest doses the early spermatids (15-21 days) appeared more sensitive than spermatozoa, and at this stage the incidence of malformations increased with dose. Expt. 2 showed a statistically significant induction of malformations at both dose levels. The relative sensitivities of male stem cells, post-meiotic stages and mature oocytes to the induction of congenital malformations were reasonably similar to their sensitivities for specific-locus mutations, except that the expected enhancing effect of the fractionation regime used was not seen.

  19. Preimplantation genetic diagnosis outcomes and meiotic segregation analysis of robertsonian translocation carriers.

    Science.gov (United States)

    Ko, Duck Sung; Cho, Jae Won; Lee, Hyoung-Song; Kim, Jin Yeong; Kang, Inn Soo; Yang, Kwang Moon; Lim, Chun Kyu

    2013-04-01

    To investigate the meiotic segregation patterns of cleavage-stage embryos from robertsonian translocation carriers and aneuploidy of chromosome 18 according to meiotic segregation patterns. Retrospective study. Infertility center and laboratory of reproductive biology and infertility. Sixty-two couples with robertsonian translocation carriers. One blastomere was biopsied from embryos and diagnosed with the use of fluorescence in situ hybridization (FISH). Translocation chromosomes were analyzed with the use of locus-specific and subtelomeric FISH probes. Aneuploidy of chromosome 18 was assessed simultaneously with translocation chromosomes. Preimplantation genetic diagnosis (PGD) outcomes, meiotic segregation patterns of robertsonian translocation, and aneuploidy of chromosome 18 depending on meiotic segregation patterns. Two hundred seventy embryos of 332 transferrable embryos were transferred in 113 cycles, and 27 healthy babies were born. The alternate segregation was significantly higher in male carriers than in female carriers (43.9% vs. 29.9%, respectively), and adjacent segregation was higher in female carriers than in male carriers (44.7% vs. 38.7%, respectively). Aneuploidy of chromosome 18 was significantly increased in 3:0-segregated or chaotic embryos. Forty-seven alternate embryos were excluded from embryo replacement owing to aneuploidy of chromosome 18. In carriers of robertsonian translocation, meiotic segregation showed differences between men and women. Frequent meiotic errors caused by premature predivision or nondisjunction and less stringent checkpoint in women might cause such differences between sexes. Aneuploidy of chromosome 18 might be influenced by meiotic segregation of translocation chromosomes. Factors that cause malsegregation, such as 3:0 or chaotic segregation, seem to play a role in aneuploidy of chromosome 18. Copyright © 2013 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  20. Effects of Pluronic F-68 on Tetrahymena cells: protection against chemical and physical stress and prolongation of survival under toxic conditions

    DEFF Research Database (Denmark)

    Hellung-Larsen, P; Assaad, F; Pankratova, Stanislava

    2000-01-01

    exposed to hyperthermia (43 degrees C). The cellular survival is increased at reduced temperatures (e.g. 4 degrees C instead of 36 degrees C) and at increased cellular concentrations (e.g. 100 cells ml(-1) instead of 25 or 10 cells ml(-1)). There is no effect of pre-incubation with Pluronic......The effects of the non-ionic surfactant Pluronic F-68 (0.01% w/v) on Tetrahymena cells have been studied. A marked protection against chemical and physical stress was observed. The chemical stress effects were studied in cells suspended in buffer (starvation) or in buffers with added ingredients....... The protective effect of Pluronic towards Tetrahymena is observed for concentrations in the range from 0.001 to 0.1% w/v....

  1. Meiotic consequences of induced chromosomal anomalies in Triticum aestivum L

    International Nuclear Information System (INIS)

    Larik, A.S.; Hafiz, H.M.I.; Ansari, N.N.

    1981-01-01

    Investigations on the mechanism of chromosome breakages, types of aberrations and their genetic consequences form an integral part of the most of the studies on radiation genetics (BROCK 1977; KONZAK et al. 1977; LARIK 1975; SEARS 1977; SHARMA & FORSBEGR 1977), covering a wide range of plants belonging to both wild and cultivated species. Mutations due to deficiency of genes with a dominant or epistatic effect occur in very high frequency (MAC KEY 1968) because the well buffered genomes of polyploids can tolerate losses of large chromosome segments and even of entire chromosomes (LARIK 1978a; LARIK & THOMAS 1979; LARIK et al. 1980a). Extensive investigations on the effect of physical and chemical mutagens on the cytological behaviour of wheat and other plants have already been reported (GAUL 1977). However, cytological studies on the M 2 and M 3 populations are very limited (LARIK et al. 1980a). An attempt has been made in the present work to extend these studies. This paper presents an analysis of meiotic anomalies in M 3 populations of bread wheat and discusses their significance with reference to genetics and plant breeding

  2. Recombination Proteins Mediate Meiotic Spatial Chromosome Organization and Pairing

    Science.gov (United States)

    Storlazzi, Aurora; Gargano, Silvana; Ruprich-Robert, Gwenael; Falque, Matthieu; David, Michelle; Kleckner, Nancy; Zickler, Denise

    2010-01-01

    SUMMARY Meiotic chromosome pairing involves not only recognition of homology but also juxtaposition of entire chromosomes in a topologically regular way. Analysis of filamentous fungus Sordaria macrospora reveals that recombination proteins Mer3, Msh4 and Mlh1 play direct roles in all of these aspects, in advance of their known roles in recombination. Absence of Mer3 helicase results in interwoven chromosomes, thereby revealing the existence of features that specifically ensure “entanglement avoidance”. Entanglements that remain at zygotene, i.e. “interlockings”, require Mlh1 for resolution, likely to eliminate constraining recombinational connections. Patterns of Mer3 and Msh4 foci along aligned chromosomes show that the double-strand breaks mediating homologous alignment have spatially separated ends, one localized to each partner axis, and that pairing involves interference among developing interhomolog interactions. We propose that Mer3, Msh4 and Mlh1 execute all of these roles during pairing by modulating the state of nascent double-strand break/partner DNA contacts within axis-associated recombination complexes. PMID:20371348

  3. On the origin of sex chromosomes from meiotic drive

    Science.gov (United States)

    Úbeda, Francisco; Patten, Manus M.; Wild, Geoff

    2015-01-01

    Most animals and many plants make use of specialized chromosomes (sex chromosomes) to determine an individual's sex. Best known are the XY and ZW sex-determination systems. Despite having evolved numerous times, sex chromosomes present something of an evolutionary puzzle. At their origin, alleles that dictate development as one sex or the other (primitive sex chromosomes) face a selective penalty, as they will be found more often in the more abundant sex. How is it possible that primitive sex chromosomes overcome this disadvantage? Any theory for the origin of sex chromosomes must identify the benefit that outweighs this cost and enables a sex-determining mutation to establish in the population. Here we show that a new sex-determining allele succeeds when linked to a sex-specific meiotic driver. The new sex-determining allele benefits from confining the driving allele to the sex in which it gains the benefit of drive. Our model requires few special assumptions and is sufficiently general to apply to the evolution of sex chromosomes in outbreeding cosexual or dioecious species. We highlight predictions of the model that can discriminate between this and previous theories of sex-chromosome origins. PMID:25392470

  4. Meiotic Chromosome Analysis of the Giant Water Bug, Lethocerus indicus

    Science.gov (United States)

    Wisoram, Wijit; Saengthong, Pradit; Ngernsiri, Lertluk

    2013-01-01

    The giant water bug, Lethocerus indicus (Lepeletier and Serville) (Heteroptera: Belostomatidae), a native species of Southeast Asia, is one of the largest insects belonging to suborder Heteroptera. In this study, the meiotic chromosome of L. indicus was studied in insect samples collected from Thailand, Myanmar, Loas, and Cambodia. Testicular cells stained with lacto-acetic orcein, Giemsa, DAPI, and silver nitrate were analyzed. The results revealed that the chromosome complement of L. indicus was 2n = 22A + neo-XY + 2m, which differed from that of previous reports. Each individual male contained testicular cells with three univalent patterns. The frequency of cells containing neo-XY chromosome univalent (∼5%) was a bit higher than that of cells with autosomal univalents (∼3%). Some cells (∼0.5%) had both sex chromosome univalents and a pair of autosomal univalents. None of the m-chromosome univalents were observed during prophase I. In addition, this report presents clear evidence about the existence of m-chromosomes in Belostomatidae. PMID:23895100

  5. A serological study of removal of UV-induced photoproducts in the DNA of tetrahymena pyriformis GL: influence of caffeine, quinacrine and chloroquine

    International Nuclear Information System (INIS)

    Lakhanisky, Th.; Hendrickx, B.; Mouton, R.F.; Cornelis, J.J.

    1979-01-01

    Antisera that recognise specifically UV-photoproducts in DNA have been used to follow the elimination of photolesions in UV irradiated Tetrahymena pyriformis. The amount of bound tritium-labelled antibodies to nuclei has been estimated by autoradiography. Curves of dose-response of DNA photo-products, their elimination by dark repair, and effect of caffeine, quinacrine, and chloroquine on the disappearance of UV-lesions have been evaluated. (author)

  6. 1+1 = 3: a fusion of 2 enzymes in the methionine salvage pathway of Tetrahymena thermophila creates a trifunctional enzyme that catalyzes 3 steps in the pathway.

    Directory of Open Access Journals (Sweden)

    Hannah M W Salim

    2009-10-01

    Full Text Available The methionine salvage pathway is responsible for regenerating methionine from its derivative, methylthioadenosine. The complete set of enzymes of the methionine pathway has been previously described in bacteria. Despite its importance, the pathway has only been fully described in one eukaryotic organism, yeast. Here we use a computational approach to identify the enzymes of the methionine salvage pathway in another eukaryote, Tetrahymena thermophila. In this organism, the pathway has two fused genes, MTNAK and MTNBD. Each of these fusions involves two different genes whose products catalyze two different single steps of the pathway in other organisms. One of the fusion proteins, mtnBD, is formed by enzymes that catalyze non-consecutive steps in the pathway, mtnB and mtnD. Interestingly the gene that codes for the intervening enzyme in the pathway, mtnC, is missing from the genome of Tetrahymena. We used complementation tests in yeast to show that the fusion of mtnB and mtnD from Tetrahymena is able to do in one step what yeast does in three, since it can rescue yeast knockouts of mtnB, mtnC, or mtnD. Fusion genes have proved to be very useful in aiding phylogenetic reconstructions and in the functional characterization of genes. Our results highlight another characteristic of fusion proteins, namely that these proteins can serve as biochemical shortcuts, allowing organisms to completely bypass steps in biochemical pathways.

  7. The fission yeast RNA binding protein Mmi1 regulates meiotic genes by controlling intron specific splicing and polyadenylation coupled RNA turnover.

    Directory of Open Access Journals (Sweden)

    Huei-Mei Chen

    Full Text Available The polyA tails of mRNAs are monitored by the exosome as a quality control mechanism. We find that fission yeast, Schizosaccharomyces pombe, adopts this RNA quality control mechanism to regulate a group of 30 or more meiotic genes at the level of both splicing and RNA turnover. In vegetative cells the RNA binding protein Mmi1 binds to the primary transcripts of these genes. We find the novel motif U(U/C/GAAAC highly over-represented in targets of Mmi1. Mmi1 can specifically regulate the splicing of particular introns in a transcript: it inhibits the splicing of introns that are in the vicinity of putative Mmi1 binding sites, while allowing the splicing of other introns that are far from such sites. In addition, binding of Mmi1, particularly near the 3' end, alters 3' processing to promote extremely long polyA tails of up to a kilobase. The hyperadenylated transcripts are then targeted for degradation by the nuclear exonuclease Rrp6. The nuclear polyA binding protein Pab2 assists this hyperadenylation-mediated RNA decay. Rrp6 also targets other hyperadenylated transcripts, which become hyperadenylated in an unknown, but Mmi1-independent way. Thus, hyperadenylation may be a general signal for RNA degradation. In addition, binding of Mmi1 can affect the efficiency of 3' cleavage. Inactivation of Mmi1 in meiosis allows meiotic expression, through splicing and RNA stabilization, of at least 29 target genes, which are apparently constitutively transcribed.

  8. Utilization during mitotic cell division of loci controlling meiotic recombination and disjunction in Drosophila melanogaster

    International Nuclear Information System (INIS)

    Baker, B.S.; Carpenter, A.T.C.; Ripoll, P.

    1978-01-01

    To inquire whether the loci identified by recombination-defective and disjunction-defective meiotic mutants in Drosophila are also utilized during mitotic cell division, the effects of 18 meiotic mutants (representing 13 loci) on mitotic chromosome stability have been examined genetically. To do this, meiotic-mutant-bearing flies heterozygous for recessive somatic cell markers were examined for the frequencies and types of spontaneous clones expressing the cell markers. In such flies, marked clones can arise via mitotic recombination, mutation, chromosome breakage, nondisjunction or chromosome loss, and clones from these different origins can be distinguished. In addition, meiotic mutants at nine loci have been examined for their effects on sensitivity to killing by uv and x rays. Mutants at six of the seven recombination-defective loci examined (mei-9, mei-41, c(3)G, mei-W68, mei-S282, mei-352, mei-218) cause mitotic chromosome instability in both sexes, whereas mutants at one locus (mei-218) do not affect mitotic chromosome stability. Thus many of the loci utilized during meiotic recombination also function in the chromosomal economy of mitotic cells

  9. MEIOB targets single-strand DNA and is necessary for meiotic recombination.

    Directory of Open Access Journals (Sweden)

    Benoit Souquet

    Full Text Available Meiotic recombination is a mandatory process for sexual reproduction. We identified a protein specifically implicated in meiotic homologous recombination that we named: meiosis specific with OB domain (MEIOB. This protein is conserved among metazoan species and contains single-strand DNA binding sites similar to those of RPA1. Our studies in vitro revealed that both recombinant and endogenous MEIOB can be retained on single-strand DNA. Those in vivo demonstrated the specific expression of Meiob in early meiotic germ cells and the co-localization of MEIOB protein with RPA on chromosome axes. MEIOB localization in Dmc1 (-/- spermatocytes indicated that it accumulates on resected DNA. Homologous Meiob deletion in mice caused infertility in both sexes, due to a meiotic arrest at a zygotene/pachytene-like stage. DNA double strand break repair and homologous chromosome synapsis were impaired in Meiob (-/- meiocytes. Interestingly MEIOB appeared to be dispensable for the initial loading of recombinases but was required to maintain a proper number of RAD51 and DMC1 foci beyond the zygotene stage. In light of these findings, we propose that RPA and this new single-strand DNA binding protein MEIOB, are essential to ensure the proper stabilization of recombinases which is required for successful homology search and meiotic recombination.

  10. Error-prone meiotic division and subfertility in mice with oocyte-conditional knockdown of pericentrin.

    Science.gov (United States)

    Baumann, Claudia; Wang, Xiaotian; Yang, Luhan; Viveiros, Maria M

    2017-04-01

    Mouse oocytes lack canonical centrosomes and instead contain unique acentriolar microtubule-organizing centers (aMTOCs). To test the function of these distinct aMTOCs in meiotic spindle formation, pericentrin (Pcnt), an essential centrosome/MTOC protein, was knocked down exclusively in oocytes by using a transgenic RNAi approach. Here, we provide evidence that disruption of aMTOC function in oocytes promotes spindle instability and severe meiotic errors that lead to pronounced female subfertility. Pcnt-depleted oocytes from transgenic (Tg) mice were ovulated at the metaphase-II stage, but show significant chromosome misalignment, aneuploidy and premature sister chromatid separation. These defects were associated with loss of key Pcnt-interacting proteins (γ-tubulin, Nedd1 and Cep215) from meiotic spindle poles, altered spindle structure and chromosome-microtubule attachment errors. Live-cell imaging revealed disruptions in the dynamics of spindle assembly and organization, together with chromosome attachment and congression defects. Notably, spindle formation was dependent on Ran GTPase activity in Pcnt-deficient oocytes. Our findings establish that meiotic division is highly error-prone in the absence of Pcnt and disrupted aMTOCs, similar to what reportedly occurs in human oocytes. Moreover, these data underscore crucial differences between MTOC-dependent and -independent meiotic spindle assembly. © 2017. Published by The Company of Biologists Ltd.

  11. Correlation of Meiotic DSB Formation and Transcription Initiation Around Fission Yeast Recombination Hotspots.

    Science.gov (United States)

    Yamada, Shintaro; Okamura, Mika; Oda, Arisa; Murakami, Hiroshi; Ohta, Kunihiro; Yamada, Takatomi

    2017-06-01

    Meiotic homologous recombination, a critical event for ensuring faithful chromosome segregation and creating genetic diversity, is initiated by programmed DNA double-strand breaks (DSBs) formed at recombination hotspots. Meiotic DSB formation is likely to be influenced by other DNA-templated processes including transcription, but how DSB formation and transcription interact with each other has not been understood well. In this study, we used fission yeast to investigate a possible interplay of these two events. A group of hotspots in fission yeast are associated with sequences similar to the cyclic AMP response element and activated by the ATF/CREB family transcription factor dimer Atf1-Pcr1. We first focused on one of those hotspots, ade6-3049 , and Atf1. Our results showed that multiple transcripts, shorter than the ade6 full-length messenger RNA, emanate from a region surrounding the ade6-3049 hotspot. Interestingly, we found that the previously known recombination-activation region of Atf1 is also a transactivation domain, whose deletion affected DSB formation and short transcript production at ade6-3049 These results point to a possibility that the two events may be related to each other at ade6-3049 In fact, comparison of published maps of meiotic transcripts and hotspots suggested that hotspots are very often located close to meiotically transcribed regions. These observations therefore propose that meiotic DSB formation in fission yeast may be connected to transcription of surrounding regions. Copyright © 2017 by the Genetics Society of America.

  12. Meiotic events in Oenothera - a non-standard pattern of chromosome behaviour.

    Science.gov (United States)

    Golczyk, Hieronim; Musiał, Krystyna; Rauwolf, Uwe; Meurer, Jörg; Herrmann, Reinhold G; Greiner, Stephan

    2008-11-01

    The genus Oenothera shows an intriguing extent of permanent translocation heterozygosity. Reciprocal translocations of chromosome arms in species or populations result in various kinds of chromosome multivalents in diakinesis. Early meiotic events conditioning such chromosome behaviour are poorly understood. We found a surprising uniformity of the leptotene-diplotene period, regardless of the chromosome configuration at diakinesis (ring of 14, 7 bivalents, mixture of bivalents and multivalents). It appears that the earliest chromosome interactions at Oenothera meiosis are untypical, since they involve pericentromeric regions. During early leptotene, proximal chromosome parts cluster and form a highly polarized Rabl configuration. Telomeres associated in pairs were seen at zygotene. The high degree of polarization of meiotic nuclei continues for an exceptionally long period, i.e., during zygotene-pachytene into the diplotene contraction stage. The Rabl-polarized meiotic architecture and clustering of pericentromeres suggest a high complexity of karyotypes, not only in structural heterozygotes but also in bivalent-forming homozygous species.

  13. A meiotic linkage map of the silver fox, aligned and compared to the canine genome.

    Science.gov (United States)

    Kukekova, Anna V; Trut, Lyudmila N; Oskina, Irina N; Johnson, Jennifer L; Temnykh, Svetlana V; Kharlamova, Anastasiya V; Shepeleva, Darya V; Gulievich, Rimma G; Shikhevich, Svetlana G; Graphodatsky, Alexander S; Aguirre, Gustavo D; Acland, Gregory M

    2007-03-01

    A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogenetic homologies between the dog and fox, and by the availability of high resolution canine genome maps and sequence data. Furthermore, the high genomic sequence identity between dog and fox allows adaptation of canine microsatellites for genotyping and meiotic mapping in foxes. Using 320 such markers, we have constructed the first meiotic linkage map of the fox genome. The resulting sex-averaged map covers 16 fox autosomes and the X chromosome with an average inter-marker distance of 7.5 cM. The total map length corresponds to 1480.2 cM. From comparison of sex-averaged meiotic linkage maps of the fox and dog genomes, suppression of recombination in pericentromeric regions of the metacentric fox chromosomes was apparent, relative to the corresponding segments of acrocentric dog chromosomes. Alignment of the fox meiotic map against the 7.6x canine genome sequence revealed high conservation of marker order between homologous regions of the two species. The fox meiotic map provides a critical tool for genetic studies in foxes and identification of genetic loci and genes implicated in fox domestication.

  14. In silico prediction of Tetrahymena pyriformis toxicity for diverse industrial chemicals with substructure pattern recognition and machine learning methods.

    Science.gov (United States)

    Cheng, Feixiong; Shen, Jie; Yu, Yue; Li, Weihua; Liu, Guixia; Lee, Philip W; Tang, Yun

    2011-03-01

    There is an increasing need for the rapid safety assessment of chemicals by both industries and regulatory agencies throughout the world. In silico techniques are practical alternatives in the environmental hazard assessment. It is especially true to address the persistence, bioaccumulative and toxicity potentials of organic chemicals. Tetrahymena pyriformis toxicity is often used as a toxic endpoint. In this study, 1571 diverse unique chemicals were collected from the literature and composed of the largest diverse data set for T. pyriformis toxicity. Classification predictive models of T. pyriformis toxicity were developed by substructure pattern recognition and different machine learning methods, including support vector machine (SVM), C4.5 decision tree, k-nearest neighbors and random forest. The results of a 5-fold cross-validation showed that the SVM method performed better than other algorithms. The overall predictive accuracies of the SVM classification model with radial basis functions kernel was 92.2% for the 5-fold cross-validation and 92.6% for the external validation set, respectively. Furthermore, several representative substructure patterns for characterizing T. pyriformis toxicity were also identified via the information gain analysis methods. Copyright © 2010 Elsevier Ltd. All rights reserved.

  15. Heteroagglomeration of zinc oxide nanoparticles with clay mineral modulates the bioavailability and toxicity of nanoparticle in Tetrahymena pyriformis.

    Science.gov (United States)

    Gupta, Govind Sharan; Senapati, Violet Aileen; Dhawan, Alok; Shanker, Rishi

    2017-06-01

    The extensive use of zinc oxide nanoparticles (ZnO NPs) in cosmetics, sunscreens and healthcare products increases their release in the aquatic environment. The present study explored the possible interaction of ZnO NPs with montmorillonite clay minerals in aqueous conditions. An addition of ZnO NPs on clay suspension significantly (pclay particles from 1652±90nm to 2158±13nm due to heteroagglomeration. The electrokinetic measurements showed a significant (pclay association (-1.37±0.03μmcm/Vs) that results to the electrostatic interaction between ZnO NPs and clay particles. The attenuated total reflectance Fourier transform infrared spectroscopy analysis of ZnO NPs-clay association demonstrated the binding of ZnO NPs with the Si-O-Al region on the edges of clay particles. The increase in size of ZnO NPs-clay heteroagglomerates further leads to their sedimentation at 24h. Although, the stability of ZnO NPs in the clay suspension was decreased due to heteroagglomeration, but the bioavailability and toxicity of ZnO NPs-clay heteroagglomerates in Tetrahymena pyriformis was enhanced. These observations provide an evidence on possible mechanisms available in natural environment that can facilitate nanoparticles entry into the organisms present in lower trophic levels of the food web. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Dissecting relative contributions of cis- and trans-determinants to nucleosome distribution by comparing Tetrahymena macronuclear and micronuclear chromatin.

    Science.gov (United States)

    Xiong, Jie; Gao, Shan; Dui, Wen; Yang, Wentao; Chen, Xiao; Taverna, Sean D; Pearlman, Ronald E; Ashlock, Wendy; Miao, Wei; Liu, Yifan

    2016-12-01

    The ciliate protozoan Tetrahymena thermophila contains two types of structurally and functionally differentiated nuclei: the transcriptionally active somatic macronucleus (MAC) and the transcriptionally silent germ-line micronucleus (MIC). Here, we demonstrate that MAC features well-positioned nucleosomes downstream of transcription start sites and flanking splice sites. Transcription-associated trans-determinants promote nucleosome positioning in MAC. By contrast, nucleosomes in MIC are dramatically delocalized. Nucleosome occupancy in MAC and MIC are nonetheless highly correlated with each other, as well as with in vitro reconstitution and predictions based upon DNA sequence features, revealing unexpectedly strong contributions from cis-determinants. In particular, well-positioned nucleosomes are often matched with GC content oscillations. As many nucleosomes are coordinately accommodated by both cis- and trans-determinants, we propose that their distribution is shaped by the impact of these nucleosomes on the mutational and transcriptional landscape, and driven by evolutionary selection. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  17. Calcium signaling in closely related protozoan groups (Alveolata): non-parasitic ciliates (Paramecium, Tetrahymena) vs. parasitic Apicomplexa (Plasmodium, Toxoplasma).

    Science.gov (United States)

    Plattner, H; Sehring, I M; Mohamed, I K; Miranda, K; De Souza, W; Billington, R; Genazzani, A; Ladenburger, E-M

    2012-05-01

    The importance of Ca2+-signaling for many subcellular processes is well established in higher eukaryotes, whereas information about protozoa is restricted. Recent genome analyses have stimulated such work also with Alveolates, such as ciliates (Paramecium, Tetrahymena) and their pathogenic close relatives, the Apicomplexa (Plasmodium, Toxoplasma). Here we compare Ca2+ signaling in the two closely related groups. Acidic Ca2+ stores have been characterized in detail in Apicomplexa, but hardly in ciliates. Two-pore channels engaged in Ca2+-release from acidic stores in higher eukaryotes have not been stingently characterized in either group. Both groups are endowed with plasma membrane- and endoplasmic reticulum-type Ca2+-ATPases (PMCA, SERCA), respectively. Only recently was it possible to identify in Paramecium a number of homologs of ryanodine and inositol 1,3,4-trisphosphate receptors (RyR, IP3R) and to localize them to widely different organelles participating in vesicle trafficking. For Apicomplexa, physiological experiments suggest the presence of related channels although their identity remains elusive. In Paramecium, IP3Rs are constitutively active in the contractile vacuole complex; RyR-related channels in alveolar sacs are activated during exocytosis stimulation, whereas in the parasites the homologous structure (inner membrane complex) may no longer function as a Ca2+ store. Scrutinized comparison of the two closely related protozoan phyla may stimulate further work and elucidate adaptation to parasitic life. See also "Conclusions" section. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. QSTR with extended topochemical atom (ETA) indices. 14. QSAR modeling of toxicity of aromatic aldehydes to Tetrahymena pyriformis

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Kunal, E-mail: kunalroy_in@yahoo.com [Drug Theoretics and Cheminformatics Laboratory, Division of Medicinal and Pharmaceutical Chemistry, Department of Pharmaceutical Technology, Jadavpur University, Kolkata 700 032 (India); Das, Rudra Narayan [Drug Theoretics and Cheminformatics Laboratory, Division of Medicinal and Pharmaceutical Chemistry, Department of Pharmaceutical Technology, Jadavpur University, Kolkata 700 032 (India)

    2010-11-15

    Aldehydes are a toxic class of chemicals causing severe health hazards. In this background, quantitative structure-toxicity relationship (QSTR) models have been developed in the present study using Extended Topochemical Atom (ETA) indices for a large group of 77 aromatic aldehydes for their acute toxicity against the protozoan ciliate Tetrahymena pyriformis. The ETA models have been compared with those developed using various non-ETA topological indices. Attempt was also made to include the n-octanol/water partition coefficient (log K{sub o/w}) as an additional descriptor considering the importance of hydrophobicity in toxicity prediction. Thirty different models were developed using different chemometric tools. All the models have been validated using internal validation and external validation techniques. The statistical quality of the ETA models was found to be comparable to that of the non-ETA models. The ETA models have shown the important effects of steric bulk, lipophilicity, presence of electronegative atom containing substituents and functionality of the aldehydic oxygen to the toxicity of the aldehydes. The best ETA model (without using log K{sub o/w}) shows encouraging statistical quality (Q{sub int}{sup 2}=0.709,Q{sub ext}{sup 2}=0.744). It is interesting to note that some of the topological models reported here are better in statistical quality than previously reported models using quantum chemical descriptors.

  19. Genomic organization and developmental fate of adjacent repeated sequences in a foldback DNA clone of Tetrahymena thermophila

    International Nuclear Information System (INIS)

    Tschunko, A.H.; Loechel, R.H.; McLaren, N.C.; Allen, S.L.

    1987-01-01

    DNA sequence elimination and rearrangement occurs during the development of somatic cell lineages of eukaryotes and was first discovered over a century ago. However, the significance and mechanism of chromatin elimination are not understood. DNA elimination also occurs during the development of the somatic macronucleus from the germinal micronucleus in unicellular ciliated protozoa such as Tetrahymena thermophila. In this study foldback DNA from the micronucleus was used as a probe to isolate ten clones. All of those tested (4/4) contained sequences that were repetitive in the micronucleus and rearranged in the macronucleus. Inverted repeated sequences were present in one clone. This clone, pTtFBl, was subjected to a detailed analysis of its developmental fate. Subregions were subcloned and used as probes against Southern blots of micronuclear and macronuclear DNA. DNA was labeled with [ 33 P]-labeled dATP. The authors found that all subregions defined repeated sequence families in the micronuclear genome. A minimum of four different families was defined, two of which are retained in the macronucleus and two of which are completely eliminated. The inverted repeat family is retained with little rearrangement. Two of the families, defined by subregions that do not contain parts of the inverted repeat are totally eliminated during macronuclear development-and contain open reading frames. The significance of retained inverted repeats to the process of elimination is discussed

  20. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    fe

    2011-11-16

    Nov 16, 2011 ... Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum,. Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable ...

  1. Insulin alone can lead to a withdrawal of meiotic arrest in the carp

    Indian Academy of Sciences (India)

    Meiotic arrest of oocyte in an Indian carp, Labeo rohita Ham. has been found for the first time to be withdrawn by insulin only. Addition of insulin to oocytes in vitro caused germinal vesicle breakdown (GVBD), one of the first visual markers to determine initiation of the final maturational process. Under the influence of insulin ...

  2. Segregation distortion in chicken and the evolutionary consequences of female meiotic drive in birds

    DEFF Research Database (Denmark)

    Axelsson, Erik Gunnar; Albrechtsen, Anders; Van, A. P.

    2010-01-01

    As all four meiotic products give rise to sperm in males, female meiosis result in a single egg in most eukaryotes. Any genetic element with the potential to influence chromosome segregation, so that it is preferentially included in the egg, should therefore gain a transmission advantage; a process...

  3. Meiotic recombination breakpoints are associated with open chromatin and enriched with Stowaway transposons in potato

    Science.gov (United States)

    Meiotic recombination is the foundation for genetic variation in natural and artificial populations of eukaryotes. Although genetic recombination maps have been developed in numerous plant species since late the 1980s, very few of these maps have provided the necessary resolution needed to investiga...

  4. SOLO: a meiotic protein required for centromere cohesion, coorientation, and SMC1 localization in Drosophila melanogaster.

    Science.gov (United States)

    Yan, Rihui; Thomas, Sharon E; Tsai, Jui-He; Yamada, Yukihiro; McKee, Bruce D

    2010-02-08

    Sister chromatid cohesion is essential to maintain stable connections between homologues and sister chromatids during meiosis and to establish correct centromere orientation patterns on the meiosis I and II spindles. However, the meiotic cohesion apparatus in Drosophila melanogaster remains largely uncharacterized. We describe a novel protein, sisters on the loose (SOLO), which is essential for meiotic cohesion in Drosophila. In solo mutants, sister centromeres separate before prometaphase I, disrupting meiosis I centromere orientation and causing nondisjunction of both homologous and sister chromatids. Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages. SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin. The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

  5. Nested Inversion Polymorphisms Predispose Chromosome 22q11.2 to Meiotic Rearrangements

    NARCIS (Netherlands)

    Demaerel, Wolfram; Hestand, Matthew S.; Vergaelen, Elfi; Swillen, Ann; López-Sánchez, Marcos; Pérez-Jurado, Luis A.; McDonald-Mcginn, Donna M.; Zackai, Elaine; Emanuel, Beverly S.; Morrow, Bernice E.; Breckpot, Jeroen; Devriendt, Koenraad; Vermeesch, Joris R.; Antshel, Kevin M.; Arango, Celso; Armando, Marco; Bassett, Anne S.; Bearden, Carrie E.; Boot, Erik; Bravo-Sanchez, Marta; Breetvelt, Elemi; Busa, Tiffany; Butcher, Nancy J.; Campbell, Linda E.; Carmel, Miri; Chow, Eva W C; Crowley, T. Blaine; Cubells, Joseph; Cutler, David; Demaerel, Wolfram; Digilio, Maria Cristina; Duijff, Sasja; Eliez, Stephan; Emanuel, Beverly S.; Epstein, Michael P.; Evers, Rens; Fernandez Garcia-Moya, Luis; Fiksinski, Ania; Fraguas, David; Fremont, Wanda; Fritsch, Rosemarie; Garcia-Minaur, Sixto; Golden, Aaron; Gothelf, Doron; Guo, Tingwei; Gur, Ruben C.; Gur, Raquel E.; Heine-Suner, Damian; Hestand, Matthew; Hooper, Stephen R.; Kates, Wendy R.; Kushan, Leila; Laorden-Nieto, Alejandra; Maeder, Johanna; Marino, Bruno; Marshall, Christian R.; McCabe, Kathryn; McDonald-Mcginn, Donna M.; Michaelovosky, Elena; Morrow, Bernice E.; Moss, Edward; Mulle, Jennifer; Murphy, Declan; Murphy, Kieran C.; Murphy, Clodagh M.; Niarchou, Maria; Ornstein, Claudia; Owen, Michael J; Philip, Nicole; Repetto, Gabriela M.; Schneider, Maude; Shashi, Vandana; Simon, Tony J.; Swillen, Ann; Tassone, Flora; Unolt, Marta; Van Amelsvoort, Therese; van den Bree, Marianne B M; Van Duin, Esther; Vergaelen, Elfi; Vermeesch, Joris R.; Vicari, Stefano; Vingerhoets, Claudia; Vorstman, Jacob; Warren, Steve; Weinberger, Ronnie; Weisman, Omri; Weizman, Abraham; Zackai, Elaine; Zhang, Zhengdong; Zwick, Michael

    2017-01-01

    Inversion polymorphisms between low-copy repeats (LCRs) might predispose chromosomes to meiotic non-allelic homologous recombination (NAHR) events and thus lead to genomic disorders. However, for the 22q11.2 deletion syndrome (22q11.2DS), the most common genomic disorder, no such inversions have

  6. Meiotic anomalies induced by X-rays in Capsicum annuum L

    Energy Technology Data Exchange (ETDEWEB)

    Subhash, K; Nizam, J [Department of Botany, Kakatiya University, Vidyaranyapuri, Warangal (A.P.) (India)

    1977-01-01

    Various types of meiotic anomalies in the M/sub 1/ generation such as multivalents, fragments, bridges, micronuclei, polyads and in particular multispindle formation, were observed after seed X-ray irradiation in Capsicum annuum L. With increasing dose the number of aberrations gradually increased.

  7. A meiotic study of two translocations and a tertiary trisomic in the mouse (Mus musculus)

    NARCIS (Netherlands)

    Boer, de P.

    1975-01-01

    In this section, the order of the articles has not been closely followed. Each point ends with the number(s) of the article(s) (as given in the contents), where the conclusion is based on.

    1) Cytological meiotic studies of T(2;8)26H and T(1;13)70H heterozygotes and Ts(1

  8. Expression analysis of genes implicated in meiotic resumption in vivo and developmental competence

    NARCIS (Netherlands)

    Algriany, O.A.

    2007-01-01

    This thesis investigated the gene expression in bovine oocytes during meiotic resumption, at 6 h post LH surge, coinciding with germinal vesicle breakdown, which was supposed to give a picture of the major cell cycle regulation changes, cytoskeleton rearrangement and chromosome alignment.

  9. Scrambling Eggs: Meiotic Drive and the Evolution of Female Recombination Rates

    Science.gov (United States)

    Brandvain, Yaniv; Coop, Graham

    2012-01-01

    Theories to explain the prevalence of sex and recombination have long been a central theme of evolutionary biology. Yet despite decades of attention dedicated to the evolution of sex and recombination, the widespread pattern of sex differences in the recombination rate is not well understood and has received relatively little theoretical attention. Here, we argue that female meiotic drivers—alleles that increase in frequency by exploiting the asymmetric cell division of oogenesis—present a potent selective pressure favoring the modification of the female recombination rate. Because recombination plays a central role in shaping patterns of variation within and among dyads, modifiers of the female recombination rate can function as potent suppressors or enhancers of female meiotic drive. We show that when female recombination modifiers are unlinked to female drivers, recombination modifiers that suppress harmful female drive can spread. By contrast, a recombination modifier tightly linked to a driver can increase in frequency by enhancing female drive. Our results predict that rapidly evolving female recombination rates, particularly around centromeres, should be a common outcome of meiotic drive. We discuss how selection to modify the efficacy of meiotic drive may contribute to commonly observed patterns of sex differences in recombination. PMID:22143919

  10. Meiotic homoeologous recombination-based alien gene introgression in the genomics era of wheat

    Science.gov (United States)

    Wheat (Triticum spp.) has a narrow genetic basis due to its allopolyploid origin. However, wheat has numerous wild relatives usable for expanding genetic variability of its genome through meiotic homoeologous recombination. Traditionally, laborious cytological analyses have been employed to detect h...

  11. Meiotic anomalies induced by X-rays in Capsicum annuum L

    International Nuclear Information System (INIS)

    Subhash, K.; Nizam, J.

    1977-01-01

    Various types of meiotic anomalies in the M 1 generation such as multivalents, fragments, bridges, micronuclei, polyads and in particular multispindle formation, were observed after seed X-ray irradiation in Capsicum annuum L. With increasing dose the number of aberrations gradually increased. (author)

  12. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    Czech Academy of Sciences Publication Activity Database

    Fučíková, K.; Pažoutová, Marie; Rindi, F.

    2015-01-01

    Roč. 51, č. 3 (2015), s. 419-430 ISSN 0022-3646 Institutional support: RVO:60077344 Keywords : algal genomes * Chlorophyta * green algae * meiotic genes * sexual reproduction * Trebouxiophyceae Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.536, year: 2015

  13. Functional Roles of Acetylated Histone Marks at Mouse Meiotic Recombination Hot Spots

    Science.gov (United States)

    Wu, Zhen; Fallahi, Mohammad; Ouizem, Souad; Liu, Qin; Li, Weimin; Costi, Roberta; Roush, William R.; Bois, Philippe R. J.

    2016-01-01

    ABSTRACT Meiotic recombination initiates following the formation of DNA double-strand breaks (DSBs) by the Spo11 endonuclease early in prophase I, at discrete regions in the genome coined “hot spots.” In mammals, meiotic DSB site selection is directed in part by sequence-specific binding of PRDM9, a polymorphic histone H3 (H3K4Me3) methyltransferase. However, other chromatin features needed for meiotic hot spot specification are largely unknown. Here we show that the recombinogenic cores of active hot spots in mice harbor several histone H3 and H4 acetylation and methylation marks that are typical of open, active chromatin. Further, deposition of these open chromatin-associated histone marks is dynamic and is manifest at spermatogonia and/or pre-leptotene-stage cells, which facilitates PRDM9 binding and access for Spo11 to direct the formation of DSBs, which are initiated at the leptotene stage. Importantly, manipulating histone acetylase and deacetylase activities established that histone acetylation marks are necessary for both hot spot activity and crossover resolution. We conclude that there are functional roles for histone acetylation marks at mammalian meiotic recombination hot spots. PMID:27821479

  14. Meiotic chromosome behaviours in M1 generation of bread wheat irradiated by gamma-rays

    International Nuclear Information System (INIS)

    Watanabe, Y.; Takato, S.

    1982-01-01

    Growing plants of bread wheat (Triticum aestivum L. 2 n=6x=42, AABBDD) were subjected to acute or chronic irradiation by gamma-rays from 60Co and meiotic chromosome behaviours of PMCS in M 1 generation were cytologically compared. Both acute and chronic irradiations produced different types of chromosomal aberrations at the meiotic stages. Among them, translocation type was the most frequent, followed by univalent type. A mixed type, i. e. translocation accompanying one or more univalents was often detected. Even normal type which lacked translocation and univalent included laggards and briclges without exception. Other meiotic abnormalities such as deletion, iso-chromosome and micronuclei were observed frequently in both treatments. Dose dependency of translocation frequency was not recognized in this experiment. In chronic irradiation, different chromosome numbers and meiotic behaviours were found not only among florets of a spike but also among anthers of a floret. A number of plants with aneuploid-like grass types occurred at a high frequency in M 1 , especially with low exposure

  15. Meiotic behaviour and spermatogenesis in male mice heterozygous for translocation types also occurring in man

    NARCIS (Netherlands)

    Nijhoff, J.H.

    1981-01-01

    In this thesis a start was made with meiotic observations of mouse translocation types - a Robertsonian translocation and a translocation between a metacentric and an acrocentric chromosome - which also occur in man. It is generally accepted that, when no chromosomal rearrangements are involved, man

  16. Mutations in Caenorhabditis elegans him-19 show meiotic defects that worsen with age.

    Science.gov (United States)

    Tang, Lois; Machacek, Thomas; Mamnun, Yasmine M; Penkner, Alexandra; Gloggnitzer, Jiradet; Wegrostek, Christina; Konrat, Robert; Jantsch, Michael F; Loidl, Josef; Jantsch, Verena

    2010-03-15

    From a screen for meiotic Caenorhabditis elegans mutants based on high incidence of males, we identified a novel gene, him-19, with multiple functions in prophase of meiosis I. Mutant him-19(jf6) animals show a reduction in pairing of homologous chromosomes and subsequent bivalent formation. Consistently, synaptonemal complex formation is spatially restricted and possibly involves nonhomologous chromosomes. Also, foci of the recombination protein RAD-51 occur delayed or cease altogether. Ultimately, mutation of him-19 leads to chromosome missegregation and reduced offspring viability. The observed defects suggest that HIM-19 is important for both homology recognition and formation of meiotic DNA double-strand breaks. It therefore seems to be engaged in an early meiotic event, resembling in this respect the regulator kinase CHK-2. Most astonishingly, him-19(jf6) hermaphrodites display worsening of phenotypes with increasing age, whereas defects are more severe in female than in male meiosis. This finding is consistent with depletion of a him-19-dependent factor during the production of oocytes. Further characterization of him-19 could contribute to our understanding of age-dependent meiotic defects in humans.

  17. DNMT3L is a regulator of X chromosome compaction and post-meiotic gene transcription.

    Directory of Open Access Journals (Sweden)

    Natasha M Zamudio

    Full Text Available Previous studies on the epigenetic regulator DNA methyltransferase 3-Like (DNMT3L, have demonstrated it is an essential regulator of paternal imprinting and early male meiosis. Dnmt3L is also a paternal effect gene, i.e., wild type offspring of heterozygous mutant sires display abnormal phenotypes suggesting the inheritance of aberrant epigenetic marks on the paternal chromosomes. In order to reveal the mechanisms underlying these paternal effects, we have assessed X chromosome meiotic compaction, XY chromosome aneuploidy rates and global transcription in meiotic and haploid germ cells from male mice heterozygous for Dnmt3L. XY bodies from Dnmt3L heterozygous males were significantly longer than those from wild types, and were associated with a three-fold increase in XY bearing sperm. Loss of a Dnmt3L allele resulted in deregulated expression of a large number of both X-linked and autosomal genes within meiotic cells, but more prominently in haploid germ cells. Data demonstrate that similar to embryonic stem cells, DNMT3L is involved in an auto-regulatory loop in germ cells wherein the loss of a Dnmt3L allele resulted in increased transcription from the remaining wild type allele. In contrast, however, within round spermatids, this auto-regulatory loop incorporated the alternative non-coding alternative transcripts. Consistent with the mRNA data, we have localized DNMT3L within spermatids and sperm and shown that the loss of a Dnmt3L allele results in a decreased DNMT3L content within sperm. These data demonstrate previously unrecognised roles for DNMT3L in late meiosis and in the transcriptional regulation of meiotic and post-meiotic germ cells. These data provide a potential mechanism for some cases of human Klinefelter's and Turner's syndromes.

  18. Unisexual reproduction drives meiotic recombination and phenotypic and karyotypic plasticity in Cryptococcus neoformans.

    Directory of Open Access Journals (Sweden)

    Sheng Sun

    2014-12-01

    Full Text Available In fungi, unisexual reproduction, where sexual development is initiated without the presence of two compatible mating type alleles, has been observed in several species that can also undergo traditional bisexual reproduction, including the important human fungal pathogens Cryptococcus neoformans and Candida albicans. While unisexual reproduction has been well characterized qualitatively, detailed quantifications are still lacking for aspects of this process, such as the frequency of recombination during unisexual reproduction, and how this compares with bisexual reproduction. Here, we analyzed meiotic recombination during α-α unisexual and a-α bisexual reproduction of C. neoformans. We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction. Specifically, we observed that in α-α unisexual reproduction, the numbers of crossovers along the chromosomes during meiosis, recombination frequencies at specific chromosomal regions, as well as meiotic recombination hot and cold spots, are all similar to those observed during a-α bisexual reproduction. The similarity in meiosis is also reflected by the fact that phenotypic segregation among progeny collected from the two modes of sexual reproduction is also similar, with transgressive segregation being observed in both. Additionally, we found diploid meiotic progeny were also produced at similar frequencies in the two modes of sexual reproduction, and transient chromosomal loss and duplication likely occurs frequently and results in aneuploidy and loss of heterozygosity that can span entire chromosomes. Furthermore, in both α-α unisexual and a-α bisexual reproduction, we observed biased allele inheritance in regions on chromosome 4, suggesting the presence of fragile chromosomal regions that might be vulnerable to mitotic recombination. Interestingly, we also observed a crossover event that occurred within the MAT locus during α-α unisexual

  19. Genome Dynamics of Hybrid Saccharomyces cerevisiae During Vegetative and Meiotic Divisions

    Directory of Open Access Journals (Sweden)

    Abhishek Dutta

    2017-11-01

    Full Text Available Mutation and recombination are the major sources of genetic diversity in all organisms. In the baker’s yeast, all mutation rate estimates are in homozygous background. We determined the extent of genetic change through mutation and loss of heterozygosity (LOH in a heterozygous Saccharomyces cerevisiae genome during successive vegetative and meiotic divisions. We measured genome-wide LOH and base mutation rates during vegetative and meiotic divisions in a hybrid (S288c/YJM789 S. cerevisiae strain. The S288c/YJM789 hybrid showed nearly complete reduction in heterozygosity within 31 generations of meioses and improved spore viability. LOH in the meiotic lines was driven primarily by the mating of spores within the tetrad. The S288c/YJM789 hybrid lines propagated vegetatively for the same duration as the meiotic lines, showed variable LOH (from 2 to 3% and up to 35%. Two of the vegetative lines with extensive LOH showed frequent and large internal LOH tracts that suggest a high frequency of recombination repair. These results suggest significant LOH can occur in the S288c/YJM789 hybrid during vegetative propagation presumably due to return to growth events. The average base substitution rates for the vegetative lines (1.82 × 10−10 per base per division and the meiotic lines (1.22 × 10−10 per base per division are the first genome-wide mutation rate estimates for a hybrid yeast. This study therefore provides a novel context for the analysis of mutation rates (especially in the context of detecting LOH during vegetative divisions, compared to previous mutation accumulation studies in yeast that used homozygous backgrounds.

  20. Unisexual Reproduction Drives Meiotic Recombination and Phenotypic and Karyotypic Plasticity in Cryptococcus neoformans

    Science.gov (United States)

    Sun, Sheng; Billmyre, R. Blake; Mieczkowski, Piotr A.; Heitman, Joseph

    2014-01-01

    In fungi, unisexual reproduction, where sexual development is initiated without the presence of two compatible mating type alleles, has been observed in several species that can also undergo traditional bisexual reproduction, including the important human fungal pathogens Cryptococcus neoformans and Candida albicans. While unisexual reproduction has been well characterized qualitatively, detailed quantifications are still lacking for aspects of this process, such as the frequency of recombination during unisexual reproduction, and how this compares with bisexual reproduction. Here, we analyzed meiotic recombination during α-α unisexual and a-α bisexual reproduction of C. neoformans. We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction. Specifically, we observed that in α-α unisexual reproduction, the numbers of crossovers along the chromosomes during meiosis, recombination frequencies at specific chromosomal regions, as well as meiotic recombination hot and cold spots, are all similar to those observed during a-α bisexual reproduction. The similarity in meiosis is also reflected by the fact that phenotypic segregation among progeny collected from the two modes of sexual reproduction is also similar, with transgressive segregation being observed in both. Additionally, we found diploid meiotic progeny were also produced at similar frequencies in the two modes of sexual reproduction, and transient chromosomal loss and duplication likely occurs frequently and results in aneuploidy and loss of heterozygosity that can span entire chromosomes. Furthermore, in both α-α unisexual and a-α bisexual reproduction, we observed biased allele inheritance in regions on chromosome 4, suggesting the presence of fragile chromosomal regions that might be vulnerable to mitotic recombination. Interestingly, we also observed a crossover event that occurred within the MAT locus during α-α unisexual reproduction. Our results

  1. Apoptosis in mouse fetal and neonatal oocytes during meiotic prophase one

    Directory of Open Access Journals (Sweden)

    Hartshorne Geraldine M

    2007-07-01

    Full Text Available Abstract Background The vast majority of oocytes formed in the fetal ovary do not survive beyond birth. Possible reasons for their loss include the elimination of non-viable genetic constitutions arising through meiosis, however, the precise relationship between meiotic stages and prenatal apoptosis of oocytes remains elusive. We studied oocytes in mouse fetal and neonatal ovaries, 14.5–21 days post coitum, to examine the relationship between oocyte development and programmed cell death during meiotic prophase I. Results Microspreads of fetal and neonatal ovarian cells underwent immunocytochemistry for meiosis- and apoptosis-related markers. COR-1 (meiosis-specific highlighted axial elements of the synaptonemal complex and allowed definitive identification of the stages of meiotic prophase I. Labelling for cleaved poly-(ADP-ribose polymerase (PARP-1, an inactivated DNA repair protein, indicated apoptosis. The same oocytes were then labelled for DNA double strand breaks (DSBs using TUNEL. 1960 oocytes produced analysable results. Oocytes at all stages of meiotic prophase I stained for cleaved PARP-1 and/or TUNEL, or neither. Oocytes with fragmented (19.8% or compressed (21.2% axial elements showed slight but significant differences in staining for cleaved PARP-1 and TUNEL to those with intact elements. However, fragmentation of axial elements alone was not a good indicator of cell demise. Cleaved PARP-1 and TUNEL staining were not necessarily coincident, showing that TUNEL is not a reliable marker of apoptosis in oocytes. Conclusion Our data indicate that apoptosis can occur throughout meiotic prophase I in mouse fetal and early postnatal oocytes, with greatest incidence at the diplotene stage. Careful selection of appropriate markers for oocyte apoptosis is essential.

  2. Meiotic sex ratio variation in natural populations of Ceratodon purpureus (Ditrichaceae).

    Science.gov (United States)

    Norrell, Tatum E; Jones, Kelly S; Payton, Adam C; McDaniel, Stuart F

    2014-09-01

    • Sex ratio variation is a common but often unexplained phenomenon in species across the tree of life. Here we evaluate the hypothesis that meiotic sex ratio variation can contribute to the biased sex ratios found in natural populations of the moss Ceratodon purpureus.• We obtained sporophytes from several populations of C. purpureus from eastern North America. From each sporophyte, we estimated the mean spore viability by germinating replicate samples on agar plates. We estimated the meiotic sex ratio of each sporophyte by inferring the sex of a random sample of germinated spores (mean = 77) using a PCR-RFLP test. We tested for among-sporophyte variation in viability using an ANOVA and for deviations from 1:1 sex ratio using a χ(2)-test and evaluated the relationship between these quantities using a linear regression.• We found among-sporophyte variation in spore viability and meiotic sex ratio, suggesting that genetic variants that contribute to variation in both of these traits segregate within populations of this species. However, we found no relationship between these quantities, suggesting that factors other than sex ratio distorters contribute to variation in spore viability within populations.• These results demonstrate that sex ratio distortion may partially explain the population sex ratio variation seen in C. purpureus, but more generally that genetic conflict over meiotic segregation may contribute to fitness variation in this species. Overall, this study lays the groundwork for future studies on the genetic basis of meiotic sex ratio variation. © 2014 Botanical Society of America, Inc.

  3. Single nucleotide polymorphisms in the SEPTIN12 gene may be associated with azoospermia by meiotic arrest in Japanese men.

    Science.gov (United States)

    Miyamoto, Toshinobu; Tsujimura, Akira; Miyagawa, Yasushi; Koh, Eitetsu; Namiki, Mikio; Horikawa, Michiharu; Saijo, Yasuaki; Sengoku, Kazuo

    2012-01-01

    To investigate the association between SEPTIN12 gene variants and the risk of azoospermia caused by meiotic arrest. Mutational analysis of the SEPTIN12 gene was performed using DNA from 30 Japanese patients with azoospermia by meiotic arrest and 140 fertile male controls. The frequencies of the c.204G>C (Gln38His) allele and the CC genotype were significantly higher in patients than in fertile controls (p C (Gln38His) variant in the SEPTIN12 gene was associated with increased susceptibility to azoospermia caused by meiotic arrest.

  4. A role for Caenorhabditis elegans chromatin-associated protein HIM-17 in the proliferation vs. meiotic entry decision.

    Science.gov (United States)

    Bessler, Jessica B; Reddy, Kirthi C; Hayashi, Michiko; Hodgkin, Jonathan; Villeneuve, Anne M

    2007-04-01

    Chromatin-associated protein HIM-17 was previously shown to function in the chromosomal events of meiotic prophase. Here we report an additional role for HIM-17 in regulating the balance between germ cell proliferation and meiotic development. A cryptic function for HIM-17 in promoting meiotic entry and/or inhibiting proliferation was revealed by defects in germline organization in him-17 mutants grown at high temperature (25 degrees) and by a synthetic tumorous germline phenotype in glp-1(ar202); him-17 mutants at 15 degrees.

  5. Temperature-dependent changes in the swimming behaviour of Tetrahymena pyriformis-NT1 and their interrelationships with electrophysiology and the state of membrane lipids.

    Science.gov (United States)

    Connolly, J G; Brown, I D; Lee, A G; Kerkut, G A

    1985-01-01

    The swimming velocity and the amplitude of the helical swimming path of T. pyriformis-NT1 cells grown at 20 degrees C (Tg 20 degrees C) and 38 degrees C (Tg 38 degrees C) were monitored between 0 and 40 degrees C in the presence and absence of electric fields. Within physiological limits the swimming velocity increased and the amplitude decreased as temperature was raised. The temperature profiles of these properties were not linear, and showed discontinuities at different temperatures for the different cultures. The break points in Arrhenius plots of the resting potential, regenerative spike magnitude, repolarization time, swimming velocity and swimming amplitude are tabulated and compared. The initial breakpoints upon cooling were clustered about the breakpoints in fluorescence polarization of D.P.H. in extracted phospholipids, and around the transition temperatures estimated from the literature for the pellicular membrane of these cells. The average of the initial breakpoints on cooling was 22.9 degrees C for Tg 38 degrees C cells and 13.7 degrees C for Tg 20 degrees C cells, a shift of 9.2 degrees C. Unlike Paramecium there is no depolarizing receptor potential in Tetrahymena upon warming. It is suggested that this may be the basis of a behavioural difference between Tetrahymena and Paramecium--namely that in Tetrahymena maximum swimming velocity occurs above growth temperature whereas in Paramecium the two points coincide. Swimming velocity and resting potential were correlated with membrane fluidity within physiological limits, but for other parameters the relationship with fluidity was more complex.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Spectral dependence of some UV-B and UV-C responses of Tetrahymena pyriformis irradiated with dye laser generated UV

    International Nuclear Information System (INIS)

    Calkins, John; Colley, Ed; Wheeler, John; Kentucky Univ., Lexington

    1987-01-01

    We have generated UV-B and UV-C radiations using a flashlamp driven tunable dye laser combined with frequency doubling crystals. Using this novel UV source, we have investigated lethality and its modification by growth phase, photoreactivation and caffeine in Tetrahymena pyriformis at 254 nm and from 260-315 nm in 5 nm steps. From the observed responses we have constructed action spectra for lethality, with or without caffeine (a repair inhibitor) and under conditions of photoreactivation. We have also estimated quantum efficiencies for these responses. Our observations suggest that complex changes in response occur at several wavelengths over the UV-C and UV-B regions. (author)

  7. Two Tetrahymena G-DNA-binding proteins, TGP1 and TGP3, share novel motifs and may play a role in micronuclear division

    OpenAIRE

    Lu, Quan; Henderson, Eric

    2000-01-01

    G-DNA is a four-stranded DNA structure with diverse putative biological roles. We have previously purified and cloned a novel G-DNA-binding protein TGP1 from the ciliate Tetrahymena thermophila. Here we report the molecular cloning of TGP3, an additional G-DNA-binding protein from the same organism. The TGP3 cDNA encodes a 365 amino acid protein that is homologous to TGP1 (34% identity and 44% similarity). The proteins share a sequence pattern that contains two novel repetitive and homologous...

  8. Effect of C2 ceramide on the inositol phospholipid metabolism (uptake of 32P, 3H-serine and 3H-palmitic acid) and apoptosis-related morphological changes in Tetrahymena

    International Nuclear Information System (INIS)

    Kovacs, P.; Hegyesi, H.; Koehidai, L.; Nemes, P.; Csaba, G.

    1999-01-01

    Sphingomyelin metabolites have significant role in the regulation of many life processes of mammalian cells. In the present experiments the influence of phospholipid turnover and apoptosis related morphologic signs by one of this metabolite, C 2 ceramide was studied, and compared to the control, untreated cells, in the unicellular Tetrahymena. The incorporation of phospholipid head group components (serine, phosphorus) show a clear time-dependence; while the incorporation of fatty acid component (palmitic acid) is very fast: no significant alterations were found between 5- and 60-min incubations. C 2 ceramide treatment didn't alter 3 H-palmitic acid incorporation into phospholipids, however 3 H-serine incorporation was mainly inhibited. The amount of total incorporated 32 P was also decreased, on the other hand the lover concentration C 2 ceramide (10 μM) elevated the synthesis of inositol phospholipids. The higher concentration of C 2 ceramide (50 μM) had inhibitory effect on the synthesis of each phospholipids examined. This means that in the presence of the C 2 ceramide the synthesis, recovery and turnover of phospholipids, participating in signal transduction, are altered. However these observations were based the uptake of labeled phospholipid precursors, which gives information on the dynamics of the process, without using lipid mass measurements. C 2 ceramide also caused the rounding off the cells, DNA degradation and nuclear condensation. These latter observations point to morphological signs of apoptosis. The results call attention to the role of sphingomyelin metabolites on signalization of unicellulars, to the cross-talk between the inositol phospholipids and sphingomyelin metabolites, and the role of these molecules in the apoptotic processes at a low evolutionary level. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Retinoic Acid signalling and the control of meiotic entry in the human fetal gonad.

    Directory of Open Access Journals (Sweden)

    Andrew J Childs

    Full Text Available The development of mammalian fetal germ cells along oogenic or spermatogenic fate trajectories is dictated by signals from the surrounding gonadal environment. Germ cells in the fetal testis enter mitotic arrest, whilst those in the fetal ovary undergo sex-specific entry into meiosis, the initiation of which is thought to be mediated by selective exposure of fetal ovarian germ cells to mesonephros-derived retinoic acid (RA. Aspects of this model are hard to reconcile with the spatiotemporal pattern of germ cell differentiation in the human fetal ovary, however. We have therefore examined the expression of components of the RA synthesis, metabolism and signalling pathways, and their downstream effectors and inhibitors in germ cells around the time of the initiation of meiosis in the human fetal gonad. Expression of the three RA-synthesising enzymes, ALDH1A1, 2 and 3 in the fetal ovary and testis was equal to or greater than that in the mesonephros at 8-9 weeks gestation, indicating an intrinsic capacity within the gonad to synthesise RA. Using immunohistochemistry to detect RA receptors RARα, β and RXRα, we find germ cells to be the predominant target of RA signalling in the fetal human ovary, but also reveal widespread receptor nuclear localization indicative of signalling in the testis, suggesting that human fetal testicular germ cells are not efficiently shielded from RA by the action of the RA-metabolising enzyme CYP26B1. Consistent with this, expression of CYP26B1 was greater in the human fetal ovary than testis, although the sexually-dimorphic expression patterns of the germ cell-intrinsic regulators of meiotic initiation, STRA8 and NANOS2, appear conserved. Finally, we demonstrate that RA induces a two-fold increase in STRA8 expression in cultures of human fetal testis, but is not sufficient to cause widespread meiosis-associated gene expression. Together, these data indicate that while local production of RA within the fetal ovary may

  10. Retinoic Acid Signalling and the Control of Meiotic Entry in the Human Fetal Gonad

    Science.gov (United States)

    Kinnell, Hazel L.; Anderson, Richard A.; Saunders, Philippa T. K.

    2011-01-01

    The development of mammalian fetal germ cells along oogenic or spermatogenic fate trajectories is dictated by signals from the surrounding gonadal environment. Germ cells in the fetal testis enter mitotic arrest, whilst those in the fetal ovary undergo sex-specific entry into meiosis, the initiation of which is thought to be mediated by selective exposure of fetal ovarian germ cells to mesonephros-derived retinoic acid (RA). Aspects of this model are hard to reconcile with the spatiotemporal pattern of germ cell differentiation in the human fetal ovary, however. We have therefore examined the expression of components of the RA synthesis, metabolism and signalling pathways, and their downstream effectors and inhibitors in germ cells around the time of the initiation of meiosis in the human fetal gonad. Expression of the three RA-synthesising enzymes, ALDH1A1, 2 and 3 in the fetal ovary and testis was equal to or greater than that in the mesonephros at 8–9 weeks gestation, indicating an intrinsic capacity within the gonad to synthesise RA. Using immunohistochemistry to detect RA receptors RARα, β and RXRα, we find germ cells to be the predominant target of RA signalling in the fetal human ovary, but also reveal widespread receptor nuclear localization indicative of signalling in the testis, suggesting that human fetal testicular germ cells are not efficiently shielded from RA by the action of the RA-metabolising enzyme CYP26B1. Consistent with this, expression of CYP26B1 was greater in the human fetal ovary than testis, although the sexually-dimorphic expression patterns of the germ cell-intrinsic regulators of meiotic initiation, STRA8 and NANOS2, appear conserved. Finally, we demonstrate that RA induces a two-fold increase in STRA8 expression in cultures of human fetal testis, but is not sufficient to cause widespread meiosis-associated gene expression. Together, these data indicate that while local production of RA within the fetal ovary may be important in

  11. Effects of four commonly used UV filters on the growth, cell viability and oxidative stress responses of the Tetrahymena thermophila.

    Science.gov (United States)

    Gao, Li; Yuan, Tao; Zhou, Chuanqi; Cheng, Peng; Bai, Qifeng; Ao, Junjie; Wang, Wenhua; Zhang, Haimou

    2013-11-01

    UV filters are increasingly used in sunscreens and other personal care products. Although their residues have been widely identified in aquatic environment, little is known about the influences of UV filters to protozoan. The growth inhibition effects, cell viability and oxidative stress responses of four commonly used UV filters, 2-ethylhexyl 4-methoxycinnamate (EHMC), benzophenone-3 (BP-3), 4-methyl-benzylidene camphor (4-MBC) and octocrylene (OC), to protozoan Tetrahymena thermophila were investigated in this study. The 24-h EC50 values with 95% confidence intervals for BP-3 and 4-MBC were 7.544 (6.561-8.675) mg L(-1) and 5.125 (4.874-5.388) mg L(-1), respectively. EHMC and OC did not inhibit the growth of T. thermophila after 24h exposure at the tested concentrations. The results of cell viability assays with propidium iodide (PI) staining were consistent with that of the growth inhibition tests. As for BP-3 and 4-MBC, the relatively higher concentrations, i.e. of 10.0 and 15.0 mg L(-1), could lead to the cell membranes impairment after 4h exposure. With the increase of the exposure time to 6h, their adverse effects on cell viability of T. thermophila were observed at the relatively lower concentration groups (1.0 mg L(-1) and 5.0 mg L(-1)). In addition, it is noticeable that at environmentally relevant concentration (1.0 μg L(-1)), BP-3 and 4-MBC could lead to the significant increase of catalase (CAT) activities of the T. thermophila cells. Especially for the BP-3, the oxidative injuries were further confirmed by the reduction of glutathione (GSH) content. It is imperative to further investigate the additive action of UV filters and seek other sensitive endpoint, especially at environmentally relevant concentration. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Ploidy-Dependent Unreductional Meiotic Cell Division in Polyploid Wheat

    Science.gov (United States)

    Meiosis includes one round of DNA replication and two successive nuclear divisions, i.e. meiosis I (reductional) and meiosis II (equational). This specialized cell division reduces chromosomes in half and generates haploid gametes in sexual reproduction of eukaryotes. It ensures faithful transmiss...

  13. Nuclear

    International Nuclear Information System (INIS)

    2014-01-01

    This document proposes a presentation and discussion of the main notions, issues, principles, or characteristics related to nuclear energy: radioactivity (presence in the environment, explanation, measurement, periods and activities, low doses, applications), fuel cycle (front end, mining and ore concentration, refining and conversion, fuel fabrication, in the reactor, back end with reprocessing and recycling, transport), the future of the thorium-based fuel cycle (motivations, benefits and drawbacks), nuclear reactors (principles of fission reactors, reactor types, PWR reactors, BWR, heavy-water reactor, high temperature reactor of HTR, future reactors), nuclear wastes (classification, packaging and storage, legal aspects, vitrification, choice of a deep storage option, quantities and costs, foreign practices), radioactive releases of nuclear installations (main released radio-elements, radioactive releases by nuclear reactors and by La Hague plant, gaseous and liquid effluents, impact of releases, regulation), the OSPAR Convention, management and safety of nuclear activities (from control to quality insurance, to quality management and to sustainable development), national safety bodies (mission, means, organisation and activities of ASN, IRSN, HCTISN), international bodies, nuclear and medicine (applications of radioactivity, medical imagery, radiotherapy, doses in nuclear medicine, implementation, the accident in Epinal), nuclear and R and D (past R and D programmes and expenses, main actors in France and present funding, main R and D axis, international cooperation)

  14. Analysis of self-fertilization and meiotic behavior of eleven Brazilian triticale cultivars at two sowing dates

    Directory of Open Access Journals (Sweden)

    Divanilde Guerra

    2011-01-01

    Full Text Available Eleven Brazilian hexaploid triticale cultivars (2n = 6x = 42, from three breeding programs, were evaluated for theirability of self-fertilization in 2006 and for meiotic behavior, meiotic index and pollen viability at two sowing dates in 2007. Highpotential of self-fertilization was observed, with values up to 89.52 %. Many irregularities were found in the meiotic analysis, suchas the presence of univalents, laggard chromosomes and micronuclei in tetrads, which compromised both meiotic behavior andmeiotic index. At the first sowing date, more suitable for normal plant development, overall mean values of 52.68 % for normal cellsand 64.95 % for meiotic index were observed. At the second sowing date, less appropriate for the crop, overall means of 52.23 %for normal cells and 58.24 % for meiotic index were obtained. Despite all the irregularities, considerable pollen viability wasobserved, reaching overall means of 92.08 % and 91.07 % for the first and second sowing dates, respectively.

  15. Differentially expressed genes of Tetrahymena thermophila in response to tributyltin (TBT) identified by suppression subtractive hybridization and real time quantitative PCR.

    Science.gov (United States)

    Feng, Lifang; Miao, Wei; Wu, Yuxuan

    2007-02-15

    Tributyltin (TBT) is widely used as antifouling paints, agriculture biocides, and plastic stabilizers around the world, resulting in great pollution problem in aquatic environments. However, it has been short of the biomonitor to detect TBT in freshwater. We constructed the suppression subtractive hybridization library of Tetrahymena thermophila exposed to TBT, and screened out 101 Expressed Sequence Tags whose expressions were significantly up- or down-regulated with TBT treatment. From this, a series of genes related to the TBT toxicity were discovered, such as glutathione-S-transferase gene (down-regulated), plasma membrane Ca2+ ATPase isoforms 3 gene (up-regulated) and NgoA (up-regulated). Furthermore, their expressions under different concentrations of TBT treatment (0.5-40 ppb) were detected by real time fluorescent quantitative PCR. The differentially expressed genes of T. thermophila in response to TBT were identified, which provide the basic to make Tetrahymena as a sensitive, rapid and convenient TBT biomonitor in freshwater based on rDNA inducible expression system.

  16. Toxicogenomic investigation of Tetrahymena thermophila exposed to dichlorodiphenyltrichloroethane (DDT), tributyltin (TBT), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

    Science.gov (United States)

    Chang, Yue; Feng, LiFang; Miao, Wei

    2011-07-01

    Dichlorodiphenyltrichloroethane (DDT), tributyltin (TBT), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are persistent in the environment and cause continuous toxic effects in humans and aquatic life. Tetrahymena thermophila has the potential for use as a model for research regarding toxicants. In this study, this organism was used to analyze a genome-wide microarray generated from cells exposed to DDT, TBT and TCDD. To accomplish this, genes differentially expressed when treated with each toxicant were identified, after which their functions were categorized using GO enrichment analysis. The results suggested that the responses of T. thermophila were similar to those of multicellular organisms. Additionally, the context likelihood of relatedness method (CLR) was applied to construct a TCDD-relevant network. The T-shaped network obtained could be functionally divided into two subnetworks. The general functions of both subnetworks were related to the epigenetic mechanism of TCDD. Based on analysis of the networks, a model of the TCDD effect on T. thermophila was inferred. Thus, Tetrahymena has the potential to be a good unicellular eukaryotic model for toxic mechanism research at the genome level.

  17. Meiotic aneuploidy: its origins and induction following chemical treatment in Sordaria brevicollis.

    Science.gov (United States)

    Bond, D J; McMillan, L

    1979-08-01

    A system suitable for the detection of meiotic aneuploidy is described in which various different origins of the aneuploidy can be distinguished. Aneuploid meiotic products are detected as black disomic spores held in asci containing all the products of a single meiosis. Aneuploidy may result from nondisjunction or from a meiosis in which an extra replica of one of the chromosomes has been generated in some other way, e.g., extra replication. By using this system it has been shown that pFPA treatment increase aneuploidy, primarily through an effect on nondisjunction. Preliminary results with trifluralin have indicated that this compound, too, may increase aneuploidy. There is a good possibility that the system can be further developed to permit a more rapid screening using a random plating method; this will allow a more efficient two-part analysis of the effects of compounds under test.

  18. Meiotic behavior of two polyploid species of genus Pleurodema (Anura: Leiuperidae from central Argentina

    Directory of Open Access Journals (Sweden)

    Nancy E. Salas

    2014-06-01

    Full Text Available Polyploidy is an important evolutionary force but rare in vertebrates. However, in anurans, the genus Pleurodema has polyploid species, two of them tetraploid and one octoploid. The manner in which the chromosomes join in diakinesis can vary among species and, crucially, if they differ in their ploidy levels. In this work, we describe the meiotic configurations in two cryptic species from central Argentina, with different ploidy levels, Pleurodema kriegi (tetraploid and P. cordobae (octoploid. A total of 306 diakineses from 19 individuals were analyzed. In meiosis, P. kriegi form 22 bivalents, whereas P. cordobae exhibits variation in meiotic figures. We discuss the possible allo- and autopolyploid origin of these species, and we consider that the autopolyploid origin of P. cordobae from P. kriegi might be the most feasible.

  19. Meiotic drive on aberrant chromosome 1 in the mouse is determined by a linked distorter.

    Science.gov (United States)

    Agulnik, S I; Sabantsev, I D; Orlova, G V; Ruvinsky, A O

    1993-04-01

    An aberrant chromosome 1 carrying an inverted fragment with two amplified DNA regions was isolated from wild populations of Mus musculus. Meiotic drive favouring the aberrant chromosome was demonstrated for heterozygous females. Its cause was preferential passage of aberrant chromosome 1 to the oocyte. Genetic analysis allowed us to identify a two-component system conditioning deviation from equal segregation of the homologues. The system consists of a postulated distorter and responder. The distorter is located on chromosome 1 distally to the responder, between the ln and Pep-3 genes, and it acts on the responder when in trans position. Polymorphism of the distorters was manifested as variation in their effect on meiotic drive level in the laboratory strain and mice from wild populations.

  20. DAF-2 and ERK Couple Nutrient Availability to Meiotic Progression during Caenorhabditis elegans Oogenesis

    Science.gov (United States)

    Lopez, Andrew L.; Chen, Jessica; Joo, Hyoe-Jin; Drake, Melanie; Shidate, Miri; Kseib, Cedric; Arur, Swathi

    2013-01-01

    Coupling the production of mature gametes and fertilized zygotes to favorable nutritional conditions improves reproductive success. In invertebrates, the proliferation of female germ line stem cells is regulated by nutritional status. But, in mammals the number of female germ line stem cells is set early in development, with oocytes progressing through meiosis later in life. Mechanisms that couple later steps of oogenesis to environmental conditions remain largely undefined. We show that in the presence of food, the DAF-2 insulin-like receptor signals through the RAS-ERK pathway to drive meiotic prophase I progression and oogenesis; in the absence of food, the resultant inactivation of insulin-like signaling leads to downregulation of RAS-ERK pathway, and oogenesis is stalled. Thus, the insulin-like signaling pathway couples nutrient sensing to meiotic I progression and oocyte production in C. elegans, ensuring that oocytes are only produced under conditions favorable for the survival of the resulting zygotes. PMID:24120884

  1. Expression of arf tumor suppressor in spermatogonia facilitates meiotic progression in male germ cells.

    Directory of Open Access Journals (Sweden)

    Michelle L Churchman

    2011-07-01

    Full Text Available The mammalian Cdkn2a (Ink4a-Arf locus encodes two tumor suppressor proteins (p16(Ink4a and p19(Arf that respectively enforce the anti-proliferative functions of the retinoblastoma protein (Rb and the p53 transcription factor in response to oncogenic stress. Although p19(Arf is not normally detected in tissues of young adult mice, a notable exception occurs in the male germ line, where Arf is expressed in spermatogonia, but not in meiotic spermatocytes arising from them. Unlike other contexts in which the induction of Arf potently inhibits cell proliferation, expression of p19(Arf in spermatogonia does not interfere with mitotic cell division. Instead, inactivation of Arf triggers germ cell-autonomous, p53-dependent apoptosis of primary spermatocytes in late meiotic prophase, resulting in reduced sperm production. Arf deficiency also causes premature, elevated, and persistent accumulation of the phosphorylated histone variant H2AX, reduces numbers of chromosome-associated complexes of Rad51 and Dmc1 recombinases during meiotic prophase, and yields incompletely synapsed autosomes during pachynema. Inactivation of Ink4a increases the fraction of spermatogonia in S-phase and restores sperm numbers in Ink4a-Arf doubly deficient mice but does not abrogate γ-H2AX accumulation in spermatocytes or p53-dependent apoptosis resulting from Arf inactivation. Thus, as opposed to its canonical role as a tumor suppressor in inducing p53-dependent senescence or apoptosis, Arf expression in spermatogonia instead initiates a salutary feed-forward program that prevents p53-dependent apoptosis, contributing to the survival of meiotic male germ cells.

  2. [Meiotic abnormalities of oocytes from patients with endometriosis submitted to ovarian stimulation].

    Science.gov (United States)

    Barcelos, Ionara Diniz Evangelista Santos; Vieira, Rodolpho Cruz; Ferreira, Elisa Melo; Araújo, Maria Cristina Picinato Medeiros de; Martins, Wellington de Paula; Ferriani, Rui Alberto; Navarro, Paula Andrea de Albuquerque Salles

    2008-08-01

    to evaluate the meiotic spindle and the chromosome distribution of in vitro mature oocytes from stimulated cycles of infertile women with endometriosis, and with male and/or tubal infertility factors (Control Group), comparing the rates of in vitro maturation (IVM) between the two groups evaluated. fourteen patients with endometriosis and eight with male and/or tubal infertility factors, submitted to ovarian stimulation for intracytoplasmatic sperm injection have been prospectively and consecutively selected, and formed a Study and Control Group, respectively. Immature oocytes (46 and 22, respectively, from the Endometriosis and Control Groups) were submitted to IVM. Oocytes presenting extrusion of the first polar corpuscle were fixed and stained for microtubules and chromatin evaluation through immunofluorescence technique. Statistical analysis has been done by the Fisher's exact test, with statistical significance at pControl Groups, respectively). The chromosome and meiotic spindle organization was observed in 18 and 11 oocytes from the Endometriosis and Control Groups, respectively. In the Endometriosis Group, eight oocytes (44.4%) presented themselves as normal metaphase II (MII), three (16.7%) as abnormal MII, five (27.8%) were in telophase stage I and two (11.1%) underwent parthenogenetic activation. In the Control Group, five oocytes (45.4%) presented themselves as normal MII, three (27.3%) as abnormal MII, one (9.1%) was in telophase stage I and two (18.2%) underwent parthenogenetic activation. There was no significant difference in meiotic anomaly rate between the oocytes in MII from both groups. the present study data did not show significant differences in the IVM or in the meiotic anomalies rate between the IVM oocytes from stimulated cycles of patients with endometriosis, as compared with controls. Nevertheless, they have suggested a delay in the outcome of oocyte meiosis I from patients with endometriosis, shown by the higher proportion of oocytes in

  3. Genomic features shaping the landscape of meiotic double-strand-break hotspots in maize.

    Science.gov (United States)

    He, Yan; Wang, Minghui; Dukowic-Schulze, Stefanie; Zhou, Adele; Tiang, Choon-Lin; Shilo, Shay; Sidhu, Gaganpreet K; Eichten, Steven; Bradbury, Peter; Springer, Nathan M; Buckler, Edward S; Levy, Avraham A; Sun, Qi; Pillardy, Jaroslaw; Kianian, Penny M A; Kianian, Shahryar F; Chen, Changbin; Pawlowski, Wojciech P

    2017-11-14

    Meiotic recombination is the most important source of genetic variation in higher eukaryotes. It is initiated by formation of double-strand breaks (DSBs) in chromosomal DNA in early meiotic prophase. The DSBs are subsequently repaired, resulting in crossovers (COs) and noncrossovers (NCOs). Recombination events are not distributed evenly along chromosomes but cluster at recombination hotspots. How specific sites become hotspots is poorly understood. Studies in yeast and mammals linked initiation of meiotic recombination to active chromatin features present upstream from genes, such as absence of nucleosomes and presence of trimethylation of lysine 4 in histone H3 (H3K4me3). Core recombination components are conserved among eukaryotes, but it is unclear whether this conservation results in universal characteristics of recombination landscapes shared by a wide range of species. To address this question, we mapped meiotic DSBs in maize, a higher eukaryote with a large genome that is rich in repetitive DNA. We found DSBs in maize to be frequent in all chromosome regions, including sites lacking COs, such as centromeres and pericentromeric regions. Furthermore, most DSBs are formed in repetitive DNA, predominantly Gypsy retrotransposons, and only one-quarter of DSB hotspots are near genes. Genic and nongenic hotspots differ in several characteristics, and only genic DSBs contribute to crossover formation. Maize hotspots overlap regions of low nucleosome occupancy but show only limited association with H3K4me3 sites. Overall, maize DSB hotspots exhibit distribution patterns and characteristics not reported previously in other species. Understanding recombination patterns in maize will shed light on mechanisms affecting dynamics of the plant genome.

  4. A meiotic linkage map of the silver fox, aligned and compared to the canine genome

    OpenAIRE

    Kukekova, Anna V.; Trut, Lyudmila N.; Oskina, Irina N.; Johnson, Jennifer L.; Temnykh, Svetlana V.; Kharlamova, Anastasiya V.; Shepeleva, Darya V.; Gulievich, Rimma G.; Shikhevich, Svetlana G.; Graphodatsky, Alexander S.; Aguirre, Gustavo D.; Acland, Gregory M.

    2007-01-01

    A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogen...

  5. Mek1/Mre4 is a master regulator of meiotic recombination in budding yeast

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    Nancy M. Hollingsworth

    2016-02-01

    Full Text Available Sexually reproducing organisms create gametes with half the somatic cell chromosome number so that fusion of gametes at fertilization does not change the ploidy of the cell. This reduction in chromosome number occurs by the specialized cell division of meiosis in which two rounds of chromosome segregation follow a single round of chromosome duplication. Meiotic crossovers formed between the non-sister chromatids of homologous chromosomes, combined with sister chromatid cohesion, physically connect homologs, thereby allowing proper segregation at the first meiotic division. Meiotic recombination is initiated by programmed double strand breaks (DSBs whose repair is highly regulated such that (1 there is a bias for recombination with homologs rather than sister chromatids, (2 crossovers are distributed throughout the genome by a process called interference, (3 crossover homeostasis regulates the balance between crossover and non-crossover repair to maintain a critical number of crossovers and (4 each pair of homologs receives at least one crossover. It was previously known that the imposition of interhomolog bias in budding yeast requires meiosis-specific modifications to the DNA damage response and the local activation of the meiosis-specific Mek1/Mre4 (hereafter Mek1 kinase at DSBs. However, because inactivation of Mek1 results in intersister, rather than interhomolog DSB repair, whether Mek1 had a role in interhomolog pathway choice was unknown. A recent study by Chen et al. (2015 reveals that Mek1 indirectly regulates the crossover/non-crossover decision between homologs as well as genetic interference. It does this by enabling phosphorylation of Zip1, the meiosis-specific transverse filament protein of the synaptonemal complex (SC, by the conserved cell cycle kinase, Cdc7-Dbf4 (DDK. These results suggest that Mek1 is a “master regulator” of meiotic recombination in budding yeast.

  6. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    KAUST Repository

    Fučíková, Karolina

    2015-04-06

    © 2015 Phycological Society of America. Sexual reproduction is widespread in eukaryotes and is well documented in chlorophytan green algae. In this lineage, however, the Trebouxiophyceae represent a striking exception: in contrast to its relatives Chlorophyceae and Ulvophyceae this group appears to be mostly asexual, as fertilization has been rarely observed. Assessments of sexual reproduction in the Trebouxiophyceae have been based on microscopic observation of gametes fusing. New genomic data offer now the opportunity to check for the presence of meiotic genes, which represent an indirect evidence of a sexual life cycle. Using genomic and transcriptomic data for 12 taxa spanning the phylogenetic breadth of the class, we tried to clarify whether genuine asexuality or cryptic sexuality is the most likely case for the numerous putatively asexual trebouxiophytes. On the basis of these data and a bibliographic review, we conclude that the view of trebouxiophytes as primarily asexual is incorrect. In contrast to the limited number of reports of fertilization, meiotic genes were found in all genomes and transcriptomes examined, even in species presumed asexual. In the taxa examined the totality or majority of the genes were present, Helicosporidium and Auxenochlorella being the only partial exceptions (only four genes present). The evidence of sex provided by the meiotic genes is phylogenetically widespread in the class and indicates that sexual reproduction is not associated with any particular morphological or ecological trait. On the basis of the results, we expect that the existence of the meiotic genes will be documented in all trebouxiophycean genomes that will become available in the future.

  7. Production and characterization of radiation-sensitive meiotic mutants of Coprinus cinereus

    International Nuclear Information System (INIS)

    Zolan, M.E.; Tremel, C.J.; Pukkila, P.J.

    1988-01-01

    We have isolated four gamma-sensitive mutants of the basidiomycete Coprinus cinereus. When homozygous, two of these (rad 3-1 and rad 9-1) produce fruiting bodies with very few viable basidiospores, the products of meiosis in this organism. A less radiation-sensitive allele of RAD 3, rad 3-2, causes no apparent meiotic defect in homozygous strains. Quantitative measurements of oidial survival of rad 3-1;rad 9-1 double mutants compared to the single mutants indicated that rad 3-1 and rad 9-1 mutants are defective in the same DNA repair pathway. In the pew viable basidiospores that are produced by these two strains, essentially normal levels of meiotic recombination can be detected. None of the mutants exhibits increased sensitivity to UV radiation. Cytological examination of meiotic chromosomes from mutant and wild-type fruiting bodies showed that rad 3-1 homozygous strains fail to condense and pair homologous chromosomes during prophase I. Although rad 9-1 strains are successful at chromosome pairing, meiosis is usually not completed in these mutants

  8. From genes to games: cooperation and cyclic dominance in meiotic drive.

    Science.gov (United States)

    Traulsen, Arne; Reed, Floyd A

    2012-04-21

    Evolutionary change can be described on a genotypic level or a phenotypic level. Evolutionary game theory is typically thought of as a phenotypic approach, although it is frequently argued that it can also be used to describe population genetic evolution. Interpreting the interaction between alleles in a diploid genome as a two player game leads to interesting alternative perspectives on genetic evolution. Here we focus on the case of meiotic drive and illustrate how meiotic drive can be directly and precisely interpreted as a social dilemma, such as the prisoners dilemma or the snowdrift game, in which the drive allele takes more than its fair share. Resistance to meiotic drive can lead to the well understood cyclic dominance found in the rock-paper-scissors game. This perspective is well established for the replicator dynamics, but there is still considerable ground for mutual inspiration between the two fields. For example, evolutionary game theorists can benefit from considering the stochastic evolutionary dynamics arising from finite population size. Population geneticists can benefit from game theoretic tools and perspectives on genetic evolution. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. AAA-ATPase FIDGETIN-LIKE 1 and Helicase FANCM Antagonize Meiotic Crossovers by Distinct Mechanisms.

    Directory of Open Access Journals (Sweden)

    Chloe Girard

    2015-07-01

    Full Text Available Meiotic crossovers (COs generate genetic diversity and are critical for the correct completion of meiosis in most species. Their occurrence is tightly constrained but the mechanisms underlying this limitation remain poorly understood. Here we identified the conserved AAA-ATPase FIDGETIN-LIKE-1 (FIGL1 as a negative regulator of meiotic CO formation. We show that Arabidopsis FIGL1 limits CO formation genome-wide, that FIGL1 controls dynamics of the two conserved recombinases DMC1 and RAD51 and that FIGL1 hinders the interaction between homologous chromosomes, suggesting that FIGL1 counteracts DMC1/RAD51-mediated inter-homologue strand invasion to limit CO formation. Further, depleting both FIGL1 and the previously identified anti-CO helicase FANCM synergistically increases crossover frequency. Additionally, we showed that the effect of mutating FANCM on recombination is much lower in F1 hybrids contrasting from the phenotype of inbred lines, while figl1 mutation equally increases crossovers in both contexts. This shows that the modes of action of FIGL1 and FANCM are differently affected by genomic contexts. We propose that FIGL1 and FANCM represent two successive barriers to CO formation, one limiting strand invasion, the other disassembling D-loops to promote SDSA, which when both lifted, leads to a large increase of crossovers, without impairing meiotic progression.

  10. Contributions of classical and molecular cytogenetic in meiotic analysis and pollen viability for plant breeding.

    Science.gov (United States)

    Lavinscky, M P; Souza, M M; Silva, G S; Melo, C A F

    2017-09-27

    The analysis of meiotic behavior has been widely used in the study of plants as they provide relevant information about the viability of a species. Meiosis boasts a host of highly conserved events and changes in genes that control these events will give rise to irregularities that can alter the normal course of meiosis and may lead to complete sterility of the plant. The recombination of genes that occur in meiosis is an important event to generate variability and has been important in studies for genetic improvement and to create viable hybrids. The use of fluorescence in situ hybridization and genomic in situ hybridization (GISH) in meiosis allows the localization of specific regions, enables to differentiate genomes in a hybrid, permits to observe the pairing of homoeologous chromosomes, and if there was a recombination between the genomes of progenitor species. Furthermore, the GISH allows us to observe the close relationship between the species involved. This article aims to report over meiosis studies on plants and hybrids, the use and importance of molecular cytogenetic in meiotic analysis and contributions of meiotic analysis in breeding programs.

  11. Translocations of chromosome end-segments and facultative heterochromatin promote meiotic ring formation in evening primroses.

    Science.gov (United States)

    Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

    2014-03-01

    Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories.

  12. Modulation of Prdm9-controlled meiotic chromosome asynapsis overrides hybrid sterility in mice.

    Science.gov (United States)

    Gregorova, Sona; Gergelits, Vaclav; Chvatalova, Irena; Bhattacharyya, Tanmoy; Valiskova, Barbora; Fotopulosova, Vladana; Jansa, Petr; Wiatrowska, Diana; Forejt, Jiri

    2018-03-14

    Hybrid sterility is one of the reproductive isolation mechanisms leading to speciation. Prdm9 , the only known vertebrate hybrid-sterility gene, causes failure of meiotic chromosome synapsis and infertility in male hybrids that are the offspring of two mouse subspecies. Within species, Prdm9 determines the sites of programmed DNA double-strand breaks (DSBs) and meiotic recombination hotspots. To investigate the relation between Prdm9 -controlled meiotic arrest and asynapsis, we inserted random stretches of consubspecific homology on several autosomal pairs in sterile hybrids, and analyzed their ability to form synaptonemal complexes and to rescue male fertility. Twenty-seven or more megabases of consubspecific (belonging to the same subspecies) homology fully restored synapsis in a given autosomal pair, and we predicted that two or more DSBs within symmetric hotspots per chromosome are necessary for successful meiosis. We hypothesize that impaired recombination between evolutionarily diverged chromosomes could function as one of the mechanisms of hybrid sterility occurring in various sexually reproducing species. © 2018, Gregorova et al.

  13. Association of poly-purine/poly-pyrimidine sequences with meiotic recombination hot spots

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    Pitt Joel PW

    2006-07-01

    Full Text Available Abstract Background Meiotic recombination events have been found to concentrate in 1–2.5 kilo base regions, but these recombination hot spots do not share a consensus sequence and why they occur at specific sites is not fully understood. Some previous evidence suggests that poly-purine/poly-pyrimidine (poly-pu/py tracts (PPTs, a class of sequence with distinctive biochemical properties, could be involved in recombination, but no general association of PPTs with meiotic recombination hot spots has previously been reported. Results We used computational methods to investigate in detail the relationship between PPTs and hot spots. We show statistical associations of PPT frequency with hot spots of meiotic recombination initiating lesions, double-strand breaks, in the genome of the yeast S. cerevisiae and with experimentally well characterized human meiotic recombination hot spots. Supporting a possible role of poly-pu/py-rich sequences in hot spot recombination, we also found that all three single nucleotide polymorphisms previously shown to be associated with human hot spot activity changes occur within sequence contexts of 14 bp or longer that are 85% or more poly-pu/py and at least 70% G/C. These polymorphisms are all close to the hot spot mid points. Comparing the sequences of experimentally characterized human hot spots with the orthologous regions of the chimpanzee genome previously shown not to contain hot spots, we found that in all five cases in which comparisons for the hot spot central regions are possible with publicly available sequence data, there are differences near the human hot spot mid points within sequences 14 bp or longer consisting of more than 80% poly-pu/py and at least 50% G/C. Conclusion Our results, along with previous evidence for the unique biochemical properties and recombination-stimulating potential of poly-pu/py-rich sequences, suggest that the possible functional involvement of this type of sequence in meiotic

  14. Onset and progress of meiotic prophase in the oocytes in the B6.YTIR sex-reversed mouse ovary.

    Science.gov (United States)

    Park, E-H; Taketo, T

    2003-12-01

    When the Y chromosome of a Mus musculus domesticus male mouse (caught in Tirano, Italy) is placed on a C57BL/6J genetic background, approximately half of the XY (B6.YTIR) progeny develop into normal-appearing but infertile females. We have previously reported that the primary cause of infertility can be attributed to their oocytes. To identify the primary defect in the XY oocyte, we examined the onset and progress of meiotic prophase in the B6.YTIR fetal ovary. Using bromo-deoxyuridine incorporation and culture, we determined that the germ cells began to enter meiosis at the developmental ages and in numbers comparable to those in the control XX ovary. Furthermore, the meiotic prophase appeared to progress normally until the late zygotene stage. However, the oocytes that entered meiosis early in the XY ovary failed to complete the meiotic prophase. On the other hand, a considerable number of oocytes entered meiosis at late developmental stages and completed the meiotic prophase in the XY ovary. We propose that the timing of entry into meiosis and the XY chromosomal composition influence the survival of oocytes during meiotic prophase in the fetal ovary.

  15. Sexual antagonism and meiotic drive cause stable linkage disequilibrium and favour reduced recombination on the X chromosome.

    Science.gov (United States)

    Rydzewski, W T; Carioscia, S A; Liévano, G; Lynch, V D; Patten, M M

    2016-06-01

    Sexual antagonism and meiotic drive are sex-specific evolutionary forces with the potential to shape genomic architecture. Previous theory has found that pairing two sexually antagonistic loci or combining sexual antagonism with meiotic drive at linked autosomal loci augments genetic variation, produces stable linkage disequilibrium (LD) and favours reduced recombination. However, the influence of these two forces has not been examined on the X chromosome, which is thought to be enriched for sexual antagonism and meiotic drive. We investigate the evolution of the X chromosome under both sexual antagonism and meiotic drive with two models: in one, both loci experience sexual antagonism; in the other, we pair a meiotic drive locus with a sexually antagonistic locus. We find that LD arises between the two loci in both models, even when the two loci freely recombine in females and that driving haplotypes will be enriched for male-beneficial alleles, further skewing sex ratios in these populations. We introduce a new measure of LD, Dz', which accounts for population allele frequencies and is appropriate for instances where these are sex specific. Both models demonstrate that natural selection favours modifiers that reduce the recombination rate. These results inform observed patterns of congealment found on driving X chromosomes and have implications for patterns of natural variation and the evolution of recombination rates on the X chromosome. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

  16. The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects.

    Science.gov (United States)

    Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A

    2016-09-19

    Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  17. Cloning and characterization of the major histone H2A genes completes the cloning and sequencing of known histone genes of Tetrahymena thermophila.

    Science.gov (United States)

    Liu, X; Gorovsky, M A

    1996-01-01

    A truncated cDNA clone encoding Tetrahymena thermophila histone H2A2 was isolated using synthetic degenerate oligonucleotide probes derived from H2A protein sequences of Tetrahymena pyriformis. The cDNA clone was used as a homologous probe to isolate a truncated genomic clone encoding H2A1. The remaining regions of the genes for H2A1 (HTA1) and H2A2 (HTA2) were then isolated using inverse PCR on circularized genomic DNA fragments. These partial clones were assembled into intact HTA1 and HTA2 clones. Nucleotide sequences of the two genes were highly homologous within the coding region but not in the noncoding regions. Comparison of the deduced amino acid sequences with protein sequences of T. pyriformis H2As showed only two and three differences respectively, in a total of 137 amino acids for H2A1, and 132 amino acids for H2A2, indicating the two genes arose before the divergence of these two species. The HTA2 gene contains a TAA triplet within the coding region, encoding a glutamine residue. In contrast with the T. thermophila HHO and HTA3 genes, no introns were identified within the two genes. The 5'- and 3'-ends of the histone H2A mRNAs; were determined by RNase protection and by PCR mapping using RACE and RLM-RACE methods. Both genes encode polyadenylated mRNAs and are highly expressed in vegetatively growing cells but only weakly expressed in starved cultures. With the inclusion of these two genes, T. thermophila is the first organism whose entire complement of known core and linker histones, including replication-dependent and basal variants, has been cloned and sequenced. PMID:8760889

  18. The roles of the Saccharomyces cerevisiae RecQ helicase SGS1 in meiotic genome surveillance.

    Directory of Open Access Journals (Sweden)

    Amit Dipak Amin

    2010-11-01

    Full Text Available The Saccharomyces cerevisiae RecQ helicase Sgs1 is essential for mitotic and meiotic genome stability. The stage at which Sgs1 acts during meiosis is subject to debate. Cytological experiments showed that a deletion of SGS1 leads to an increase in synapsis initiation complexes and axial associations leading to the proposal that it has an early role in unwinding surplus strand invasion events. Physical studies of recombination intermediates implicate it in the dissolution of double Holliday junctions between sister chromatids.In this work, we observed an increase in meiotic recombination between diverged sequences (homeologous recombination and an increase in unequal sister chromatid events when SGS1 is deleted. The first of these observations is most consistent with an early role of Sgs1 in unwinding inappropriate strand invasion events while the second is consistent with unwinding or dissolution of recombination intermediates in an Mlh1- and Top3-dependent manner. We also provide data that suggest that Sgs1 is involved in the rejection of 'second strand capture' when sequence divergence is present. Finally, we have identified a novel class of tetrads where non-sister spores (pairs of spores where each contains a centromere marker from a different parent are inviable. We propose a model for this unusual pattern of viability based on the inability of sgs1 mutants to untangle intertwined chromosomes. Our data suggest that this role of Sgs1 is not dependent on its interaction with Top3. We propose that in the absence of SGS1 chromosomes may sometimes remain entangled at the end of pre-meiotic replication. This, combined with reciprocal crossing over, could lead to physical destruction of the recombined and entangled chromosomes. We hypothesise that Sgs1, acting in concert with the topoisomerase Top2, resolves these structures.This work provides evidence that Sgs1 interacts with various partner proteins to maintain genome stability throughout

  19. VDE-initiated intein homing in Saccharomyces cerevisiae proceeds in a meiotic recombination-like manner.

    Science.gov (United States)

    Fukuda, Tomoyuki; Nogami, Satoru; Ohya, Yoshikazu

    2003-07-01

    Inteins and group I introns found in prokaryotic and eukaryotic organisms occasionally behave as mobile genetic elements. During meiosis of the yeast Saccharomyces cerevisiae, the site-specific endonuclease encoded by VMA1 intein, VDE, triggers a single double-strand break (DSB) at an inteinless allele, leading to VMA1 intein homing. Besides the accumulating information on the in vitro activity of VDE, very little has been known about the molecular mechanism of intein homing in yeast nucleus. We developed an assay to detect the product of VMA1 intein homing in yeast genome. We analysed mutant phenotypes of RecA homologs, Rad51p and Dmc1p, and their interacting proteins, Rad54p and Tid1p, and found that they all play critical roles in intein inheritance. The absence of DSB end processing proteins, Sae2p and those in the Mre11-Rad50-Xrs2 complex, also causes partial reduction in homing efficiency. As with meiotic recombination, crossover events are frequently observed during intein homing. We also observed that the absence of premeiotic DNA replication caused by hydroxyurea (HU) or clb5delta clb6delta mutation reduces VDE-mediated DSBs. The repairing system working in intein homing shares molecular machinery with meiotic recombination induced by Spo11p. Moreover, like Spo11p-induced DNA cleavage, premeiotic DNA replication is a prerequisite for a VDE-induced DSB. VMA1 intein thus utilizes several host factors involved in meiotic and recombinational processes to spread its genetic information and guarantee its progeny through establishment of a parasitic relationship with the organism.

  20. Radiation-induced mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Parry, J M; Sharp, D; Tippins, R S; Parry, E M

    1979-06-01

    A number of genetic systems are described which in yeast may be used to monitor the induction of chromosome aneuploidy during both mitotic and meiotic cell division. Using these systems we have been able to demonstrate the induction of both monosomic and trisomic cells in mitotically dividing cells and disomic spores in meiotically dividing cells after both UV light and X-ray exposure. The frequency of UV-light-induced monosomic colonies were reduced by post-treatment with photoreactivity light and both UV-light- and X-ray-induced monosomic colonies were reduced by liquid holding post-treatment under non-nutrient conditions. Both responses indicate an involvement of DNA-repair mechanisms in the removal of lesions which may lead to monosomy in yeast. This was further confirmed by the response of an excision-defective yeast strain which showed considerably increased sensitivity to the induction of monosomic colonies by UV-light treatment at low doses. Yeast cultures irradiated at different stages of growth showed variation in their responses to both UV-light and X-rays, cells at the exponential phase of growth show maximum sensitivity to the induction of monosomic colonies at low doses whereas stationary phase cultures showed maximum induction of monosomic colonies at high does. The frequencies of X-ray-induced chromosome aneuploidy during meiosis leading to the production of disomic spores was shown to be dependent upon the stage of meiosis at which the yeast cells were exposed to radiation. Cells which had proceeded beyond the DNA synthetic stage of meiosis were shown to produce disomic spores at considerably lower radiation doses than those cells which had only recently been inoculated into sporulation medium. The results obtained suggest that the yeast sustem may be suitable for the study of sensitivities of the various stages of meiotic cell division to the induction of chromosome aneuploidy after radiation exposure.

  1. Ex-vivo assessment of chronic toxicity of low levels of cadmium on testicular meiotic cells

    Energy Technology Data Exchange (ETDEWEB)

    Geoffroy-Siraudin, Cendrine [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Perrard, Marie-Hélène [Institut de Génomique Fonctionnelle de Lyon, UMR 5242 CNRS INRA Ecole Normale Supérieure de Lyon 1, 46 allée d' Italie, F-69364 Lyon Cedex 07 (France); Ghalamoun-Slaimi, Rahma [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Ali, Sazan [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Chaspoul, Florence [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Unité de Chimie-Physique, Faculté de Pharmacie 13005, Marseille (France); Lanteaume, André [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Achard, Vincent [Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Gallice, Philippe [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Unité de Chimie-Physique, Faculté de Pharmacie 13005, Marseille (France); Durand, Philippe [Institut de Génomique Fonctionnelle de Lyon, UMR 5242 CNRS INRA Ecole Normale Supérieure de Lyon 1, 46 allée d' Italie, F-69364 Lyon Cedex 07 (France); and others

    2012-08-01

    Using a validated model of culture of rat seminiferous tubules, we assessed the effects of 0.1, 1 and 10 μg/L cadmium (Cd) on spermatogenic cells over a 2‐week culture period. With concentrations of 1 and 10 μg/L in the culture medium, the Cd concentration in the cells, determined by ICP-MS, increased with concentration in the medium and the day of culture. Flow cytometric analysis enabled us to evaluate changes in the number of Sertoli cells and germ cells during the culture period. The number of Sertoli cells did not appear to be affected by Cd. By contrast, spermatogonia and meiotic cells were decreased by 1 and 10 μg/L Cd in a time and dose dependent manner. Stage distribution of the meiotic prophase I and qualitative study of the synaptonemal complexes (SC) at the pachytene stage were performed by immunocytochemistry with an anti SCP3 antibody. Cd caused a time-and-dose-dependent increase of total abnormalities, of fragmented SC and of asynapsis from concentration of 0.1 μg/L. Additionally, we observed a new SC abnormality, the “motheaten” SC. This abnormality is frequently associated with asynapsis and SC widening which increased with both the Cd concentration and the duration of exposure. This abnormality suggests that Cd disrupts the structure and function of proteins involved in pairing and/or meiotic recombination. These results show that Cd induces dose-and-time-dependent alterations of the meiotic process of spermatogenesis ex-vivo, and that the lowest metal concentration, which induces an adverse effect, may vary with the cell parameter studied. -- Highlights: ► Cadmium induces ex-vivo severe time- and dose-dependent germ cell abnormalities. ► Cadmium at very low concentration (0.1 µg/l) induces synaptonemal complex abnormalities. ► The lowest concentration inducing adverse effect varied with the cell parameter studied. ► Cadmium alters proteins involved in pairing and recombination. ► Cadmium leads to achiasmate univalents and

  2. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids

    Czech Academy of Sciences Publication Activity Database

    Bhattacharyya, Tanmoy; Reifová, R.; Gregorová, Soňa; Šimeček, Petr; Gergelits, Václav; Mistrik, M.; Martincová, Iva; Piálek, Jaroslav; Forejt, Jiří

    2014-01-01

    Roč. 10, č. 2 (2014), e1004088 ISSN 1553-7404 R&D Projects: GA AV ČR Premium Academiae of the Academy of Sciences of the Czech Republic; GA MŠk(CZ) LD11079; GA ČR GA206/08/0640; GA MŠk ED1.1.00/02.0109 Institutional support: RVO:68081766 ; RVO:68378050 Keywords : hybrid sterility * meiotic asynapsis * chromosome substitution strains Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 8.167, year: 2013

  3. Mitotic and meiotic chromosomes of a southern Brazilian population of Boophilus microplus (Acari, Ixodidae

    Directory of Open Access Journals (Sweden)

    Rosane Nunes Garcia

    Full Text Available Using conventional staining with acetic orcein and C-banding techniques it was investigated constitutive heterochromatin chromosomal polymorphisms and the mitotic and the meiotic behavior of male and female chromosomes of Boophilus microplus (Canestrini, 1887. Some differences were detected in the population of southern Brazil as compared to the data of other authors for populations in other latitudes. The differences being mainly concerned with the distribution of constitutive centromeric heterochromatin and variation in the length of heterochromatic blocks in the pericentromeric regions of some chromosome pairs.

  4. Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast.

    Directory of Open Access Journals (Sweden)

    Bilge Argunhan

    Full Text Available Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs. The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI whereas no significant reduction was found in smaller chromosomes (III and VI. On the other hand, the absence of Rad17 (a critical component of the ATR pathway lead to an increase in DSB formation (chromosomes VII and II were tested. We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation.

  5. Nuclear

    International Nuclear Information System (INIS)

    Anon.

    2000-01-01

    The first text deals with a new circular concerning the collect of the medicine radioactive wastes, containing radium. This campaign wants to incite people to let go their radioactive wastes (needles, tubes) in order to suppress any danger. The second text presents a decree of the 31 december 1999, relative to the limitations of noise and external risks resulting from the nuclear facilities exploitation: noise, atmospheric pollution, water pollution, wastes management and fire prevention. (A.L.B.)

  6. Absence of SUN-domain protein Slp1 blocks karyogamy and switches meiotic recombination and synapsis from homologs to sister chromatids

    Science.gov (United States)

    Vasnier, Christelle; de Muyt, Arnaud; Zhang, Liangran; Tessé, Sophie; Kleckner, Nancy E.; Zickler, Denise; Espagne, Eric

    2014-01-01

    Karyogamy, the process of nuclear fusion is required for two haploid gamete nuclei to form a zygote. Also, in haplobiontic organisms, karyogamy is required to produce the diploid nucleus/cell that then enters meiosis. We identify sun like protein 1 (Slp1), member of the mid–Sad1p, UNC-84–domain ubiquitous family, as essential for karyogamy in the filamentous fungus Sordaria macrospora, thus uncovering a new function for this protein family. Slp1 is required at the last step, nuclear fusion, not for earlier events including nuclear movements, recognition, and juxtaposition. Correspondingly, like other family members, Slp1 localizes to the endoplasmic reticulum and also to its extensions comprising the nuclear envelope. Remarkably, despite the absence of nuclear fusion in the slp1 null mutant, meiosis proceeds efficiently in the two haploid “twin” nuclei, by the same program and timing as in diploid nuclei with a single dramatic exception: the normal prophase program of recombination and synapsis between homologous chromosomes, including loading of recombination and synaptonemal complex proteins, occurs instead between sister chromatids. Moreover, the numbers of recombination-initiating double-strand breaks (DSBs) and ensuing recombinational interactions, including foci of the essential crossover factor Homo sapiens enhancer of invasion 10 (Hei10), occur at half the diploid level in each haploid nucleus, implying per-chromosome specification of DSB formation. Further, the distribution of Hei10 foci shows interference like in diploid meiosis. Centromere and spindle dynamics, however, still occur in the diploid mode during the two meiotic divisions. These observations imply that the prophase program senses absence of karyogamy and/or absence of a homolog partner and adjusts the interchromosomal interaction program accordingly. PMID:25210014

  7. Senataxin plays an essential role with DNA damage response proteins in meiotic recombination and gene silencing.

    Directory of Open Access Journals (Sweden)

    Olivier J Becherel

    2013-04-01

    Full Text Available Senataxin, mutated in the human genetic disorder ataxia with oculomotor apraxia type 2 (AOA2, plays an important role in maintaining genome integrity by coordination of transcription, DNA replication, and the DNA damage response. We demonstrate that senataxin is essential for spermatogenesis and that it functions at two stages in meiosis during crossing-over in homologous recombination and in meiotic sex chromosome inactivation (MSCI. Disruption of the Setx gene caused persistence of DNA double-strand breaks, a defect in disassembly of Rad51 filaments, accumulation of DNA:RNA hybrids (R-loops, and ultimately a failure of crossing-over. Senataxin localised to the XY body in a Brca1-dependent manner, and in its absence there was incomplete localisation of DNA damage response proteins to the XY chromosomes and ATR was retained on the axial elements of these chromosomes, failing to diffuse out into chromatin. Furthermore persistence of RNA polymerase II activity, altered ubH2A distribution, and abnormal XY-linked gene expression in Setx⁻/⁻ revealed an essential role for senataxin in MSCI. These data support key roles for senataxin in coordinating meiotic crossing-over with transcription and in gene silencing to protect the integrity of the genome.

  8. Xenopus laevis Kif18A is a highly processive kinesin required for meiotic spindle integrity

    Directory of Open Access Journals (Sweden)

    Martin M. Möckel

    2017-04-01

    Full Text Available The assembly and functionality of the mitotic spindle depends on the coordinated activities of microtubule-associated motor proteins of the dynein and kinesin superfamily. Our current understanding of the function of motor proteins is significantly shaped by studies using Xenopus laevis egg extract as its open structure allows complex experimental manipulations hardly feasible in other model systems. Yet, the Kinesin-8 orthologue of human Kif18A has not been described in Xenopus laevis so far. Here, we report the cloning and characterization of Xenopus laevis (Xl Kif18A. Xenopus Kif18A is expressed during oocyte maturation and its depletion from meiotic egg extract results in severe spindle defects. These defects can be rescued by wild-type Kif18A, but not Kif18A lacking motor activity or the C-terminus. Single-molecule microscopy assays revealed that Xl_Kif18A possesses high processivity, which depends on an additional C-terminal microtubule-binding site. Human tissue culture cells depleted of endogenous Kif18A display mitotic defects, which can be rescued by wild-type, but not tail-less Xl_Kif18A. Thus, Xl_Kif18A is the functional orthologue of human Kif18A whose activity is essential for the correct function of meiotic spindles in Xenopus oocytes.

  9. Meiotic double-strand breaks at the interface of chromosome movement, chromosome remodeling, and reductional division

    Science.gov (United States)

    Storlazzi, Aurora; Tessé, Sophie; Gargano, Silvana; James, Françoise; Kleckner, Nancy; Zickler, Denise

    2003-01-01

    Chromosomal processes related to formation and function of meiotic chiasmata have been analyzed in Sordaria macrospora. Double-strand breaks (DSBs), programmed or γ-rays-induced, are found to promote four major events beyond recombination and accompanying synaptonemal complex formation: (1) juxtaposition of homologs from long-distance interactions to close presynaptic coalignment at midleptotene; (2) structural destabilization of chromosomes at leptotene/zygotene, including sister axis separation and fracturing, as revealed in a mutant altered in the conserved, axis-associated cohesin-related protein Spo76/Pds5p; (3) exit from the bouquet stage, with accompanying global chromosome movements, at zygotene/pachytene (bouquet stage exit is further found to be a cell-wide regulatory transition and DSB transesterase Spo11p is suggested to have a new noncatalytic role in this transition); (4) normal occurrence of both meiotic divisions, including normal sister separation. Functional interactions between DSBs and the spo76-1 mutation suggest that Spo76/Pds5p opposes local destabilization of axes at developing chiasma sites and raise the possibility of a regulatory mechanism that directly monitors the presence of chiasmata at metaphase I. Local chromosome remodeling at DSB sites appears to trigger an entire cascade of chromosome movements, morphogenetic changes, and regulatory effects that are superimposed upon a foundation of DSB-independent processes. PMID:14563680

  10. Correlation between pairing initiation sites, recombination nodules and meiotic recombination in Sordaria macrospora.

    Science.gov (United States)

    Zickler, D; Moreau, P J; Huynh, A D; Slezec, A M

    1992-09-01

    The decrease of meiotic exchanges (crossing over and conversion) in two mutants of Sordaria macrospora correlated strongly with a reduction of chiasmata and of both types of "recombination nodules." Serial section reconstruction electron microscopy was used to compare the synapsis pattern of meiotic prophase I in wild type and mutants. First, synapsis occurred but the number of synaptonemal complex initiation sites was reduced in both mutants. Second, this reduction was accompanied by, or resulted in, modifications of the pattern of synapsis. Genetic and synaptonemal complex maps were compared in three regions along one chromosome arm divided into well marked intervals. Reciprocal exchange frequencies and number of recombination nodules correlated in wild type in the three analyzed intervals, but disparity was found between the location of recombination nodules and exchanges in the mutants. Despite the twofold exchange decrease, sections of the genome such as the short arm of chromosome 2 and telomere regions were sheltered from nodule decrease and from pairing modifications. This indicated a certain amount of diversity in the control of these features and suggested that exchange frequency was dependent not only on the amount of effective pairing but also on the localization of the pairing sites, as revealed by the synaptonemal complex progression in the mutants.

  11. Meiotic UV-sensitive mutant that causes deletion of duplications in neurospora

    International Nuclear Information System (INIS)

    Newmeyer, D.; Galeazzi, D.R.

    1978-01-01

    The meiotic-3 (mei-3) mutant of Neurospora crassa has several effects: (1) when homozygous, it almost completely blocks meiosis and ascospore formation, (2) it is sensitive to uv, (3) its growth is inhibited by histidine, and (4) it increases the instability of nontandem duplications. This was shown for duplications produced by five different rearrangements and was demonstrated by two different criteria. The effects on meiosis and duplication instability are expressed strongly at 25 0 ; the effects on sensitivity to uv and to histidine are expressed strongly at 38.5 0 but only slightly at 25 0 . Nevertheless, all four effects were shown to be due to a single gene. Mei-3 is not allelic with previously reported uv-sensitive mutants. Two other results were obtained that are not necessarily due to mei-3: (1) a cross involving mei-3 produced a new unlinked meiotic mutant, mei-4, which is not sensitive to uv or histidine, and (2) a burst of several new mutants occurred in a different mei-3 stock, including a partial revertant to mei-3. Mei-3 has previously been shown to cause frequent complete loss of a terminal duplicate segment, beginning exactly at the original rearrangement breakpoint. Possible mechanisms are discussed by which a uv-sensitive mutant could cause such precise deletions

  12. Identification of new genes required for meiotic recombination in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Ajimura, M.; Lee, S.H.; Ogawa, H.

    1993-01-01

    Mutants defective in meiotic recombination were isolated from a disomic haploid strain of Saccharomyces cerevisiae by examining recombination within the leu2 and his4 heteroalleles located on chromosome III. The mutants were classified into two new complementation groups (MRE2 and MRE11) and eight previously identified groups, which include SPO11, HOP1, REC114, MRE4/MEK1 and genes in the RAD52 epistasis group. All of the mutants, in which the mutations in the new complementation groups are homozygous and diploid, can undergo premeiotic DNA synthesis and produce spores. The spores are, however, not viable. The mre2 and mre11 mutants produce viable spores in a spo13 background, in which meiosis I is bypassed, suggesting that these mutants are blocked at an early step in meiotic recombination. The mre2 mutant does not exhibit any unusual phenotype during mitosis and it is, thus, considered to have a mutation in a meiosis-specific gene. By contrast, the mre11 mutant is sensitive to damage to DNA by methyl methanesulfonate and exhibits a hyperrecombination phenotype in mitosis. Among six alleles of HOP1 that were isolated, an unusual pattern of intragenic complementation was observed

  13. The RTR complex as caretaker of genome stability and its unique meiotic function in plants

    Directory of Open Access Journals (Sweden)

    Alexander eKnoll

    2014-02-01

    Full Text Available The RTR complex consisting of a RecQ helicase, a type IA topoisomerase and the structural protein RMI1 is involved in the processing of DNA recombination intermediates in all eukaryotes. In Arabidopsis thaliana the complex partners RECQ4A, topoisomerase 3α and RMI1 have been shown to be involved in DNA repair and in the suppression of homologous recombination (HR in somatic cells. Interestingly, mutants of AtTOP3A and AtRMI1 are also sterile due to extensive chromosome breakage in meiosis I, a phenotype that seems to be specific for plants. Although both proteins are essential for meiotic recombination it is still elusive on what kind of intermediates they are acting on. Recent data indicate that the pattern of non-crossover (NCO-associated meiotic gene conversion (GC differs between plants and other eukaryotes, as less NCOs in comparison to crossovers (CO could be detected in Arabidopsis. This indicates that NCOs happen either more rarely in plants or that the conversion tract length is significantly shorter than in other organisms. As the TOP3α/RMI1-mediated dissolution of recombination intermediates results exclusively in NCOs, we suggest that the peculiar GC pattern found in plants is connected to the unique role, members of the RTR complex play in plant meiosis.

  14. Competition between meiotic and apomictic pathways during ovule and seed development results in clonality.

    Science.gov (United States)

    Hojsgaard, Diego H; Martínez, Eric J; Quarin, Camilo L

    2013-01-01

    Meiotic and apomictic reproductive pathways develop simultaneously in facultative aposporous species, and compete to form a seed as a final goal. This developmental competition was evaluated in tetraploid genotypes of Paspalum malacophyllum in order to understand the low level of sexuality in facultative apomictic populations. Cyto-embryology on ovules, flow cytometry on seeds and progeny tests by DNA fingerprinting were used to measure the relative incidence of each meiotic or apomictic pathway along four different stages of the plant's life cycle, namely the beginning and end of gametogenesis, seed formation and adult offspring. A high variation in the frequencies of sexual and apomictic pathways occurred at the first two stages. A trend of radical decline in realized sexuality was then observed. Sexual and apomictic seeds were produced, but the efficiency of the sexual pathway dropped drastically, and exclusively clonal offspring remained. Both reproductive pathways are unstable at the beginning of development, and only the apomictic one remains functional. Key factors reducing sexuality are the faster growth and parthenogenetic development in the aposporous pathway, and an (epi)genetically negative background related to the extensive gene de-regulation pattern responsible for apomixis. The effects of inbreeding depression during post-fertilization development may further decrease the frequency of effective sexuality. No claim to original US government works. New Phytologist © 2012 New Phytologist Trust.

  15. DNA Sequence-Mediated, Evolutionarily Rapid Redistribution of Meiotic Recombination Hotspots

    Science.gov (United States)

    Wahls, Wayne P.; Davidson, Mari K.

    2011-01-01

    Hotspots regulate the position and frequency of Spo11 (Rec12)-initiated meiotic recombination, but paradoxically they are suicidal and are somehow resurrected elsewhere in the genome. After the DNA sequence-dependent activation of hotspots was discovered in fission yeast, nearly two decades elapsed before the key realizations that (A) DNA site-dependent regulation is broadly conserved and (B) individual eukaryotes have multiple different DNA sequence motifs that activate hotspots. From our perspective, such findings provide a conceptually straightforward solution to the hotspot paradox and can explain other, seemingly complex features of meiotic recombination. We describe how a small number of single-base-pair substitutions can generate hotspots de novo and dramatically alter their distribution in the genome. This model also shows how equilibrium rate kinetics could maintain the presence of hotspots over evolutionary timescales, without strong selective pressures invoked previously, and explains why hotspots localize preferentially to intergenic regions and introns. The model is robust enough to account for all hotspots of humans and chimpanzees repositioned since their divergence from the latest common ancestor. PMID:22084420

  16. Contrasted patterns of crossover and non-crossover at Arabidopsis thaliana meiotic recombination hotspots.

    Directory of Open Access Journals (Sweden)

    Jan Drouaud

    2013-11-01

    Full Text Available The vast majority of meiotic recombination events (crossovers (COs and non-crossovers (NCOs cluster in narrow hotspots surrounded by large regions devoid of recombinational activity. Here, using a new molecular approach in plants, called "pollen-typing", we detected and characterized hundreds of CO and NCO molecules in two different hotspot regions in Arabidopsis thaliana. This analysis revealed that COs are concentrated in regions of a few kilobases where their rates reach up to 50 times the genome average. The hotspots themselves tend to cluster in regions less than 8 kilobases in size with overlapping CO distribution. Non-crossover (NCO events also occurred in the two hotspots but at very different levels (local CO/NCO ratios of 1/1 and 30/1 and their track lengths were quite small (a few hundred base pairs. We also showed that the ZMM protein MSH4 plays a role in CO formation and somewhat unexpectedly we also found that it is involved in the generation of NCOs but with a different level of effect. Finally, factors acting in cis and in trans appear to shape the rate and distribution of COs at meiotic recombination hotspots.

  17. Pattern of callose deposition during the course of meiotic diplospory in Chondrilla juncea (Asteraceae, Cichorioideae).

    Science.gov (United States)

    Musiał, Krystyna; Kościńska-Pająk, Maria

    2017-07-01

    Total absence of callose in the ovules of diplosporous species has been previously suggested. This paper is the first description of callose events in the ovules of Chondrilla juncea, which exhibits meiotic diplospory of the Taraxacum type. We found the presence of callose in the megasporocyte wall and stated that the pattern of callose deposition is dynamically changing during megasporogenesis. At the premeiotic stage, no callose was observed in the ovules. Callose appeared at the micropylar pole of the cell entering prophase of the first meioticdivision restitution but did not surround the megasporocyte. After the formation of a restitution nucleus, a conspicuous callose micropylar cap and dispersed deposits of callose were detected in the megasporocyte wall. During the formation of a diplodyad, the micropylar callose cap decreased and the walls of a newly formed megaspores showed scattered distribution of callose. Within the older diplodyad, callose was mainly accumulated in the wall between megaspores, as well as in the wall of the micropylar cell; however, a dotted fluorescence of callose was also visible in the wall of the chalazal megaspore. Gradual degradation of callose in the wall of the chalazal cell and intense callose accumulation in the wall of the micropylar cell were related to the selection of the functional megaspore. Thus, our findings may suggest that callose fulfills a similar role both during megasporogenesis in sexual angiosperms and in the course of meiotic diplospory in apomicts and seems to form a regulatory interface between reproductive and somatic cells.

  18. Nested Inversion Polymorphisms Predispose Chromosome 22q11.2 to Meiotic Rearrangements.

    Science.gov (United States)

    Demaerel, Wolfram; Hestand, Matthew S; Vergaelen, Elfi; Swillen, Ann; López-Sánchez, Marcos; Pérez-Jurado, Luis A; McDonald-McGinn, Donna M; Zackai, Elaine; Emanuel, Beverly S; Morrow, Bernice E; Breckpot, Jeroen; Devriendt, Koenraad; Vermeesch, Joris R

    2017-10-05

    Inversion polymorphisms between low-copy repeats (LCRs) might predispose chromosomes to meiotic non-allelic homologous recombination (NAHR) events and thus lead to genomic disorders. However, for the 22q11.2 deletion syndrome (22q11.2DS), the most common genomic disorder, no such inversions have been uncovered as of yet. Using fiber-FISH, we demonstrate that parents transmitting the de novo 3 Mb LCR22A-D 22q11.2 deletion, the reciprocal duplication, and the smaller 1.5 Mb LCR22A-B 22q11.2 deletion carry inversions of LCR22B-D or LCR22C-D. Hence, the inversions predispose chromosome 22q11.2 to meiotic rearrangements and increase the individual risk for transmitting rearrangements. Interestingly, the inversions are nested or flanking rather than coinciding with the deletion or duplication sizes. This finding raises the possibility that inversions are a prerequisite not only for 22q11.2 rearrangements but also for all NAHR-mediated genomic disorders. Copyright © 2017. Published by Elsevier Inc.

  19. Temperature dependence of intracellular Ca2+ homeostasis in rat meiotic and postmeiotic spermatogenic cells.

    Science.gov (United States)

    Herrera, E; Salas, K; Lagos, N; Benos, D J; Reyes, J G

    2001-10-01

    The hypothesis that intracellular [Ca2+] is a cell parameter responsive to extreme temperatures in rat meiotic and postmeiotic spermatogenic cells was tested using intracellular fluorescent probes for Ca2+ and pH. In agreement with this hypothesis, extreme temperatures induced a rapid increase of cytosolic [Ca2+] in rat pachytene spermatocytes and round spermatids. Oscillatory changes in temperature can induce oscillations in cytosolic [Ca2+] in these cells. Intracellular [Ca2+] homeostasis in round spermatids was more sensitive to high temperatures compared with pachytene spermatocytes. The calculated activation energies for SERCA ATPase-mediated fluxes in pachytene spermatocytes and round spermatids were 62 and 75 kJ mol(-1), respectively. The activation energies for leak fluxes from intracellular Ca2+ stores were 55 and 68 kJ mol(-1) for pachytene spermatocytes and round spermatids, respectively. Together with changes in cytosolic [Ca2+], round spermatids undergo a decrease in pH(i) at high temperatures. This temperature-induced decrease in pH(i) appears to be partially responsible for the increase in cytosolic [Ca2+] of round spermatids induced by high temperatures. This characteristic of rat meiotic and postmeiotic spermatogenic cells to undergo an increment in cytosolic Ca2+ at temperatures > 33 degrees C can be related to the induction of programmed cell death by high temperatures in these cells.

  20. Male and female meiotic behaviour of an intrachromosomal insertion determined by preimplantation genetic diagnosis

    Directory of Open Access Journals (Sweden)

    Doshi Alpesh

    2010-02-01

    Full Text Available Abstract Background Two related family members, a female and a male balanced carrier of an intrachromosomal insertion on chromosome 7 were referred to our centre for preimplantation genetic diagnosis. This presented a rare opportunity to investigate the behaviour of the insertion chromosome during meiosis in two related carriers. The aim of this study was to carry out a detailed genetic analysis of the preimplantation embryos that were generated from the three treatment cycles for the male and two for the female carrier. Patients underwent in vitro fertilization and on day 3, 22 embryos from the female carrier and 19 embryos from the male carrier were biopsied and cells analysed by fluorescent in situ hybridization. Follow up analysis of 29 untransferred embryos was also performed for confirmation of the diagnosis and to obtain information on meiotic and mitotic outcome. Results In this study, the female carrier produced more than twice as many chromosomally balanced embryos as the male (76.5% vs. 36%, and two pregnancies were achieved for her. Follow up analysis showed that the male carrier had produced more highly abnormal embryos than the female (25% and 15% respectively and no pregnancies occurred for the male carrier and his partner. Conclusion This study compares how an intrachromosomal insertion has behaved in the meiotic and preimplantation stages of development in sibling male and female carriers. It confirms that PGD is an appropriate treatment in such cases. Reasons for the differing outcome for the two carriers are discussed.

  1. B microchromosomes in the family Curimatidae (Characiformes): mitotic and meiotic behavior.

    Science.gov (United States)

    Sampaio, Tatiane Ramos; Gravena, Waleska; Gouveia, Juceli Gonzalez; Giuliano-Caetano, Lucia; Dias, Ana Lúcia

    2011-01-01

    Cyphocharax voga (Hensel, 1870), Cyphocharax spilotus (Vari, 1987), Cyphocharax saladensis (Meinken, 1933), Cyphocharax modestus (Fernández-Yépez, 1948), Steindachnerina biornata (Braga & Azpelicueta, 1987) and Steindachnerina insculpta (Fernández-Yépez, 1948) collected from two hydrographic basins. All samples presented 2n=54 meta-submetacentric (m-sm) chromosomes and FN equal to 108, and 1 or 2 B microchromosomes in the mitotic and meiotic cells of the six sampled populations showing inter-and intraindividual variation. The analysis of the meiotic cells in Cyphocharax saladensis, Cyphocharax spilotus, and Cyphocharax voga showed a modal number of 54 chromosomes in the spermatogonial metaphases and 27 bivalents in the pachytene, diplotene, diakinesis and in metaphase I stages, and 27 chromosomes in metaphase II; in Cyphocharax modestus, Steindachnerina biornata, and Steindachnerina insculpta, spermatogonial metaphases with 54 chromosomes and pachytene and metaphase I with 27 bivalents were observed. The B microchromosome was observed as univalent in the spermatogonial metaphase of Cyphocharax spilotus, in the pachytene stage in the other species, with the exception of Cyphocharax saladensis, and Steindachnerina biornata in metaphase I. New occurrences of the B microchromosome in Cyphocharax voga, Cyphocharax saladensis and Steindachnerina biornata were observed, confirming that the presence of this type of chromosome is a striking characteristic of this group of fish.

  2. Histone H2AFX Links Meiotic Chromosome Asynapsis to Prophase I Oocyte Loss in Mammals.

    Directory of Open Access Journals (Sweden)

    Jeffrey M Cloutier

    2015-10-01

    Full Text Available Chromosome abnormalities are common in the human population, causing germ cell loss at meiotic prophase I and infertility. The mechanisms driving this loss are unknown, but persistent meiotic DNA damage and asynapsis may be triggers. Here we investigate the contribution of these lesions to oocyte elimination in mice with chromosome abnormalities, e.g. Turner syndrome (XO and translocations. We show that asynapsed chromosomes trigger oocyte elimination at diplonema, which is linked to the presence of phosphorylated H2AFX (γH2AFX. We find that DNA double-strand break (DSB foci disappear on asynapsed chromosomes during pachynema, excluding persistent DNA damage as a likely cause, and demonstrating the existence in mammalian oocytes of a repair pathway for asynapsis-associated DNA DSBs. Importantly, deletion or point mutation of H2afx restores oocyte numbers in XO females to wild type (XX levels. Unexpectedly, we find that asynapsed supernumerary chromosomes do not elicit prophase I loss, despite being enriched for γH2AFX and other checkpoint proteins. These results suggest that oocyte loss cannot be explained simply by asynapsis checkpoint models, but is related to the gene content of asynapsed chromosomes. A similar mechanistic basis for oocyte loss may operate in humans with chromosome abnormalities.

  3. Location of RAD51-like protein during meiotic prophase in Eimeria tenella.

    Science.gov (United States)

    Del Cacho, Emilio; Gallego, Margarita; Pagés, Marc; Barbero, José Luís; Monteagudo, Luís; Sánchez-Acedo, Caridad

    2011-05-31

    This study focuses on reporting events in Eimeria tenella oocysts from early to late prophase I in terms of RAD51 protein in association with the synaptonemal complex formed between homologous chromosomes. The aim of the study was the sequential localization of RAD51 protein, which is involved in the repair of double-strand breaks (DSBs) on the eimerian chromosomes as they synapse and desynapse. Structural Maintenance of Chromosome protein SMC3, which plays a role in synaptonemal complex formation, was labeled to identify initiation and progress of chromosome synapsis and desynapsis in parallel with the appearance and disappearance of RAD51 foci. Antibodies directed against RAD51 and cohesin subunit SMC3 proteins were labeled with either fluorescence or colloidal gold to visualize RAD51 protein foci and synaptonemal complexes. RAD51 protein localization during prophase I was studied on meiotic chromosomes spreads obtained from oocysts at different points in time after the start of sporulation. The present findings showed that foci detected with the antibody directed against RAD51 protein first appeared at the pre-leptotene stage before homologous chromosomes began pairing. Subsequently, the foci were detected in association with the lateral elements at the precise sites where synapsis were in progress. These findings lead us to suggest that in E. tenella, homologous chromosome pairing was a DSB-dependent mechanism and reinforced the participation of RAD51 protein in meiotic homology search, alignment and pairing of chromosomes. Copyright © 2010 Elsevier B.V. All rights reserved.

  4. Histone H2AFX Links Meiotic Chromosome Asynapsis to Prophase I Oocyte Loss in Mammals

    Science.gov (United States)

    Cloutier, Jeffrey M.; Mahadevaiah, Shantha K.; ElInati, Elias; Nussenzweig, André; Tóth, Attila; Turner, James M. A.

    2015-01-01

    Chromosome abnormalities are common in the human population, causing germ cell loss at meiotic prophase I and infertility. The mechanisms driving this loss are unknown, but persistent meiotic DNA damage and asynapsis may be triggers. Here we investigate the contribution of these lesions to oocyte elimination in mice with chromosome abnormalities, e.g. Turner syndrome (XO) and translocations. We show that asynapsed chromosomes trigger oocyte elimination at diplonema, which is linked to the presence of phosphorylated H2AFX (γH2AFX). We find that DNA double-strand break (DSB) foci disappear on asynapsed chromosomes during pachynema, excluding persistent DNA damage as a likely cause, and demonstrating the existence in mammalian oocytes of a repair pathway for asynapsis-associated DNA DSBs. Importantly, deletion or point mutation of H2afx restores oocyte numbers in XO females to wild type (XX) levels. Unexpectedly, we find that asynapsed supernumerary chromosomes do not elicit prophase I loss, despite being enriched for γH2AFX and other checkpoint proteins. These results suggest that oocyte loss cannot be explained simply by asynapsis checkpoint models, but is related to the gene content of asynapsed chromosomes. A similar mechanistic basis for oocyte loss may operate in humans with chromosome abnormalities. PMID:26509888

  5. Molecular Basis for Enhancement of the Meiotic DMCI Recombinase by RAD51AP1

    Energy Technology Data Exchange (ETDEWEB)

    Dray, Eloise; Dunlop, Myun Hwa; Kauppi, Liisa; San Filippo, Joseph San; Wiese, Claudia; Tsai, Miaw-Sheue; Begovic, Sead; Schild, David; Jasin, Maria; Keeney, Scott; Sung, Patrick

    2010-11-05

    Homologous recombination is needed for meiotic chromosome segregation, genome maintenance, and tumor suppression. RAD51AP1 (RAD51 Associated Protein 1) has been shown to interact with and enhance the recombinase activity of RAD51. Accordingly, genetic ablation of RAD51AP1 leads to enhanced sensitivity to and also chromosome aberrations upon DNA damage, demonstrating a role for RAD51AP1 in mitotic homologous recombination. Here we show physical association of RAD51AP1 with the meiosis-specific recombinase DMC1 and a stimulatory effect of RAD51AP1 on the DMC1-mediated D-loop reaction. Mechanistic studies have revealed that RAD51AP1 enhances the ability of the DMC1 presynaptic filament to capture the duplex DNA partner and to assemble the synaptic complex, in which the recombining DNA strands are homologously aligned. We also provide evidence that functional co-operation is dependent on complex formation between DMC1 and RAD51AP1, and that distinct epitopes in RAD51AP1 mediate interactions with RAD51 and DMC1. Finally, we show that RAD51AP1 is expressed in mouse testes, and that RAD51AP1 foci co-localize with a subset of DMC1 foci in spermatocytes. These results suggest that RAD51AP1 also serves an important role in meiotic homologous recombination.

  6. The Chromatin Protein DUET/MMD1 Controls Expression of the Meiotic Gene TDM1 during Male Meiosis in Arabidopsis.

    Science.gov (United States)

    Andreuzza, Sébastien; Nishal, Bindu; Singh, Aparna; Siddiqi, Imran

    2015-09-01

    Meiosis produces haploid cells essential for sexual reproduction. In yeast, entry into meiosis activates transcription factors which trigger a transcriptional cascade that results in sequential co-expression of early, middle and late meiotic genes. However, these factors are not conserved, and the factors and regulatory mechanisms that ensure proper meiotic gene expression in multicellular eukaryotes are poorly understood. Here, we report that DUET/MMD1, a PHD finger protein essential for Arabidopsis male meiosis, functions as a transcriptional regulator in plant meiosis. We find that DUET-PHD binds H3K4me2 in vitro, and show that this interaction is critical for function during meiosis. We also show that DUET is required for proper microtubule organization during meiosis II, independently of its function in meiosis I. Remarkably, DUET protein shows stage-specific expression, confined to diplotene. We identify two genes TDM1 and JAS with critical functions in cell cycle transitions and spindle organization in male meiosis, as DUET targets, with TDM1 being a direct target. Thus, DUET is required to regulate microtubule organization and cell cycle transitions during male meiosis, and functions as a direct transcription activator of the meiotic gene TDM1. Expression profiling showed reduced expression of a subset comprising about 12% of a known set of meiosis preferred genes in the duet mutant. Our results reveal the action of DUET as a transcriptional regulator during male meiosis in plants, and suggest that transcription of meiotic genes is under stagewise control in plants as in yeast.

  7. Comparative Meiotic Studies in Triatoma sordida (Stål and T. guasayana Wygodzinsky & Abalos (Reduviidae, Heteroptera

    Directory of Open Access Journals (Sweden)

    P Rebagliati

    1998-05-01

    Full Text Available Triatoma sordida and T. guasayana are competent Trypanosoma cruzi vectors, with overlapping distribution areas in Argentina. Both species are morphologically similar, and their immature stages are hard to discriminate. Cytogenetic studies in the genus Triatoma reveal scarce karyotypic variations, being 2n= 20 + XY the most frequent diploid number in males. In the present work the meiotic behaviour of different Argentinian populations of T. sordida and T. guasayana has been analyzed; the meiotic karyotype of both species has also been compared. The species differ in total chromosome area and in the relative area of the sex chromosomes. These meiotic karyotypic differences constitute an additional tool for the taxonomic characterization of T. sordida and T. guasayana. The analysis of an interpopulation hybrid of T. sordida (Brazil x Argentina reveals a regular meiotic behaviour, despite the presence of heteromorphic bivalents. Our observations support the hypothesis that karyotype variations through the gain or loss of heterochromatin can not be considered as a primary mechanism of reproductive isolation in Triatoma.

  8. ZIP4H (TEX11 deficiency in the mouse impairs meiotic double strand break repair and the regulation of crossing over.

    Directory of Open Access Journals (Sweden)

    Carrie A Adelman

    2008-03-01

    Full Text Available We have recently shown that hypomorphic Mre11 complex mouse mutants exhibit defects in the repair of meiotic double strand breaks (DSBs. This is associated with perturbation of synaptonemal complex morphogenesis, repair and regulation of crossover formation. To further assess the Mre11 complex's role in meiotic progression, we identified testis-specific NBS1-interacting proteins via two-hybrid screening in yeast. In this screen, Zip4h (Tex11, a male germ cell specific X-linked gene was isolated. Based on sequence and predicted structural similarity to the S. cerevisiae and A. thaliana Zip4 orthologs, ZIP4H appears to be the mammalian ortholog. In S. cerevisiae and A. thaliana, Zip4 is a meiosis-specific protein that regulates the level of meiotic crossovers, thus influencing homologous chromosome segregation in these organisms. As is true for hypomorphic Nbs1 (Nbs1(DeltaB/DeltaB mice, Zip4h(-/Y mutant mice were fertile. Analysis of spermatocytes revealed a delay in meiotic double strand break repair and decreased crossover formation as inferred from DMC1 and MLH1 staining patterns, respectively. Achiasmate chromosomes at the first meiotic division were also observed in Zip4h(-/Y mutants, consistent with the observed reduction in MLH1 focus formation. These results indicate that meiotic functions of Zip4 family members are conserved and support the view that the Mre11 complex and ZIP4H interact functionally during the execution of the meiotic program in mammals.

  9. The Saccharomyces cerevisiae MUM2 gene interacts with the DNA replication machinery and is required for meiotic levels of double strand breaks.

    Science.gov (United States)

    Davis, L; Barbera, M; McDonnell, A; McIntyre, K; Sternglanz, R; Jin , Q; Loidl, J; Engebrecht, J

    2001-01-01

    The Saccharomyces cerevisiae MUM2 gene is essential for meiotic, but not mitotic, DNA replication and thus sporulation. Genetic interactions between MUM2 and a component of the origin recognition complex and polymerase alpha-primase suggest that MUM2 influences the function of the DNA replication machinery. Early meiotic gene expression is induced to a much greater extent in mum2 cells than in meiotic cells treated with the DNA synthesis inhibitor hydroxyurea. This result indicates that the mum2 meiotic arrest is downstream of the arrest induced by hydroxyurea and suggests that DNA synthesis is initiated in the mutant. Genetic analyses indicate that the recombination that occurs in mum2 mutants is dependent on the normal recombination machinery and on synaptonemal complex components and therefore is not a consequence of lesions created by incompletely replicated DNA. Both meiotic ectopic and allelic recombination are similarly reduced in the mum2 mutant, and the levels are consistent with the levels of meiosis-specific DSBs that are generated. Cytological analyses of mum2 mutants show that chromosome pairing and synapsis occur, although at reduced levels compared to wild type. Given the near-wild-type levels of meiotic gene expression, pairing, and synapsis, we suggest that the reduction in DNA replication is directly responsible for the reduced level of DSBs and meiotic recombination. PMID:11238403

  10. Depletion of Key Meiotic Genes and Transcriptome-Wide Abiotic Stress Reprogramming Mark Early Preparatory Events Ahead of Apomeiotic Transition

    Directory of Open Access Journals (Sweden)

    Jubin N Shah

    2016-10-01

    Full Text Available Molecular dissection of apomixis - an asexual reproductive mode - is anticipated to solve the enigma of loss of meiotic sex, and to help fixing elite agronomic traits. The Brassicaceae genus Boechera comprises of both sexual and apomictic species, permitting comparative analyses of meiotic circumvention (apomeiosis and parthenogenesis. Whereas previous studies reported local transcriptome changes during these events, it remained unclear whether global changes associated with hybridization, polyploidy and environmental adaptation that arose during evolution of Boechera might hint as (epigenetic regulators of early development prior apomictic initiation. To identify these signatures during vegetative stages, we compared seedling RNA-seq transcriptomes of an obligate triploid apomict and a diploid sexual, both isolated from a drought-prone habitat. Uncovered were several genes differentially expressed between sexual and apomictic seedlings, including homologues of meiotic genes ASYNAPTIC 1 (ASY1 and MULTIPOLAR SPINDLE 1 (MPS1 that were down-regulated in apomicts. An intriguing class of apomict-specific deregulated genes included several NAC transcription factors, homologues of which are known to be transcriptionally reprogrammed during abiotic stress in other plants. Deregulation of both meiotic and stress-response genes during seedling stages might possibly be important in preparation for meiotic circumvention, as similar transcriptional alteration was discernible in apomeiotic floral buds too. Furthermore, we noted that the apomict showed better tolerance to osmotic stress in vitro than the sexual, in conjunction with significant upregulation of a subset of NAC genes. In support of the current model that DNA methylation epigenetically regulates stress, ploidy, hybridization and apomixis, we noted that ASY1, MPS1 and NAC019 homologues were deregulated in Boechera seedlings upon DNA demethylation, and ASY1 in particular seems to be repressed by

  11. Regulatory complexity revealed by integrated cytological and RNA-seq analyses of meiotic substages in mouse spermatocytes.

    Science.gov (United States)

    Ball, Robyn L; Fujiwara, Yasuhiro; Sun, Fengyun; Hu, Jianjun; Hibbs, Matthew A; Handel, Mary Ann; Carter, Gregory W

    2016-08-12

    The continuous and non-synchronous nature of postnatal male germ-cell development has impeded stage-specific resolution of molecular events of mammalian meiotic prophase in the testis. Here the juvenile onset of spermatogenesis in mice is analyzed by combining cytological and transcriptomic data in a novel computational analysis that allows decomposition of the transcriptional programs of spermatogonia and meiotic prophase substages. Germ cells from testes of individual mice were obtained at two-day intervals from 8 to 18 days post-partum (dpp), prepared as surface-spread chromatin and immunolabeled for meiotic stage-specific protein markers (STRA8, SYCP3, phosphorylated H2AFX, and HISTH1T). Eight stages were discriminated cytologically by combinatorial antibody labeling, and RNA-seq was performed on the same samples. Independent principal component analyses of cytological and transcriptomic data yielded similar patterns for both data types, providing strong evidence for substage-specific gene expression signatures. A novel permutation-based maximum covariance analysis (PMCA) was developed to map co-expressed transcripts to one or more of the eight meiotic prophase substages, thereby linking distinct molecular programs to cytologically defined cell states. Expression of meiosis-specific genes is not substage-limited, suggesting regulation of substage transitions at other levels. This integrated analysis provides a general method for resolving complex cell populations. Here it revealed not only features of meiotic substage-specific gene expression, but also a network of substage-specific transcription factors and relationships to potential target genes.

  12. Estimation of pre-meiotic DNA synthesis period in the dog spermatozoa

    International Nuclear Information System (INIS)

    Ghosal, S.K.; Bandyopadhyay, T.; De, S.; Beauregard, L.J.

    1976-01-01

    About 10 μCi of 3 H-thymidine was injected into each of 4 arbitarary sites in each testis of 6 dogs. Biopsies were taken at 4-hour intervals coverning a period from 20.0 to 22.2 days post-injection. Kinetics of labelled spermatocytes was followed employing Kodak NTB-3 emulsion to conventionally prepared air-dried slides. The technique for calculating pre-meiosis DNA synthesis duration is same as that for estimating S period in mitotic cells. Current investigation suggests that the mean duration of pre-meiotic S period of Canine spermatocytes is 20.4 hrs as compared to 29 and 40 hrs in spermatocytes of mouse and golden hamster respectively. (author)

  13. Ascospores of large-spored Metschnikowia species are genuine meiotic products of these yeasts

    DEFF Research Database (Denmark)

    Marinoni, G.; Piskur, Jure; Lachance, M.A.

    2003-01-01

    continentalis var. continentalis, and M. continentalis var. borealis. Asci were dissected and the segregation patterns for various phenotypes analyzed. In all cases (n = 47) both mating types (h(+) and h(-)) were recovered in pairs of sister spores, casting further uncertainty as to whether normal meiosis takes...... place. However, the segregation patterns for cycloheximide resistance and several auxotrophic markers were random, suggesting that normal meiosis indeed occurs. To explain the lack of second-division segregation of mating types, we concluded that crossing-over does not occur between the mating......-type locus and the centromere, and that meiosis I is tied to spore formation, which explains why the number of spores is limited to two. The latter assumption was also supported by fluorescence microscopy. The second meiotic division takes place inside the spores and is followed by the resorption of two...

  14. Mapping genes by meiotic and UV-induced mitotic recombination in Coprinus cinereus

    International Nuclear Information System (INIS)

    Amirkhanian, J.D.; Cowan, J.W.

    1985-01-01

    Three morphological mutants in Coprinus cinereus—one spontaneous (den-2) and two chemically induced (zigand sta)—were assigned to linkage groups and utilized in meiotic and mitotic mapping. Mutants den-2 and zig belong to linkage group III, den-2 being close to the centromere and about 20 map units (mu) from zig. The mutant sta in linkage group ‘G’ is at a distance of about 37 mu from ade-3. Mitotic mapping confirmed the gene order in linkage group III and provided evidence that trp-2 in linkage group ‘G’ was between the centromere and ade-3. These morphological mutants are compact in colony growth and therefore suited to high-density plating. The rarity of spontaneously occurring mitotic segregants suggests that diploids of Coprinus cinereus, heterozygous for morphoiogical markers in repuision, could serve as useful test systems for rapid screening of chemical mutagen/carcinogens via mitotic recombination studies

  15. Fine-scale variation in meiotic recombination in Mimulus inferred from population shotgun sequencing

    Energy Technology Data Exchange (ETDEWEB)

    Hellsten, Uffe [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Wright, Kevin M. [Harvard Univ., Cambridge, MA (United States); Jenkins, Jerry [USDOE Joint Genome Inst., Walnut Creek, CA (United States); HudsonAlpha Inst. of Biotechnology, Huntsville, AL (United States); Shu, Shengqiang [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Yuan, Yao-Wu [Univ. of Connecticut, Storrs, CT (United States); Wessler, Susan R. [Univ. of California, Riverside, CA (United States); Schmutz, Jeremy [USDOE Joint Genome Inst., Walnut Creek, CA (United States); HudsonAlpha Inst. of Biotechnology, Huntsville, AL (United States); Willis, John H. [Duke Univ., Durham, NC (United States); Rokhsar, Daniel S. [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Univ. of California, Berkeley, CA (United States)

    2013-11-13

    Meiotic recombination rates can vary widely across genomes, with hotspots of intense activity interspersed among cold regions. In yeast, hotspots tend to occur in promoter regions of genes, whereas in humans and mice hotspots are largely defined by binding sites of the PRDM9 protein. To investigate the detailed recombination pattern in a flowering plant we use shotgun resequencing of a wild population of the monkeyflower Mimulus guttatus to precisely locate over 400,000 boundaries of historic crossovers or gene conversion tracts. Their distribution defines some 13,000 hotspots of varying strengths, interspersed with cold regions of undetectably low recombination. Average recombination rates peak near starts of genes and fall off sharply, exhibiting polarity. Within genes, recombination tracts are more likely to terminate in exons than in introns. The general pattern is similar to that observed in yeast, as well as in PRDM9-knockout mice, suggesting that recombination initiation described here in Mimulus may reflect ancient and conserved eukaryotic mechanisms

  16. Gamma radiations induced meiotic abnormalities in cape gosseberry (Physalis peruviana Linn.)

    International Nuclear Information System (INIS)

    Gupta, S.K.

    1987-01-01

    The cytological alterations were systematically scored in Physalis peruviana after treatment with 5 to 60 Krads of gamma radiation. In control plant diplotenediakinesis revealed 24 bivalents and cytokinesis produced normal tetrads, whereas PMCs of differently treated plants showed various anomalies viz., altered configuration of chromosomes, clumping/sickness, fragments, bridges, laggards, unequal segregation and non-orientation of chromosomes and unequal groupings of chromosomes. Abnormal karyokinesis and/or cytokinesis led to the formation of abnormal sporads which later on causes pollen and plant sterility. While every type of anomaly is dose-dependent and tend to increase with advancing dose showing a fair degree of correlation with the dose of radiation. The persistence of meiotic abnormalities with reduce d frequency in M 2 generation also bears correlation with administered dose. (author). 10 refs

  17. Meiotic transmission of an in vitro-assembled autonomous maize minichromosome.

    Directory of Open Access Journals (Sweden)

    Shawn R Carlson

    2007-10-01

    Full Text Available Autonomous chromosomes are generated in yeast (yeast artificial chromosomes and human fibrosarcoma cells (human artificial chromosomes by introducing purified DNA fragments that nucleate a kinetochore, replicate, and segregate to daughter cells. These autonomous minichromosomes are convenient for manipulating and delivering DNA segments containing multiple genes. In contrast, commercial production of transgenic crops relies on methods that integrate one or a few genes into host chromosomes; extensive screening to identify insertions with the desired expression level, copy number, structure, and genomic location; and long breeding programs to produce varieties that carry multiple transgenes. As a step toward improving transgenic crop production, we report the development of autonomous maize minichromosomes (MMCs. We constructed circular MMCs by combining DsRed and nptII marker genes with 7-190 kb of genomic maize DNA fragments containing satellites, retroelements, and/or other repeats commonly found in centromeres and using particle bombardment to deliver these constructs into embryogenic maize tissue. We selected transformed cells, regenerated plants, and propagated their progeny for multiple generations in the absence of selection. Fluorescent in situ hybridization and segregation analysis demonstrated that autonomous MMCs can be mitotically and meiotically maintained. The MMC described here showed meiotic segregation ratios approaching Mendelian inheritance: 93% transmission as a disome (100% expected, 39% transmission as a monosome crossed to wild type (50% expected, and 59% transmission in self crosses (75% expected. The fluorescent DsRed reporter gene on the MMC was expressed through four generations, and Southern blot analysis indicated the encoded genes were intact. This novel approach for plant transformation can facilitate crop biotechnology by (i combining several trait genes on a single DNA fragment, (ii arranging genes in a defined

  18. Asy2/Mer2: an evolutionarily conserved mediator of meiotic recombination, pairing, and global chromosome compaction.

    Science.gov (United States)

    Tessé, Sophie; Bourbon, Henri-Marc; Debuchy, Robert; Budin, Karine; Dubois, Emeline; Liangran, Zhang; Antoine, Romain; Piolot, Tristan; Kleckner, Nancy; Zickler, Denise; Espagne, Eric

    2017-09-15

    Meiosis is the cellular program by which a diploid cell gives rise to haploid gametes for sexual reproduction. Meiotic progression depends on tight physical and functional coupling of recombination steps at the DNA level with specific organizational features of meiotic-prophase chromosomes. The present study reveals that every step of this coupling is mediated by a single molecule: Asy2/Mer2. We show that Mer2, identified so far only in budding and fission yeasts, is in fact evolutionarily conserved from fungi (Mer2/Rec15/Asy2/Bad42) to plants (PRD3/PAIR1) and mammals (IHO1). In yeasts, Mer2 mediates assembly of recombination-initiation complexes and double-strand breaks (DSBs). This role is conserved in the fungus Sordaria However, functional analysis of 13 mer2 mutants and successive localization of Mer2 to axis, synaptonemal complex (SC), and chromatin revealed, in addition, three further important functions. First, after DSB formation, Mer2 is required for pairing by mediating homolog spatial juxtaposition, with implications for crossover (CO) patterning/interference. Second, Mer2 participates in the transfer/maintenance and release of recombination complexes to/from the SC central region. Third, after completion of recombination, potentially dependent on SUMOylation, Mer2 mediates global chromosome compaction and post-recombination chiasma development. Thus, beyond its role as a recombinosome-axis/SC linker molecule, Mer2 has important functions in relation to basic chromosome structure. © 2017 Tessé et al.; Published by Cold Spring Harbor Laboratory Press.

  19. ARG-walker: inference of individual specific strengths of meiotic recombination hotspots by population genomics analysis.

    Science.gov (United States)

    Chen, Hao; Yang, Peng; Guo, Jing; Kwoh, Chee Keong; Przytycka, Teresa M; Zheng, Jie

    2015-01-01

    Meiotic recombination hotspots play important roles in various aspects of genomics, but the underlying mechanisms for regulating the locations and strengths of recombination hotspots are not yet fully revealed. Most existing algorithms for estimating recombination rates from sequence polymorphism data can only output average recombination rates of a population, although there is evidence for the heterogeneity in recombination rates among individuals. For genome-wide association studies (GWAS) of recombination hotspots, an efficient algorithm that estimates the individualized strengths of recombination hotspots is highly desirable. In this work, we propose a novel graph mining algorithm named ARG-walker, based on random walks on ancestral recombination graphs (ARG), to estimate individual-specific recombination hotspot strengths. Extensive simulations demonstrate that ARG-walker is able to distinguish the hot allele of a recombination hotspot from the cold allele. Integrated with output of ARG-walker, we performed GWAS on the phased haplotype data of the 22 autosome chromosomes of the HapMap Asian population samples of Chinese and Japanese (JPT+CHB). Significant cis-regulatory signals have been detected, which is corroborated by the enrichment of the well-known 13-mer motif CCNCCNTNNCCNC of PRDM9 protein. Moreover, two new DNA motifs have been identified in the flanking regions of the significantly associated SNPs (single nucleotide polymorphisms), which are likely to be new cis-regulatory elements of meiotic recombination hotspots of the human genome. Our results on both simulated and real data suggest that ARG-walker is a promising new method for estimating the individual recombination variations. In the future, it could be used to uncover the mechanisms of recombination regulation and human diseases related with recombination hotspots.

  20. Variation and Evolution of the Meiotic Requirement for Crossing Over in Mammals.

    Science.gov (United States)

    Dumont, Beth L

    2017-01-01

    The segregation of homologous chromosomes at the first meiotic division is dependent on the presence of at least one well-positioned crossover per chromosome. In some mammalian species, however, the genomic distribution of crossovers is consistent with a more stringent baseline requirement of one crossover per chromosome arm. Given that the meiotic requirement for crossing over defines the minimum frequency of recombination necessary for the production of viable gametes, determining the chromosomal scale of this constraint is essential for defining crossover profiles predisposed to aneuploidy and understanding the parameters that shape patterns of recombination rate evolution across species. Here, I use cytogenetic methods for in situ imaging of crossovers in karyotypically diverse house mice (Mus musculus domesticus) and voles (genus Microtus) to test how chromosome number and configuration constrain the distribution of crossovers in a genome. I show that the global distribution of crossovers in house mice is thresholded by a minimum of one crossover per chromosome arm, whereas the crossover landscape in voles is defined by a more relaxed requirement of one crossover per chromosome. I extend these findings in an evolutionary metaanalysis of published recombination and karyotype data for 112 mammalian species and demonstrate that the physical scale of the genomic crossover distribution has undergone multiple independent shifts from one crossover per chromosome arm to one per chromosome during mammalian evolution. Together, these results indicate that the chromosomal scale constraint on crossover rates is itself a trait that evolves among species, a finding that casts light on an important source of crossover rate variation in mammals. Copyright © 2017 by the Genetics Society of America.

  1. Computer-aided meiotic maturation assay (CAMMA) of zebrafish (danio rerio) oocytes in vitro.

    Science.gov (United States)

    Lessman, Charles A; Nathani, Ravikanth; Uddin, Rafique; Walker, Jamie; Liu, Jianxiong

    2007-01-01

    We have developed a new technique called Computer-Aided Meiotic Maturation Assay (CAMMA) for imaging large arrays of zebrafish oocytes and automatically collecting image files at regular intervals during meiotic maturation. This novel method uses a transparency scanner interfaced to a computer with macro programming that automatically scans and archives the image files. Images are stacked and analyzed with ImageJ to quantify changes in optical density characteristic of zebrafish oocyte maturation. Major advantages of CAMMA include (1) ability to image very large arrays of oocytes and follow individual cells over time, (2) simultaneously image many treatment groups, (3) digitized images may be stacked, animated, and analyzed in programs such as ImageJ, NIH-Image, or ScionImage, and (4) CAMMA system is inexpensive, costing less than most microscopes used in traditional assays. We have used CAMMA to determine the dose response and time course of oocyte maturation induced by 17alpha-hydroxyprogesterone (HP). Maximal decrease in optical density occurs around 5 hr after 0.1 micro g/ml HP (28.5 degrees C), approximately 3 hr after germinal vesicle migration (GVM) and dissolution (GVD). In addition to changes in optical density, GVD is accompanied by streaming of ooplasm to the animal pole to form a blastodisc. These dynamic changes are readily visualized by animating image stacks from CAMMA; thus, CAMMA provides a valuable source of time-lapse movies for those studying zebrafish oocyte maturation. The oocyte clearing documented by CAMMA is correlated to changes in size distribution of major yolk proteins upon SDS-PAGE, and, this in turn, is related to increased cyclin B(1) protein.

  2. The ability to form full-length intron RNA circles is a general property of nuclear group I introns

    DEFF Research Database (Denmark)

    Nielsen, Henrik; Fiskaa, Tonje; Birgisdottir, Asa Birna

    2003-01-01

    at the expense of the host. The circularization pathway has distinct structural requirements that differ from those of splicing and appears to be specifically suppressed in vivo. The ability to form full-length circles is found in all types of nuclear group I introns, including those from the Tetrahymena...... ribosomal DNA. The biological function of the full-length circles is not known, but the fact that the circles contain the entire genetic information of the intron suggests a role in intron mobility....

  3. Prediction of acute toxicity of phenol derivatives using multiple linear regression approach for Tetrahymena pyriformis contaminant identification in a median-size database.

    Science.gov (United States)

    Dieguez-Santana, Karel; Pham-The, Hai; Villegas-Aguilar, Pedro J; Le-Thi-Thu, Huong; Castillo-Garit, Juan A; Casañola-Martin, Gerardo M

    2016-12-01

    In this article, the modeling of inhibitory grown activity against Tetrahymena pyriformis is described. The 0-2D Dragon descriptors based on structural aspects to gain some knowledge of factors influencing aquatic toxicity are mainly used. Besides, it is done by some enlarged data of phenol derivatives described for the first time and composed of 358 chemicals. It overcomes the previous datasets with about one hundred compounds. Moreover, the results of the model evaluation by the parameters in the training, prediction and validation give adequate results comparable with those of the previous works. The more influential descriptors included in the model are: X3A, MWC02, MWC10 and piPC03 with positive contributions to the dependent variable; and MWC09, piPC02 and TPC with negative contributions. In a next step, a median-size database of nearly 8000 phenolic compounds extracted from ChEMBL was evaluated with the quantitative-structure toxicity relationship (QSTR) model developed providing some clues (SARs) for identification of ecotoxicological compounds. The outcome of this report is very useful to screen chemical databases for finding the compounds responsible of aquatic contamination in the biomarker used in the current work. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Regulation of galactokinase gene expression in Tetrahymena thermophila. II. Identification of 3,4-dihydroxyphenylalanine as a primary effector of adrenergic control of galactokinase expression.

    Science.gov (United States)

    Ness, J C; Morse, D E

    1985-08-25

    Intracellular concentrations of catecholamines were determined in wild-type and mutant Tetrahymena thermophila, using the highly sensitive techniques of high-performance liquid chromatography and electro-chemical detection. Catecholamines were determined in these cell strains grown under various steady-state conditions, including those which initiate and maintain repression of galactokinase gene expression. Wild-type cells grown in defined minimal medium supplemented with 1% glycerol, exhibiting derepressed galactokinase synthesis, were found to contain considerable quantities of dopa (3,4-dihydroxyphenylalanine) and dopamine, but no detectable levels of either norepinephrine or epinephrine. Analyses of wild-type cells revealed a strong positive correlation between the internal concentration of dopa and expression of the galactokinase gene, both of which are regulated by exogenous carbohydrates, catecholamine agonists, or dibutyryl-cAMP; an analogous relationship between intracellular dopamine concentrations and galactokinase activity was not found. In addition, a correlation between intracellular dopa content and the phenotypic expression of galactokinase in various mutants deficient in the catecholamine biosynthetic pathway or in glucokinase further confirms the role of dopa as a primary effector in the regulation of galactokinase gene expression.

  5. Vacuum ultraviolet photolysis of diclofenac and the effects of its treated aqueous solutions on the proliferation and migratory responses of Tetrahymena pyriformis

    International Nuclear Information System (INIS)

    Arany, Eszter; Láng, Júlia; Somogyvári, Dávid; Láng, Orsolya; Alapi, Tünde; Ilisz, István

    2014-01-01

    The effects of dissolved O 2 , phosphate buffer and the initial concentration of diclofenac on the vacuum ultraviolet photolysis of this contaminant molecule were studied. Besides kinetic measurements, the irradiated, multicomponent samples were characterized via the proliferation and migratory responses (in sublethal concentrations) of the bioindicator eukaryotic ciliate Tetrahymena pyriformis. The results suggest that hydroxyl radicals, hydrogen atoms and hydroperoxyl radicals may all contribute to the degradation of diclofenac. The aromatic by-products of diclofenac were presumed to include a hydroxylated derivative, 1-(8-chlorocarbazolyl)acetic acid and 1-(8-hydroxycarbazolyl)acetic acid. The biological activity of photoexposed samples reflected the chemical transformation of diclofenac and was also dependent on the level of dissolved O 2 . The increase in toxicity of samples taken after different irradiation times did not exceed a factor of two. Our results suggest that the combination of vacuum ultraviolet photolysis with toxicity and chemotactic measurements can be a valuable method for the investigation of the elimination of micropollutants. - Highlights: • The radical-scavenging effect of phosphates seems to be negligible. • Only higher concentrations of HO 2 · contribute to the degradation of diclofenac. • Toxicity of VUV-treated samples decreases with increasing rate of mineralization. • Dissolved O 2 enhances the mineralization of diclofenac by affecting the radical set. • Treated samples retain the chemorepellent character of the parent compound

  6. Tetrahymena telomerase protein p65 induces conformational changes throughout telomerase RNA (TER) and rescues telomerase reverse transcriptase and TER assembly mutants.

    Science.gov (United States)

    Berman, Andrea J; Gooding, Anne R; Cech, Thomas R

    2010-10-01

    The biogenesis of the Tetrahymena telomerase ribonucleoprotein particle (RNP) is enhanced by p65, a La family protein. Single-molecule and biochemical studies have uncovered a hierarchical assembly of the RNP, wherein the binding of p65 to stems I and IV of telomerase RNA (TER) causes a conformational change that facilitates the subsequent binding of telomerase reverse transcriptase (TERT) to TER. We used purified p65 and variants of TERT and TER to investigate the conformational rearrangements that occur during RNP assembly. Nuclease protection assays and mutational analysis revealed that p65 interacts with and stimulates conformational changes in regions of TER beyond stem IV. Several TER mutants exhibited telomerase activity only in the presence of p65, revealing the importance of p65 in promoting the correct RNP assembly pathway. In addition, p65 rescued TERT assembly mutants but not TERT activity mutants. Taken together, these results suggest that p65 stimulates telomerase assembly and activity in two ways. First, by sequestering stems I and IV, p65 limits the ensemble of structural conformations of TER, thereby presenting TERT with the active conformation of TER. Second, p65 acts as a molecular buttress within the assembled RNP, mutually stabilizing TER and TERT in catalytically active conformations.

  7. Vacuum ultraviolet photolysis of diclofenac and the effects of its treated aqueous solutions on the proliferation and migratory responses of Tetrahymena pyriformis

    Energy Technology Data Exchange (ETDEWEB)

    Arany, Eszter [Research Group of Environmental Chemistry, Institute of Chemistry, University of Szeged, H-6720 Szeged, Rerrich Béla tér 1 (Hungary); Láng, Júlia [Department of Genetics, Cell- and Immunobiology, Semmelweis University, H-1089 Budapest, Nagyvárad tér 4 (Hungary); Somogyvári, Dávid [Research Group of Environmental Chemistry, Institute of Chemistry, University of Szeged, H-6720 Szeged, Rerrich Béla tér 1 (Hungary); Láng, Orsolya [Department of Genetics, Cell- and Immunobiology, Semmelweis University, H-1089 Budapest, Nagyvárad tér 4 (Hungary); Alapi, Tünde [Research Group of Environmental Chemistry, Institute of Chemistry, University of Szeged, H-6720 Szeged, Rerrich Béla tér 1 (Hungary); Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary); Ilisz, István [Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary); and others

    2014-01-01

    The effects of dissolved O{sub 2}, phosphate buffer and the initial concentration of diclofenac on the vacuum ultraviolet photolysis of this contaminant molecule were studied. Besides kinetic measurements, the irradiated, multicomponent samples were characterized via the proliferation and migratory responses (in sublethal concentrations) of the bioindicator eukaryotic ciliate Tetrahymena pyriformis. The results suggest that hydroxyl radicals, hydrogen atoms and hydroperoxyl radicals may all contribute to the degradation of diclofenac. The aromatic by-products of diclofenac were presumed to include a hydroxylated derivative, 1-(8-chlorocarbazolyl)acetic acid and 1-(8-hydroxycarbazolyl)acetic acid. The biological activity of photoexposed samples reflected the chemical transformation of diclofenac and was also dependent on the level of dissolved O{sub 2}. The increase in toxicity of samples taken after different irradiation times did not exceed a factor of two. Our results suggest that the combination of vacuum ultraviolet photolysis with toxicity and chemotactic measurements can be a valuable method for the investigation of the elimination of micropollutants. - Highlights: • The radical-scavenging effect of phosphates seems to be negligible. • Only higher concentrations of HO{sub 2}{sup ·} contribute to the degradation of diclofenac. • Toxicity of VUV-treated samples decreases with increasing rate of mineralization. • Dissolved O{sub 2} enhances the mineralization of diclofenac by affecting the radical set. • Treated samples retain the chemorepellent character of the parent compound.

  8. Tetrahymena pyriformis cells are deficient in all mannose-P-dolichol-dependent mannosyltransferases but not in mannose-P-dolichol synthesis

    International Nuclear Information System (INIS)

    Yagodnik, C.; de la Canal, L.; Parodi, A.J.

    1987-01-01

    Cells of the ciliated protozoan Tetrahymena pyriformis incubated with [ 14 C]glucose were found to synthesize Man-P-dolichol and Glc-P-dolichol, as well as Glc 3 Man 5 GlcNAc 2 -P-P-dolichol, the latter being the main and largest lipid derivative formed. The missing mannose residues were those known to be transferred from Man-P-dolichol in other systems. Formation of Man-P-dolichol and of dolichol-P-P-oligosaccharides containing up to five mannose units was detected in cell-free assays containing protozoan membranes, rat liver dolichol-P, unlabeled Man/sub 4-9/GlcNAc 2 -P-P-dolichol from pig liver, and GDP-[ 14 C]Man. Under exactly the same conditions but with UDP-[ 14 C]Glc instead of GDP-[ 14 C]Man, Glc-P-dolichol and dolichol-P-P-oligosaccharides containing five mannose and one to three glucose residues were formed in the absence of the pig liver compounds. In the presence of the latter, dolichol-P-P derivatives containing nine mannose and one to three glucose units were also synthesized. It is concluded that T. pyriformis cells are deficient in all Man-P-dolichol-dependent mannosyltransferases but not in Man-P-dolichol synthesis. The role of the latter compound in this microorganism is unknown

  9. SAD-3, a Putative Helicase Required for Meiotic Silencing by Unpaired DNA, Interacts with Other Components of the Silencing Machinery

    Science.gov (United States)

    Hammond, Thomas M.; Xiao, Hua; Boone, Erin C.; Perdue, Tony D.; Pukkila, Patricia J.; Shiu, Patrick K. T.

    2011-01-01

    In Neurospora crassa, genes lacking a pairing partner during meiosis are suppressed by a process known as meiotic silencing by unpaired DNA (MSUD). To identify novel MSUD components, we have developed a high-throughput reverse-genetic screen for use with the N. crassa knockout library. Here we describe the screening method and the characterization of a gene (sad-3) subsequently discovered. SAD-3 is a putative helicase required for MSUD and sexual spore production. It exists in a complex with other known MSUD proteins in the perinuclear region, a center for meiotic silencing activity. Orthologs of SAD-3 include Schizosaccharomyces pombe Hrr1, a helicase required for RNAi-induced heterochromatin formation. Both SAD-3 and Hrr1 interact with an RNA-directed RNA polymerase and an Argonaute, suggesting that certain aspects of silencing complex formation may be conserved between the two fungal species. PMID:22384347

  10. Comparison of meiotic abnormalities induced by gamma-rays between a diploid and a tetraploid species of physalis

    International Nuclear Information System (INIS)

    Gupta, S.K.; Roy, S.K.

    1985-01-01

    Radiosensitivity of a diploid (P. ixocarpa) and a tetraploid (P. peruviana) species of Physalis has been studied. Meiotic abnormalities induced by γ-rays were compared in both species and found that it was always greater in tetraploid than in diploid species at each corresponding dose. The tetraploid plant due to greater chromosomal volume is more vulnerable to radiation hits and its immediate consequences are expected to contribute to the formation of sterile pollen, but this defect could be overcome by the buffering action of the unaltered genes over the altered ones at multiple loci, which normalizes the induced plant sterility. The diploid P. ixocarpa exhibited higher radiosensitivity than the tetraploid P. peruviana. Comparison between the frequencies of meiotic anomalies of M 2 and M 1 indicated that the latter has exaggerated values on these at all exposure levels. The lowered values of M 2 indicated their elimination through diplontic selection or intrasomatic or competitive elimination during the course of time lapse. (author)

  11. mlh3 mutations in baker's yeast alter meiotic recombination outcomes by increasing noncrossover events genome-wide.

    Directory of Open Access Journals (Sweden)

    Najla Al-Sweel

    2017-08-01

    Full Text Available Mlh1-Mlh3 is an endonuclease hypothesized to act in meiosis to resolve double Holliday junctions into crossovers. It also plays a minor role in eukaryotic DNA mismatch repair (MMR. To understand how Mlh1-Mlh3 functions in both meiosis and MMR, we analyzed in baker's yeast 60 new mlh3 alleles. Five alleles specifically disrupted MMR, whereas one (mlh3-32 specifically disrupted meiotic crossing over. Mlh1-mlh3 representatives for each class were purified and characterized. Both Mlh1-mlh3-32 (MMR+, crossover- and Mlh1-mlh3-45 (MMR-, crossover+ displayed wild-type endonuclease activities in vitro. Msh2-Msh3, an MSH complex that acts with Mlh1-Mlh3 in MMR, stimulated the endonuclease activity of Mlh1-mlh3-32 but not Mlh1-mlh3-45, suggesting that Mlh1-mlh3-45 is defective in MSH interactions. Whole genome recombination maps were constructed for wild-type and MMR+ crossover-, MMR- crossover+, endonuclease defective and null mlh3 mutants in an S288c/YJM789 hybrid background. Compared to wild-type, all of the mlh3 mutants showed increases in the number of noncrossover events, consistent with recombination intermediates being resolved through alternative recombination pathways. Our observations provide a structure-function map for Mlh3 that reveals the importance of protein-protein interactions in regulating Mlh1-Mlh3's enzymatic activity. They also illustrate how defective meiotic components can alter the fate of meiotic recombination intermediates, providing new insights for how meiotic recombination pathways are regulated.

  12. DMC1 functions in a Saccharomyces cerevisiae meiotic pathway that is largely independent of the RAD51 pathway

    International Nuclear Information System (INIS)

    Dresser, M.E.; Ewing, D.J.; Conrad, M.N.; Dominguez, A.M.; Barstead, R.; Jiang, H.; Kodadek, T.

    1997-01-01

    Meiotic recombination in the yeast Saccharomyces cerevisiae requires two similar recA-like proteins, Dmc1p and Rad51p. A screen for dominant meiotic mutants provided DMC1-G126D, a dominant allele mutated in the conserved ATP-binding site (specifically, the A-loop motif) that confers a null phenotype. A recessive null allele, dmc1-K69E, was isolated as an intragenic suppressor of DMC1-G126D. Dmc1-K69Ep, unlike Dmc1p, does not interact homotypically in a two-hybrid assay, although it does interact with other fusion proteins identified by two-hybrid screen with Dmc1p. Dmc1p, unlike Rad51p, does not interact in the two-hybrid assay with Rad52p or Rad54p. However, Dmc1p does interact with Tid1p, a Rad54p homologue, with Tid4p, a Rad16p homologue, and with other fusion proteins that do not interact with Rad51p, suggesting that Dmc1p and Rad51p function in separate, though possibly overlapping, recombinational repair complexes. Epistasis analysis suggests that DMC1 and RAD51 function in separate pathways responsible for meiotic recombination. Taken together, our results are consistent with a requirement for DMC1 for meiosis-specific entry of DNA double-strand break ends into chromatin. Interestingly, the pattern on CHEF gels of chromosome fragments that result from meiotic DNA double-strand break formation is different in DMC1 mutant strains from that seen in rad50S strains. (author)

  13. BRIT1/MCPH1 is essential for mitotic and meiotic recombination DNA repair and maintaining genomic stability in mice.

    Directory of Open Access Journals (Sweden)

    Yulong Liang

    2010-01-01

    Full Text Available BRIT1 protein (also known as MCPH1 contains 3 BRCT domains which are conserved in BRCA1, BRCA2, and other important molecules involved in DNA damage signaling, DNA repair, and tumor suppression. BRIT1 mutations or aberrant expression are found in primary microcephaly patients as well as in cancer patients. Recent in vitro studies suggest that BRIT1/MCPH1 functions as a novel key regulator in the DNA damage response pathways. To investigate its physiological role and dissect the underlying mechanisms, we generated BRIT1(-/- mice and identified its essential roles in mitotic and meiotic recombination DNA repair and in maintaining genomic stability. Both BRIT1(-/- mice and mouse embryonic fibroblasts (MEFs were hypersensitive to gamma-irradiation. BRIT1(-/- MEFs and T lymphocytes exhibited severe chromatid breaks and reduced RAD51 foci formation after irradiation. Notably, BRIT1(-/- mice were infertile and meiotic homologous recombination was impaired. BRIT1-deficient spermatocytes exhibited a failure of chromosomal synapsis, and meiosis was arrested at late zygotene of prophase I accompanied by apoptosis. In mutant spermatocytes, DNA double-strand breaks (DSBs were formed, but localization of RAD51 or BRCA2 to meiotic chromosomes was severely impaired. In addition, we found that BRIT1 could bind to RAD51/BRCA2 complexes and that, in the absence of BRIT1, recruitment of RAD51 and BRCA2 to chromatin was reduced while their protein levels were not altered, indicating that BRIT1 is involved in mediating recruitment of RAD51/BRCA2 to the damage site. Collectively, our BRIT1-null mouse model demonstrates that BRIT1 is essential for maintaining genomic stability in vivo to protect the hosts from both programmed and irradiation-induced DNA damages, and its depletion causes a failure in both mitotic and meiotic recombination DNA repair via impairing RAD51/BRCA2's function and as a result leads to infertility and genomic instability in mice.

  14. The role of meiotic cohesin REC8 in chromosome segregation in {gamma} irradiation-induced endopolyploid tumour cells

    Energy Technology Data Exchange (ETDEWEB)

    Erenpreisa, Jekaterina [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Cragg, Mark S. [Tenovus Laboratory, Cancer Sciences Division, Southampton University School of Medicine, General Hospital, Southampton SO16 6YD (United Kingdom); Salmina, Kristine [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Hausmann, Michael [Kirchhoff Inst. fuer Physik, Univ. of Heidelberg, D-69120 Heidelberg (Germany); Scherthan, Harry, E-mail: scherth@web.de [Inst. fuer Radiobiologie der Bundeswehr in Verbindung mit der Univ. Ulm, D-80937 Munich (Germany); MPI for Molec. Genetics, 14195 Berlin (Germany)

    2009-09-10

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  15. Reticulate Evolution of the Rock Lizards: Meiotic Chromosome Dynamics and Spermatogenesis in Diploid and Triploid Males of the Genus Darevskia.

    Science.gov (United States)

    Spangenberg, Victor; Arakelyan, Marine; Galoyan, Eduard; Matveevsky, Sergey; Petrosyan, Ruzanna; Bogdanov, Yuri; Danielyan, Felix; Kolomiets, Oxana

    2017-05-24

    Knowing whether triploid hybrids resulting from natural hybridization of parthenogenetic and bisexual species are fertile is crucial for understanding the mechanisms of reticulate evolution in rock lizards. Here, using males of the bisexual diploid rock lizard species Darevskia raddei nairensis and Darevskia valentini and a triploid hybrid male Darevskia unisexualis × Darevskia valentini , we performed karyotyping and comparative immunocytochemistry of chromosome synapsis and investigated the distribution of RAD51 and MLH1 foci in spread spermatocyte nuclei in meiotic prophase I. Three chromosome sets were found to occur in cell nuclei in the D. unisexualis × D. valentini hybrid, two originating from a parthenogenetic D. unisexualis female and one from the D. valentini male. Despite this distorted chromosome synapsis and incomplete double-strand breaks repair in meiotic prophase I, the number of mismatch repair foci in the triploid hybrid was enough to pass through both meiotic divisions. The defects in synapsis and repair did not arrest meiosis or spermatogenesis. Numerous abnormal mature spermatids were observed in the testes of the studied hybrid.

  16. The role of meiotic cohesin REC8 in chromosome segregation in γ irradiation-induced endopolyploid tumour cells

    International Nuclear Information System (INIS)

    Erenpreisa, Jekaterina; Cragg, Mark S.; Salmina, Kristine; Hausmann, Michael; Scherthan, Harry

    2009-01-01

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  17. The role of meiotic cohesin REC8 in chromosome segregation in gamma irradiation-induced endopolyploid tumour cells.

    Science.gov (United States)

    Erenpreisa, Jekaterina; Cragg, Mark S; Salmina, Kristine; Hausmann, Michael; Scherthan, Harry

    2009-09-10

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  18. Meiotic behaviour and its implication on species inter-relationship in the genus Curcuma (Linnaeus, 1753 (Zingiberaceae

    Directory of Open Access Journals (Sweden)

    Judith Mary Lamo

    2017-10-01

    Full Text Available In this paper, detailed meiotic analysis was investigated in seven species of Curcuma (Linnaeus, 1753 which can contribute significantly to our understanding about species inter-relationship, speciation and evolution. The species were divided into two groups viz., Group I having 2n = 42 (C. comosa Roxburgh, 1810, C. haritha Mangaly & M.Sabu, 1993, C. mangga Valeton & Zijp, 1917, and C. motana Roxburgh, 1800 and Group II with 2n = 63 (C. caesia Roxburgh, 1810, C. longa Linnaeus, 1753 and C. sylvatica Valeton, 1918. Both groups display varying degree of chromosome associations. Group I species showed the prevalence of bivalents, however occasional quadrivalents besides univalents were also encountered. About 48% of the PMCs analyzed in C. mangga showed 21 bivalents (II meiotic configurations, 32% in C. comosa and 16% in C. haritha. Group II species as expected showed the presence of trivalents besides bivalents, univalents and quadrivalents. About 32% of the PMCs analyzed at MI in C. sylvatica showed 21 trivalents (III meiotic configurations, 24% in C. longa and 8% in C. caesia. Overall, low frequency of multivalent associations as compared to bivalents indicates that Curcuma is an allopolyploid complex. Moreover, x = 21 is too high a basic number, therefore, we suggest that the genus Curcuma has evolved by hybridization of species with different chromosome numbers of 2n = 24 and 18, resulting in a dibasic amphidiploid species.

  19. Translocations of Chromosome End-Segments and Facultative Heterochromatin Promote Meiotic Ring Formation in Evening Primroses[W][OPEN

    Science.gov (United States)

    Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

    2014-01-01

    Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories. PMID:24681616

  20. A quantitative study of the second meiotic metaphase in male mice (Mus musculus).

    Science.gov (United States)

    Beatty, R A; Lim, M C; Coulter, V J

    1975-01-01

    Over 11,000 second meiotic metaphase spreads stained for the pericentromeric region have been studied quantitatively in male mice of 14 strains. The sex-chromosome constitution of a cell could be judged objectively if X and Y chromosomes and ploidy were all scored. A bias arose if only Y chromosomes and ploidy were scored but could be corrected statistically. There was no sign of other forms of bias. The original contiguity of X and Y second metaphases in vivo was very occasionally evident in the preparations. Most of the subhaploid aneuploid counts were assumed to be artifactual. The incidence of truly aneuploid second metaphases in 13 strains was estimated as 0.38+/-0.12%. The estimated average rate per chromosome was 0.019+/-0.006%, with a comparable order of magnitude for the sex chromosomes alone. Simultaneous aneuploidy of two or more chromosomes of the haploid set was estimated to be very rare. Of the spreads from 13 strains, 9.6% were polyploid (2N, 3N, 4N) and showed most of the possible combinations of sex chromosomes. Nearly all the polyploid spreads were considered to arise by artifactual cell fusion at the time of second metaphase during the preparative technique, especially of the X and Y daughter-cell products of the first meiotic division. Other modes of origin (true polyploidy, accidental superposition of cells during preparation) were unlikely. The data could be accommodated by a statistical model with only four parameters. It allowed for artifactual fusion mainly between daughter cells but also between non-daughter cells, bias in one scoring method, and bias in the numbers of cells with given ploidy successfully mounted. Current techniques of chromosome preparation were thought to be wholly unsuitable for the recognition of true polyploidy. The artifactual origin of polyploid spreads was borne out by an absence of polyploid spermatozoa in 14 strains. There appeared to be a virtually constant transmission rate of paternal X and Y chromosomes from

  1. Meiotic Studies on Combinations of Chromosomes With Different Sized Centromeres in Maize

    Directory of Open Access Journals (Sweden)

    Fangpu Han

    2018-06-01

    Full Text Available Multiple centromere misdivision derivatives of a translocation between the supernumerary B chromosome and the short arm of chromosome 9 (TB-9Sb permit investigation of how centromeres of different sizes behave in meiosis in opposition or in competition with each other. In the first analysis, heterozygotes were produced between the normal TB-9Sb and derivatives of it that resulted from centromere misdivision that reduced the amounts of centromeric DNA. These heterozygotes could test whether these drastic differences would result in meiotic drive of the larger chromosome in female meiosis. Cytological determinations of the segregation of large and small centromeres among thousands of progeny of four combinations were made. The recovery of the larger centromere was at a few percent higher frequency in two of four combinations. However, examination of phosphorylated histone H2A-Thr133, a characteristic of active centromeres, showed a lack of correlation with the size of the centromeric DNA, suggesting an expansion of the basal protein features of the kinetochore in two of the three cases despite the reduction in the size of the underlying DNA. In the second analysis, plants containing different sizes of the B chromosome centromere were crossed to plants with TB-9Sb with a foldback duplication of 9S (TB-9Sb-Dp9. In the progeny, plants containing large and small versions of the B chromosome centromere were selected by FISH. A meiotic “tug of war” occurred in hybrid combinations by recombination between the normal 9S and the foldback duplication in those cases in which pairing occurred. Such pairing and recombination produce anaphase I bridges but in some cases the large and small centromeres progressed to the same pole. In one combination, new dicentric chromosomes were found in the progeny. Collectively, the results indicate that the size of the underlying DNA of a centromere does not dramatically affect its segregation properties or its ability

  2. LDsplit: screening for cis-regulatory motifs stimulating meiotic recombination hotspots by analysis of DNA sequence polymorphisms.

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    Yang, Peng; Wu, Min; Guo, Jing; Kwoh, Chee Keong; Przytycka, Teresa M; Zheng, Jie

    2014-02-17

    As a fundamental genomic element, meiotic recombination hotspot plays important roles in life sciences. Thus uncovering its regulatory mechanisms has broad impact on biomedical research. Despite the recent identification of the zinc finger protein PRDM9 and its 13-mer binding motif as major regulators for meiotic recombination hotspots, other regulators remain to be discovered. Existing methods for finding DNA sequence motifs of recombination hotspots often rely on the enrichment of co-localizations between hotspots and short DNA patterns, which ignore the cross-individual variation of recombination rates and sequence polymorphisms in the population. Our objective in this paper is to capture signals encoded in genetic variations for the discovery of recombination-associated DNA motifs. Recently, an algorithm called "LDsplit" has been designed to detect the association between single nucleotide polymorphisms (SNPs) and proximal meiotic recombination hotspots. The association is measured by the difference of population recombination rates at a hotspot between two alleles of a candidate SNP. Here we present an open source software tool of LDsplit, with integrative data visualization for recombination hotspots and their proximal SNPs. Applying LDsplit on SNPs inside an established 7-mer motif bound by PRDM9 we observed that SNP alleles preserving the original motif tend to have higher recombination rates than the opposite alleles that disrupt the motif. Running on SNP windows around hotspots each containing an occurrence of the 7-mer motif, LDsplit is able to guide the established motif finding algorithm of MEME to recover the 7-mer motif. In contrast, without LDsplit the 7-mer motif could not be identified. LDsplit is a software tool for the discovery of cis-regulatory DNA sequence motifs stimulating meiotic recombination hotspots by screening and narrowing down to hotspot associated SNPs. It is the first computational method that utilizes the genetic variation of

  3. In silico prediction of toxicity of phenols to Tetrahymena pyriformis by using genetic algorithm and decision tree-based modeling approach.

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    Abbasitabar, Fatemeh; Zare-Shahabadi, Vahid

    2017-04-01

    Risk assessment of chemicals is an important issue in environmental protection; however, there is a huge lack of experimental data for a large number of end-points. The experimental determination of toxicity of chemicals involves high costs and time-consuming process. In silico tools such as quantitative structure-toxicity relationship (QSTR) models, which are constructed on the basis of computational molecular descriptors, can predict missing data for toxic end-points for existing or even not yet synthesized chemicals. Phenol derivatives are known to be aquatic pollutants. With this background, we aimed to develop an accurate and reliable QSTR model for the prediction of toxicity of 206 phenols to Tetrahymena pyriformis. A multiple linear regression (MLR)-based QSTR was obtained using a powerful descriptor selection tool named Memorized_ACO algorithm. Statistical parameters of the model were 0.72 and 0.68 for R training 2 and R test 2 , respectively. To develop a high-quality QSTR model, classification and regression tree (CART) was employed. Two approaches were considered: (1) phenols were classified into different modes of action using CART and (2) the phenols in the training set were partitioned to several subsets by a tree in such a manner that in each subset, a high-quality MLR could be developed. For the first approach, the statistical parameters of the resultant QSTR model were improved to 0.83 and 0.75 for R training 2 and R test 2 , respectively. Genetic algorithm was employed in the second approach to obtain an optimal tree, and it was shown that the final QSTR model provided excellent prediction accuracy for the training and test sets (R training 2 and R test 2 were 0.91 and 0.93, respectively). The mean absolute error for the test set was computed as 0.1615. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. The SMC-5/6 Complex and the HIM-6 (BLM Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

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    Ye Hong

    2016-03-01

    Full Text Available Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs to generate crossovers (COs during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

  5. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

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    Hong, Ye; Sonneville, Remi; Agostinho, Ana; Meier, Bettina; Wang, Bin; Blow, J Julian; Gartner, Anton

    2016-03-01

    Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs) to generate crossovers (COs) during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC) family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM) during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

  6. Haplotype mapping of a diploid non-meiotic organism using existing and induced aneuploidies.

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    Melanie Legrand

    2008-01-01

    Full Text Available Haplotype maps (HapMaps reveal underlying sequence variation and facilitate the study of recombination and genetic diversity. In general, HapMaps are produced by analysis of Single-Nucleotide Polymorphism (SNP segregation in large numbers of meiotic progeny. Candida albicans, the most common human fungal pathogen, is an obligate diploid that does not appear to undergo meiosis. Thus, standard methods for haplotype mapping cannot be used. We exploited naturally occurring aneuploid strains to determine the haplotypes of the eight chromosome pairs in the C. albicans laboratory strain SC5314 and in a clinical isolate. Comparison of the maps revealed that the clinical strain had undergone a significant amount of genome rearrangement, consisting primarily of crossover or gene conversion recombination events. SNP map haplotyping revealed that insertion and activation of the UAU1 cassette in essential and non-essential genes can result in whole chromosome aneuploidy. UAU1 is often used to construct homozygous deletions of targeted genes in C. albicans; the exact mechanism (trisomy followed by chromosome loss versus gene conversion has not been determined. UAU1 insertion into the essential ORC1 gene resulted in a large proportion of trisomic strains, while gene conversion events predominated when UAU1 was inserted into the non-essential LRO1 gene. Therefore, induced aneuploidies can be used to generate HapMaps, which are essential for analyzing genome alterations and mitotic recombination events in this clonal organism.

  7. High-Resolution Patterns of Meiotic Recombination across the Human Major Histocompatibility Complex

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    Cullen, Michael; Perfetto, Stephen P.; Klitz, William; Nelson, George; Carrington, Mary

    2002-01-01

    Definitive characteristics of meiotic recombination events over large (i.e., >1 Mb) segments of the human genome remain obscure, yet they are essential for establishing the haplotypic structure of the genome and for efficient mapping of complex traits. We present a high-resolution map of recombination at the kilobase level across a 3.3-Mb interval encompassing the major histocompatibility complex (MHC). Genotyping of 20,031 single sperm from 12 individuals resulted in the identification and fine mapping of 325 recombinant chromosomes within genomic intervals as small as 7 kb. Several principal characteristics of recombination in this region were observed: (1) rates of recombination can differ significantly between individuals; (2) intense hot spots of recombination occur at least every 0.8 Mb but are not necessarily evenly spaced; (3) distribution in the location of recombination events can differ significantly among individuals; (4) between hot spots, low levels of recombination occur fairly evenly across 100-kb segments, suggesting the presence of warm spots of recombination; and (5) specific sequence motifs associate significantly with recombination distribution. These data provide a plausible model for recombination patterns of the human genome overall. PMID:12297984

  8. Sordaria, a model system to uncover links between meiotic pairing and recombination.

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    Zickler, Denise; Espagne, Eric

    2016-06-01

    The mycelial fungus Sordaria macrospora was first used as experimental system for meiotic recombination. This review shows that it provides also a powerful cytological system for dissecting chromosome dynamics in wild-type and mutant meioses. Fundamental cytogenetic findings include: (1) the identification of presynaptic alignment as a key step in pairing of homologous chromosomes. (2) The discovery that biochemical complexes that mediate recombination at the DNA level concomitantly mediate pairing of homologs. (3) This pairing process involves not only resolution but also avoidance of chromosomal entanglements and the resolution system includes dissolution of constraining DNA recombination interactions, achieved by a unique role of Mlh1. (4) Discovery that the central components of the synaptonemal complex directly mediate the re-localization of the recombination proteins from on-axis to in-between homologue axis positions. (5) Identification of putative STUbL protein Hei10 as a structure-based signal transduction molecule that coordinates progression and differentiation of recombinational interactions at multiple stages. (6) Discovery that a single interference process mediates both nucleation of the SC and designation of crossover sites, thereby ensuring even spacing of both features. (7) Discovery of local modulation of sister-chromatid cohesion at sites of crossover recombination. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Ultrastructural characterization of the meiotic prophase. A tool in the assessment of radiation damage in man

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    Holm, P.B.; Rasmussen, S.W.; von Wettstein, D. (Carlsberg Lab., Copenhagen (Denmark). Dept. of Physiology)

    1982-01-01

    The three-dimensional reconstruction of meiotic nuclei from serial sections micrographed in the electron microscope has provided information about man and several other organisms that is not obtainable by light microscopy or biochemical analysis. At zygotene, the previously unpaired chromosomes align and form synaptonemal complexes between homologous chromosome segments either by progressive initiation from the telomeres or by interstitial recognition. Chromosome and bivalent interlocking at zygotene is a regular phenomenon and occurs at a frequency of 0.7-4.0 per nucleus in samples of meiocytes analyzed from different organisms. This frequency is reduced to 0.1 per nucleus at pachytene. The interlockings are resolved by breakage and precise rejoining of the broken ends. This breakage and rejoining can also occur in the absence of the DNA nicking and repair involved in crossing-over. The synaptonemal complexes combining homologous chromosome segments are stabilized by recombination nodules, after which a second round of synaptonemal complex formation between as yet unpaired or unstably paired chromosome segments occurs, apparently for optimization of bivalent formation. Nonhomologous pairing with the synaptonemal complex can take place in this phase of pachytene.

  10. Meiotic inheritance of a fungal supernumerary chromosome and its effect on sexual fertility in Nectria haematococca.

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    Garmaroodi, Hamid S; Taga, Masatoki

    2015-10-01

    PDA1-conditionally dispensable chromosome (CDC) of Nectria haematococca MP VI has long served as a model of supernumerary chromosomes in plant pathogenic fungi because of pathogenicity-related genes located on it. In our previous study, we showed the dosage effects of PDA1-CDC on pathogenicity and homoserine utilization by exploiting tagged PDA1-CDC with a marker gene. CDC content of mating partners and progenies analyzed by PCR, PFGE combined with Southern analysis and chromosome painting via FISH. In this study, we analyzed mode of meiotic inheritance of PDA1-CDC in several mating patterns with regard to CDC content and found a correlation between CDC content of parental strains with fertility of crosses. The results showed non-Mendelian inheritance of this chromosome followed by duplication or loss of the CDC in haploid genome through meiosis that probably were due to premature centromere division, not by nondisjunction as reported for the supernumerary chromosomes in other species. Correlation of CDC with fertility is the first time to be examined in fungi in this study. Copyright © 2015 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

  11. Meiotic changes in Vicia faba L. subsequent to treatments of hydrazine hydrate and maleic hydrazide

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    Shaheen Husain

    2013-01-01

    Full Text Available Assessing the impact of mutagens for creating variations in crops like faba bean (Vicia faba L. is an important criterion in the contemporary world where food insecurity and malnutrition is alarming at the doors of various nations. Impact of two chemical mutagens viz. hydrazine hydrate (HZ and maleic hydrazide (MH on the two varieties (NDF-1 and HB-405 of Vicia faba were analysed in terms of meiotic behavior and pollen sterility. Since there are not enough data about the effect of these mutagens on the chromosomal behaviors of Vicia faba, this study presents the role of hydrazine hydrate and maleic hydrazide as well as various types of chromosomal aberrations in crop improvement. The lower concentration of mutagens showed less pollen sterility compared to the higher concentrations. Manipulation of plant structural component to induce desirable alternations provides valuable material for the breeders and could be used favorably for increasing mutation rate and obtaining a desirable spectrum of mutation in faba beans based on preliminary studies of cell division.

  12. Meiotic recombination analyses of individual chromosomes in male domestic pigs (Sus scrofa domestica.

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    Nicolas Mary

    Full Text Available For the first time in the domestic pig, meiotic recombination along the 18 porcine autosomes was directly studied by immunolocalization of MLH1 protein. In total, 7,848 synaptonemal complexes from 436 spermatocytes were analyzed, and 13,969 recombination sites were mapped. Individual chromosomes for 113 of the 436 cells (representing 2,034 synaptonemal complexes were identified by immunostaining and fluorescence in situ hybridization (FISH. The average total length of autosomal synaptonemal complexes per cell was 190.3 µm, with 32.0 recombination sites (crossovers, on average, per cell. The number of crossovers and the lengths of the autosomal synaptonemal complexes showed significant intra- (i.e. between cells and inter-individual variations. The distributions of recombination sites within each chromosomal category were similar: crossovers in metacentric and submetacentric chromosomes were concentrated in the telomeric regions of the p- and q-arms, whereas two hotspots were located near the centromere and in the telomeric region of acrocentrics. Lack of MLH1 foci was mainly observed in the smaller chromosomes, particularly chromosome 18 (SSC18 and the sex chromosomes. All autosomes displayed positive interference, with a large variability between the chromosomes.

  13. Disruption of CHTF18 causes defective meiotic recombination in male mice.

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    Karen M Berkowitz

    Full Text Available CHTF18 (chromosome transmission fidelity factor 18 is an evolutionarily conserved subunit of the Replication Factor C-like complex, CTF18-RLC. CHTF18 is necessary for the faithful passage of chromosomes from one daughter cell to the next during mitosis in yeast, and it is crucial for germline development in the fruitfly. Previously, we showed that mouse Chtf18 is expressed throughout the germline, suggesting a role for CHTF18 in mammalian gametogenesis. To determine the role of CHTF18 in mammalian germ cell development, we derived mice carrying null and conditional mutations in the Chtf18 gene. Chtf18-null males exhibit 5-fold decreased sperm concentrations compared to wild-type controls, resulting in subfertility. Loss of Chtf18 results in impaired spermatogenesis; spermatogenic cells display abnormal morphology, and the stereotypical arrangement of cells within seminiferous tubules is perturbed. Meiotic recombination is defective and homologous chromosomes separate prematurely during prophase I. Repair of DNA double-strand breaks is delayed and incomplete; both RAD51 and γH2AX persist in prophase I. In addition, MLH1 foci are decreased in pachynema. These findings demonstrate essential roles for CHTF18 in mammalian spermatogenesis and meiosis, and suggest that CHTF18 may function during the double-strand break repair pathway to promote the formation of crossovers.

  14. The sea lamprey meiotic map improves resolution of ancient vertebrate genome duplications.

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    Smith, Jeramiah J; Keinath, Melissa C

    2015-08-01

    It is generally accepted that many genes present in vertebrate genomes owe their origin to two whole-genome duplications that occurred deep in the ancestry of the vertebrate lineage. However, details regarding the timing and outcome of these duplications are not well resolved. We present high-density meiotic and comparative genomic maps for the sea lamprey (Petromyzon marinus), a representative of an ancient lineage that diverged from all other vertebrates ∼550 million years ago. Linkage analyses yielded a total of 95 linkage groups, similar to the estimated number of germline chromosomes (1n ∼ 99), spanning a total of 5570.25 cM. Comparative mapping data yield strong support for the hypothesis that a single whole-genome duplication occurred in the basal vertebrate lineage, but do not strongly support a hypothetical second event. Rather, these comparative maps reveal several evolutionarily independent segmental duplications occurring over the last 600+ million years of chordate evolution. This refined history of vertebrate genome duplication should permit more precise investigations of vertebrate evolution. © 2015 Smith and Keinath; Published by Cold Spring Harbor Laboratory Press.

  15. Reduced polymorphism associated with X chromosome meiotic drive in the stalk-eyed fly Teleopsis dalmanni.

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    Sarah J Christianson

    Full Text Available Sex chromosome meiotic drive has been suggested as a cause of several evolutionary genetic phenomena, including genomic conflicts that give rise to reproductive isolation between new species. In this paper we present a population genetic analysis of X chromosome drive in the stalk-eyed fly, Teleopsis dalmanni, to determine how this natural polymorphism influences genetic diversity. We analyzed patterns of DNA sequence variation at two X-linked regions (comprising 1325 bp approximately 50 cM apart and one autosomal region (comprising 921 bp for 50 males, half of which were collected in the field from one of two allopatric locations and the other half were derived from lab-reared individuals with known brood sex ratios. These two populations are recently diverged but exhibit partial postzygotic reproductive isolation, i.e. crosses produce sterile hybrid males and fertile females. We find no nucleotide or microsatellite variation on the drive X chromosome, whereas the same individuals show levels of variation at autosomal regions that are similar to field-collected flies. Furthermore, one field-caught individual collected 10 years previously had a nearly identical X haplotype to the drive X, and is over 2% divergent from other haplotypes sampled from the field. These results are consistent with a selective sweep that has removed genetic variation from much of the drive X chromosome. We discuss how this finding may relate to the rapid evolution of postzygotic reproductive isolation that has been documented for these flies.

  16. A specific family of interspersed repeats (SINEs facilitates meiotic synapsis in mammals

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    Johnson Matthew E

    2013-01-01

    Full Text Available Abstract Background Errors during meiosis that affect synapsis and recombination between homologous chromosomes contribute to aneuploidy and infertility in humans. Despite the clinical relevance of these defects, we know very little about the mechanisms by which homologous chromosomes interact with one another during mammalian meiotic prophase. Further, we remain ignorant of the way in which chromosomal DNA complexes with the meiosis-specific structure that tethers homologs, the synaptonemal complex (SC, and whether specific DNA elements are necessary for this interaction. Results In the present study we utilized chromatin immunoprecipitation (ChIP and DNA sequencing to demonstrate that the axial elements of the mammalian SC are markedly enriched for a specific family of interspersed repeats, short interspersed elements (SINEs. Further, we refine the role of the repeats to specific sub-families of SINEs, B1 in mouse and AluY in old world monkey (Macaca mulatta. Conclusions Because B1 and AluY elements are the most actively retrotransposing SINEs in mice and rhesus monkeys, respectively, our observations imply that they may serve a dual function in axial element binding; i.e., as the anchoring point for the SC but possibly also as a suppressor/regulator of retrotransposition.

  17. Meiotic drive influences the outcome of sexually antagonistic selection at a linked locus.

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    Patten, M M

    2014-11-01

    Most meiotic drivers, such as the t-haplotype in Mus and the segregation distorter (SD) in Drosophila, act in a sex-specific manner, gaining a transmission advantage through one sex although suffering only the fitness costs associated with the driver in the other. Their inheritance is thus more likely through one of the two sexes, a property they share with sexually antagonistic alleles. Previous theory has shown that pairs of linked loci segregating for sexually antagonistic alleles are more likely to remain polymorphic and that linkage disequilibrium accrues between them. I probe this similarity between drive and sexual antagonism and examine the evolution of chromosomes experiencing these selection pressures simultaneously. Reminiscent of previous theory, I find that: the opportunity for polymorphism increases for a sexually antagonistic locus that is physically linked to a driving locus; the opportunity for polymorphism at a driving locus also increases when linked to a sexually antagonistic locus; and stable linkage disequilibrium accompanies any polymorphic equilibrium. Additionally, I find that drive at a linked locus favours the fixation of sexually antagonistic alleles that benefit the sex in which drive occurs. Further, I show that under certain conditions reduced recombination between these two loci is selectively favoured. These theoretical results provide clear, testable predictions about the nature of sexually antagonistic variation on driving chromosomes and have implications for the evolution of genomic architecture. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  18. Random and non-random mating populations: Evolutionary dynamics in meiotic drive.

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    Sarkar, Bijan

    2016-01-01

    Game theoretic tools are utilized to analyze a one-locus continuous selection model of sex-specific meiotic drive by considering nonequivalence of the viabilities of reciprocal heterozygotes that might be noticed at an imprinted locus. The model draws attention to the role of viability selections of different types to examine the stable nature of polymorphic equilibrium. A bridge between population genetics and evolutionary game theory has been built up by applying the concept of the Fundamental Theorem of Natural Selection. In addition to pointing out the influences of male and female segregation ratios on selection, configuration structure reveals some noted results, e.g., Hardy-Weinberg frequencies hold in replicator dynamics, occurrence of faster evolution at the maximized variance fitness, existence of mixed Evolutionarily Stable Strategy (ESS) in asymmetric games, the tending evolution to follow not only a 1:1 sex ratio but also a 1:1 different alleles ratio at particular gene locus. Through construction of replicator dynamics in the group selection framework, our selection model introduces a redefining bases of game theory to incorporate non-random mating where a mating parameter associated with population structure is dependent on the social structure. Also, the model exposes the fact that the number of polymorphic equilibria will depend on the algebraic expression of population structure. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Effects of Mild and Severe Vitamin B Deficiencies on the Meiotic Maturation of Mice Oocytes

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    Ai Tsuji

    2017-03-01

    Full Text Available We investigated the effects of vitamin B 1 deficiency on the meiosis maturation of oocytes. Female Crl:CD1 (ICR mice were fed a 20% casein diet (control group or a vitamin B 1 –free diet (test group. The vitamin B 1 concentration in ovary was approximately 30% lower in the test group than in the control group. Oocyte meiosis was not affected by vitamin B 1 deficiency when the deficiency was not accompanied by body weight loss. On the contrary, frequency of abnormal oocyte was increased by vitamin B 1 deficiency when deficiency was accompanied by body weight loss (referred to as severe vitamin B 1 deficiency; frequency of abnormal oocyte, 13.8% vs 43.7%, P  = .0071. The frequency of abnormal oocytes was decreased by refeeding of a vitamin B 1 –containing diet (13.9% vs 22.9%, P  = .503. These results suggest that severe vitamin B 1 deficiency inhibited meiotic maturation of oocytes but did not damage immature oocytes.

  20. Influence of Meiotic Stages on Developmental Competence of Goat’ Oocyte After Vitrification

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    Wahyuningsih, S.; Ihsan, M. N.

    2018-02-01

    This objective of this research was to investigate effect of goat oocyte meiotic stages on developmental competence after cryopreservation. Ovaries were collected from slaugterhouse and oocytes was aspirated from2-6 mm of follicles. Oocyte with compacted cumulus cells and evenly granulated ooplasm were selected for this experiment. The lenght of in vitro maturation before vitrification was 8 or 22 h in IVM media TCM 199 + FCS 10 % + PMSG 10 IU + hCG 10 IU at 38.5 °C in a humidified atmosphere of 5 % CO2 in air and were vitrified. After vitrification process, GVBD and MII oocyte were matured for 18 or 4 h to fullfill 26 h maturation requirement and then oocytes were subjected to IVF and culture. Cleavage and blastocyst formation rate were to asses their developmental competence. Cleavage rates were obtained for both GVBD ( 56.78 %) and MII (69.64 % ) oocytes (PGoat oocytes in different maturation stages response to vitrification differently and MII stages have better developmental competence than GVBD.

  1. Double trouble: combined action of meiotic drive and Wolbachia feminization in Eurema butterflies.

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    Kern, Peter; Cook, James M; Kageyama, Daisuke; Riegler, Markus

    2015-05-01

    Arthropod sex ratios can be manipulated by a diverse range of selfish genetic elements, including maternally inherited Wolbachia bacteria. Feminization by Wolbachia is rare but has been described for Eurema mandarina butterflies. In this species, some phenotypic and functional females, thought to be ZZ genetic males, are infected with a feminizing Wolbachia strain, wFem. Meanwhile, heterogametic WZ females are not infected with wFem. Here, we establish a quantitative PCR assay allowing reliable sexing in three Eurema species. Against expectation, all E. mandarina females, including wFem females, had only one Z chromosome that was paternally inherited. Observation of somatic interphase nuclei confirmed that W chromatin was absent in wFem females, but present in females without wFem. We conclude that the sex bias in wFem lines is due to meiotic drive (MD) that excludes the maternal Z and thus prevents formation of ZZ males. Furthermore, wFem lines may have lost the W chromosome or harbour a dysfunctional version, yet rely on wFem for female development; removal of wFem results in all-male offspring. This is the first study that demonstrates an interaction between MD and Wolbachia feminization, and it highlights endosymbionts as potentially confounding factors in MD of sex chromosomes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  2. Meiotic and mitotic analyses of a reciprocal translocation in pisum sativum

    International Nuclear Information System (INIS)

    Muller, D.

    1974-01-01

    After X-irradiation of air-dried seeds of Pisum sativum, mutant 210 A was selected on the basis of the characteristic 'low number of seeds per pod', that segregates during following generations. Studies of pollen show a reduced fertility of 49.4% in about 50% of the plants. In meiotic metaphase I association of 4 chromosomes were observed in about 90% PMC in which more than half showed co-orientation of centromeres. A 3:1 segregation of the 4 linking chromosomes appeared in about 24% of all cases. Laggards, bridges and fragments reached a frequency of 11% in anaphase II. Seed production per pod in 2 vegetative periods varied from 63-67%; seed setting per plant fluctuated in the same year, between 55% and 43%. The analysis of karyotype proved the presumption of a simple reciprocal translocation. The exchange occurred between the long arms of the chromosomes 3 and 5. The break position is believed to be situated near the centromers of chromosome 3 and the lower half of the long arm of chromosome 5. (author)

  3. PRDM9 variation strongly influences recombination hot-spot activity and meiotic instability in humans.

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    Berg, Ingrid L; Neumann, Rita; Lam, Kwan-Wood G; Sarbajna, Shriparna; Odenthal-Hesse, Linda; May, Celia A; Jeffreys, Alec J

    2010-10-01

    PRDM9 has recently been identified as a likely trans regulator of meiotic recombination hot spots in humans and mice. PRDM9 contains a zinc finger array that, in humans, can recognize a short sequence motif associated with hot spots, with binding to this motif possibly triggering hot-spot activity via chromatin remodeling. We now report that human genetic variation at the PRDM9 locus has a strong effect on sperm hot-spot activity, even at hot spots lacking the sequence motif. Subtle changes within the zinc finger array can create hot-spot nonactivating or enhancing variants and can even trigger the appearance of a new hot spot, suggesting that PRDM9 is a major global regulator of hot spots in humans. Variation at the PRDM9 locus also influences aspects of genome instability-specifically, a megabase-scale rearrangement underlying two genomic disorders as well as minisatellite instability-implicating PRDM9 as a risk factor for some pathological genome rearrangements.

  4. Downregulation of surface sodium pumps by endocytosis during meiotic maturation of Xenopus laevis oocytes

    International Nuclear Information System (INIS)

    Schmalzing, G.; Eckard, P.; Kroener, S.P.; Passow, H.

    1990-01-01

    During meiotic maturation, plasma membranes of Xenopus laevis oocytes completely lose the capacity to transport Na and K and to bind ouabain. To explore whether the downregulation might be due to an internalization of the sodium pump molecules, the intracellular binding of ouabain was determined. Selective permeabilization of the plasma membrane of mature oocytes (eggs) by digitonin almost failed to disclose ouabain binding sites. However, when the eggs were additionally treated with 0.02% sodium dodecyl sulfate (SDS) to permeabilize inner membranes, all sodium pumps present before maturation were recovered. Phosphorylation by [gamma-32P]ATP combined with SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiography showed that sodium pumps were greatly reduced in isolated plasma membranes of eggs. According to sucrose gradient fractionation, maturation induced a shift of sodium pumps from the plasma membrane fraction to membranes of lower buoyant density with a protein composition different from that of the plasma membrane. Endocytosed sodium pumps identified on the sucrose gradient from [3H]ouabain bound to the cell surface before maturation could be phosphorylated with inorganic [32P]phosphate. The findings suggest that downregulation of sodium pumps during maturation is brought about by translocation of surface sodium pumps to an intracellular compartment, presumably endosomes. This contrasts the mechanism of downregulation of Na-dependent cotransport systems, the activities of which are reduced as a consequence of a maturation-induced depolarization of the membrane without a removal of the corresponding transporter from the plasma membrane

  5. Arabidopsis PCH2 Mediates Meiotic Chromosome Remodeling and Maturation of Crossovers.

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    Christophe Lambing

    2015-07-01

    Full Text Available Meiotic chromosomes are organized into linear looped chromatin arrays by a protein axis localized along the loop-bases. Programmed remodelling of the axis occurs during prophase I of meiosis. Structured illumination microscopy (SIM has revealed dynamic changes in the chromosome axis in Arabidopsis thaliana and Brassica oleracea. We show that the axis associated protein ASY1 is depleted during zygotene concomitant with synaptonemal complex (SC formation. Study of an Atpch2 mutant demonstrates this requires the conserved AAA+ ATPase, PCH2, which localizes to the sites of axis remodelling. Loss of PCH2 leads to a failure to deplete ASY1 from the axes and compromizes SC polymerisation. Immunolocalization of recombination proteins in Atpch2 indicates that recombination initiation and CO designation during early prophase I occur normally. Evidence suggests that CO interference is initially functional in the mutant but there is a defect in CO maturation following designation. This leads to a reduction in COs and a failure to form COs between some homologous chromosome pairs leading to univalent chromosomes at metaphase I. Genetic analysis reveals that CO distribution is also affected in some chromosome regions. Together these data indicate that the axis remodelling defect in Atpch2 disrupts normal patterned formation of COs.

  6. Aberrant Meiotic Modulation Partially Contributes to the Lower Germination Rate of Pollen Grains in Maize (Zea mays L.) Under Low Nitrogen Supply.

    Science.gov (United States)

    Zheng, Hongyan; Wu, Huamao; Pan, Xiaoying; Jin, Weiwei; Li, Xuexian

    2017-02-01

    Pollen germination is an essential step towards successful pollination during maize reproduction. How low niutrogen (N) affects pollen germination remains an interesting biological question to be addressed. We found that only low N resulted in a significantly lower germination rate of pollen grains after 4 weeks of low N, phosphorus or potassium treatment in maize production. Importantly, cytological analysis showed 7-fold more micronuclei in male meiocytes under the low N treatment than in the control, indicating that the lower germination rate of pollen grains was partially due to numerous chromosome loss events resulting from preceding meiosis. The appearance of 10 bivalents in the control and low N cells at diakinesis suggested that chromosome pairing and recombination in meiosis I was not affected by low N. Further gene expression analysis revealed dramatic down-regulation of Nuclear Division Cycle 80 (Ndc80) and Regulator of Chromosome Condensation 1 (Rcc1-1) expression and up-regulation of Cell Division Cycle 20 (Cdc20-1) expression, although no significant difference in the expression level of kinetochore foundation proteins Centromeric Histone H3 (Cenh3) and Centromere Protein C (Cenpc) and cohesion regulators Recombination 8 (Rec8) and Shugoshin (Sgo1) was observed. Aberrant modulation of three key meiotic regulators presumably resulted in a high likelihood of erroneous chromosome segregation, as testified by pronounced lagging chromosomes at anaphase I or cell cycle disruption at meiosis II. Thus, we proposed a cytogenetic mechanism whereby low N affects male meiosis and causes a higher chromosome loss frequency and eventually a lower germination rate of pollen grains in a staple crop plant. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  7. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids.

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    Tanmoy Bhattacharyya

    2014-02-01

    Full Text Available Hybrid sterility (HS belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2(Mmm allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes.

  8. Meiotic gene-conversion rate and tract length variation in the human genome.

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    Padhukasahasram, Badri; Rannala, Bruce

    2013-02-27

    Meiotic recombination occurs in the form of two different mechanisms called crossing-over and gene-conversion and both processes have an important role in shaping genetic variation in populations. Although variation in crossing-over rates has been studied extensively using sperm-typing experiments, pedigree studies and population genetic approaches, our knowledge of variation in gene-conversion parameters (ie, rates and mean tract lengths) remains far from complete. To explore variability in population gene-conversion rates and its relationship to crossing-over rate variation patterns, we have developed and validated using coalescent simulations a comprehensive Bayesian full-likelihood method that can jointly infer crossing-over and gene-conversion rates as well as tract lengths from population genomic data under general variable rate models with recombination hotspots. Here, we apply this new method to SNP data from multiple human populations and attempt to characterize for the first time the fine-scale variation in gene-conversion parameters along the human genome. We find that the estimated ratio of gene-conversion to crossing-over rates varies considerably across genomic regions as well as between populations. However, there is a great degree of uncertainty associated with such estimates. We also find substantial evidence for variation in the mean conversion tract length. The estimated tract lengths did not show any negative relationship with the local heterozygosity levels in our analysis.European Journal of Human Genetics advance online publication, 27 February 2013; doi:10.1038/ejhg.2013.30.

  9. Mitotic and meiotic irregularities in somatic hybrids of Lycopersicon esculentum and Solanum tuberosum.

    Science.gov (United States)

    Wolters, A M; Schoenmakers, H C; Kamstra, S; Eden, J; Koornneef, M; Jong, J H

    1994-10-01

    Chromosome numbers were determined in metaphase complements of root-tip meristems of 107 tomato (+) potato somatic hybrids, obtained from five different combinations of parental genotypes. Of these hybrids 79% were aneuploid, lacking one or two chromosomes in most cases. All four hybrids that were studied at mitotic anaphase of root tips showed laggards and bridges, the three aneuploids in a higher frequency than the single euploid. Hybrid K2H2-1C, which showed the highest percentage of aberrant anaphases, possessed 46 chromosomes. Fluorescence in situ hybridization with total genomic DNA showed that this hybrid contained 23 tomato, 22 potato, and 1 recombinant chromosome consisting of a tomato chromosome arm and a potato chromosome arm. The potato parent of K2H2-1C was aneusomatic in its root tips with a high frequency of monosomic and trisomic cells and a relatively high frequency of cells with one fragment or telosome. Meiotic analyses of three tomato (+) potato somatic hybrids revealed laggards, which occurred most frequently in the triploid hybrids, and bridges, which were frequently present in pollen mother cells (PMCs) at anaphase I of hypotetraploid K2H2-1C. We observed putative trivalents in PMCs at diakinesis and metaphase I of eutriploid A7-82A and quadrivalents in part of the PMCs of hypotetraploid K2H2-1C, suggesting that homoeologous recombination between tomato and potato chromosomes occurred in these hybrids. All three hybrids showed a high percentage of first division restitution, giving rise to unreduced gametes. However, shortly after the tetrad stage all microspores completely degenerated, resulting in exclusively sterile pollen.

  10. Reproductive isolation in hybrid mice due to spermatogenesis defects at three meiotic stages.

    Science.gov (United States)

    Oka, Ayako; Mita, Akihiko; Takada, Yuki; Koseki, Haruhiko; Shiroishi, Toshihiko

    2010-09-01

    Early in the process of speciation, reproductive failures occur in hybrid animals between genetically diverged populations. The sterile hybrid animals are often males in mammals and they exhibit spermatogenic disruptions, resulting in decreased number and/or malformation of mature sperms. Despite the generality of this phenomenon, comparative study of phenotypes in hybrid males from various crosses has not been done, and therefore the comprehensive genetic basis of the disruption is still elusive. In this study, we characterized the spermatogenic phenotype especially during meiosis in four different cases of reproductive isolation: B6-ChrX(MSM), PGN-ChrX(MSM), (B6 × Mus musculus musculus-NJL/Ms) F(1), and (B6 × Mus spretus) F(1). The first two are consomic strains, both bearing the X chromosome of M. m. molossinus; in B6-ChrX(MSM), the genetic background is the laboratory strain C57BL/6J (predominantly M. m. domesticus), while in PGN-ChrX(MSM) the background is the PGN2/Ms strain purely derived from wild M. m. domesticus. The last two cases are F(1) hybrids between mouse subspecies or species. Each of the hybrid males exhibited cell-cycle arrest and/or apoptosis at either one or two of three distinct meiotic stages: premeiotic stage, zygotene-to-pachytene stage of prophase I, and metaphase I. This study shows that the sterility in hybrid males is caused by spermatogenic disruptions at multiple stages, suggesting that the responsible genes function in different cellular processes. Furthermore, the stages with disruptions are not correlated with the genetic distance between the respective parental strains.

  11. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids.

    Science.gov (United States)

    Bhattacharyya, Tanmoy; Reifova, Radka; Gregorova, Sona; Simecek, Petr; Gergelits, Vaclav; Mistrik, Martin; Martincova, Iva; Pialek, Jaroslav; Forejt, Jiri

    2014-02-01

    Hybrid sterility (HS) belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X) harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2(Mmm) allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes.

  12. Meiotic sex chromosome inactivation is disrupted in sterile hybrid male house mice.

    Science.gov (United States)

    Campbell, Polly; Good, Jeffrey M; Nachman, Michael W

    2013-03-01

    In male mammals, the X and Y chromosomes are transcriptionally silenced in primary spermatocytes by meiotic sex chromosome inactivation (MSCI) and remain repressed for the duration of spermatogenesis. Here, we test the longstanding hypothesis that disrupted MSCI might contribute to the preferential sterility of heterogametic hybrid males. We studied a cross between wild-derived inbred strains of Mus musculus musculus and M. m. domesticus in which sterility is asymmetric: F1 males with a M. m. musculus mother are sterile or nearly so while F1 males with a M. m. domesticus mother are normal. In previous work, we discovered widespread overexpression of X-linked genes in the testes of sterile but not fertile F1 males. Here, we ask whether this overexpression is specifically a result of disrupted MSCI. To do this, we isolated cells from different stages of spermatogenesis and measured the expression of several genes using quantitative PCR. We found that X overexpression in sterile F1 primary spermatocytes is coincident with the onset of MSCI and persists in postmeiotic spermatids. Using a series of recombinant X genotypes, we then asked whether X overexpression in hybrids is controlled by cis-acting loci across the X chromosome. We found that it is not. Instead, one large interval in the proximal portion of the M. m. musculus X chromosome is associated with both overexpression and the severity of sterility phenotypes in hybrids. These results demonstrate a strong association between X-linked hybrid male sterility and disruption of MSCI and suggest that trans-acting loci on the X are important for the transcriptional regulation of the X chromosome during spermatogenesis.

  13. X Chromosome Control of Meiotic Chromosome Synapsis in Mouse Inter-Subspecific Hybrids

    Science.gov (United States)

    Bhattacharyya, Tanmoy; Reifova, Radka; Gregorova, Sona; Simecek, Petr; Gergelits, Vaclav; Mistrik, Martin; Martincova, Iva; Pialek, Jaroslav; Forejt, Jiri

    2014-01-01

    Hybrid sterility (HS) belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X) harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2Mmm allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes. PMID:24516397

  14. Dicer1 depletion in male germ cells leads to infertility due to cumulative meiotic and spermiogenic defects.

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    Yannick Romero

    Full Text Available BACKGROUND: Spermatogenesis is a complex biological process that requires a highly specialized control of gene expression. In the past decade, small non-coding RNAs have emerged as critical regulators of gene expression both at the transcriptional and post-transcriptional level. DICER1, an RNAse III endonuclease, is essential for the biogenesis of several classes of small RNAs, including microRNAs (miRNAs and endogenous small interfering RNAs (endo-siRNAs, but is also critical for the degradation of toxic transposable elements. In this study, we investigated to which extent DICER1 is required for germ cell development and the progress of spermatogenesis in mice. PRINCIPAL FINDINGS: We show that the selective ablation of Dicer1 at the early onset of male germ cell development leads to infertility, due to multiple cumulative defects at the meiotic and post-meiotic stages culminating with the absence of functional spermatozoa. Alterations were observed in the first spermatogenic wave and include delayed progression of spermatocytes to prophase I and increased apoptosis, resulting in a reduced number of round spermatids. The transition from round to mature spermatozoa was also severely affected, since the few spermatozoa formed in mutant animals were immobile and misshapen, exhibiting morphological defects of the head and flagellum. We also found evidence that the expression of transposable elements of the SINE family is up-regulated in Dicer1-depleted spermatocytes. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that DICER1 is dispensable for spermatogonial stem cell renewal and mitotic proliferation, but is required for germ cell differentiation through the meiotic and haploid phases of spermatogenesis.

  15. LDSplitDB: a database for studies of meiotic recombination hotspots in MHC using human genomic data.

    Science.gov (United States)

    Guo, Jing; Chen, Hao; Yang, Peng; Lee, Yew Ti; Wu, Min; Przytycka, Teresa M; Kwoh, Chee Keong; Zheng, Jie

    2018-04-20

    Meiotic recombination happens during the process of meiosis when chromosomes inherited from two parents exchange genetic materials to generate chromosomes in the gamete cells. The recombination events tend to occur in narrow genomic regions called recombination hotspots. Its dysregulation could lead to serious human diseases such as birth defects. Although the regulatory mechanism of recombination events is still unclear, DNA sequence polymorphisms have been found to play crucial roles in the regulation of recombination hotspots. To facilitate the studies of the underlying mechanism, we developed a database named LDSplitDB which provides an integrative and interactive data mining and visualization platform for the genome-wide association studies of recombination hotspots. It contains the pre-computed association maps of the major histocompatibility complex (MHC) region in the 1000 Genomes Project and the HapMap Phase III datasets, and a genome-scale study of the European population from the HapMap Phase II dataset. Besides the recombination profiles, related data of genes, SNPs and different types of epigenetic modifications, which could be associated with meiotic recombination, are provided for comprehensive analysis. To meet the computational requirement of the rapidly increasing population genomics data, we prepared a lookup table of 400 haplotypes for recombination rate estimation using the well-known LDhat algorithm which includes all possible two-locus haplotype configurations. To the best of our knowledge, LDSplitDB is the first large-scale database for the association analysis of human recombination hotspots with DNA sequence polymorphisms. It provides valuable resources for the discovery of the mechanism of meiotic recombination hotspots. The information about MHC in this database could help understand the roles of recombination in human immune system. DATABASE URL: http://histone.scse.ntu.edu.sg/LDSplitDB.

  16. Casein kinase 1 alpha regulates chromosome congression and separation during mouse oocyte meiotic maturation and early embryo development.

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    Lu Wang

    Full Text Available Casein kinase I alpha (CK1α is a member of serine/threonine protein kinase, generally present in all eukaryotes. In mammals, CK1α regulates the transition from interphase to metaphase in mitosis. However, little is known about its role in meiosis. Here we examined Ck1α mRNA and protein expression, as well as its subcellular localization in mouse oocytes from germinal vesicle to the late 1-cell stage. Our results showed that the expression level of CK1α was increased in metaphase. Immunostaining results showed that CK1α colocalized with condensed chromosomes during oocyte meiotic maturation and early embryo development. We used the loss-of-function approach by employing CK1α specific morpholino injection to block the function of CK1α. This functional blocking leads to failure of polar body 1 (PB1 extrusion, chromosome misalignment and MII plate incrassation. We further found that D4476, a specific and efficient CK1 inhibitor, decreased the rate of PB1 extrusion. Moreover, D4476 resulted in giant polar body extrusion, oocyte pro-MI arrest, chromosome congression failure and impairment of embryo developmental potential. In addition, we employed pyrvinium pamoate (PP, an allosteric activator of CK1α, to enhance CK1α activity in oocytes. Supplementation of PP induced oocyte meiotic maturation failure, severe congression abnormalities and misalignment of chromosomes. Taken together, our study for the first time demonstrates that CK1α is required for chromosome alignment and segregation during oocyte meiotic maturation and early embryo development.

  17. Comportamiento meiótico de diferentes especies de lulo, Solanum sp Meiotic behavior of lulo species, Solanum sp

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    Nancy Maricela Pareja Ordóñez

    2010-10-01

    Full Text Available Se realizó un análisis del comportamiento meiótico de las especies de lulo S. hirtum, S. quitoense y S. sessiliflorum, siguiendo la metodología convencional para los estudios de microsporogénesis. Se tomaron botones florales en diferentes estados de desarrollo, fijándolos por 24 horas en una solución de tres partes de etanol por una parte de ácido acético, saturada con trazas de cristales de cloruro férrico. Para la preparación de las placas se siguió la técnica de aplastamiento, se liberaron las células madres del grano de polen y finalmente se hicieron las observaciones bajo microscopía de luz. El análisis mostró que la meiosis se presenta en longitudes de antera que van desde los 2,79 mm hasta los 4,45 mm. La normalidad meiótica fue del 100%, tanto para meiosis I, como para la meiosis II. El índice meiótico en las tres especies fue del 99,98% lo cual indica que son buenos parentales y que pueden utilizarse en programas de cruzamiento. Las tres especies evaluadas tienen igual número de cromosomas (2n=2X=24. La frecuencia de anormalidades durante el proceso meiótico fue baja para S. hirtum, y alta para S. quitoense; sin embargo, la viabilidad polínica fue de gran magnitud (91,2-97,3%.An analysis of meiotic behavior of lulo species S. hirtum, S. quitoense and S. sessiliflorum, following the conventional methodology for studies of microsporogenesis was realized. Flower buds were taken at different stages of development, fixing them for 24 hours in a solution of three parts of ethanol per one part of acetic acid, saturated with traces of ferric chloride crystals. For the preparation of the slides following the technique of squash, releasing pollen mother cells and finally made the observations under light microscopy. The analysis showed that meiosis occurs in anther ranging from 2.79 to 4.45 mm. Meiotic normality was 100% for both meiosis I and II. The meiotic index in all three species was 99,98% indicating that they are

  18. OSD1 promotes meiotic progression via APC/C inhibition and forms a regulatory network with TDM and CYCA1;2/TAM.

    Science.gov (United States)

    Cromer, Laurence; Heyman, Jefri; Touati, Sandra; Harashima, Hirofumi; Araou, Emilie; Girard, Chloe; Horlow, Christine; Wassmann, Katja; Schnittger, Arp; De Veylder, Lieven; Mercier, Raphael

    2012-01-01

    Cell cycle control is modified at meiosis compared to mitosis, because two divisions follow a single DNA replication event. Cyclin-dependent kinases (CDKs) promote progression through both meiosis and mitosis, and a central regulator of their activity is the APC/C (Anaphase Promoting Complex/Cyclosome) that is especially required for exit from mitosis. We have shown previously that OSD1 is involved in entry into both meiosis I and meiosis II in Arabidopsis thaliana; however, the molecular mechanism by which OSD1 controls these transitions has remained unclear. Here we show that OSD1 promotes meiotic progression through APC/C inhibition. Next, we explored the functional relationships between OSD1 and the genes known to control meiotic cell cycle transitions in Arabidopsis. Like osd1, cyca1;2/tam mutation leads to a premature exit from meiosis after the first division, while tdm mutants perform an aberrant third meiotic division after normal meiosis I and II. Remarkably, while tdm is epistatic to tam, osd1 is epistatic to tdm. We further show that the expression of a non-destructible CYCA1;2/TAM provokes, like tdm, the entry into a third meiotic division. Finally, we show that CYCA1;2/TAM forms an active complex with CDKA;1 that can phosphorylate OSD1 in vitro. We thus propose that a functional network composed of OSD1, CYCA1;2/TAM, and TDM controls three key steps of meiotic progression, in which OSD1 is a meiotic APC/C inhibitor.

  19. Confocal Analysis of Nuclear Lamina Behavior during Male Meiosis and Spermatogenesis in Drosophila melanogaster.

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    Fabiana Fabbretti

    Full Text Available Lamin family proteins are structural components of a filamentous framework, the nuclear lamina (NL, underlying the inner membrane of nuclear envelope. The NL not only plays a role in nucleus mechanical support and nuclear shaping, but is also involved in many cellular processes including DNA replication, gene expression and chromatin positioning. Spermatogenesis is a very complex differentiation process in which each stage is characterized by nuclear architecture dramatic changes, from the early mitotic stage to the sperm differentiation final stage. Nevertheless, very few data are present in the literature on the NL behavior during this process. Here we show the first and complete description of NL behavior during meiosis and spermatogenesis in Drosophila melanogaster. By confocal imaging, we characterized the NL modifications from mitotic stages, through meiotic divisions to sperm differentiation with an anti-laminDm0 antibody against the major component of the Drosophila NL. We observed that continuous changes in the NL structure occurred in parallel with chromatin reorganization throughout the whole process and that meiotic divisions occurred in a closed context. Finally, we analyzed NL in solofuso meiotic mutant, where chromatin segregation is severely affected, and found the strict correlation between the presence of chromatin and that of NL.

  20. Combinatorial regulation of meiotic holliday junction resolution in C. elegans by HIM-6 (BLM) helicase, SLX-4, and the SLX-1, MUS-81 and XPF-1 nucleases.

    Science.gov (United States)

    Agostinho, Ana; Meier, Bettina; Sonneville, Remi; Jagut, Marlène; Woglar, Alexander; Blow, Julian; Jantsch, Verena; Gartner, Anton

    2013-01-01

    Holliday junctions (HJs) are cruciform DNA structures that are created during recombination events. It is a matter of considerable importance to determine the resolvase(s) that promote resolution of these structures. We previously reported that C. elegans GEN-1 is a symmetrically cleaving HJ resolving enzyme required for recombinational repair, but we could not find an overt role in meiotic recombination. Here we identify C. elegans proteins involved in resolving meiotic HJs. We found no evidence for a redundant meiotic function of GEN-1. In contrast, we discovered two redundant HJ resolution pathways likely coordinated by the SLX-4 scaffold protein and also involving the HIM-6/BLM helicase. SLX-4 associates with the SLX-1, MUS-81 and XPF-1 nucleases and has been implicated in meiotic recombination in C. elegans. We found that C. elegans [mus-81; xpf-1], [slx-1; xpf-1], [mus-81; him-6] and [slx-1; him-6] double mutants showed a similar reduction in survival rates as slx-4. Analysis of meiotic diakinesis chromosomes revealed a distinct phenotype in these double mutants. Instead of wild-type bivalent chromosomes, pairs of "univalents" linked by chromatin bridges occur. These linkages depend on the conserved meiosis-specific transesterase SPO-11 and can be restored by ionizing radiation, suggesting that they represent unresolved meiotic HJs. This suggests the existence of two major resolvase activities, one provided by XPF-1 and HIM-6, the other by SLX-1 and MUS-81. In all double mutants crossover (CO) recombination is reduced but not abolished, indicative of further redundancy in meiotic HJ resolution. Real time imaging revealed extensive chromatin bridges during the first meiotic division that appear to be eventually resolved in meiosis II, suggesting back-up resolution activities acting at or after anaphase I. We also show that in HJ resolution mutants, the restructuring of chromosome arms distal and proximal to the CO still occurs, suggesting that CO initiation

  1. Reproductive Performance of Holstein Dairy Cows Grazing in Dry-summer Subtropical Climatic Conditions: Effect of Heat Stress and Heat Shock on Meiotic Competence and In vitro Fertilization.

    Science.gov (United States)

    Pavani, Krishna; Carvalhais, Isabel; Faheem, Marwa; Chaveiro, Antonio; Reis, Francisco Vieira; da Silva, Fernando Moreira

    2015-03-01

    The present study was designed to evaluate how environmental factors in a dry-summer subtropical climate in Terceira-Azores (situated in the North Atlantic Ocean: 38° 43' N 27° 12' W) can affect dairy cow (Holstein) fertility, as well as seasonal influence on in vitro oocytes maturation and embryos development. Impact of heat shock (HS) effects on in vitro oocyte's maturation and further embryo development after in vitro fertilization (IVF) was also evaluated. For such purpose the result of the first artificial insemination (AI) performed 60 to 90 days after calving of 6,300 cows were recorded for one year. In parallel, climatic data was obtained at different elevation points (n = 5) from 0 to 1,000 m and grazing points from 0 to 500 m, in Terceira island, and the temperature humidity index (THI) was calculated. For in vitro experiments, oocytes (n = 706) were collected weekly during all year, for meiotic maturation and IVF. Further, to evaluate HS effect, 891 oocytes were collected in the cold moths (December, January, February and March) and divided in three groups treated to HS for 24 h during in vitro maturation at: C (Control = 38.5°C), HS1 (39.5°C) and HS2 (40.5°C). Oocytes from each group were used for meiotic assessment and IVF. Cleavage, morula and blastocyst development were evaluated respectively on day 2, 6, and 9 after IVF. A negative correlation between cow's conception rate (CR) and THI in grazing points (-91.3%; p<0.001) was observed. Mean THI in warmer months (June, July, August and September) was 71.7±0.7 and the CR (40.2±1.5%) while in cold months THI was 62.8±0.2 and CR was 63.8±0.4%. A similar impact was obtained with in vitro results in which nuclear maturation rate (NMR) ranged from 78.4% (±8.0) to 44.3% (±8.1), while embryos development ranged from 53.8% (±5.8) to 36.3% (±3.3) in cold and warmer months respectively. In vitro HS results showed a significant decline (p<0.05) on NMR of oocytes for every 1°C rising temperature (78

  2. Reproductive Performance of Holstein Dairy Cows Grazing in Dry-summer Subtropical Climatic Conditions: Effect of Heat Stress and Heat Shock on Meiotic Competence and Fertilization

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    Krishna Pavani

    2015-03-01

    Full Text Available The present study was designed to evaluate how environmental factors in a dry-summer subtropical climate in Terceira-Azores (situated in the North Atlantic Ocean: 38° 43′ N 27° 12′ W can affect dairy cow (Holstein fertility, as well as seasonal influence on in vitro oocytes maturation and embryos development. Impact of heat shock (HS effects on in vitro oocyte’s maturation and further embryo development after in vitro fertilization (IVF was also evaluated. For such purpose the result of the first artificial insemination (AI performed 60 to 90 days after calving of 6,300 cows were recorded for one year. In parallel, climatic data was obtained at different elevation points (n = 5 from 0 to 1,000 m and grazing points from 0 to 500 m, in Terceira island, and the temperature humidity index (THI was calculated. For in vitro experiments, oocytes (n = 706 were collected weekly during all year, for meiotic maturation and IVF. Further, to evaluate HS effect, 891 oocytes were collected in the cold moths (December, January, February and March and divided in three groups treated to HS for 24 h during in vitro maturation at: C (Control = 38.5°C, HS1 (39.5°C and HS2 (40.5°C. Oocytes from each group were used for meiotic assessment and IVF. Cleavage, morula and blastocyst development were evaluated respectively on day 2, 6, and 9 after IVF. A negative correlation between cow’s conception rate (CR and THI in grazing points (−91.3%; p<0.001 was observed. Mean THI in warmer months (June, July, August and September was 71.7±0.7 and the CR (40.2±1.5% while in cold months THI was 62.8±0.2 and CR was 63.8±0.4%. A similar impact was obtained with in vitro results in which nuclear maturation rate (NMR ranged from 78.4% (±8.0 to 44.3% (±8.1, while embryos development ranged from 53.8% (±5.8 to 36.3% (±3.3 in cold and warmer months respectively. In vitro HS results showed a significant decline (p<0.05 on NMR of oocytes for every 1°C rising

  3. SLX-1 is required for maintaining genomic integrity and promoting meiotic noncrossovers in the Caenorhabditis elegans germline.

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    Takamune T Saito

    2012-08-01

    Full Text Available Although the SLX4 complex, which includes structure-specific nucleases such as XPF, MUS81, and SLX1, plays important roles in the repair of several kinds of DNA damage, the function of SLX1 in the germline remains unknown. Here we characterized the endonuclease activities of the Caenorhabditis elegans SLX-1-HIM-18/SLX-4 complex co-purified from human 293T cells and determined SLX-1 germline function via analysis of slx-1(tm2644 mutants. SLX-1 shows a HIM-18/SLX-4-dependent endonuclease activity toward replication forks, 5'-flaps, and Holliday junctions. slx-1 mutants exhibit hypersensitivity to UV, nitrogen mustard, and camptothecin, but not gamma irradiation. Consistent with a role in DNA repair, recombination intermediates accumulate in both mitotic and meiotic germ cells in slx-1 mutants. Importantly, meiotic crossover distribution, but not crossover frequency, is altered on chromosomes in slx-1 mutants compared to wild type. This alteration is not due to changes in either the levels or distribution of double-strand breaks (DSBs along chromosomes. We propose that SLX-1 is required for repair at stalled or collapsed replication forks, interstrand crosslink repair, and nucleotide excision repair during mitosis. Moreover, we hypothesize that SLX-1 regulates the crossover landscape during meiosis by acting as a noncrossover-promoting factor in a subset of DSBs.

  4. Caenorhabditis elegans histone methyltransferase MET-2 shields the male X chromosome from checkpoint machinery and mediates meiotic sex chromosome inactivation.

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    Paula M Checchi

    2011-09-01

    Full Text Available Meiosis is a specialized form of cellular division that results in the precise halving of the genome to produce gametes for sexual reproduction. Checkpoints function during meiosis to detect errors and subsequently to activate a signaling cascade that prevents the formation of aneuploid gametes. Indeed, asynapsis of a homologous chromosome pair elicits a checkpoint response that can in turn trigger germline apoptosis. In a heterogametic germ line, however, sex chromosomes proceed through meiosis with unsynapsed regions and are not recognized by checkpoint machinery. We conducted a directed RNAi screen in Caenorhabditis elegans to identify regulatory factors that prevent recognition of heteromorphic sex chromosomes as unpaired and uncovered a role for the SET domain histone H3 lysine 9 histone methyltransferase (HMTase MET-2 and two additional HMTases in shielding the male X from checkpoint machinery. We found that MET-2 also mediates the transcriptional silencing program of meiotic sex chromosome inactivation (MSCI but not meiotic silencing of unsynapsed chromatin (MSUC, suggesting that these processes are distinct. Further, MSCI and checkpoint shielding can be uncoupled, as double-strand breaks targeted to an unpaired, transcriptionally silenced extra-chromosomal array induce checkpoint activation in germ lines depleted for met-2. In summary, our data uncover a mechanism by which repressive chromatin architecture enables checkpoint proteins to distinguish between the partnerless male X chromosome and asynapsed chromosomes thereby shielding the lone X from inappropriate activation of an apoptotic program.

  5. Cytoplasmic and Genomic Effects on Meiotic Pairing in Brassica Hybrids and Allotetraploids from Pair Crosses of Three Cultivated Diploids

    Science.gov (United States)

    Cui, Cheng; Ge, Xianhong; Gautam, Mayank; Kang, Lei; Li, Zaiyun

    2012-01-01

    Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and “fixed heterosis” in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids. PMID:22505621

  6. PRDM9 drives evolutionary erosion of hotspots in Mus musculus through haplotype-specific initiation of meiotic recombination.

    Science.gov (United States)

    Baker, Christopher L; Kajita, Shimpei; Walker, Michael; Saxl, Ruth L; Raghupathy, Narayanan; Choi, Kwangbom; Petkov, Petko M; Paigen, Kenneth

    2015-01-01

    Meiotic recombination generates new genetic variation and assures the proper segregation of chromosomes in gametes. PRDM9, a zinc finger protein with histone methyltransferase activity, initiates meiotic recombination by binding DNA at recombination hotspots and directing the position of DNA double-strand breaks (DSB). The DSB repair mechanism suggests that hotspots should eventually self-destruct, yet genome-wide recombination levels remain constant, a conundrum known as the hotspot paradox. To test if PRDM9 drives this evolutionary erosion, we measured activity of the Prdm9Cst allele in two Mus musculus subspecies, M.m. castaneus, in which Prdm9Cst arose, and M.m. domesticus, into which Prdm9Cst was introduced experimentally. Comparing these two strains, we find that haplotype differences at hotspots lead to qualitative and quantitative changes in PRDM9 binding and activity. Using Mus spretus as an outlier, we found most variants affecting PRDM9Cst binding arose and were fixed in M.m. castaneus, suppressing hotspot activity. Furthermore, M.m. castaneus×M.m. domesticus F1 hybrids exhibit novel hotspots, with large haplotype biases in both PRDM9 binding and chromatin modification. These novel hotspots represent sites of historic evolutionary erosion that become activated in hybrids due to crosstalk between one parent's Prdm9 allele and the opposite parent's chromosome. Together these data support a model where haplotype-specific PRDM9 binding directs biased gene conversion at hotspots, ultimately leading to hotspot erosion.

  7. CENTRAL REGION COMPONENT1, a Novel Synaptonemal Complex Component, Is Essential for Meiotic Recombination Initiation in Rice[C][W

    Science.gov (United States)

    Miao, Chunbo; Tang, Ding; Zhang, Honggen; Wang, Mo; Li, Yafei; Tang, Shuzhu; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2013-01-01

    In meiosis, homologous recombination entails programmed DNA double-strand break (DSB) formation and synaptonemal complex (SC) assembly coupled with the DSB repair. Although SCs display extensive structural conservation among species, their components identified are poorly conserved at the sequence level. Here, we identified a novel SC component, designated CENTRAL REGION COMPONENT1 (CRC1), in rice (Oryza sativa). CRC1 colocalizes with ZEP1, the rice SC transverse filament protein, to the central region of SCs in a mutually dependent fashion. Consistent with this colocalization, CRC1 interacts with ZEP1 in yeast two-hybrid assays. CRC1 is orthologous to Saccharomyces cerevisiae pachytene checkpoint2 (Pch2) and Mus musculus THYROID RECEPTOR-INTERACTING PROTEIN13 (TRIP13) and may be a conserved SC component. Additionally, we provide evidence that CRC1 is essential for meiotic DSB formation. CRC1 interacts with HOMOLOGOUS PAIRING ABERRATION IN RICE MEIOSIS1 (PAIR1) in vitro, suggesting that these proteins act as a complex to promote DSB formation. PAIR2, the rice ortholog of budding yeast homolog pairing1, is required for homologous chromosome pairing. We found that CRC1 is also essential for the recruitment of PAIR2 onto meiotic chromosomes. The roles of CRC1 identified here have not been reported for Pch2 or TRIP13. PMID:23943860

  8. Central region component1, a novel synaptonemal complex component, is essential for meiotic recombination initiation in rice.

    Science.gov (United States)

    Miao, Chunbo; Tang, Ding; Zhang, Honggen; Wang, Mo; Li, Yafei; Tang, Shuzhu; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2013-08-01

    In meiosis, homologous recombination entails programmed DNA double-strand break (DSB) formation and synaptonemal complex (SC) assembly coupled with the DSB repair. Although SCs display extensive structural conservation among species, their components identified are poorly conserved at the sequence level. Here, we identified a novel SC component, designated central region component1 (CRC1), in rice (Oryza sativa). CRC1 colocalizes with ZEP1, the rice SC transverse filament protein, to the central region of SCs in a mutually dependent fashion. Consistent with this colocalization, CRC1 interacts with ZEP1 in yeast two-hybrid assays. CRC1 is orthologous to Saccharomyces cerevisiae pachytene checkpoint2 (Pch2) and Mus musculus THYROID receptor-interacting protein13 (TRIP13) and may be a conserved SC component. Additionally, we provide evidence that CRC1 is essential for meiotic DSB formation. CRC1 interacts with homologous pairing aberration in rice meiosis1 (PAIR1) in vitro, suggesting that these proteins act as a complex to promote DSB formation. PAIR2, the rice ortholog of budding yeast homolog pairing1, is required for homologous chromosome pairing. We found that CRC1 is also essential for the recruitment of PAIR2 onto meiotic chromosomes. The roles of CRC1 identified here have not been reported for Pch2 or TRIP13.

  9. Stage sensitivity and dose response of meiotic chromosomes of pollen mother cells of Tradescantia to X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Ma, T H; Kontos, Jr, G J; Anderson, V A [Western Illinois Univ., Macomb (USA). Dept. of Biological Sciences

    1980-05-01

    Chromosome damage induced by physical and chemical mutagens can be quantitated by the frequencies of micronuclei (MCN) produced in tetrads of the meiotic pollen mother cells of Tradescantia, i.e. the 'MCN-in-Tetrad' test. The stage sensitivity and dose response of these meiocytes to low exposures of X-rays was studied to improve the efficiency and reliability of this test. Stage sensitivity was determined by observing, at 3 hr intervals, the frequencies of X-ray (35 rads)-induced MCN in tetrads from a series of 16 fixations of tetrad-containing inflorescences. Late stages of meiosis (3-9 hr post-irradiation fixation groups) were insensitive (5-14 MCN/100 tetrads). Relatively high sensitivity was exhibited in the early stages of meiosis. The first and second sensitive peaks (62 and 61 MCN/100 tetrads) centered around the 21 and 39 hr post-irradiation fixation groups respectively. Control groups yielded around 3-4 MCN/100 tetrads. A dose-response relation for MCN was determined by treating early stages of meiotic pollen mother cells with X-ray exposures ranging from 9.5 to 57.5 rads. A linear regression line was established with about 20 MCN/100 tetrads per 10 rad increment.

  10. Stage sensitivity and dose response of meiotic chromosomes of pollen mother cells of Tradescantia to X-rays

    International Nuclear Information System (INIS)

    Ma, T.-H.; Kontos, G.J. Jr.; Anderson, V.A.

    1980-01-01

    Chromosome damage induced by physical and chemical mutagens can be quantitated by the frequencies of micronuclei (MCN) produced in tetrads of the meiotic pollen mother cells of Tradescantia, i.e. the 'MCN-in-Tetrad' test. The stage sensitivity and dose response of these meiocytes to low exposures of X-rays was studied to improve the efficiency and reliability of this test. Stage sensitivity was determined by observing, at 3 hr intervals, the frequencies of X-ray (35 rads)-induced MCN in tetrads from a series of 16 fixations of tetrad-containing inflorescences. Late stages of meiosis (3-9 hr post-irradiation fixation groups) were insensitive (5-14 MCN/100 tetrads). Relatively high sensitivity was exhibited in the early stages of meiosis. The first and second sensitive peaks (62 and 61 MCN/100 tetrads) centered around the 21 and 39 hr post-irradiation fixation groups respectively. Control groups yielded around 3-4 MCN/100 tetrads. A dose-response relation for MCN was determined by treating early stages of meiotic pollen mother cells with X-ray exposures ranging from 9.5 to 57.5 rads. A linear regression line was established with about 20 MCN/100 tetrads per 10 rad increment. (author)

  11. Slow Freezing or Vitrification of Oocytes: Their Effects on Survival and Meiotic Spindles, and the Time Schedule for Clinical Practice

    Directory of Open Access Journals (Sweden)

    Shee-Uan Chen

    2009-03-01

    Full Text Available Both the slow-freezing method with increased sucrose concentration and new vitrification techniques significantly improve the results of cryopreservation of human oocytes. The recent perfection for vitrification includes the concepts of increase of cooling and warming rates using minimum volume methods, and decrease of toxicity by reducing the concentration of cryoprotectants. In the recent literature, the survival of cryopreserved oocytes ranged from 74% to 90% using the slow-freezing method and from 84% to 99% by vitrification. Overall, the survival rate of oocytes from vitrification (95%, 899/948 appeared higher than that of the slow-freezing method (75%, 1,275/1,683. The microtubules of meiotic spindles are vulnerable to the thermal changes and will depolymerize. After incubation, the microtubules repolymerize. Spindle recovery is faster after vitrification than slow freezing. Even so, after 3 hours of incubation, spindle recuperation is similar between vitrification and slow freezing. Considering both aspects of spindle recovery and oocyte aging, the time schedule for oocyte cryopreservation program makes fertilization in the optimal time. Intracytoplasmic sperm injection is performed for oocytes at 3 hours of post-thaw incubation from the slow-freezing method and 2 hours from vitrification, with restoration of meiotic spindles. The pregnancy potential of cryopreserved oocytes is comparable to that of fresh oocytes or frozen embryos. Cryopreservation of oocytes would importantly contribute to oocyte donation and preservation of fertility for cancer patients.

  12. Local and sex-specific biases in crossover vs. noncrossover outcomes at meiotic recombination hot spots in mice

    Science.gov (United States)

    de Boer, Esther; Jasin, Maria; Keeney, Scott

    2015-01-01

    Meiotic recombination initiated by programmed double-strand breaks (DSBs) yields two types of interhomolog recombination products, crossovers and noncrossovers, but what determines whether a DSB will yield a crossover or noncrossover is not understood. In this study, we analyzed the influence of sex and chromosomal location on mammalian recombination outcomes by constructing fine-scale recombination maps in both males and females at two mouse hot spots located in different regions of the same chromosome. These include the most comprehensive maps of recombination hot spots in oocytes to date. One hot spot, located centrally on chromosome 1, behaved similarly in male and female meiosis: Crossovers and noncrossovers formed at comparable levels and ratios in both sexes. In contrast, at a distal hot spot, crossovers were recovered only in males even though noncrossovers were obtained at similar frequencies in both sexes. These findings reveal an example of extreme sex-specific bias in recombination outcome. We further found that estimates of relative DSB levels are surprisingly poor predictors of relative crossover frequencies between hot spots in males. Our results demonstrate that the outcome of mammalian meiotic recombination can be biased, that this bias can vary depending on location and cellular context, and that DSB frequency is not the only determinant of crossover frequency. PMID:26251527

  13. Sex chromosome-specific regulation in the Drosophila male germline but little evidence for chromosomal dosage compensation or meiotic inactivation.

    Directory of Open Access Journals (Sweden)

    Colin D Meiklejohn

    2011-08-01

    Full Text Available The evolution of heteromorphic sex chromosomes (e.g., XY in males or ZW in females has repeatedly elicited the evolution of two kinds of chromosome-specific regulation: dosage compensation--the equalization of X chromosome gene expression in males and females--and meiotic sex chromosome inactivation (MSCI--the transcriptional silencing and heterochromatinization of the X during meiosis in the male (or Z in the female germline. How the X chromosome is regulated in the Drosophila melanogaster male germline is unclear. Here we report three new findings concerning gene expression from the X in Drosophila testes. First, X chromosome-wide dosage compensation appears to be absent from most of the Drosophila male germline. Second, microarray analysis provides no evidence for X chromosome-specific inactivation during meiosis. Third, we confirm the previous discovery that the expression of transgene reporters driven by autosomal spermatogenesis-specific promoters is strongly reduced when inserted on the X chromosome versus the autosomes; but we show that this chromosomal difference in expression is established in premeiotic cells and persists in meiotic cells. The magnitude of the X-autosome difference in transgene expression cannot be explained by the absence of dosage compensation, suggesting that a previously unrecognized mechanism limits expression from the X during spermatogenesis in Drosophila. These findings help to resolve several previously conflicting reports and have implications for patterns of genome evolution and speciation in Drosophila.

  14. Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour

    Science.gov (United States)

    Lavia, Graciela Inés; Ortiz, Alejandra Marcela; Robledo, Germán; Fernández, Aveliano; Seijo, Guillermo

    2011-01-01

    Background and Aims Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Methods Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. Key Results The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S–26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Conclusions Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms

  15. Excess single-stranded DNA inhibits meiotic double-strand break repair.

    Directory of Open Access Journals (Sweden)

    Rebecca Johnson

    2007-11-01

    Full Text Available During meiosis, self-inflicted DNA double-strand breaks (DSBs are created by the protein Spo11 and repaired by homologous recombination leading to gene conversions and crossovers. Crossover formation is vital for the segregation of homologous chromosomes during the first meiotic division and requires the RecA orthologue, Dmc1. We analyzed repair during meiosis of site-specific DSBs created by another nuclease, VMA1-derived endonuclease (VDE, in cells lacking Dmc1 strand-exchange protein. Turnover and resection of the VDE-DSBs was assessed in two different reporter cassettes that can repair using flanking direct repeat sequences, thereby obviating the need for a Dmc1-dependent DNA strand invasion step. Access of the single-strand binding complex replication protein A, which is normally used in all modes of DSB repair, was checked in chromatin immunoprecipitation experiments, using antibody against Rfa1. Repair of the VDE-DSBs was severely inhibited in dmc1Delta cells, a defect that was associated with a reduction in the long tract resection required to initiate single-strand annealing between the flanking repeat sequences. Mutants that either reduce Spo11-DSB formation or abolish resection at Spo11-DSBs rescued the repair block. We also found that a replication protein A component, Rfa1, does not accumulate to expected levels at unrepaired single-stranded DNA (ssDNA in dmc1Delta cells. The requirement of Dmc1 for VDE-DSB repair using flanking repeats appears to be caused by the accumulation of large quantities of ssDNA that accumulate at Spo11-DSBs when Dmc1 is absent. We propose that these resected DSBs sequester both resection machinery and ssDNA binding proteins, which in wild-type cells would normally be recycled as Spo11-DSBs repair. The implication is that repair proteins are in limited supply, and this could reflect an underlying mechanism for regulating DSB repair in wild-type cells, providing protection from potentially harmful effects

  16. Temporal analysis of meiotic DNA double-strand break formation and repair in Drosophila females.

    Science.gov (United States)

    Mehrotra, S; McKim, K S

    2006-11-24

    Using an antibody against the phosphorylated form of His2Av (gamma-His2Av), we have described the time course for the series of events leading from the formation of a double-strand break (DSB) to a crossover in Drosophila female meiotic prophase. MEI-P22 is required for DSB formation and localizes to chromosomes prior to gamma-His2Av foci. Drosophila females, however, are among the group of organisms where synaptonemal complex (SC) formation is not dependent on DSBs. In the absence of two SC proteins, C(3)G and C(2)M, the number of DSBs in oocytes is significantly reduced. This is consistent with the appearance of SC protein staining prior to gamma-His2Av foci. However, SC formation is incomplete or absent in the neighboring nurse cells, and gamma-His2Av foci appear with the same kinetics as in oocytes and do not depend on SC proteins. Thus, competence for DSB formation in nurse cells occurs with a specific timing that is independent of the SC, whereas in the oocytes, some SC proteins may have a regulatory role to counteract the effects of a negative regulator of DSB formation. The SC is not sufficient for DSB formation, however, since DSBs were absent from the heterochromatin even though SC formation occurs in these regions. All gamma-His2Av foci disappear before the end of prophase, presumably as repair is completed and crossovers are formed. However, oocytes in early prophase exhibit a slower response to X-ray-induced DSBs compared to those in the late pachytene stage. Assuming all DSBs appear as gamma-His2Av foci, there is at least a 3:1 ratio of noncrossover to crossover products. From a comparison of the frequency of gamma-His2Av foci and crossovers, it appears that Drosophila females have only a weak mechanism to ensure a crossover in the presence of a low number of DSBs.

  17. Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour.

    Science.gov (United States)

    Lavia, Graciela Inés; Ortiz, Alejandra Marcela; Robledo, Germán; Fernández, Aveliano; Seijo, Guillermo

    2011-07-01

    Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S-26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms involved in the origin of economically important species

  18. Release from Xenopus oocyte prophase I meiotic arrest is independent of a decrease in cAMP levels or PKA activity.

    Science.gov (United States)

    Nader, Nancy; Courjaret, Raphael; Dib, Maya; Kulkarni, Rashmi P; Machaca, Khaled

    2016-06-01

    Vertebrate oocytes arrest at prophase of meiosis I as a result of high levels of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) activity. In Xenopus, progesterone is believed to release meiotic arrest by inhibiting adenylate cyclase, lowering cAMP levels and repressing PKA. However, the exact timing and extent of the cAMP decrease is unclear, with conflicting reports in the literature. Using various in vivo reporters for cAMP and PKA at the single-cell level in real time, we fail to detect any significant changes in cAMP or PKA in response to progesterone. More interestingly, there was no correlation between the levels of PKA inhibition and the release of meiotic arrest. Furthermore, we devised conditions whereby meiotic arrest could be released in the presence of sustained high levels of cAMP. Consistently, lowering endogenous cAMP levels by >65% for prolonged time periods failed to induce spontaneous maturation. These results argue that the release of oocyte meiotic arrest in Xenopus is independent of a reduction in either cAMP levels or PKA activity, but rather proceeds through a parallel cAMP/PKA-independent pathway. © 2016. Published by The Company of Biologists Ltd.

  19. Specific deletion of Cdc42 does not affect meiotic spindle organization/migration and homologous chromosome segregation but disrupts polarity establishment and cytokinesis in mouse oocytes

    DEFF Research Database (Denmark)

    Wang, Zhen-Bo; Jiang, Zong-Zhe; Zhang, Qing-Hua

    2013-01-01

    Mammalian oocyte maturation is distinguished by highly asymmetric meiotic divisions during which a haploid female gamete is produced and almost all the cytoplasm is maintained in the egg for embryo development. Actin-dependent meiosis I spindle positioning to the cortex induces the formation...

  20. Inducible protective processes in animal systems XV: Hyperthermia enhances the Ethyl methanesulfonate induced adaptive response in meiotic cells of grasshopper Poecilocerus pictus

    Directory of Open Access Journals (Sweden)

    R. Venu

    2016-04-01

    Conclusion: There is a protection against EMS induced anomalies by hyperthermia in in vivo P. pictus. As far as our knowledge is concerned, this is the first report to demonstrate that hyperthermia enhances the EMS induced adaptive response in in vivo meiotic cells.

  1. Assessing fluctuating evolutionary pressure in yeast and mammal evolutionary rate covariation using bioinformatics of meiotic protein genetic sequences

    Science.gov (United States)

    Dehipawala, Sunil; Nguyen, A.; Tremberger, G.; Cheung, E.; Holden, T.; Lieberman, D.; Cheung, T.

    2013-09-01

    The evolutionary rate co-variation in meiotic proteins has been reported for yeast and mammal using phylogenic branch lengths which assess retention, duplication and mutation. The bioinformatics of the corresponding DNA sequences could be classified as a diagram of fractal dimension and Shannon entropy. Results from biomedical gene research provide examples on the diagram methodology. The identification of adaptive selection using entropy marker and functional-structural diversity using fractal dimension would support a regression analysis where the coefficient of determination would serve as evolutionary pathway marker for DNA sequences and be an important component in the astrobiology community. Comparisons between biomedical genes such as EEF2 (elongation factor 2 human, mouse, etc), WDR85 in epigenetics, HAR1 in human specificity, clinical trial targeted cancer gene CD47, SIRT6 in spermatogenesis, and HLA-C in mosquito bite immunology demonstrate the diagram classification methodology. Comparisons to the SEPT4-XIAP pair in stem cell apoptosis, testesexpressed taste genes TAS1R3-GNAT3 pair, and amyloid beta APLP1-APLP2 pair with the yeast-mammal DNA sequences for meiotic proteins RAD50-MRE11 pair and NCAPD2-ICK pair have accounted for the observed fluctuating evolutionary pressure systematically. Regression with high R-sq values or a triangular-like cluster pattern for concordant pairs in co-variation among the studied species could serve as evidences for the possible location of common ancestors in the entropy-fractal dimension diagram, consistent with an example of the human-chimp common ancestor study using the FOXP2 regulated genes reported in human fetal brain study. The Deinococcus radiodurans R1 Rad-A could be viewed as an outlier in the RAD50 diagram and also in the free energy versus fractal dimension regression Cook's distance, consistent with a non-Earth source for this radiation resistant bacterium. Convergent and divergent fluctuating evolutionary

  2. Oocyte Polarization Is Coupled to the Chromosomal Bouquet, a Conserved Polarized Nuclear Configuration in Meiosis.

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    Yaniv M Elkouby

    2016-01-01

    Full Text Available The source of symmetry breaking in vertebrate oocytes is unknown. Animal-vegetal oocyte polarity is established by the Balbiani body (Bb, a conserved structure found in all animals examined that contains an aggregate of specific mRNAs, proteins, and organelles. The Bb specifies the oocyte vegetal pole, which is key to forming the embryonic body axes as well as the germline in most vertebrates. How Bb formation is regulated and how its asymmetric position is established are unknown. Using quantitative image analysis, we trace oocyte symmetry breaking in zebrafish to a nuclear asymmetry at the onset of meiosis called the chromosomal bouquet. The bouquet is a universal feature of meiosis where all telomeres cluster to one pole on the nuclear envelope, facilitating chromosomal pairing and meiotic recombination. We show that Bb precursor components first localize with the centrosome to the cytoplasm adjacent to the telomere cluster of the bouquet. They then aggregate around the centrosome in a specialized nuclear cleft that we identified, assembling the early Bb. We show that the bouquet nuclear events and the cytoplasmic Bb precursor localization are mechanistically coordinated by microtubules. Thus the animal-vegetal axis of the oocyte is aligned to the nuclear axis of the bouquet. We further show that the symmetry breaking events lay upstream to the only known regulator of Bb formation, the Bucky ball protein. Our findings link two universal features of oogenesis, the Bb and the chromosomal bouquet, to oocyte polarization. We propose that a meiotic-vegetal center couples meiosis and oocyte patterning. Our findings reveal a novel mode of cellular polarization in meiotic cells whereby cellular and nuclear polarity are aligned. We further reveal that in zygotene nests, intercellular cytoplasmic bridges remain between oocytes and that the position of the cytoplasmic bridge coincides with the location of the centrosome meiotic-vegetal organizing center

  3. Solving a meiotic LEGO puzzle: transverse filaments and the assembly of the synaptonemal complex in Caenorhabditis elegans.

    Science.gov (United States)

    Hawley, R Scott

    2011-10-01

    The structure of the meiosis-specific synaptonemal complex, which is perhaps the central visible characteristic of meiotic prophase, has been a matter of intense interest for decades. Although a general picture of the interactions between the transverse filament proteins that create this structure has emerged from studies in a variety of organisms, a recent analysis of synaptonemal complex structure in Caenorhabditis elegans by Schild-Prüfert et al. (2011) has provided the clearest picture of the structure of the architecture of a synaptonemal complex to date. Although the transverse filaments of the worm synaptonemal complex are assembled differently then those observed in yeast, mammalian, and Drosophila synaptonemal complexes, a comparison of the four assemblies shows that achieving the overall basic structure of the synaptonemal complex is far more crucial than conserving the structures of the individual transverse filaments.

  4. Molecular Basis of Meiotic Maturation and Apoptosis of Oocytes, Sperm-Oocyte Interactions and Early Cleavage of Embryos in Mice, Role of Phosphatidylinositol 3-Kinase, Mos, Fas-Fas Ligand, Integrinα6 and MAP Kinase

    OpenAIRE

    Yumi Hoshino; Ken-ichi Yamanaka; Ikuo Tomioka; Noritaka Fukunaga; Mehdi Abbasi; Eimei Sato

    2005-01-01

    The interaction between molecular biology and embryology made an extensive progress in the research on gametogenesis, fertilization and early embryogenesis in mice. In this article, molecules involving in meiotic maturation and apoptosis of oocytes, sperm-oocyte interactions and early cleavage of fertilized embryos in mice are described including our recent following experiments. 1) Phosphatidylinositol 3-kinase and Akt participate in the follicle stimulating hormone-induced meiotic maturatio...

  5. The meiotic consequences of chromosomal aberrations induced by separate and simultaneous applications of gamma rays and NMU in lentil (Lens culinaris Med.)

    International Nuclear Information System (INIS)

    Dixit, Pratibha; Dubey, D.K.

    1983-01-01

    Certain meiotic abnormalities were induced by the application of 5, 10 or 15 Kr of gamma rays and/or 0.02 percent of NMU on seeds of lentil (Lens culinaris Med.) var. T36. Univalents, quadrivalents or higher multivalent associations were induced by gamma rays individually or in combination with NMU, while no such associations were recorded in plants treated with NMU alone. But nucleolar fragmentation, chromatin bridges and non-orientation of chromosome fragments were induced by both the mutagens. The percentage of cells showing meiotic abnormalities in the gamma ray treatments increased with an increase in the irradiation dose, however, the combined treatments of the two mutagens did not show a synergestic influence of the two mutagens in inducing such abnormalities. (author)

  6. Effects of selected endocrine disruptors on meiotic maturation, cumulus expansion, syntesis of hyaluronan and progesterone by porcine oocyte-cumulus complexes

    Czech Academy of Sciences Publication Activity Database

    Mlynarčíková, A.; Nagyová, Eva; Ficková, M.; Scsuková, S.

    2009-01-01

    Roč. 23, - (2009), s. 371-377 ISSN 0887-2333 R&D Projects: GA ČR GA305/05/0960 Grant - others:VEGA(SK) 2/6171/26; EU(XE) QLK4-CT-2002-02637 Institutional research plan: CEZ:AV0Z50450515 Keywords : oocyte-cumulus complex * meiotic maturation * cumulus expansion Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.060, year: 2009

  7. Cows are not mice: the role of cyclic AMP, phosphodiesterases, and adenosine monophosphate-activated protein kinase in the maintenance of meiotic arrest in bovine oocytes.

    Science.gov (United States)

    Bilodeau-Goeseels, Sylvie

    2011-01-01

    Meiotic maturation in mammalian oocytes is initiated during fetal development, and is then arrested at the dictyate stage - possibly for several years. Oocyte meiosis resumes in preovulatory follicles in response to the lutenizing hormone (LH) surge or spontaneously when competent oocytes are removed from follicles and cultured. The mechanisms involved in meiotic arrest and resumption in bovine oocytes are not fully understood, and several studies point to important differences between oocytes from rodent and livestock species. This paper reviews earlier and contemporary studies on the effects of cAMP-elevating agents and phosphodiesterase (PDE) enzyme inhibitors on the maintenance of meiotic arrest in bovine oocytes in vitro. Contrary to results obtained with mouse oocytes, bovine oocyte meiosis is inhibited by activators of the energy sensor adenosine monophosphate-activated protein kinase (AMPK, mammalian gene PRKA), which is activated by AMP, the degradation product of cAMP. It is not clear whether or not the effects were due to AMPK activation, and they may depend on culture conditions. Evidence suggests that other signaling pathways (for example, the cGMP/nitric oxide pathway) are involved in bovine oocyte meiotic arrest, but further studies are needed to understand the interactions between the signaling pathways that lead to maturation promoting factor (MPF) being inactive or active. An improved understanding of the mechanisms involved in the control of bovine oocyte meiosis will facilitate better control of the process in vitro, resulting in increased developmental competence and increased efficiency of in vitro embryo production procedures. Copyright © 2011 Wiley Periodicals, Inc.

  8. Budding yeast ATM/ATR control meiotic double-strand break (DSB levels by down-regulating Rec114, an essential component of the DSB-machinery.

    Directory of Open Access Journals (Sweden)

    Jesús A Carballo

    2013-06-01

    Full Text Available An essential feature of meiosis is Spo11 catalysis of programmed DNA double strand breaks (DSBs. Evidence suggests that the number of DSBs generated per meiosis is genetically determined and that this ability to maintain a pre-determined DSB level, or "DSB homeostasis", might be a property of the meiotic program. Here, we present direct evidence that Rec114, an evolutionarily conserved essential component of the meiotic DSB-machinery, interacts with DSB hotspot DNA, and that Tel1 and Mec1, the budding yeast ATM and ATR, respectively, down-regulate Rec114 upon meiotic DSB formation through phosphorylation. Mimicking constitutive phosphorylation reduces the interaction between Rec114 and DSB hotspot DNA, resulting in a reduction and/or delay in DSB formation. Conversely, a non-phosphorylatable rec114 allele confers a genome-wide increase in both DSB levels and in the interaction between Rec114 and the DSB hotspot DNA. These observations strongly suggest that Tel1 and/or Mec1 phosphorylation of Rec114 following Spo11 catalysis down-regulates DSB formation by limiting the interaction between Rec114 and DSB hotspots. We also present evidence that Ndt80, a meiosis specific transcription factor, contributes to Rec114 degradation, consistent with its requirement for complete cessation of DSB formation. Loss of Rec114 foci from chromatin is associated with homolog synapsis but independent of Ndt80 or Tel1/Mec1 phosphorylation. Taken together, we present evidence for three independent ways of regulating Rec114 activity, which likely contribute to meiotic DSBs-homeostasis in maintaining genetically determined levels of breaks.

  9. Budding Yeast ATM/ATR Control Meiotic Double-Strand Break (DSB) Levels by Down-Regulating Rec114, an Essential Component of the DSB-machinery

    Science.gov (United States)

    Carballo, Jesús A.; Panizza, Silvia; Serrentino, Maria Elisabetta; Johnson, Anthony L.; Geymonat, Marco; Borde, Valérie; Klein, Franz; Cha, Rita S.

    2013-01-01

    An essential feature of meiosis is Spo11 catalysis of programmed DNA double strand breaks (DSBs). Evidence suggests that the number of DSBs generated per meiosis is genetically determined and that this ability to maintain a pre-determined DSB level, or “DSB homeostasis”, might be a property of the meiotic program. Here, we present direct evidence that Rec114, an evolutionarily conserved essential component of the meiotic DSB-machinery, interacts with DSB hotspot DNA, and that Tel1 and Mec1, the budding yeast ATM and ATR, respectively, down-regulate Rec114 upon meiotic DSB formation through phosphorylation. Mimicking constitutive phosphorylation reduces the interaction between Rec114 and DSB hotspot DNA, resulting in a reduction and/or delay in DSB formation. Conversely, a non-phosphorylatable rec114 allele confers a genome-wide increase in both DSB levels and in the interaction between Rec114 and the DSB hotspot DNA. These observations strongly suggest that Tel1 and/or Mec1 phosphorylation of Rec114 following Spo11 catalysis down-regulates DSB formation by limiting the interaction between Rec114 and DSB hotspots. We also present evidence that Ndt80, a meiosis specific transcription factor, contributes to Rec114 degradation, consistent with its requirement for complete cessation of DSB formation. Loss of Rec114 foci from chromatin is associated with homolog synapsis but independent of Ndt80 or Tel1/Mec1 phosphorylation. Taken together, we present evidence for three independent ways of regulating Rec114 activity, which likely contribute to meiotic DSBs-homeostasis in maintaining genetically determined levels of breaks. PMID:23825959

  10. A high incidence of meiotic silencing of unsynapsed chromatin is not associated with substantial pachytene loss in heterozygous male mice carrying multiple simple robertsonian translocations.

    Directory of Open Access Journals (Sweden)

    Marcia Manterola

    2009-08-01

    Full Text Available Meiosis is a complex type of cell division that involves homologous chromosome pairing, synapsis, recombination, and segregation. When any of these processes is altered, cellular checkpoints arrest meiosis progression and induce cell elimination. Meiotic impairment is particularly frequent in organisms bearing chromosomal translocations. When chromosomal translocations appear in heterozygosis, the chromosomes involved may not correctly complete synapsis, recombination, and/or segregation, thus promoting the activation of checkpoints that lead to the death of the meiocytes. In mammals and other organisms, the unsynapsed chromosomal regions are subject to a process called meiotic silencing of unsynapsed chromatin (MSUC. Different degrees of asynapsis could contribute to disturb the normal loading of MSUC proteins, interfering with autosome and sex chromosome gene expression and triggering a massive pachytene cell death. We report that in mice that are heterozygous for eight multiple simple Robertsonian translocations, most pachytene spermatocytes bear trivalents with unsynapsed regions that incorporate, in a stage-dependent manner, proteins involved in MSUC (e.g., gammaH2AX, ATR, ubiquitinated-H2A, SUMO-1, and XMR. These spermatocytes have a correct MSUC response and are not eliminated during pachytene and most of them proceed into diplotene. However, we found a high incidence of apoptotic spermatocytes at the metaphase stage. These results suggest that in Robertsonian heterozygous mice synapsis defects on most pachytene cells do not trigger a prophase-I checkpoint. Instead, meiotic impairment seems to mainly rely on the action of a checkpoint acting at the metaphase stage. We propose that a low stringency of the pachytene checkpoint could help to increase the chances that spermatocytes with synaptic defects will complete meiotic divisions and differentiate into viable gametes. This scenario, despite a reduction of fertility, allows the spreading

  11. Meiotic gene conversion mutants in Saccharomyces cerevisiae. I. Isolation and characterization of PMS1-1 and PMS1-2

    International Nuclear Information System (INIS)

    Williamson, M.S.; Game, J.C.; Fogel, S.

    1985-01-01

    The PMS1 mutants, isolated on the basis of sharply elevated meiotic prototroph frequencies for two closely linked HIS4 alleles, display pleiotropic phenotypes in meiotic and mitotic cells. Two isolates carrying recessive mutations in PMS1 were characterized. They identify a function required to maintain low postmeiotic segregation (PMS) frequencies at many heterozygous sites. In addition, they are mitotic mutators. In mutant diploids, spore viability is reduced, and among survivors, gene conversion and postmeiotic segregation frequencies are increased, but reciprocal exchange frequencies are not affected. The conversion event pattern is also dramatically changed in multiply marked regions in PMS1 homozygotes. The PMS1 locus maps near MET4 on chromosome XIV. The PMS1 gene may identify an excision-resynthesis long patch mismatch correction function or a function that facilitates correction tract elongation. The PMS1 gene product may also play an important role in spontaneous mitotic mutation avoidance and correction of mismatches in heteroduplex DNA formed during spontaneous and UV-induced mitotic recombination. Based on meiotic recombination models emphasizing mismatch correction in heteroduplex DNA intermediates, this interpretation is favored, but alternative interpretations involving longer recombination intermediates in the mutants are also considered

  12. Variation in genome-wide levels of meiotic recombination is established at the onset of prophase in mammalian males.

    Directory of Open Access Journals (Sweden)

    Brian Baier

    2014-01-01

    Full Text Available Segregation of chromosomes during the first meiotic division relies on crossovers established during prophase. Although crossovers are strictly regulated so that at least one occurs per chromosome, individual variation in crossover levels is not uncommon. In an analysis of different inbred strains of male mice, we identified among-strain variation in the number of foci for the crossover-associated protein MLH1. We report studies of strains with "low" (CAST/EiJ, "medium" (C3H/HeJ, and "high" (C57BL/6J genome-wide MLH1 values to define factors responsible for this variation. We utilized immunofluorescence to analyze the number and distribution of proteins that function at different stages in the recombination pathway: RAD51 and DMC1, strand invasion proteins acting shortly after double-strand break (DSB formation, MSH4, part of the complex stabilizing double Holliday junctions, and the Bloom helicase BLM, thought to have anti-crossover activity. For each protein, we identified strain-specific differences that mirrored the results for MLH1; i.e., CAST/EiJ mice had the lowest values, C3H/HeJ mice intermediate values, and C57BL/6J mice the highest values. This indicates that differences in the numbers of DSBs (as identified by RAD51 and DMC1 are translated into differences in the number of crossovers, suggesting that variation in crossover levels is established by the time of DSB formation. However, DSBs per se are unlikely to be the primary determinant, since allelic variation for the DSB-inducing locus Spo11 resulted in differences in the numbers of DSBs but not the number of MLH1 foci. Instead, chromatin conformation appears to be a more important contributor, since analysis of synaptonemal complex length and DNA loop size also identified consistent strain-specific differences; i.e., crossover frequency increased with synaptonemal complex length and was inversely related to chromatin loop size. This indicates a relationship between recombination

  13. Nicotine-induced Disturbances of Meiotic Maturation in Cultured Mouse Oocytes: Alterations of Spindle Integrity and Chromosome Alignment

    Directory of Open Access Journals (Sweden)

    Zenzes Maria

    2004-09-01

    Full Text Available Abstract We investigated whether nicotine exposure in vitro of mouse oocytes affects spindle and chromosome function during meiotic maturation (M-I and M-II. Oocytes in germinal vesicle (GV stage were cultured in nicotine for 8 h or for 16 h, to assess effects in M-I and in metaphase II (M-II. The latter culture setting used the three protocols: 8 h nicotine then 8 h medium (8N + 8M; 16 h nicotine (16N; 8 h medium then 8 h nicotine (8M + 8N. Non-toxic concentrations of nicotine at 1.0, 2.5, 5.0 and 10.0 mmol/L were used. Spindle-chromosome configurations were analyzed with wide-field optical sectioning microscopy. In 8 h cultures, nicotine exposure resulted in dose-related increased proportions of M-I oocytes with defective spindle-chromosome configurations. A dose-related delayed entry into anaphase I was also detected. In 16 h cultures, nicotine exposure for the first 8 h (8N + 8M, or for 16 h (16N, resulted in dose- and time-related increased proportions of oocytes arrested in M-I (10 mmol/L; 8 h: 53.2%, controls 9.6%; 16 h: 87.6%, controls 8.5%. Defects in M-I spindles and chromosomes caused M-I arrest leading to dose-related decreased proportions of oocytes that reached metaphase-II (10 mmol/L 8 h: 46.8%, controls 90.4%;16 h: 12.4%, controls 91.5%. A delayed anaphase-I affected the normal timing of M-II, leading to abnormal oocytes with dispersed chromosomes, or with double spindles and no polar body. Nicotine exposure during the second 8 h (8M + 8N resulted in dose-related, increased proportions of M-II oocytes with defective spindles and chromosomes (10 mmol/L: 42.9%, controls 2.0%. Nicotine has no adverse effects on GV break down, but induces spindle and chromosome defects compromising oocyte meiotic maturation and development.

  14. Comparative studies on the photosensitizing potency of 5-methoxypsoralen and 8-methoxypsoralen as measured by cytolysis in Paramecium caudatam and Tetrahymena pyriformis, and growth inhibition and survival in Candida albicans

    International Nuclear Information System (INIS)

    Young, A.R.; Barth, J.

    1982-01-01

    The photosensitizing potencies of 5-methoxypsoralen and 8-methoxypsoralen were investigated using the following biological end-points for lethality: (i) cytolysis in the protozoans Paramecium caudatum and Tetrahymena pyriformis, (ii) inhibition of growth in the yeast Candida albicans and (iii) survival as measured by colony counts in Candida albicans. In all cases, 5-methoxypsoralen proved to be the more potent photosensitizing agent. The preliminary action spectra of the 2 compounds for growth inhibition in C. albicans were similar and showed maximal spectral efficiency in the 320-340 nm waveband. The molecular basis for the described end-points is unknown. Although it is well known that 5-methoxypsoralen and 8-methoxypsoralen readily photoreact with DNA, it is considered that photoreaction with protein should also be given serious consideration as the possible lethal event. The superior effect of 5-methoxypsoralen is in accordance with some of the physical and photochemical properties of this molecule, but this result is at variance with other studies in different test systems that have been used to compare the photobiological efficacy of these 2 compounds. (author)

  15. Comparative studies on the photosensitizing potency of 5-methoxypsoralen and 8-methoxypsoralen as measured by cytolysis in Paramecium caudatam and Tetrahymena pyriformis, and growth inhibition and survival in Candida albicans

    Energy Technology Data Exchange (ETDEWEB)

    Young, A.R. (Institute of Dermatology, London (UK)); Barth, J. (Karl-Marx-Universitaet, Leipzig (German Democratic Republic))

    1982-01-01

    The photosensitizing potencies of 5-methoxypsoralen and 8-methoxypsoralen were investigated using the following biological end-points for lethality: (i) cytolysis in the protozoans Paramecium caudatum and Tetrahymena pyriformis, (ii) inhibition of growth in the yeast Candida albicans and (iii) survival as measured by colony counts in Candida albicans. In all cases, 5-methoxypsoralen proved to be the more potent photosensitizing agent. The preliminary action spectra of the 2 compounds for growth inhibition in C. albicans were similar and showed maximal spectral efficiency in the 320-340 nm waveband. The molecular basis for the described end-points is unknown. Although it is well known that 5-methoxypsoralen and 8-methoxypsoralen readily photoreact with DNA, it is considered that photoreaction with protein should also be given serious consideration as the possible lethal event. The superior effect of 5-methoxypsoralen is in accordance with some of the physical and photochemical properties of this molecule, but this result is at variance with other studies in different test systems that have been used to compare the photobiological efficacy of these 2 compounds.

  16. Fine structure of meiotic prophase chromosomes and modified synaptonemal complexes in diploid and triploid Rhoeo spathacea.

    Science.gov (United States)

    Lin, Y J

    1979-06-01

    The synaptonemal complex (SC) in the diploid Rhoeo consists of 2 amorphous lateral elements, each about 46.0 nm thick, and one amorphous central element about 30.0 nm thick. The central region is about 115.0 nm wide. SC in the triploid have essentially the same dimensions as those of the diploid; both lateral (46.0 nm) and central (30.0 nm) elements are amorphous, and the central region is about 117.5 nm wide. The coil, observed in both diploid and triploid, is a modified short segment of SC with several twists at the end of a synapsed bivalent that is attached to the nuclear membrane. Serial sections in a diploid cell reveal that a coil extends inwards about 3.5 micron from the nuclear membrane and makes a complete turn at a distance of every 0.5 micron. There is a correlation between the modified ends of SC and terminal chiasmata in Rhoeo. The coils might have a positive role in the process of crossing over, or alternatively might be involved in ring formation by holding chromosome ends together while chiasmata are not involved. SC are present in chromocentres of both diploid and triploid. Chromocentres in diploid and triploid are indistinguishable, and appear to be formed from the aggregation of pericentromeric heterochromatin as a result of translocations which occured close to the centromeres. 3-dimensional hypothetical pachytene configuration of the diploid is presented.

  17. Meiotic restitution mechanisms involved in the formation of 2n pollen in Agave tequilana Weber and Agave angustifolia Haw.

    Science.gov (United States)

    Gómez-Rodríguez, Víctor Manuel; Rodríguez-Garay, Benjamín; Barba-Gonzalez, Rodrigo

    2012-01-01

    A cytological analysis of the microsporogenesis was carried out in the Agave tequilana and A. angustifolia species. Several abnormalities such as chromosomal bridges, lagging chromosomes, micronuclei, monads, dyads and triads were found. The morphological analysis of the pollen, together with the above-mentioned 2n microspores, allowed us to confirm the presence of 2n pollen as well as its frequency. In both A. tequilana and A. angustifolia two different mechanisms were observed: the first mechanism, a failure in the cytokinesis in meiosis II caused the formation of dyads with two 2n cells and triads containing two n cells and one 2n cell; the second mechanism, involves an abnormal spindle, which caused the formation of triads with two n cells and one 2n cell. Likewise, the presence of monads was detected in both species, these, might be caused by a failure of the cytokinesis in both meiotic divisions. This is the first report about the presence of a Second Division Restitution mechanism (SDR) which causes the formation of 2n pollen in the genus Agave. The genetic implications of the presence of 2n pollen in the genus Agave are discussed.

  18. Genesis by meiotic unequal crossover of a de novo deletion that contributes to steroid 21-hydroxylase deficiency

    International Nuclear Information System (INIS)

    Sinnott, P.; Collier, S.; Dyer, P.A.; Harris, R.; Strachan, T.; Costigan, C.

    1990-01-01

    The HLA-linked human steroid 21-hydroxylase gene CYP21B and its closely homologous pseudogene CYP21A are each normally located centromeric to a fourth component of complement (C4) gene, C4B and C4A, respectively, in an organization suggesting tandem duplication of a ca. 30-kilobase DNA unit containing a CYP21 gene and a C4 gene. Such an organization has been considered to facilitate gene deletion and addition events by unequal crossover between the tandem repeats. The authors have identified a steroid 21-hydroxylase deficiency patient who has a maternally inherited disease haplotype that carries a de novo deletion of a ca. 30-kilobase repeat unit including the CYP21B gene and associated C4B gene. This disease haplotype appears to have been generated as a result of meiotic unequal crossover between maternal homologous chromosomes. One of the maternal haplotypes is the frequently occurring HLA-DR3,B8,A1 haplotype that normally carries a deletion of a ca. 30-kilobase unit including the CYP21A gene and C4A gene. Haplotypes of this type may possible act as premutations, increasing the susceptibility of developing a 21-hydroxylase deficiency mutation by facilitating unequal chromosome pairing

  19. Controlling meiotic recombinational repair - specifying the roles of ZMMs, Sgs1 and Mus81/Mms4 in crossover formation.

    Directory of Open Access Journals (Sweden)

    Ashwini Oke

    2014-10-01

    Full Text Available Crossovers (COs play a critical role in ensuring proper alignment and segregation of homologous chromosomes during meiosis. How the cell balances recombination between CO vs. noncrossover (NCO outcomes is not completely understood. Further lacking is what constrains the extent of DNA repair such that multiple events do not arise from a single double-strand break (DSB. Here, by interpreting signatures that result from recombination genome-wide, we find that synaptonemal complex proteins promote crossing over in distinct ways. Our results suggest that Zip3 (RNF212 promotes biased cutting of the double Holliday-junction (dHJ intermediate whereas surprisingly Msh4 does not. Moreover, detailed examination of conversion tracts in sgs1 and mms4-md mutants reveal distinct aberrant recombination events involving multiple chromatid invasions. In sgs1 mutants, these multiple invasions are generally multichromatid involving 3-4 chromatids; in mms4-md mutants the multiple invasions preferentially resolve into one or two chromatids. Our analysis suggests that Mus81/Mms4 (Eme1, rather than just being a minor resolvase for COs is crucial for both COs and NCOs in preventing chromosome entanglements by removing 3'- flaps to promote second-end capture. Together our results force a reevaluation of how key recombination enzymes collaborate to specify the outcome of meiotic DNA repair.

  20. Improving ethanol fermentation performance of Saccharomyces cerevisiae in very high-gravity fermentation through chemical mutagenesis and meiotic recombination

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jing-Jing; Ding, Wen-Tao; Zhang, Guo-Chang; Wang, Jing-Yu [Tianjin Univ. (China). Dept. of Biochemical Engineering

    2011-08-15

    Genome shuffling is an efficient way to improve complex phenotypes under the control of multiple genes. For the improvement of strain's performance in very high-gravity (VHG) fermentation, we developed a new method of genome shuffling. A diploid ste2/ste2 strain was subjected to EMS (ethyl methanesulfonate) mutagenesis followed by meiotic recombination-mediated genome shuffling. The resulting haploid progenies were intrapopulation sterile and therefore haploid recombinant cells with improved phenotypes were directly selected under selection condition. In VHG fermentation, strain WS1D and WS5D obtained by this approach exhibited remarkably enhanced tolerance to ethanol and osmolarity, increased metabolic rate, and 15.12% and 15.59% increased ethanol yield compared to the starting strain W303D, respectively. These results verified the feasibility of the strain improvement strategy and suggested that it is a powerful and high throughput method for development of Saccharomyces cerevisiae strains with desired phenotypes that is complex and cannot be addressed with rational approaches. (orig.)

  1. Mlh1-Mlh3, a Meiotic Crossover and DNA Mismatch Repair Factor, Is a Msh2-Msh3-stimulated Endonuclease*

    Science.gov (United States)

    Rogacheva, Maria V.; Manhart, Carol M.; Chen, Cheng; Guarne, Alba; Surtees, Jennifer; Alani, Eric

    2014-01-01

    Crossing over between homologous chromosomes is initiated in meiotic prophase in most sexually reproducing organisms by the appearance of programmed double strand breaks throughout the genome. In Saccharomyces cerevisiae the double-strand breaks are resected to form three prime single-strand tails that primarily invade complementary sequences in unbroken homologs. These invasion intermediates are converted into double Holliday junctions and then resolved into crossovers that facilitate homolog segregation during Meiosis I. Work in yeast suggests that Msh4-Msh5 stabilizes invasion intermediates and double Holliday junctions, which are resolved into crossovers in steps requiring Sgs1 helicase, Exo1, and a putative endonuclease activity encoded by the DNA mismatch repair factor Mlh1-Mlh3. We purified Mlh1-Mlh3 and showed that it is a metal-dependent and Msh2-Msh3-stimulated endonuclease that makes single-strand breaks in supercoiled DNA. These observations support a direct role for an Mlh1-Mlh3 endonuclease activity in resolving recombination intermediates and in DNA mismatch repair. PMID:24403070

  2. The Fanconi anemia ortholog FANCM ensures ordered homologous recombination in both somatic and meiotic cells in Arabidopsis.

    Science.gov (United States)

    Knoll, Alexander; Higgins, James D; Seeliger, Katharina; Reha, Sarah J; Dangel, Natalie J; Bauknecht, Markus; Schröpfer, Susan; Franklin, F Christopher H; Puchta, Holger

    2012-04-01

    The human hereditary disease Fanconi anemia leads to severe symptoms, including developmental defects and breakdown of the hematopoietic system. It is caused by single mutations in the FANC genes, one of which encodes the DNA translocase FANCM (for Fanconi anemia complementation group M), which is required for the repair of DNA interstrand cross-links to ensure replication progression. We identified a homolog of FANCM in Arabidopsis thaliana that is not directly involved in the repair of DNA lesions but suppresses spontaneous somatic homologous recombination via a RecQ helicase (At-RECQ4A)-independent pathway. In addition, it is required for double-strand break-induced homologous recombination. The fertility of At-fancm mutant plants is compromised. Evidence suggests that during meiosis At-FANCM acts as antirecombinase to suppress ectopic recombination-dependent chromosome interactions, but this activity is antagonized by the ZMM pathway to enable the formation of interference-sensitive crossovers and chromosome synapsis. Surprisingly, mutation of At-FANCM overcomes the sterility phenotype of an At-MutS homolog4 mutant by apparently rescuing a proportion of crossover-designated recombination intermediates via a route that is likely At-MMS and UV sensitive81 dependent. However, this is insufficient to ensure the formation of an obligate crossover. Thus, At-FANCM is not only a safeguard for genome stability in somatic cells but is an important factor in the control of meiotic crossover formation.

  3. Dynamic maintenance of asymmetric meiotic spindle position through Arp2/3 complex-driven cytoplasmic streaming in mouse oocytes

    Science.gov (United States)

    Yi, Kexi; Unruh, Jay R.; Deng, Manqi; Slaughter, Brian D.; Rubinstein, Boris; Li, Rong

    2012-01-01

    Mature mammalian oocytes are poised for the completion of second polar body extrusion upon fertilization by positioning the metaphase spindle in close proximity to an actomyosin-rich cortical cap. Loss of this spindle position asymmetry is often associated with poor oocyte quality and infertility 1–3. Here, we report a novel role for the Arp2/3 actin nucleation complex in the maintenance of asymmetric spindle position in mature mouse oocytes. The Arp2/3 complex localizes to the cortical cap in a Ran GTPase-dependent manner and accounts for the nucleation of the majority of actin filaments in both the cortical cap and a cytoplasmic actin network. Inhibition of Arp2/3 complex activity or localization leads to rapid dissociation of the spindle from the cortex. High resolution live imaging and spatiotemporal image correlation spectroscopy (STICS) analysis reveal that in normal oocytes actin filaments flow continuously away from the Arp2/3-rich cortex, generating a cytoplamic streaming that results in a net pushing force on the spindle toward the actomyosin cap. Arp2/3 inhibition not only diminishes this actin flow and cytoplamic streaming but also enables a reverse streaming driven by myosin-II-based cortical contraction, leading to spindle movement away from the cortex. We conclude that the Arp2/3 complex maintains asymmetric meiotic spindle position by generating an actin polymerization-driven cytoplamic streaming and by suppressing a counteracting force from myosin-II-based contractility. PMID:21874009

  4. Molecular signature of epistatic selection: interrogating genetic interactions in the sex-ratio meiotic drive of Drosophila simulans.

    Science.gov (United States)

    Chevin, Luis-Miguel; Bastide, Héloïse; Montchamp-Moreau, Catherine; Hospital, Frédéric

    2009-06-01

    Fine scale analyses of signatures of selection allow assessing quantitative aspects of a species' evolutionary genetic history, such as the strength of selection on genes. When several selected loci lie in the same genomic region, their epistatic interactions may also be investigated. Here, we study how the neutral polymorphism pattern was shaped by two close recombining loci that cause 'sex-ratio' meiotic drive in Drosophila simulans, as an example of strong selection with potentially strong epistasis. We compare the polymorphism data observed in a natural population with the results of forward stochastic simulations under several contexts of epistasis between the candidate loci for the drive. We compute the likelihood of different possible scenarios, in order to determine which configuration is most consistent with the data. Our results highlight that fine scale analyses of well-chosen candidate genomic regions provide information-rich data that can be used to investigate the genotype-phenotype-fitness map, which can hardly be studied in genome-wide analyses. We also emphasize that initial conditions and time of observation (here, time after the interruption of a partial selective sweep) are crucial parameters in the interpretation of real data, while these are often overlooked in theoretical studies.

  5. Nuclear law - Nuclear safety

    International Nuclear Information System (INIS)

    Pontier, Jean-Marie; Roux, Emmanuel; Leger, Marc; Deguergue, Maryse; Vallar, Christian; Pissaloux, Jean-Luc; Bernie-Boissard, Catherine; Thireau, Veronique; Takahashi, Nobuyuki; Spencer, Mary; Zhang, Li; Park, Kyun Sung; Artus, J.C.

    2012-01-01

    This book contains the contributions presented during a one-day seminar. The authors propose a framework for a legal approach to nuclear safety, a discussion of the 2009/71/EURATOM directive which establishes a European framework for nuclear safety in nuclear installations, a comment on nuclear safety and environmental governance, a discussion of the relationship between citizenship and nuclear, some thoughts about the Nuclear Safety Authority, an overview of the situation regarding the safety in nuclear waste burying, a comment on the Nome law with respect to electricity price and nuclear safety, a comment on the legal consequences of the Fukushima accident on nuclear safety in the Japanese law, a presentation of the USA nuclear regulation, an overview of nuclear safety in China, and a discussion of nuclear safety in the medical sector

  6. Proteomic strategy for the identification of critical actors in reorganization of the post-meiotic male genome.

    Science.gov (United States)

    Govin, Jerome; Gaucher, Jonathan; Ferro, Myriam; Debernardi, Alexandra; Garin, Jerome; Khochbin, Saadi; Rousseaux, Sophie

    2012-01-01

    After meiosis, during the final stages of spermatogenesis, the haploid male genome undergoes major structural changes, resulting in a shift from a nucleosome-based genome organization to the sperm-specific, highly compacted nucleoprotamine structure. Recent data support the idea that region-specific programming of the haploid male genome is of high importance for the post-fertilization events and for successful embryo development. Although these events constitute a unique and essential step in reproduction, the mechanisms by which they occur have remained completely obscure and the factors involved have mostly remained uncharacterized. Here, we sought a strategy to significantly increase our understanding of proteins controlling the haploid male genome reprogramming, based on the identification of proteins in two specific pools: those with the potential to bind nucleic acids (basic proteins) and proteins capable of binding basic proteins (acidic proteins). For the identification of acidic proteins, we developed an approach involving a transition-protein (TP)-based chromatography, which has the advantage of retaining not only acidic proteins due to the charge interactions, but also potential TP-interacting factors. A second strategy, based on an in-depth bioinformatic analysis of the identified proteins, was then applied to pinpoint within the lists obtained, male germ cells expressed factors relevant to the post-meiotic genome organization. This approach reveals a functional network of DNA-packaging proteins and their putative chaperones and sheds a new light on the way the critical transitions in genome organizations could take place. This work also points to a new area of research in male infertility and sperm quality assessments.

  7. Cytoplasmic movement profiles of mouse surrounding nucleolus and not-surrounding nucleolus antral oocytes during meiotic resumption.

    Science.gov (United States)

    Bui, Thi Thu Hien; Belli, Martina; Fassina, Lorenzo; Vigone, Giulia; Merico, Valeria; Garagna, Silvia; Zuccotti, Maurizio

    2017-05-01

    Full-grown mouse antral oocytes are classified as surrounding nucleolus (SN) or not-surrounding nucleolus (NSN), depending on the respective presence or absence of a ring of Hoechst-positive chromatin surrounding the nucleolus. In culture, both types of oocytes resume meiosis and reach the metaphase II (MII) stage, but following insemination, NSN oocytes arrest at the two-cell stage whereas SN oocytes may develop to term. By coupling time-lapse bright-field microscopy with image analysis based on particle image velocimetry, we provide the first systematic measure of the changes to the cytoplasmic movement velocity (CMV) occurring during the germinal vesicle-to-MII (GV-to-MII) transition of these two types of oocytes. Compared to SN oocytes, NSN oocytes display a delayed GV-to-MII transition, which can be mostly explained by retarded germinal vesicle break down and first polar body extrusion. SN and NSN oocytes also exhibit significantly different CMV profiles at four main time-lapse intervals, although this difference was not predictive of SN or NSN oocyte origin because of the high variability in CMV. When CMV profile was analyzed through a trained artificial neural network, however, each single SN or NSN oocyte was blindly identified with a probability of 92.2% and 88.7%, respectively. Thus, the CMV profile recorded during meiotic resumption may be exploited as a cytological signature for the non-invasive assessment of the oocyte developmental potential, and could be informative for the analysis of the GV-to-MII transition of oocytes of other species. © 2017 Wiley Periodicals, Inc.

  8. Boule gene expression underpins the meiotic arrest in spermatogenesis in male rainbow trout (Oncorhynchus mykiss) exposed to DEHP and butachlor.

    Science.gov (United States)

    Ahmadivand, Sohrab; Farahmand, Hamid; Teimoori-Toolabi, Ladan; Mirvaghefi, Alireza; Eagderi, Soheil; Geerinckx, Tom; Shokrpoor, Sara; Rahmati-Holasoo, Hooman

    2016-01-01

    Boule, the ancestor of the DAZ (Deleted in AZoospermia) gene family, in most organisms is mainly involved in male meiosis. The present study investigates the effects of the plasticizer DEHP (50mg/kg body weight) and herbicide butachlor (0.39mg/L) on male rainbow trout (Oncorhynchus mykiss) for a 10-day period in two independent experiments. The results showed that plasma testosterone (T) concentrations were significantly lower in fish exposed to either DEHP or butachlor compared to the control fish (P0.05). In addition, no significant differences were found in the gonadosomatic index (GSI) in both DEHP and butachlor treatments (P>0.05). Histologically, testes of male trout in the control groups were well differentiated and filled with large numbers of cystic structures containing spermatozoa. In contrast, the testes of male trout contained mostly spermatocytes with few spermatozoa in both treated group, suggesting that DEHP and butachlor may inhibit the progression of meiosis. Also, boule gene expression was significantly lower in the testes of male trout affected by DEHP and butachlor in comparison with their control groups (Ptrout. Based on the results, the present study demonstrated that DEHP and butachlor can inhibit the progression of spermatogenesis in male trout, potentially by causing an arrest of meiosis, maybe due to down-regulation of boule gene expression through T and/or IGF1 via ERK1/2 signaling in T-independent pathways. In addition, these results confirmed that boule can be considered as a predictive marker to assess meiotic efficiency. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Differences in meiotic recombination rates in childhood acute lymphoblastic leukemia at an MHC class II hotspot close to disease associated haplotypes.

    Directory of Open Access Journals (Sweden)

    Pamela Thompson

    Full Text Available Childhood Acute Lymphoblastic Leukemia (ALL is a malignant lymphoid disease of which B-cell precursor- (BCP and T-cell- (T ALL are subtypes. The role of alleles encoded by major histocompatibility loci (MHC have been examined in a number of previous studies and results indicating weak, multi-allele associations between the HLA-DPB1 locus and BCP-ALL suggested a role for immunosusceptibility and possibly infection. Two independent SNP association studies of ALL identified loci approximately 37 kb from one another and flanking a strong meiotic recombination hotspot (DNA3, adjacent to HLA-DOA and centromeric of HLA-DPB1. To determine the relationship between this observation and HLA-DPB1 associations, we constructed high density SNP haplotypes of the 316 kb region from HLA-DMB to COL11A2 in childhood ALL and controls using a UK GWAS data subset and the software PHASE. Of four haplotype blocks identified, predicted haplotypes in Block 1 (centromeric of DNA3 differed significantly between BCP-ALL and controls (P = 0.002 and in Block 4 (including HLA-DPB1 between T-ALL and controls (P = 0.049. Of specific common (>5% haplotypes in Block 1, two were less frequent in BCP-ALL, and in Block 4 a single haplotype was more frequent in T-ALL, compared to controls. Unexpectedly, we also observed apparent differences in ancestral meiotic recombination rates at DNA3, with BCP-ALL showing increased and T-ALL decreased levels compared to controls. In silico analysis using LDsplit sotware indicated that recombination rates at DNA3 are influenced by flanking loci, including SNPs identified in childhood ALL association studies. The observed differences in rates of meiotic recombination at this hotspot, and potentially others, may be a characteristic of childhood leukemia and contribute to disease susceptibility, alternatively they may reflect interactions between ALL-associated haplotypes in this region.

  10. RAD51AP2, a novel vertebrate- and meiotic-specific protein, sharesa conserved RAD51-interacting C-terminal domain with RAD51AP1/PIR51

    Energy Technology Data Exchange (ETDEWEB)

    Kovalenko, Oleg V.; Wiese, Claudia; Schild, David

    2006-07-25

    Many interacting proteins regulate and/or assist the activities of RAD51, a recombinase which plays a critical role in both DNA repair and meiotic recombination. Yeast two-hybrid screening of a human testis cDNA library revealed a new protein, RAD51AP2 (RAD51 Associated Protein 2), that interacts strongly with RAD51. A full-length cDNA clone predicts a novel vertebrate specific protein of 1159 residues, and the RAD51AP2 transcript was observed only in meiotic tissue (i.e. adult testis and fetal ovary), suggesting a meiotic-specific function for RAD51AP2. In HEK293 cells the interaction of RAD51 with an ectopically-expressed recombinant large fragment of RAD51AP2 requires the C-terminal 57 residues of RAD51AP2. This RAD51-binding region shows 81% homology to the C-terminus of RAD51AP1/PIR51, an otherwise totally unrelated RAD51-binding partner that is ubiquitously expressed. Analyses using truncations and point mutations in both RAD51AP1 and RAD51AP2 demonstrate that these proteins use the same structural motif for RAD51 binding. RAD54 shares some homology with this RAD51-binding motif, but this homologous region plays only an accessory role to the adjacent main RAD51-interacting region, which has been narrowed here to 40 amino acids. A novel protein, RAD51AP2, has been discovered that interacts with RAD51 through a C-terminal motif also present in RAD51AP1.

  11. Changes in homologous and heterologous gap junction contacts during maturation-inducing hormone-dependent meiotic resumption in ovarian follicles of Atlantic croaker

    Science.gov (United States)

    Bolamba, D.; Patino, R.; Yoshizaki, G.; Thomas, P.

    2003-01-01

    Homologous (granulosa cell-granulosa cell) gap junction (GJ) contacts increase in ovarian follicles of Atlantic croaker (Micropogonias undulatus) during the early (first) stage of maturation, but their profile during the second stage [i.e., during maturation-inducing hormone (MIH)-mediated meiotic resumption] is unknown. The profile of homologous GJ contacts during the second stage of maturation in croaker follicles was examined in this study and compared to that of heterologous (granulosa cell-oocyte) GJ, for which changes have been previously documented. Follicles were incubated with human chorionic gonadotropin to induce maturational competence (first stage), and then with MIH to induce meiotic resumption. The follicles were collected for examination immediately before and after different durations of MIH exposure until the oocyte had reached the stage of germinal vesicle breakdown (GVBD; index of meiotic resumption). Ultrathin sections were observed by transmission electron microscopy, and homologous and heterologous GJ contacts were quantified along a 100-??m segment of granulosa cell-zona radiata complex per follicle (three follicles/time/fish, n=3 fish). Relatively high numbers of both types of GJ were observed before and after the first few hours of MIH exposure (up to the stage of oil droplet coalescence). GJ numbers declined during partial yolk globule coalescence (at or near GVBD) and were just under 50% of starting values after the completion of GVBD (P<0.05). These results confirm earlier observations that GVBD temporally correlates with declining heterologous GJ contacts, and for the first time in teleosts show that there is a parallel decline in homologous GJ. The significance of the changes in homologous and heterologous GJ is uncertain and deserves further study. ?? 2003 Elsevier Science (USA). All rights reserved.

  12. Topoisomerase 3alpha and RMI1 suppress somatic crossovers and are essential for resolution of meiotic recombination intermediates in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Frank Hartung

    2008-12-01

    Full Text Available Topoisomerases are enzymes with crucial functions in DNA metabolism. They are ubiquitously present in prokaryotes and eukaryotes and modify the steady-state level of DNA supercoiling. Biochemical analyses indicate that Topoisomerase 3alpha (TOP3alpha functions together with a RecQ DNA helicase and a third partner, RMI1/BLAP75, in the resolution step of homologous recombination in a process called Holliday Junction dissolution in eukaryotes. Apart from that, little is known about the role of TOP3alpha in higher eukaryotes, as knockout mutants show early lethality or strong developmental defects. Using a hypomorphic insertion mutant of Arabidopsis thaliana (top3alpha-2, which is viable but completely sterile, we were able to define three different functions of the protein in mitosis and meiosis. The top3alpha-2 line exhibits fragmented chromosomes during mitosis and sensitivity to camptothecin, suggesting an important role in chromosome segregation partly overlapping with that of type IB topoisomerases. Furthermore, AtTOP3alpha, together with AtRECQ4A and AtRMI1, is involved in the suppression of crossover recombination in somatic cells as well as DNA repair in both mammals and A. thaliana. Surprisingly, AtTOP3alpha is also essential for meiosis. The phenotype of chromosome fragmentation, bridges, and telophase I arrest can be suppressed by AtSPO11 and AtRAD51 mutations, indicating that the protein is required for the resolution of recombination intermediates. As Atrmi1 mutants have a similar meiotic phenotype to Attop3alpha mutants, both proteins seem to be involved in a mechanism safeguarding the entangling of homologous chromosomes during meiosis. The requirement of AtTOP3alpha and AtRMI1 in a late step of meiotic recombination strongly hints at the possibility that the dissolution of double Holliday Junctions via a hemicatenane intermediate is indeed an indispensable step of meiotic recombination.

  13. Abnormal meiotic behavior in three species of Crotalaria Comportamento meiótico anormal em três espécies de Crotalaria

    Directory of Open Access Journals (Sweden)

    Kátia Ferreira

    2009-12-01

    Full Text Available The objective of this work was to compare the meiotic behavior and pollen grain viability of three species of Crotalaria. Slides for meiotic analysis were prepared by the air-drying technique. Pollen grain viability was measured by three staining procedures (Alexander's solution, tetrazolium chloride and fluorescein diacetate and in vitro germination in a sucrose solution. Eight bivalents were observed, confirming previous reports on populations from other regions of Brazil, as well as from other countries. All species showed abnormal meiotic behavior as follows: in Crotalaria micans, cytomixis and abnormal chromosome pairing in diakinesis; in C. spectabilis, abnormal chromosome pairing in diplotene; in C. zanzibarica, shrunk nuclei in leptotene and zygotene. Pollen grains of all three species show low viability, which may be associated with the irregularities of the meiotic behavior.O objetivo deste trabalho foi comparar o comportamento meiótico e a viabilidade dos grãos de pólen de três espécies de Crotalaria. A análise meiótica foi realizada por meio da técnica de secagem ao ar. A viabilidade dos grãos de pólen foi avaliada por testes de coloração (corante de Alexander, cloreto de tetrazólio e diacetato de fluoresceína e por teste de germinação em solução de sacarose. Foram observados oito bivalentes, confirmando relatos prévios em populações de outras regiões do Brasil e de outros países. As três espécies apresentaram comportamento meiótico irregular: em Crotalaria micans, citomixia e pareamento irregular na diacinese; em C. spectabilis, pareamento irregular no diplóteno; e em C. zanzibarica, núcleo fortemente condensado nas fases de leptóteno e zigóteno. A viabilidade dos grãos de pólen das três espécies é baixa, o que pode estar associado às irregularidades do comportamento meiótico.

  14. Mouse Y-linked Zfy1 and Zfy2 are expressed during the male-specific interphase between meiosis I and meiosis II and promote the 2nd meiotic division.

    Science.gov (United States)

    Vernet, Nadège; Mahadevaiah, Shantha K; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J; Ward, Monika A; Burgoyne, Paul S

    2014-06-01

    Mouse Zfy1 and Zfy2 encode zinc finger transcription factors that map to the short arm of the Y chromosome (Yp). They have previously been shown to promote meiotic quality control during pachytene (Zfy1 and Zfy2) and at the first meiotic metaphase (Zfy2). However, from these previous studies additional roles for genes encoded on Yp during meiotic progression were inferred. In order to identify these genes and investigate their function in later stages of meiosis, we created three models with diminishing Yp and Zfy gene complements (but lacking the Y-long-arm). Since the Y-long-arm mediates pairing and exchange with the X via their pseudoautosomal regions (PARs) we added a minute PAR-bearing X chromosome derivative to enable formation of a sex bivalent, thus avoiding Zfy2-mediated meiotic metaphase I (MI) checkpoint responses to the unpaired (univalent) X chromosome. Using these models we obtained definitive evidence that genetic information on Yp promotes meiosis II, and by transgene addition identified Zfy1 and Zfy2 as the genes responsible. Zfy2 was substantially more effective and proved to have a much more potent transactivation domain than Zfy1. We previously established that only Zfy2 is required for the robust apoptotic elimination of MI spermatocytes in response to a univalent X; the finding that both genes potentiate meiosis II led us to ask whether there was de novo Zfy1 and Zfy2 transcription in the interphase between meiosis I and meiosis II, and this proved to be the case. X-encoded Zfx was also expressed at this stage and Zfx over-expression also potentiated meiosis II. An interphase between the meiotic divisions is male-specific and we previously hypothesised that this allows meiosis II critical X and Y gene reactivation following sex chromosome silencing in meiotic prophase. The interphase transcription and meiosis II function of Zfx, Zfy1 and Zfy2 validate this hypothesis.

  15. Proliferating cell nuclear antigen (PCNA) interacts with a meiosis-specific RecA homologues, Lim15/Dmc1, but does not stimulate its strand transfer activity

    International Nuclear Information System (INIS)

    Hamada, Fumika N.; Koshiyama, Akiyo; Namekawa, Satoshi H.; Ishii, Satomi; Iwabata, Kazuki; Sugawara, Hiroko; Nara, Takayuki Y.; Sakaguchi, Kengo; Sawado, Tomoyuki

    2007-01-01

    PCNA is a multi-functional protein that is involved in various nuclear events. Here we show that PCNA participates in events occurring during early meiotic prophase. Analysis of protein-protein interactions using surface plasmon resonance indicates that Coprinus cinereus PCNA (CoPCNA) specifically interacts with a meiotic specific RecA-like factor, C. cinereus Lim15/Dmc1 (CoLim15) in vitro. The binding efficiency increases with addition of Mg 2+ ions, while ATP inhibits the interaction. Co-immunoprecipitation experiments indicate that the CoLim15 protein interacts with the CoPCNA protein in vitro and in the cell extracts. Despite the interaction between these two factors, no enhancement of CoLim15-dependent strand transfer activity by CoPCNA was found in vitro. We propose that the interaction between Lim15/Dmc1 and PCNA mediates the recombination-associated DNA synthesis during meiosis

  16. Mre11 and Exo1 contribute to the initiation and processivity of resection at meiotic double-strand breaks made independently of Spo11.

    Science.gov (United States)

    Hodgson, Adam; Terentyev, Yaroslav; Johnson, Rebecca A; Bishop-Bailey, Anna; Angevin, Thibaut; Croucher, Adam; Goldman, Alastair S H

    2011-02-07

    During meiosis DNA double-strand breaks (DSBs) are induced and repaired by homologous recombination to create gene conversion and crossover products. Mostly these DSBs are made by Spo11, which covalently binds to the DSB ends. More rarely in Saccharomyces cerevisiae, other meiotic DSBs are formed by self-homing endonucleases such as VDE, which is site specific and does not covalently bind to the DSB ends. We have used experimentally located VDE-DSB sites to analyse an intermediate step in homologous recombination, resection of the single-strand ending 5' at the DSB site. Analysis of strains with different mutant alleles of MRE11 (mre11-58S and mre11-H125N) and deleted for EXO1 indicated that these two nucleases make significant contributions to repair of VDE-DSBs. Physical analysis of single-stranded repair intermediates indicates that efficient initiation and processivity of resection at VDE-DSBs require both Mre11 and Exo1, with loss of function for either protein causing severe delay in resection. We propose that these experiments model what happens at Spo11-DSBs after removal of the covalently bound protein, and that Mre11 and Exo1 are the major nucleases involved in creating resection tracts of widely varying lengths typical of meiotic recombination. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. An essential role for trimethylguanosine RNA caps in Saccharomyces cerevisiae meiosis and their requirement for splicing of SAE3 and PCH2 meiotic pre-mRNAs.

    Science.gov (United States)

    Qiu, Zhicheng R; Shuman, Stewart; Schwer, Beate

    2011-07-01

    Tgs1 is the enzyme that converts m(7)G RNA caps to the 2,2,7-trimethylguanosine (TMG) caps characteristic of spliceosomal snRNAs. Fungi grow vegetatively without TMG caps, thereby raising the question of what cellular transactions, if any, are TMG cap-dependent. Here, we report that Saccharomyces cerevisiae Tgs1 methyltransferase activity is essential for meiosis. tgs1Δ cells are specifically defective in splicing PCH2 and SAE3 meiotic pre-mRNAs. The TMG requirement for SAE3 splicing is alleviated by two intron mutations: a UAUUAAC to UACUAAC change that restores a consensus branchpoint and disruption of a stem-loop encompassing the branchpoint. The TMG requirement for PCH2 splicing is alleviated by a CACUAAC to UACUAAC change restoring a consensus branchpoint and by shortening the PCH2 5' exon. Placing the SAE3 and PCH2 introns within a HIS3 reporter confers Tgs1-dependent histidine prototrophy, signifying that the respective introns are portable determinants of TMG-dependent gene expression. Analysis of in vitro splicing in extracts of TGS1 versus tgs1Δ cells showed that SAE3 intron removal was enfeebled without TMG caps, whereas splicing of ACT1 was unaffected. Our findings illuminate a new mode of tunable splicing, a reliance on TMG caps for an essential developmental RNA transaction, and three genetically distinct meiotic splicing regulons in budding yeast.

  18. In vitro growth and maturation of isolated caprine preantral follicles: Influence of insulin and FSH concentration, culture dish, coculture, and oocyte size on meiotic resumption.

    Science.gov (United States)

    Silva, G M; Brito, I R; Sales, A D; Aguiar, F L N; Duarte, A B G; Araújo, V R; Vieira, L A; Magalhães-Padilha, D M; Lima, L F; Alves, B G; Silveira, L B R; Lo Turco, E G; Rodrigues, A P; Campello, C C; Wheeler, M B; Figueiredo, J R

    2017-03-01

    The aims of this study were: (1) to evaluate the effect of different insulin concentrations, alone or in combination with either a fixed FSH concentration or increasing FSH concentrations on the in vitro culture of isolated caprine preantral follicles and (2) to analyze the efficiency of two IVM media and maturation culture systems (with or without coculture with in vivo grown oocytes) on the meiosis resumption. Secondary follicles were cultured for 18 days in a basic medium supplemented with low- or high-insulin concentration alone or with a fixed FSH concentration or with increasing FSH concentrations. Oocytes grown in vivo or in vitro were matured alone or cocultured. The high-insulin concentration associated with fixed FSH treatment had higher meiotic resumption rate (P media. In conclusion, a basic medium supplemented with 10-μg/mL insulin and 100-μg/mL FSH throughout the culture period improved meiotic resumption rate and produced MII oocytes from caprine preantral follicles cultured in vitro. The MII rate was similar between in vivo and in vitro grown oocytes ≥110 μm. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Nuclear Medicine

    Science.gov (United States)

    ... Parents/Teachers Resource Links for Students Glossary Nuclear Medicine What is nuclear medicine? What are radioactive tracers? ... funded researchers advancing nuclear medicine? What is nuclear medicine? Nuclear medicine is a medical specialty that uses ...

  20. CHEMERIN (RARRES2) decreases in vitro granulosa cell steroidogenesis and blocks oocyte meiotic progression in bovine species.

    Science.gov (United States)

    Reverchon, Maxime; Bertoldo, Michael J; Ramé, Christelle; Froment, Pascal; Dupont, Joëlle

    2014-05-01

    CHEMERIN, or RARRES2, is a new adipokine that is involved in the regulation of adipogenesis, energy metabolism, and inflammation. Recent data suggest that it also plays a role in reproductive function in rats and humans. Here we studied the expression of CHEMERIN and its three receptors (CMKLR1, GPR1, and CCRL2) in the bovine ovary and investigated the in vitro effects of this hormone on granulosa cell steroidogenesis and oocyte maturation. By RT-PCR, immunoblotting, and immunohistochemistry, we found CHEMERIN, CMKLR1, GPR1, and CCRL2 in various ovarian cells, including granulosa and theca cells, corpus luteum, and oocytes. In cultured bovine granulosa cells, INSULIN, IGF1, and two insulin sensitizers-metformin and rosiglitazone-increased rarres2 mRNA expression whereas they decreased cmklr1, gpr1, and cclr2 mRNA expression. Furthermore, TNF alpha and ADIPONECTIN significantly increased rarres2 and cmklr1 expression, respectively. In cultured bovine granulosa cells, human recombinant CHEMERIN (hRec, 200 ng/ml) reduced production of both progesterone and estradiol, cholesterol content, STAR abundance, CYP19A1 and HMGCR proteins, and the phosphorylation levels of MAPK3/MAPK1 in the presence or absence of FSH (10(-8) M) and IGF1 (10(-8) M). All of these effects were abolished by using an anti-CMKLR1 antibody. In bovine cumulus-oocyte complexes, the addition of hRec (200 ng/ml) in the maturation medium arrested most oocytes at the germinal vesicle stage, and this was associated with a decrease in MAPK3/1 phosphorylation in both oocytes and cumulus cells. Thus, in cultured bovine granulosa cells, hRec decreases steroidogenesis, cholesterol synthesis, and MAPK3/1 phosphorylation, probably through CMKLR1. Moreover, in cumulus-oocyte complexes, it blocked meiotic progression at the germinal vesicle stage and inhibited MAPK3/1 phosphorylation in both the oocytes and cumulus cells during in vitro maturation. © 2014 by the Society for the Study of Reproduction, Inc.

  1. Nuclear safety. Seguranca nuclear

    Energy Technology Data Exchange (ETDEWEB)

    Aveline, A [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica

    1981-01-01

    What is nuclear safety Is there any technical way to reduce risks Is it possible to put them at reasonable levels Are there competitiveness and economic reliability to employ the nuclear energy by means of safety technics Looking for answers to these questions the author describes the sources of potential risks to nuclear reactors and tries to apply the answers to the Brazilian Nuclear Programme. (author).

  2. Invisible nuclear; converting nuclear

    International Nuclear Information System (INIS)

    Park, Jongmoon

    1993-03-01

    This book consists of 14 chapters which are CNN era and big science, from East and West to North and South, illusory nuclear strategy, UN and nuclear arms reduction, management of armaments, advent of petroleum period, the track of nuclear power generation, view of energy, internationalization of environment, the war over water in the Middle East, influence of radiation and an isotope technology transfer and transfer armament into civilian industry, the end of nuclear period and the nuclear Nonproliferation, national scientific and technological power and political organ and executive organ.

  3. Meiotic non-disjunction induced by fission neutrons relative to X-rays observed in mouse secondary spermatocytes. Pt. 1. The response of different cell stages to a single radiation dose

    Energy Technology Data Exchange (ETDEWEB)

    Russo, A.; Pacchierotti, F.; Metalli, P. (Nuclear Energy Agency, Rome (Italy). Div. of Physics and Biomedical Sciences)

    1983-03-01

    (C57BL/CnexC3H/Cne)F/sub 1/ male mice were irradiated with 2 Gy of 250-kV X-rays or 0.56 Gy of attenuated fission spectrum neutrons, and killed at various times after treatment. Second meiotic metaphases of spermatogenetic cells irradiated in various meiotic and premeiotic stages were observed. These stages were first meiotic metaphase, diplotene, late pachytene, mid-pachytene, zygotene, pre-leptotene and spermatogonia. Cells were classified by chromosome counting, and those with 18 <=n<=22 were recorded. An index of induction of non-disjunction events was obtained by the frequency of hyper-haploid spermatocytes relative to the sum of hyper-haploid and normal haploid spreads. The frequency of hyper-haploid spermatocytes was 0.7+-0.4 in control mice. It was higher after treatment with both types of radiation at all meiotic stages tested, with a peak of induction at and shortly before metaphase I-diakinesis (16-19%). Irradiated gonial cells also yielded values higher than did controls. The difference was statistically significant after irradiation with neutrons, showing that radiation can induce non-disjunction events in stem cells.

  4. [Nuclear theory

    International Nuclear Information System (INIS)

    Haxton, W.

    1990-01-01

    This report discusses research in nuclear physics. Topics covered in this paper are: symmetry principles; nuclear astrophysics; nuclear structure; quark-gluon plasma; quantum chromodynamics; symmetry breaking; nuclear deformation; and cold fusion

  5. Plasma membrane events associated with the meiotic divisions in the amphibian oocyte: insights into the evolution of insulin transduction systems and cell signaling

    Directory of Open Access Journals (Sweden)

    Morrill Gene A

    2013-01-01

    Full Text Available Abstract Background Insulin and its plasma membrane receptor constitute an ancient response system critical to cell growth and differentiation. Studies using intact Rana pipiens oocytes have shown that insulin can act at receptors on the oocyte surface to initiate resumption of the first meiotic division. We have reexamined the insulin-induced cascade of electrical and ion transport-related plasma membrane events using both oocytes and intact plasma membranes in order to characterize the insulin receptor-steroid response system associated with the meiotic divisions. Results [125I]Insulin binding (Kd = 54 ± 6 nM at the oocyte plasma membrane activates membrane serine protease(s, followed by the loss of low affinity ouabain binding sites, with a concomitant 3–4 fold increase in high affinity ouabain binding sites. The changes in protease activity and ouabain binding are associated with increased Na+/Ca2+ exchange, increased endocytosis, decreased Na+ conductance resulting in membrane hyperpolarization, increased 2-deoxy-D-glucose uptake and a sustained elevation of intracellular pH (pHi. Hyperpolarization is largely due to Na+-channel inactivation and is the main driving force for glucose uptake by the oocyte via Na+/glucose cotransport. The Na+ sym- and antiporter systems are driven by the Na+ free energy gradient generated by Na+/K+-ATPase. Shifts in α and/or β Na+-pump subunits to caveolar (lipid raft membrane regions may activate Na/K-ATPase and contribute to the Na+ free energy gradient and the increase in both Na+/glucose co-transport and pHi. Conclusions Under physiological conditions, resumption of meiosis results from the concerted action of insulin and progesterone at the cell membrane. Insulin inactivates Na+ channels and mobilizes fully functional Na+-pumps, generating a Na+ free energy gradient which serves as the energy source for several membrane anti- and symporter systems.

  6. Short periods of high temperature during meiosis prevent normal meiotic progression and reduce grain number in hexaploid wheat (Triticum aestivum L.).

    Science.gov (United States)

    Draeger, Tracie; Moore, Graham

    2017-09-01

    Exposure of wheat to high temperatures during male meiosis prevents normal meiotic progression and reduces grain number. We define a temperature-sensitive period and link heat tolerance to chromosome 5D. This study assesses the effects of heat on meiotic progression and grain number in hexaploid wheat (Triticum aestivum L. var. Chinese Spring), defines a heat-sensitive stage and evaluates the role of chromosome 5D in heat tolerance. Plants were exposed to high temperatures (30 or 35 °C) in a controlled environment room for 20-h periods during meiosis and the premeiotic interphase just prior to meiosis. Examination of pollen mother cells (PMCs) from immature anthers immediately before and after heat treatment enabled precise identification of the developmental phases being exposed to heat. A temperature-sensitive period was defined, lasting from premeiotic interphase to late leptotene, during which heat can prevent PMCs from progressing through meiosis. PMCs exposed to 35 °C were less likely to progress than those exposed to 30 °C. Grain number per spike was reduced at 30 °C, and reduced even further at 35 °C. Chinese Spring nullisomic 5D-tetrasomic 5B (N5DT5B) plants, which lack chromosome 5D, were more susceptible to heat during premeiosis-leptotene than Chinese Spring plants with the normal (euploid) chromosome complement. The proportion of plants with PMCs progressing through meiosis after heat treatment was lower for N5DT5B plants than for euploids, but the difference was not significant. However, following exposure to 30 °C, in euploid plants grain number was reduced (though not significantly), whereas in N5DT5B plants the reduction was highly significant. After exposure to 35 °C, the reduction in grain number was highly significant for both genotypes. Implications of these findings for the breeding of thermotolerant wheat are discussed.

  7. Mlh1 is required for female fertility in Drosophila melanogaster: An outcome of effects on meiotic crossing over, ovarian follicles and egg activation.

    Science.gov (United States)

    Vimal, Divya; Kumar, Saurabh; Pandey, Ashutosh; Sharma, Divya; Saini, Sanjay; Gupta, Snigdha; Ravi Ram, Kristipati; Chowdhuri, Debapratim Kar

    2018-03-01

    Mismatch repair (MMR) system, a conserved DNA repair pathway, plays crucial role in DNA recombination and is involved in gametogenesis. The impact of alterations in MMR family of proteins (bacterial MutS and MutL homologues) on mammalian fertility is well documented. However, an insight to the role of MMR in reproduction of non-mammalian organisms is limited. Hence, in the present study, we analysed the impact of mlh1 (a MutL homologue) on meiotic crossing over/recombination and fertility in a genetically tractable model, Drosophila melanogaster. Using mlh1 e00130 hypomorphic allele, we report female specific adverse reproductive outcome for reduced mlh1 in Drosophila: mlh1 e00130 homozygous females had severely reduced fertility while males were fertile. Further, mlh1 e00130 females contained small ovaries with large number of early stages as well as significantly reduced mature oocytes, and laid fewer eggs, indicating discrepancies in egg production and ovulation. These observations contrast the sex independent and/or male specific sterility and normal follicular development as well as ovulation reported so far for MMR family proteins in mammals. However, analogous to the role(s) of mlh1 in meiotic crossing over and DNA repair processes underlying mammalian fertility, ovarian follicles from mlh1 e00130 females contained significantly increased DNA double strand breaks (DSBs) and reduced synaptonemal complex foci. In addition, large proportion of fertilized eggs display discrepancies in egg activation and fail to proceed beyond stage 5 of embryogenesis. Hence, reduction of the Mlh1 protein level leads to defective oocytes that fail to complete embryogenesis after fertilization thereby reducing female fertility. Copyright © 2017 Elsevier GmbH. All rights reserved.

  8. Genome-Wide Analysis of Heteroduplex DNA in Mismatch Repair–Deficient Yeast Cells Reveals Novel Properties of Meiotic Recombination Pathways

    Science.gov (United States)

    Martini, Emmanuelle; Borde, Valérie; Legendre, Matthieu; Audic, Stéphane; Regnault, Béatrice; Soubigou, Guillaume; Dujon, Bernard; Llorente, Bertrand

    2011-01-01

    Meiotic DNA double-strand breaks (DSBs) initiate crossover (CO) recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs). Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR) protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs). First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR–proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans–hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs) during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates. PMID

  9. Genome-wide analysis of heteroduplex DNA in mismatch repair-deficient yeast cells reveals novel properties of meiotic recombination pathways.

    Directory of Open Access Journals (Sweden)

    Emmanuelle Martini

    2011-09-01

    Full Text Available Meiotic DNA double-strand breaks (DSBs initiate crossover (CO recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs. Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs. First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR-proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans-hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates.

  10. Evidence that meiotic pairing starts at the telomeres: Molecular analysis of recombination in a family with a pericentric X chromosome inversion

    Energy Technology Data Exchange (ETDEWEB)

    Shashi, V.; Allinson, P.S.; Golden, W.L.; Kelly, T.E. [Univ. of Virginia, Charlottesville, VA (United States)

    1994-09-01

    Recent studies in yeast have shown that telomeres rather than centromeres lead in chromosome movement just prior to meiosis and may have a role in recombination. Cytological studies of meiosis in Drosophila and mice have shown that in pericentric inversion heterozygotes there is lack of loop formation, with recobmination seen only outside the inversion. In a family with Duchenne muscular dystrophy (DMD) we recognized that only affected males and carrier females had a pericentric X chromosome inversion (inv X(p11.4;q26)). Since the short arm inversion breakpoint was proximal to the DMD locus, it could not be implicated in the mutational event causing DMD. There was no history of infertility, recurrent miscarriages or liveborn unbalanced females to suggest there was recombination within the inversion. We studied 22 members over three generations to understand the pattern of meiotic recombination between the normal and the inverted X chromosome. In total, 17 meioses involving the inverted X chromosome in females were studied by cytogenetic analysis and 16 CA repeat polymorphisms along the length of the X chromosome. Results: (a) There was complete concordance between the segregation of the DMD mutation and the inverted X chromosome. (b) On DNA analysis, there was complete absence of recombination within the inverted segment. We also found no recombination at the DMD locus. Recombination was seen only at Xp22 and Xq27-28. (c) Recombination was seen in the same individual at both Xp22 and Xq27-28 without recombination otherwise. Conclusions: (1) Pericentric X inversions reduce the genetic map length of the chromosome, with the physical map length being normal. (2) Meiotic X chromosome pairing in this family is initiated at the telomeres. (3) Following telomeric pairing in pericentric X chromosome inversions, there is inhibition of recombination within the inversion and adjacent regions.

  11. Prdm9, a major determinant of meiotic recombination hotspots, is not functional in dogs and their wild relatives, wolves and coyotes.

    Directory of Open Access Journals (Sweden)

    Violeta Muñoz-Fuentes

    Full Text Available Meiotic recombination is a fundamental process needed for the correct segregation of chromosomes during meiosis in sexually reproducing organisms. In humans, 80% of crossovers are estimated to occur at specific areas of the genome called recombination hotspots. Recently, a protein called PRDM9 was identified as a major player in determining the location of genome-wide meiotic recombination hotspots in humans and mice. The origin of this protein seems to be ancient in evolutionary time, as reflected by its fairly conserved structure in lineages that diverged over 700 million years ago. Despite its important role, there are many animal groups in which Prdm9 is absent (e.g. birds, reptiles, amphibians, diptera and it has been suggested to have disruptive mutations and thus to be a pseudogene in dogs. Because of the dog's history through domestication and artificial selection, we wanted to confirm the presence of a disrupted Prdm9 gene in dogs and determine whether this was exclusive of this species or whether it also occurred in its wild ancestor, the wolf, and in a close relative, the coyote. We sequenced the region in the dog genome that aligned to the last exon of the human Prdm9, containing the entire zinc finger domain, in 4 dogs, 17 wolves and 2 coyotes. Our results show that the three canid species possess mutations that likely make this gene non functional. Because these mutations are shared across the three species, they must have appeared prior to the split of the wolf and the coyote, millions of years ago, and are not related to domestication. In addition, our results suggest that in these three canid species recombination does not occur at hotspots or hotspot location is controlled through a mechanism yet to be determined.

  12. Meiosis, egg activation, and nuclear envelope breakdown are differentially reliant on Ca2+, whereas germinal vesicle breakdown is Ca2+ independent in the mouse oocyte

    Science.gov (United States)

    Tombes, R. M.; Simerly, C.; Borisy, G. G.; Schatten, G.

    1992-01-01

    During early development, intracellular Ca2+ mobilization is not only essential for fertilization, but has also been implicated during other meiotic and mitotic events, such as germinal vesicle breakdown (GVBD) and nuclear envelope breakdown (NEBD). In this study, the roles of intracellular and extracellular Ca2+ were examined during meiotic maturation and reinitiation at parthenogenetic activation and during first mitosis in a single species using the same methodologies. Cumulus-free metaphase II mouse oocytes immediately resumed anaphase upon the induction of a large, transient Ca2+ elevation. This resumption of meiosis and associated events, such as cortical granule discharge, were not sensitive to extracellular Ca2+ removal, but were blocked by intracellular Ca2+ chelators. In contrast, meiosis I was dependent on external Ca2+; in its absence, the formation and function of the first meiotic spindle was delayed, the first polar body did not form and an interphase-like state was induced. GVBD was not dependent on external Ca2+ and showed no associated Ca2+ changes. NEBD at first mitosis in fertilized eggs, on the other hand, was frequently, but not always associated with a brief Ca2+ transient and was dependent on Ca2+ mobilization. We conclude that GVBD is Ca2+ independent, but that the dependence of NEBD on Ca2+ suggests regulation by more than one pathway. As cells develop from Ca(2+)-independent germinal vesicle oocytes to internal Ca(2+)-dependent pronuclear eggs, internal Ca2+ pools increase by approximately fourfold.

  13. Nuclear topics

    International Nuclear Information System (INIS)

    Lukner, C.

    1982-07-01

    The pamphlet touches on all aspects of nuclear energy, from the world energy demands and consumption, the energy program of the Federal Government, nuclear power plants in the world, nuclear fusion, nuclear liability up to the nuclear fuel cycle and the shutdown of nuclear power plants. (HSCH) [de

  14. Nuclear power and nuclear weapons

    International Nuclear Information System (INIS)

    Vaughen, V.C.A.

    1983-01-01

    The proliferation of nuclear weapons and the expanded use of nuclear energy for the production of electricity and other peaceful uses are compared. The difference in technologies associated with nuclear weapons and nuclear power plants are described

  15. Distinct DNA-binding surfaces in the ATPase and linker domains of MutLγ determine its substrate specificities and exert separable functions in meiotic recombination and mismatch repair.

    Directory of Open Access Journals (Sweden)

    Corentin Claeys Bouuaert

    2017-05-01

    Full Text Available Mlh1-Mlh3 (MutLγ is a mismatch repair factor with a central role in formation of meiotic crossovers, presumably through resolution of double Holliday junctions. MutLγ has DNA-binding, nuclease, and ATPase activities, but how these relate to one another and to in vivo functions are unclear. Here, we combine biochemical and genetic analyses to characterize Saccharomyces cerevisiae MutLγ. Limited proteolysis and atomic force microscopy showed that purified recombinant MutLγ undergoes ATP-driven conformational changes. In vitro, MutLγ displayed separable DNA-binding activities toward Holliday junctions (HJ and, surprisingly, single-stranded DNA (ssDNA, which was not predicted from current models. MutLγ bound DNA cooperatively, could bind multiple substrates simultaneously, and formed higher-order complexes. FeBABE hydroxyl radical footprinting indicated that the DNA-binding interfaces of MutLγ for ssDNA and HJ substrates only partially overlap. Most contacts with HJ substrates were located in the linker regions of MutLγ, whereas ssDNA contacts mapped within linker regions as well as the N-terminal ATPase domains. Using yeast genetic assays for mismatch repair and meiotic recombination, we found that mutations within different DNA-binding surfaces exert separable effects in vivo. For example, mutations within the Mlh1 linker conferred little or no meiotic phenotype but led to mismatch repair deficiency. Interestingly, mutations in the N-terminal domain of Mlh1 caused a stronger meiotic defect than mlh1Δ, suggesting that the mutant proteins retain an activity that interferes with alternative recombination pathways. Furthermore, mlh3Δ caused more chromosome missegregation than mlh1Δ, whereas mlh1Δ but not mlh3Δ partially alleviated meiotic defects of msh5Δ mutants. These findings illustrate functional differences between Mlh1 and Mlh3 during meiosis and suggest that their absence impinges on chromosome segregation not only via reduced

  16. Robertsonian chromosome polymorphism of Akodon molinae (Rodentia: Sigmodontinae: analysis of trivalents in meiotic prophase Polimorfismo cromosómico Robertsoniano de Akodon molinae (Rodentia: Sigmodontinae

    Directory of Open Access Journals (Sweden)

    RAÚL FERNÁNDEZ-DONOSO

    2001-03-01

    Full Text Available Akodon molinae (with 2n = 42-43-44 and an FN = 44 shows a remarkable polymorphism of chromosome 1 in natural and laboratory populations. Specimens 2n = 42, named single homozygotes (SH, have a chromosome pair 1 formed by two large metacentric chromosomes. Specimens 2n = 3, heterozygotes (Ht, have one chromosome 1 and two medium-sized subtelocentric chromosomes, 1a and 1b, which are homologous with the long and short arms of chromosome 1 respectively. Specimens 2n = 44 are double homozygotes (DH, with just two pairs of medium-sized subtelocentric chromosomes, 1a and 1b. Analysis of meiotic metaphases I and II showed that anomalous segregation occurs more frequently in spermatocytes carrying the 1a and 1b chromosomes. This would disturb gametogenesis and other reproductive and developmental processes, producing a marked decrease in viability of DH individuals. There is, as yet, no satisfactory explanation for these phenomena. To investigate structural elements which might explain such segregational anomalies, we have studied bivalent and trivalent synapsis in pachytene spermatocytes from SH, Ht and DH specimens. Of a total of 80 spermatocyte nuclei microspreads, the following results were obtained: of 16 microspreads from two SH individuals, 20 autosomic bivalents plus the XY bivalent were observed; of 48 microspreads from three Ht individuals, 19 autosomic bivalents, 1 trivalent and an XY bivalent were seen; and of the 16 microspreads from two DH individuals, 21 autosomic bivalents plus the XY bivalent were found. Trivalents analysed showed complete pairing between the short arms of 1a and 1b, and having an apparently normal synaptonemal complex (SC with lengths of 1 and 2.8 µm. The trivalent SC showed three telomeric ends, corresponding to arms: q1 and q1a; p1 and q1b; and p1a and p1b, with attachment plates to the nuclear envelope of normal organisation. None of the trivalents showed asynapsis or desynapsis between p1a and p1b, nor an

  17. The Roles of Fission Yeast Ase1 in Mitotic Cell Division, Meiotic Nuclear Oscillation, and Cytokinesis Checkpoint SignalingD⃞V⃞

    OpenAIRE

    Yamashita, Akira; Sato, Masamitsu; Fujita, Akiko; Yamamoto, Masayuki; Toda, Takashi

    2005-01-01

    The Ase1/Prc1 proteins constitute a conserved microtubule-associated protein family that is implicated in central spindle formation and cytokinesis. Here we characterize a role for fission yeast Ase1. Ase1 localizes to microtubule overlapping zones and displays dynamic alterations of localization during the cell cycle. In particular, its spindle localization during metaphase is reduced substantially, followed by robust appearance at the spindle midzone in anaphase. ase1 deletions are viable b...

  18. Nuclear rights - nuclear wrongs

    Energy Technology Data Exchange (ETDEWEB)

    Paul, E.F.; Miller, F.D.; Paul, J.; Ahrens, J.

    1986-01-01

    This book contains 11 selections. The titles are: Three Ways to Kill Innocent Bystanders: Some Conundrums Concerning the Morality of War; The International Defense of Liberty; Two Concepts of Deterrence; Nuclear Deterrence and Arms Control; Ethical Issues for the 1980s; The Moral Status of Nuclear Deterrent Threats; Optimal Deterrence; Morality and Paradoxical Deterrence; Immoral Risks: A Deontological Critique of Nuclear Deterrence; No War Without Dictatorship, No Peace Without Democracy: Foreign Policy as Domestic Politics; Marxism-Leninism and its Strategic Implications for the United States; Tocqueveille War.

  19. Nuclear moments

    CERN Document Server

    Kopferman, H; Massey, H S W

    1958-01-01

    Nuclear Moments focuses on the processes, methodologies, reactions, and transformations of molecules and atoms, including magnetic resonance and nuclear moments. The book first offers information on nuclear moments in free atoms and molecules, including theoretical foundations of hyperfine structure, isotope shift, spectra of diatomic molecules, and vector model of molecules. The manuscript then takes a look at nuclear moments in liquids and crystals. Discussions focus on nuclear paramagnetic and magnetic resonance and nuclear quadrupole resonance. The text discusses nuclear moments and nucl

  20. Targeted disruption of exons 1 to 6 of the Fanconi Anemia group A gene leads to growth retardation, strain-specific microphthalmia, meiotic defects and primordial germ cell hypoplasia.

    Science.gov (United States)

    Wong, Jasmine C Y; Alon, Noa; Mckerlie, Colin; Huang, Jun R; Meyn, M Stephen; Buchwald, Manuel

    2003-08-15

    Fanconi Anemia (FA) is an autosomal recessive disorder characterized by cellular hypersensitivity to DNA cross-linking agents. Recent studies suggest that FA proteins share a common pathway with BRCA proteins. To study the in vivo role of the FA group A gene (Fanca), gene-targeting techniques were used to generate Fanca(tm1Hsc) mice in which Fanca exons 1-6 were replaced by a beta-galactosidase reporter construct. Fanca(tm1.1Hsc) mice were generated by Cre-mediated removal of the neomycin cassette in Fanca(tm1Hsc) mice. Fanca(tm1.1Hsc) homozygotes display FA-like phenotypes including growth retardation, microphthalmia and craniofacial malformations that are not found in other Fanca mouse models, and the genetic background affects manifestation of certain phenotypes. Both male and female mice homozygous for Fanca mutation exhibit hypogonadism, and homozygous females demonstrate premature reproductive senescence and an increased incidence of ovarian cysts. We showed that fertility defects in Fanca(tm1.1Hsc) homozygotes might be related to a diminished population of primordial germ cells (PGCs) during migration into the gonadal ridges. We also found a high level of Fanca expression in pachytene spermatocytes. Fanca(tm1Hsc) homozygous males exhibited an elevated frequency of mispaired meiotic chromosomes and increased apoptosis in germ cells, implicating a role for Fanca in meiotic recombination. However, the localization of Rad51, Brca1, Fancd2 and Mlh1 appeared normal on Fanca(tm1Hsc) homozygous meiotic chromosomes. Taken together, our results suggest that the FA pathway plays a role in the maintenance of reproductive germ cells and in meiotic recombination.

  1. The inhibitor of calcium activated neutral proteinase is an anti-meiotic agent. The spermicidal and anti-viral action

    OpenAIRE

    Logothetou-Rella, H.

    1995-01-01

    In situ cytogenetic morphology and analysis showed that Epstein-Barr Virus (EBV)-infected Raji and EBV-producing P3HR-1 cells divide by meiosis and follow the life cycle of malignant cells in vitro. Meiosis was documented by the presence of condensed chromosomes, «o» chromosome, nuclear vlimata (NVs), NV invasion, extrusion of chromosomes, chromosomal transfer, metaphase fusion and aneuploidy. EBV-Raji, EBV-producing P3HR, HIV1-infected MOLT-4 cells (dividi...

  2. Acetylated Histone H3K9 is associated with meiotic recombination hotspots, and plays a role in recombination redundantly with other factors including the H3K4 methylase Set1 in fission yeast

    Science.gov (United States)

    Yamada, Shintaro; Ohta, Kunihiro; Yamada, Takatomi

    2013-01-01

    Histone modifications are associated with meiotic recombination hotspots, discrete sites with augmented recombination frequency. For example, trimethylation of histone H3 lysine4 (H3K4me3) marks most hotspots in budding yeast and mouse. Modified histones are known to regulate meiotic recombination partly by promoting DNA double-strand break (DSB) formation at hotspots, but the role and precise landscape of involved modifications remain unclear. Here, we studied hotspot-associated modifications in fission yeast and found general features: acetylation of H3 lysine9 (H3K9ac) is elevated, and H3K4me3 is not significantly enriched. Mutating H3K9 to non-acetylatable alanine mildly reduced levels of the DSB-inducing protein Rec12 (the fission yeast homologue of Spo11) and DSB at hotspots, indicating that H3K9ac may be involved in DSB formation by enhancing the interaction between Rec12 and hotspots. In addition, we found that the lack of the H3K4 methyltransferase Set1 generally increased Rec12 binding to chromatin but partially reduced DSB formation at some loci, suggesting that Set1 is also involved in DSB formation. These results suggest that meiotic DSB formation is redundantly regulated by multiple chromatin-related factors including H3K9ac and Set1 in fission yeast. PMID:23382177

  3. Synaptonemal complex analysis of interracial hybrids between the Moscow and Neroosa chromosomal races of the common shrew Sorex araneus showing regular formation of a complex meiotic configuration (ring-of-four).

    Science.gov (United States)

    Matveevsky, Sergey N; Pavlova, Svetlana V; Maret M Acaeva; Oxana L Kolomiets

    2012-01-01

    Immunocytochemical and electron microscopic analysis of synaptonemal complexes (SCs) was carried out for the first time in homozygotes and complex Robertsonian heterozygotes (hybrids) of the common shrew, Sorex araneus Linnaeus, 1758, from a newly discovered hybrid zone between the Moscow and the Neroosa chromosomal races. These races differ in four monobrachial homologous metacentrics, and closed SC tetravalent is expected to be formed in meiosis of a hybrid. Indeed, such a multivalent was found at meiotic prophase I in hybrids. Interactions between multivalent and both autosomes and/or the sex chromosomes were observed. For the first time we have used immunocytochemical techniques to analyse asynapsis in Sorex araneus and show that the multivalent pairs in an orderly fashion with complete synapsis. Despite some signs of spermatocytes arrested in the meiotic prophase I, hybrids had large number of active sperm. Thus, Moscow - Neroosa hybrid males that form a ring-of-four meiotic configuration are most likely not sterile. Our results support previous demonstrations that monobrachial homology of metacentrics of the common shrew does not lead to complete reproductive isolation between parapatric chromosomal races of the species.

  4. Synaptonemal complex analysis of interracial hybrids between the Moscow and Neroosa chromosomal races of the common shrew Sorex araneus showing regular formation of a complex meiotic configuration (ring-of-four

    Directory of Open Access Journals (Sweden)

    Sergey Matveevsky

    2012-09-01

    Full Text Available Immunocytochemical and electron microscopic analysis of synaptonemal complexes (SCs was carried out for the first time in homozygotes and complex Robertsonian heterozygotes (hybrids of the common shrew, Sorex araneus Linnaeus, 1758, from a newly discovered hybrid zone between the Moscow and the Neroosa chromosomal races. These races differ in four monobrachial homologous metacentrics, and closed SC tetravalent is expected to be formed in meiosis of a hybrid. Indeed, such a multivalent was found at meiotic prophase I in hybrids. Interactions between multivalent and both autosomes and/or the sex chromosomes were observed. For the first time we have used immunocytochemical techniques to analyse asynapsis in S. araneus and show that the multivalent pairs in an orderly fashion with complete synapsis. Despite some signs of spermatocytes arrested in the meiotic prophase I, hybrids had large number of active sperm. Thus, Moscow – Neroosa hybrid males that form a ring-of-four meiotic configuration are most likely not sterile. Our results support previous demonstrations that monobrachial homology of metacentrics of the common shrew does not lead to complete reproductive isolation between parapatric chromosomal races of the species.

  5. Nuclear power

    International Nuclear Information System (INIS)

    Abd Khalik Wood

    2005-01-01

    This chapter discussed the following topics related to the nuclear power: nuclear reactions, nuclear reactors and its components - reactor fuel, fuel assembly, moderator, control system, coolants. The topics titled nuclear fuel cycle following subtopics are covered: , mining and milling, tailings, enrichment, fuel fabrication, reactor operations, radioactive waste and fuel reprocessing. Special topic on types of nuclear reactor highlighted the reactors for research, training, production, material testing and quite detail on reactors for electricity generation. Other related topics are also discussed: sustainability of nuclear power, renewable nuclear fuel, human capital, environmental friendly, emission free, impacts on global warming and air pollution, conservation and preservation, and future prospect of nuclear power

  6. Nuclear science

    International Nuclear Information System (INIS)

    1989-01-01

    This fact sheet answers specific questions about the Department of Energy's possible acquisition and conversion of a partially completed commercial nuclear power plant to a nuclear materials production facility. The nuclear power plant is the Washington Nuclear Plant number sign 1 owned by the Washington Public Power Supply System and is located on DOE's Hanford Reservation near Richland, Washington

  7. Nuclear science

    International Nuclear Information System (INIS)

    1989-04-01

    This report answers questions about the Department of Energy's possible acquisition and conversion of a partially completed commercial nuclear power plant to a nuclear materials production facility. The nuclear power plant is the Washington Nuclear Plant No.1 owned by the Washington Public Power Supply System and is located on DOE's Hanford Reservation near Richland, Washington

  8. Nuclear medicine

    International Nuclear Information System (INIS)

    Lentle, B.C.

    1986-01-01

    Several growth areas for nuclear medicine were defined. Among them were: cardiac nuclear medicine, neuro-psychiatric nuclear medicine, and cancer diagnosis through direct tumor imaging. A powerful new tool, Positron Emission Tomography (PET) was lauded as the impetus for new developments in nuclear medicine. The political environment (funding, degree of autonomy) was discussed, as were the economic and scientific environments

  9. Nuclear option

    Energy Technology Data Exchange (ETDEWEB)

    Kemm, K R

    1978-05-01

    The global outlook is that nuclear reactors are here to stay and South Africa has already entered the nuclear power stakes. This article discusses the rocketing oil prices, and the alternatives that can be used in power generation, the good safety record of the nuclear industry and the effect that South Africa's first nuclear power station should have on the environment.

  10. Nuclear resisters

    International Nuclear Information System (INIS)

    1981-01-01

    The booklet contains six papers by different authors, under the headings: dangers along the nuclear fuel cycle; the nuclear profiteers; the nuclear state is a police state; a non-disposable future (renewable energy sources, energy conservation); nuclear weapons - out of control; man made madness. (U.K.)

  11. Nuclear links

    International Nuclear Information System (INIS)

    1981-01-01

    The subject is dealt with in sections: introduction; energy and the third world; world energy consumption 1978; oil -the energy dilemma; nuclear chains - introduction; uranium; Namibia; enrichment and reprocessing; countries with enrichment and reprocessing facilities; waste; conclusion; why take the nuclear option; third world countries with nuclear reactors; the arms connection; government spending and human resources 1977 (by countries); nuclear power - the final solution; the fascists; world bank; campaigns; community action in Plogoff; Australian labour movement; NUM against nuclear power; Scottish campaign; students against nuclear energy; anti-nuclear campaign; partizans; 3W1 disarmament and development; campaign ATOM; CANUC; 3W1; SANE. (U.K.)

  12. Meiotic and mitotic behaviour of a ring/deleted chromosome 22 in human embryos determined by preimplantation genetic diagnosis for a maternal carrier

    Directory of Open Access Journals (Sweden)

    Laver Sarah

    2009-01-01

    Full Text Available Abstract Background Ring chromosomes are normally associated with developmental anomalies and are rarely inherited. An exception to this rule is provided by deletion/ring cases. We were provided with a unique opportunity to investigate the meiotic segregation at oogenesis in a woman who is a carrier of a deleted/ring 22 chromosome. The couple requested preimplantation genetic diagnosis (PGD following the birth of a son with a mosaic karyotype. The couple underwent two cycles of PGD. Studies were performed on lymphocytes, single embryonic cells removed from 3 day-old embryos and un-transferred embryos. Analysis was carried out using fluorescence in situ hybridisation (FISH with specific probe sets in two rounds of hybridization. Results In total, 12 embryos were biopsied, and follow up information was obtained for 10 embryos. No embryos were completely normal or balanced for chromosome 22 by day 5. There was only one embryo diagnosed as balanced of 12 biopsied but that accumulated postzygotic errors by day 5. Three oocytes apparently had a balanced chromosome 22 complement but all had the deleted and the ring 22 and not the intact chromosome 22. After fertilisation all the embryos accumulated postzygotic errors for chromosome 22. Conclusion The study of the preimplantation embryos in this case provided a rare and significant chance to study and understand the phenomena associated with this unusual type of anomaly during meiosis and in the earliest stages of development. It is the first reported PGD attempt for a ring chromosome abnormality.

  13. The Rho-GTPase effector ROCK regulates meiotic maturation of the bovine oocyte via myosin light chain phosphorylation and cofilin phosphorylation.

    Science.gov (United States)

    Lee, So-Rim; Xu, Yong-Nan; Jo, Yu-Jin; Namgoong, Suk; Kim, Nam-Hyung

    2015-11-01

    Oocyte meiosis involves a unique asymmetric division involving spindle movement from the central cytoplasm to the cortex, followed by polar body extrusion. ROCK is a Rho-GTPase effector involved in various cellular functions in somatic cells as well as oocyte meiosis. ROCK was previously shown to promote actin organization by phosphorylating several downstream targets, including LIM domain kinase (LIMK), phosphorylated cofilin (p-cofilin), and myosin light chain (MLC). In this study, we investigated the roles of ROCK and MLC during bovine oocyte meiosis. We found that ROCK was localized around the nucleus at the oocyte's germinal-vesicle (GV) stage, but spreads to the rest of the cytoplasm in later developmental stages. On the other hand, phosphorylated MLC (p-MLC) localized at the cortex, and its abundance decreased by the metaphase-II stage. Disrupting ROCK activity, via RNAi or the chemical inhibitor Y-27632, blocked both cell cycle progression and polar body extrusion. ROCK inhibition also resulted in decreased cortical actin, p-cofilin, and p-MLC levels. Similar to the phenotype associated with inhibition of ROCK activity, inhibition of MLC kinase by the chemical inhibitor ML-7 caused defects in polar body extrusion. Collectively, our results suggest that the ROCK/MLC/actomyosin as well as ROCK/LIMK/cofilin pathways regulate meiotic spindle migration and cytokinesis during bovine oocyte maturation. © 2015 Wiley Periodicals, Inc.

  14. Melatonin protects against maternal obesity-associated oxidative stress and meiotic defects in oocytes via the SIRT3-SOD2-dependent pathway.

    Science.gov (United States)

    Han, Longsen; Wang, Haichao; Li, Ling; Li, Xiaoyan; Ge, Juan; Reiter, Russel J; Wang, Qiang

    2017-10-01

    Maternal obesity in humans is associated with poor outcomes across the reproductive spectrum. Emerging evidence indicates that these defects are likely attributed to factors within the oocyte. Although various molecules and pathways may contribute to impaired oocyte quality, prevention of fertility issues associated with maternal obesity is a challenge. Using mice fed a high-fat diet (HFD) as an obesity model, we document spindle disorganization, chromosome misalignment, and elevated reactive oxygen species (ROS) levels in oocytes from obese mice. Oral administration of melatonin to HFD mice not only reduces ROS generation, but also prevents spindle/chromosome anomalies in oocytes, consequently promoting the developmental potential of early embryos. Consistent with this finding, we find that melatonin supplement during in vitro maturation also markedly attenuates oxidative stress and meiotic defects in HFD oocytes. Finally, by performing morpholino knockdown and acetylation-mimetic mutant overexpression assays, we reveal that melatonin ameliorates maternal obesity-induced defective phenotypes in oocytes through the SIRT3-SOD2-dependent mechanism. In sum, our data uncover the marked beneficial effects of melatonin on oocyte quality from obese females; this opens a new area for optimizing culture system as well as fertility management. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. Nuclear Power

    International Nuclear Information System (INIS)

    Douglas-Hamilton, J.; Home Robertson, J.; Beith, A.J.

    1987-01-01

    In this debate the Government's policy on nuclear power is discussed. Government policy is that nuclear power is the safest and cleanest way of generating electricity and is cheap. Other political parties who do not endorse a nuclear energy policy are considered not to be acting in the people's best interests. The debate ranged over the risks from nuclear power, the UK safety record, safety regulations, and the environmental effects of nuclear power. The Torness nuclear power plant was mentioned specifically. The energy policy of the opposition parties is strongly criticised. The debate lasted just over an hour and is reported verbatim. (UK)

  16. Antimutators of mitochodrial and nuclear DNA in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Bianchi, L.; Foury, F.

    1982-01-01

    In Saccharomyces cerevisiae ten antimutator mutants have been isolated. The spontaneous occurrence of mitochondrial mutants resistant to erythromycin, oligomycin, and diuron is decreased 2-60-fold in these strains. The rate of forward and reverse spontaneous mutations of the nuclear genome is also reduced. The meiotic progenies arising from the crosses of seven mutants (LB 1 , LB 2 , LB 4 , LB 5 , LB 6 , LB 7 , LB 10 ) with an isogenic parental strain exhibit 2:2 segregations and therefore are the result of mutations in a single nuclear gene. The six mutants LB 1 , LB 2 , LB 4 , LB 6 , LB 7 , LB 10 are semidominant and determine six complementation groups. The mutant LB 5 is dominant and therefore cannot be assigned to any complementation group. The mutants. LB 1 , LB 4 and LB 1 0 are gamma-ray sensitive and, by tetrad analysis, it has been shown that gamma-ray sensitivity and spontaneous antimutability are the result of a single nuclear gene mutation. The other three mutants LB 3 , LB 8 and LB 9 exhibit complex tetrad segregations, typical of cytoplasmic inheritance and do not complement each other. However, although the mutations are semidominant, it has not been possible to detect any antimutator cytoductant among some 500 cytoductants carrying the karl 1-1 nucleus. (orig./AJ)

  17. JPRS Report, Nuclear Developments

    National Research Council Canada - National Science Library

    1991-01-01

    Partial Contents: Medium Range Missiles, Rocket Engine, Nuclear Submarine, Nuclear Reactor, Nuclear Inspection, Nuclear Weapons, Transfer Technology, Scud, Safety, Nuclear Power, Chernobyl Trial, ,CHemical Weapons...

  18. Nuclear forensics

    International Nuclear Information System (INIS)

    Venugopal, V.

    2010-01-01

    Nuclear forensics is the analysis of nuclear materials recovered from either the capture of unused materials, or from the radioactive debris following a nuclear explosion and can contribute significantly to the identification of the sources of the materials and the industrial processes used to obtain them. In the case of an explosion, nuclear forensics can also reconstruct key features of the nuclear device. Nuclear forensic analysis works best in conjunction with other law enforcement, radiological protection dosimetry, traditional forensics, and intelligence work to provide the basis for attributing the materials and/or nuclear device to its originators. Nuclear forensics is a piece of the overall attribution process, not a stand-alone activity

  19. Nuclear power

    International Nuclear Information System (INIS)

    1987-01-01

    ''Nuclear Power'' describes how a reactor works and examines the different designs including Magnox, AGR, RBMK and PWR. It charts the growth of nuclear generation in the world and its contributions to world energy resources. (author)

  20. Nuclear Scans

    Science.gov (United States)

    Nuclear scans use radioactive substances to see structures and functions inside your body. They use a special ... images. Most scans take 20 to 45 minutes. Nuclear scans can help doctors diagnose many conditions, including ...

  1. Nuclear energy

    International Nuclear Information System (INIS)

    Kuhn, W.

    1986-01-01

    This loose-leaf collection is made up of five didactically prepared units covering the following subjects: basic knowledge on nuclear energy, nuclear energy in relation to energy economy, site issues, environmental compatibility of nuclear energy, and nuclear energy in the focus of political and social action. To this was added a comprehensive collection of material: specific scientific background material, a multitude of tables, diagrams, charts etc. for copying, as well as 44 transparent charts, mostly in four colours. (orig./HP) [de

  2. Nuclear structure

    International Nuclear Information System (INIS)

    Eastham, D.A.; Joy, T.

    1986-01-01

    The paper on 'nuclear structure' is the Appendix to the Daresbury (United Kingdom) Annual Report 1985/86, and contains the research work carried out at the Nuclear Structure Facility, Daresbury, within that period. During the year a total of 74 experiments were scheduled covering the main areas of activity including: nuclear collective motion, nuclei far from stability, and nuclear collisions. The Appendix contains brief reports on these experiments and associated theory. (U.K.)

  3. The influence of large deletions on the mutation frequency induced by tritiated water and X-radiation in male Drosophila melanogaster post-meiotic germ cells

    International Nuclear Information System (INIS)

    Fossett, N.G.; Byrne, B.J.; Kelley, S.J.; Tucker, A.B.; Arbour-Reily, P.; Lee, W.R.

    1994-01-01

    Tritium beta radiation ( 3 H β-radiation) in the form of tritiated water was used to induce mutations at the alcohol dehydrogenase (Adh) locus in male Drosophila melanogaster post-meiotic germ cells. All 23 Adh null mutations were large deletions (>20 kb), determined by genetic complementation and Southern blot analyses. 27 Adh null mutations have been induced by 100-kVp X-rays and have been genetically and molecularly characterized. In contrast to 3 H β-radiation, 100-kVp X-rays induced a bimodal distribution of Adh null mutations, intragenic mutations, ≤250 bp, and large deletions, >100 kb. A statistically significant difference was observed between the frequency of large deletions (23/23 or 1.0) induced by 3 H β-radiation and the frequency of large deletions (19/27 or 0.7) induced by 100-kVp X-rays. However, a statistical difference was not observed between the size distribution of the large deletions induced by 3 H β-radiation and X-rays. The relative deletion frequency (RDF) induced by 3 H β-radiation and 100-kVp X-rays was (1.0/0.7=1.4). The relative biological effectiveness (RBE) of these two radiation sources was 1.4, determined from the ratio of the regression coefficients of the respective 3 H β-radiation and X-ray sex-linked recessive lethal (SLRL) dose-response data. The large difference in size between the two classes of X-ray-induced Adh null mutations and the increase in mutation frequency and deletion frequency for 3 H β-radiation with respect to X-rays may indicate that the relative deletion frequency (RDF) is the molecular biological basis for the increase in the RBE for radiation sources with a mean LET value ≤10 keV/μm

  4. Laboratory studies on insecticide resistance, alcohol tolerance and sex ratio distortion by meiotic drive in the Mediterranean fruit fly, Ceratitis capitata (Wied.)

    International Nuclear Information System (INIS)

    Wood, R.J.

    1990-01-01

    Three approaches to developing a genetic sexing technique for the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), are discussed. Laboratory studies in late third instar larvae of the medfly revealed a potential for dieldrin resistance. A programme of sib selection produced the DiR strain, more than 60x resistante to dieldrin with cross-resistance to other cyclodienes, HCH, malathion and permethrin. Adults were not resistant. Crosses showed dieldrin resistance to be monofactorial, subject to a modifying effect from the genetic background on the expression of the homozygote. The 'backcrossing with selection' technique was used to separate dieldrin and malathion resistance but, in the process, resistance to both insecticides was lost after four to eight generations. Attempts to induce male linkage of the R gene by X irradiation were unsuccessful. Further genetic studies on resistance are recommended. With a view to producing an ethanol sensitive strain homozygous for an ADH null mutation (Adh - /Adh - ), pentenol selection of late third instar larvae was carried out, combined with ethyl methane sulphonate (EMS) treatments of adults. This produced a maximum of 15x tolerance of pentenol but no associated change in ethanol tolerance. Electrophoresis (PAGE) showed that two major ADH systems were at their most active in late third instar larvae. A gene causing a male distorted sex ratio in the progeny of males carrying it was isolated after X irradiation. The expression of the gene, which appears to be an example of meiotic drive, was enhanced by reducing the ambient temperature of parent flies from 26 deg. C+-2.0 to 18 deg. C+-1.5 during days 2-5 of pupal development. Selection to increase the expression of the gene produced families with less than 20% females but sex ratio tended to revert towards normal in subsequent generations. A potential is seen for producing strains in which sex ratio can be regulated by temperature. (author). 30 refs, 5 figs, 2

  5. The mismatch repair and meiotic recombination endonuclease Mlh1-Mlh3 is activated by polymer formation and can cleave DNA substrates in trans.

    Science.gov (United States)

    Manhart, Carol M; Ni, Xiaodan; White, Martin A; Ortega, Joaquin; Surtees, Jennifer A; Alani, Eric

    2017-04-01

    Crossing over between homologs is initiated in meiotic prophase by the formation of DNA double-strand breaks that occur throughout the genome. In the major interference-responsive crossover pathway in baker's yeast, these breaks are resected to form 3' single-strand tails that participate in a homology search, ultimately forming double Holliday junctions (dHJs) that primarily include both homologs. These dHJs are resolved by endonuclease activity to form exclusively crossovers, which are critical for proper homolog segregation in Meiosis I. Recent genetic, biochemical, and molecular studies in yeast are consistent with the hypothesis of Mlh1-Mlh3 DNA mismatch repair complex acting as the major endonuclease activity that resolves dHJs into crossovers. However, the mechanism by which the Mlh1-Mlh3 endonuclease is activated is unknown. Here, we provide evidence that Mlh1-Mlh3 does not behave like a structure-specific endonuclease but forms polymers required to generate nicks in DNA. This conclusion is supported by DNA binding studies performed with different-sized substrates that contain or lack polymerization barriers and endonuclease assays performed with varying ratios of endonuclease-deficient and endonuclease-proficient Mlh1-Mlh3. In addition, Mlh1-Mlh3 can generate religatable double-strand breaks and form an active nucleoprotein complex that can nick DNA substrates in trans. Together these observations argue that Mlh1-Mlh3 may not act like a canonical, RuvC-like Holliday junction resolvase and support a novel model in which Mlh1-Mlh3 is loaded onto DNA to form an activated polymer that cleaves DNA.

  6. The organization and evolution of the Responder satellite in species of the Drosophila melanogaster group: dynamic evolution of a target of meiotic drive.

    Science.gov (United States)

    Larracuente, Amanda M

    2014-11-25

    Satellite DNA can make up a substantial fraction of eukaryotic genomes and has roles in genome structure and chromosome segregation. The rapid evolution of satellite DNA can contribute to genomic instability and genetic incompatibilities between species. Despite its ubiquity and its contribution to genome evolution, we currently know little about the dynamics of satellite DNA evolution. The Responder (Rsp) satellite DNA family is found in the pericentric heterochromatin of chromosome 2 of Drosophila melanogaster. Rsp is well-known for being the target of Segregation Distorter (SD)- an autosomal meiotic drive system in D. melanogaster. I present an evolutionary genetic analysis of the Rsp family of repeats in D. melanogaster and its closely-related species in the melanogaster group (D. simulans, D. sechellia, D. mauritiana, D. erecta, and D. yakuba) using a combination of available BAC sequences, whole genome shotgun Sanger reads, Illumina short read deep sequencing, and fluorescence in situ hybridization. I show that Rsp repeats have euchromatic locations throughout the D. melanogaster genome, that Rsp arrays show evidence for concerted evolution, and that Rsp repeats exist outside of D. melanogaster, in the melanogaster group. The repeats in these species are considerably diverged at the sequence level compared to D. melanogaster, and have a strikingly different genomic distribution, even between closely-related sister taxa. The genomic organization of the Rsp repeat in the D. melanogaster genome is complex-it exists of large blocks of tandem repeats in the heterochromatin and small blocks of tandem repeats in the euchromatin. My discovery of heterochromatic Rsp-like sequences outside of D. melanogaster suggests that SD evolved after its target satellite and that the evolution of the Rsp satellite family is highly dynamic over a short evolutionary time scale (<240,000 years).

  7. Nuclear terrorism

    International Nuclear Information System (INIS)

    2002-01-01

    Recent reports of alleged terrorist plans to build a 'dirty bomb' have heightened longstanding concerns about nuclear terrorism. This briefing outlines possible forms of attack, such as: detonation of a nuclear weapon; attacks involving radioactive materials; attacks on nuclear facilities. Legislation addressing these risks and the UK's strategy for coping with them are also considered

  8. Nuclear power

    International Nuclear Information System (INIS)

    d'Easum, Lille.

    1976-03-01

    An environmentalist's criticism of nuclear energy is given, on a layman's level. Such subjects as conflict of interest in controlling bodies, low-level radiation, reactor safety, liability insurance, thermal pollution, economics, heavy water production, export of nuclear technology, and the history of the anti-nuclear movement are discussed in a sensationalistic tone. (E.C.B.)

  9. Nuclear alerts

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    Anti-nuclear demonstrations against the deployment of new US missiles were held in Nato Europe. As no agreement has yet been reached at the US-Soviet Intermediate Nuclear Forces talks in Geneva, the deployment of nuclear missiles in Europe has started

  10. Nuclear questions

    International Nuclear Information System (INIS)

    Berg, Eugene

    2012-01-01

    Civilian and military nuclear questions fill a multitude of publications these days, especially after the Japanese tsunami and the Fukushima disaster. The author analyses some of them and highlights the links between civil and military nuclear industries, the realities of the nuclear cycle and related industrial questions before concluding on the controversial issue of weapons and their proliferation potential

  11. Nuclear decommissioning

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    The paper on nuclear decommissioning was presented by Dr H. Lawton to a meeting of the British Nuclear Energy Society and Institution of Nuclear Engineers, 1986. The decommissioning work currently being undertaken on the Windscale advanced gas cooled reactor (WAGR) is briefly described, along with projects in other countries, development work associated with the WAGR operation and costs. (U.K.)

  12. Nuclear electronics

    International Nuclear Information System (INIS)

    Friese, T.

    1981-09-01

    A short survey is given on nuclear radiation detectors and nuclear electronics. It is written for newcomers and those, who are not very familiar with this technique. Some additional information is given on typical failures in nuclear measurement systems. (orig.) [de

  13. In vitro acute exposure to DEHP affects oocyte meiotic maturation, energy and oxidative stress parameters in a large animal model.

    Science.gov (United States)

    Ambruosi, Barbara; Uranio, Manuel Filioli; Sardanelli, Anna Maria; Pocar, Paola; Martino, Nicola Antonio; Paternoster, Maria Stefania; Amati, Francesca; Dell'Aquila, Maria Elena

    2011-01-01

    Phthalates are ubiquitous environmental contaminants because of their use in plastics and other common consumer products. Di-(2-ethylhexyl) phthalate (DEHP) is the most abundant phthalate and it impairs fertility by acting as an endocrine disruptor. The aim of the present study was to analyze the effects of in vitro acute exposure to DEHP on oocyte maturation, energy and oxidative status in the horse, a large animal model. Cumulus cell (CC) apoptosis and oxidative status were also investigated. Cumulus-oocyte complexes from the ovaries of slaughtered mares were cultured in vitro in presence of 0.12, 12 and 1200 µM DEHP. After in vitro maturation (IVM), CCs were removed and evaluated for apoptosis (cytological assessment and TUNEL) and intracellular reactive oxygen species (ROS) levels. Oocytes were evaluated for nuclear chromatin configuration. Matured (Metaphase II stage; MII) oocytes were further evaluated for cytoplasmic energy and oxidative parameters. DEHP significantly inhibited oocyte maturation when added at low doses (0.12 µM; P<0.05). This effect was related to increased CC apoptosis (P<0.001) and reduced ROS levels (P<0.0001). At higher doses (12 and 1200 µM), DEHP induced apoptosis (P<0.0001) and ROS increase (P<0.0001) in CCs without affecting oocyte maturation. In DEHP-exposed MII oocytes, mitochondrial distribution patterns, apparent energy status (MitoTracker fluorescence intensity), intracellular ROS localization and levels, mt/ROS colocalization and total SOD activity did not vary, whereas increased ATP content (P<0.05), possibly of glycolytic origin, was found. Co-treatment with N-Acetyl-Cysteine reversed apoptosis and efficiently scavenged excessive ROS in DEHP-treated CCs without enhancing oocyte maturation. In conclusion, acute in vitro exposure to DEHP inhibits equine oocyte maturation without altering ooplasmic energy and oxidative stress parameters in matured oocytes which retain the potential to be fertilized and develop into embryos

  14. Meiotic maturation and developmental capability of ovine oocytes at germinal vesicle stage following vitrification using different cryodevices.

    Science.gov (United States)

    Quan, Guo Bo; Wu, Guo Quan; Wang, Ya Jing; Ma, Yuan; Lv, Chun Rong; Hong, Qiong Hua

    2016-02-01

    In order to assess effects of vitrification on ovine oocytes at the germinal vesicle (GV) stage, the conventional plastic straw (CS), the open-pulled straw (OPS), and Cryoloop were used to vitrify ovine oocytes. Oocytes were randomly divided into five groups: (1) Control; (2) Oocytes exposed to vitrification and dilution solutions without any cryopreservation (toxicity); (3) Oocytes vitrified using CS (CS); (4) Oocytes vitrified using OPS (OPS), and (5) Oocytes vitrified using Cryoloop (Cryoloop). The viability, cumulus cell expansion, nuclear maturation after in vitro maturation (IVM), and developmental capability of vitrified oocytes following parthenogenetic activation (PA) or in vitro fertilization (IVF) were assessed. The pretreatment in the vitrification and dilution solutions without any freezing or thawing did not adversely influence oocytes. The viability of vitrified oocytes were significantly declined compared to unfrozen oocytes (P straws or Cryoloop was significantly higher than that in the CS group (P plastic straws was significantly less than those of the other freezing groups (P straws. However, the cleavage rate of vitrified oocytes in the CS group was significantly less than that in the OPS or Cryoloop group (P plastic straw developed to the blastocyst stage following IVF. There was no significant difference existing between OPS and Cryoloop with respect to the blastocyst rate. After staining with cFDA and PI, cumulus cells surrounding oocytes were partly damaged by vitrification and thawing while the membrane of vitrified oocyte still remained intact. In conclusion, vitrification can seriously damage ovine immature oocytes and cumulus cells surrounding oocytes, which may subsequently affect their developmental capability. Finally, this study further proves that increasing the freezing and thawing velocity benefits survival of vitrified immature oocytes. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. The fate and role of macromolecules synthesized during mammalian oocyte meiotic maturation. I. Autoradiographic topography of newly synthesized RNA and protein in the germinal vesicle of the pig and rabbit

    International Nuclear Information System (INIS)

    Motlik, J.; Kopecny, V.; Pivko, J.

    1978-01-01

    Pig and rabbit oocytes were cytoautoradiographically checked for their synthetic activities during meiotic maturation. Tritiated uridine and lysine or 35 S-methionine were introduced into the culture medium in which the oocytes were maintained either immediately at the beginning of the germinal vesicle breakdown in vitro or after reaching a more advanced stage of this process in vitro or in vivo. Some oocytes were maintained thereafter in a cold medium to trace the metabolism of the labelled protein. In addition to uridine- 3 H incorporation into the nucleolus and nucleoplasm, during pig oocyte maturation it was found that an intensive RNA synthesis site appeared in association with condensing chromocentres of the GV II. A considerable proportion of oocytes from slaughterhouse material did not show intensive GV activity in RNA synthesis during maturation in vitro. In the pig and rabbit oocyte it was shown that the newly synthesized 3 H-lysine-labelled protein accumulated to a high degree in the GV and in the nucleolus. The labelled protein accumulated in the GV up to the stage of GV IV (pig) and persisted during the chase period in the ooplasm; it was found to be associated with chromosomes of metaphase I (pig) or metaphase II (rabbit) of the meiotic division. The process of protein accumulation in the GV was not influenced by meiotic arrest during oocyte culture in autologous follicular fluid. A similar accumulation of the label in the GV was detected in oocytes which were cultured in a medium enriched by 35 S-methionine. In some oocytes the labelled protein failed to accumulate in the nucleolar area during maturation in vitro

  16. Assignment of the human gene for pregnancy-associated plasma protein A (PAPPA) to 9q33.1 by fluorescence in situ hybridization to mitotic and meiotic chromosomes

    DEFF Research Database (Denmark)

    Silahtaroglu, A N; Tümer, Z; Kristensen, Torsten

    1993-01-01

    Low levels of pregnancy-associated plasma protein A (PAPPA) during the first trimester has been suggested as a biochemical indicator of pregnancies with aneuploid fetuses. Furthermore, the complete absence of PAPPA in pregnancies associated with Cornelia de Lange syndrome (CL) has suggested...... a causal connection between PAPPA and the development of CL. We have assigned the locus for PAPPA to chromosome region 9q33.1 on mitotic and meiotic chromosomes by fluorescence in situ hybridization, using a 3.7-kb partial PAPPA cDNA probe...

  17. Nuclear energy

    International Nuclear Information System (INIS)

    2007-01-01

    This digest document was written by members of the union of associations of ex-members and retired people of the Areva group (UARGA). It gives a comprehensive overview of the nuclear industry world, starting from radioactivity and its applications, and going on with the fuel cycle (front-end, back-end, fuel reprocessing, transports), the nuclear reactors (PWR, BWR, Candu, HTR, generation 4 systems), the effluents from nuclear facilities, the nuclear wastes (processing, disposal), and the management and safety of nuclear activities. (J.S.)

  18. Nuclear orientation and nuclear structure

    International Nuclear Information System (INIS)

    Krane, K.S.

    1988-01-01

    The present generation of on-line nuclear orientation facilities promises to revolutionize the gathering of nuclear structure information, especially for the hitherto poorly known and understood nuclei far from stability. Following a brief review of the technological developments that have facilitated these experiments, the nuclear spectroscopic information that can be obtained is summarized. Applications to understanding nuclear structure are reviewed, and challenges for future studies are discussed. (orig.)

  19. In vitro acute exposure to DEHP affects oocyte meiotic maturation, energy and oxidative stress parameters in a large animal model.

    Directory of Open Access Journals (Sweden)

    Barbara Ambruosi

    Full Text Available Phthalates are ubiquitous environmental contaminants because of their use in plastics and other common consumer products. Di-(2-ethylhexyl phthalate (DEHP is the most abundant phthalate and it impairs fertility by acting as an endocrine disruptor. The aim of the present study was to analyze the effects of in vitro acute exposure to DEHP on oocyte maturation, energy and oxidative status in the horse, a large animal model. Cumulus cell (CC apoptosis and oxidative status were also investigated. Cumulus-oocyte complexes from the ovaries of slaughtered mares were cultured in vitro in presence of 0.12, 12 and 1200 µM DEHP. After in vitro maturation (IVM, CCs were removed and evaluated for apoptosis (cytological assessment and TUNEL and intracellular reactive oxygen species (ROS levels. Oocytes were evaluated for nuclear chromatin configuration. Matured (Metaphase II stage; MII oocytes were further evaluated for cytoplasmic energy and oxidative parameters. DEHP significantly inhibited oocyte maturation when added at low doses (0.12 µM; P<0.05. This effect was related to increased CC apoptosis (P<0.001 and reduced ROS levels (P<0.0001. At higher doses (12 and 1200 µM, DEHP induced apoptosis (P<0.0001 and ROS increase (P<0.0001 in CCs without affecting oocyte maturation. In DEHP-exposed MII oocytes, mitochondrial distribution patterns, apparent energy status (MitoTracker fluorescence intensity, intracellular ROS localization and levels, mt/ROS colocalization and total SOD activity did not vary, whereas increased ATP content (P<0.05, possibly of glycolytic origin, was found. Co-treatment with N-Acetyl-Cysteine reversed apoptosis and efficiently scavenged excessive ROS in DEHP-treated CCs without enhancing oocyte maturation. In conclusion, acute in vitro exposure to DEHP inhibits equine oocyte maturation without altering ooplasmic energy and oxidative stress parameters in matured oocytes which retain the potential to be fertilized and develop into

  20. Nuclear power

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    The committee concludes that the nature of the proliferation problem is such that even stopping nuclear power completely could not stop proliferation completely. Countries can acquire nuclear weapons by means independent of commercial nuclear power. It is reasonable to suppose if a country is strongly motivated to acquire nuclear weapons, it will have them by 2010, or soon thereafter, no matter how nuclear power is managed in the meantime. Unilateral and international diplomatic measures to reduce the motivations that lead to proliferation should be high on the foreign policy agenda of the United States. A mimimum antiproliferation prescription for the management of nuclear power is to try to raise the political barriers against proliferation through misuse of nuclear power by strengthening the Non-Proliferation Treaty, and to seek to raise the technological barriers by placing fuel-cycle operations involving weapons-usable material under international control. Any such measures should be considered tactics to slow the spread of nuclear weapons and thus earn time for the exercise of statesmanship. The committee concludes the following about technical factors that should be considered in formulating nuclear policy: (1) rate of growth of electricity use is a primary factor; (2) growth of conventional nuclear power will be limited by producibility of domestic uranium sources; (3) greater contribution of nuclear power beyond 400 GWe past the year 2000 can only be supported by advanced reactor systems; and (4) several different breeder reactors could serve in principle as candidates for an indefinitely sustainable source of energy

  1. Nuclear physics

    International Nuclear Information System (INIS)

    Kamal, Anwar

    2014-01-01

    Explains the concepts in detail and in depth. Provides step-by-step derivations. Contains numerous tables and diagrams. Supports learning and teaching with numerous worked examples, questions and problems with answers. Sketches also the historical development of the subject. This textbook explains the experimental basics, effects and theory of nuclear physics. It supports learning and teaching with numerous worked examples, questions and problems with answers. Numerous tables and diagrams help to better understand the explanations. A better feeling to the subject of the book is given with sketches about the historical development of nuclear physics. The main topics of this book include the phenomena associated with passage of charged particles and radiation through matter which are related to nuclear resonance fluorescence and the Moessbauer effect., Gamov's theory of alpha decay, Fermi theory of beta decay, electron capture and gamma decay. The discussion of general properties of nuclei covers nuclear sizes and nuclear force, nuclear spin, magnetic dipole moment and electric quadrupole moment. Nuclear instability against various modes of decay and Yukawa theory are explained. Nuclear models such as Fermi Gas Model, Shell Model, Liquid Drop Model, Collective Model and Optical Model are outlined to explain various experimental facts related to nuclear structure. Heavy ion reactions, including nuclear fusion, are explained. Nuclear fission and fusion power production is treated elaborately.

  2. Nuclear chemistry

    International Nuclear Information System (INIS)

    Vertes, A.; Kiss, I.

    1987-01-01

    This book is an introduction to the application of nuclear science in modern chemistry. The first group of chapters discuss the basic phenomena and concepts of nuclear physics with emphasis on their relation to chemical problems, including the main properties and the composition of atomic nuclei, nuclear reactions, radioactive decay and interactions of radiation with matter. These chapters provide the basis for understanding the following chapters which encompass the wide scope of nuclear chemistry. The methods of the investigation of chemical structure based on the interaction of nuclear radiation with matter including positronium chemistry and other exotic atoms is elaborated in particular detail. Separate chapters are devoted to the use of radioactive tracers, the chemical consequences of nuclear processes (i.e. hot atom chemistry), radiation chemistry, isotope effects and their applications, and the operation of nuclear reactors

  3. Nuclear chemistry

    International Nuclear Information System (INIS)

    Vertes, A.; Kiss, I.

    1987-01-01

    This book is an introduction to the application of nuclear science in modern chemistry. The first group of chapters discuss the basic phenomena and concepts of nuclear physics with emphasis on their relation to chemical problems, including the main properties and the composition of atomic nuclei, nuclear reactions, radioactive decay and interactions of radiation with matter. These chapters provide the basis for understanding the following chapters which encompass the wide scope of nuclear chemistry. The methods of the investigation of chemical structure based on the interaction of nuclear radiation with matter including positronium chemistry and other exotic atoms is elaborated in particular detail. Separate chapters are devoted to the use of radioactive tracers, the chemical consequences of nuclear processes (i.e. hot atom chemistry), radiation chemistry, isotope effects and their applications, and the operation of nuclear reactors. (Auth.)

  4. Nuclear forensics

    International Nuclear Information System (INIS)

    Karadeniz, O.; Guenalp, G.

    2010-01-01

    This review discusses the methodology of nuclear forensics and illicit trafficking of nuclear materials. Nuclear forensics is relatively new scientific branch whose aim it is to read out material inherent from nuclear material. Nuclear forensics investigations have to be considered as part of a comprehensive set of measures for detection,interception, categorization and characterization of illicitly trafficking nuclear material. Prevention, detection and response are the main elements in combating illicit trafficking. Forensics is a key element in the response process. Forensic science is defined as the application of a broad spectrum of sciences to answer questions of interest to the legal system. Besides, in this study we will explain age determination of nuclear materials.

  5. Nuclear fuels

    International Nuclear Information System (INIS)

    Gangwani, Saloni; Chakrabortty, Sumita

    2011-01-01

    Nuclear fuel is a material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned for energy. Nuclear fuels are the most dense sources of energy available. Nuclear fuel in a nuclear fuel cycle can refer to the fuel itself, or to physical objects (for example bundles composed of fuel rods) composed of the fuel material, mixed with structural, neutron moderating, or neutron reflecting materials. Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives. Depending on what a nuclear reactor is fueled with, the actinide composition in the SNF will be different. The following paper will also include the uses. advancements, advantages, disadvantages, various processes and behavior of nuclear fuels

  6. Nuclear networking.

    Science.gov (United States)

    Xie, Wei; Burke, Brian

    2017-07-04

    Nuclear lamins are intermediate filament proteins that represent important structural components of metazoan nuclear envelopes (NEs). By combining proteomics and superresolution microscopy, we recently reported that both A- and B-type nuclear lamins form spatially distinct filament networks at the nuclear periphery of mouse fibroblasts. In particular, A-type lamins exhibit differential association with nuclear pore complexes (NPCs). Our studies reveal that the nuclear lamina network in mammalian somatic cells is less ordered and more complex than that of amphibian oocytes, the only other system in which the lamina has been visualized at high resolution. In addition, the NPC component Tpr likely links NPCs to the A-type lamin network, an association that appears to be regulated by C-terminal modification of various A-type lamin isoforms. Many questions remain, however, concerning the structure and assembly of lamin filaments, as well as with their mode of association with other nuclear components such as peripheral chromatin.

  7. Characterization of germ cell-specific expression of the orphan nuclear receptor, germ cell nuclear factor.

    Science.gov (United States)

    Katz, D; Niederberger, C; Slaughter, G R; Cooney, A J

    1997-10-01

    Nuclear receptors, such as those for androgens, estrogens, and progesterones, control many reproductive processes. Proteins with structures similar to these receptors, but for which ligands have not yet been identified, have been termed orphan nuclear receptors. One of these orphans, germ cell nuclear factor (GCNF), has been shown to be germ cell specific in the adult and, therefore, may also participate in the regulation of reproductive functions. In this paper, we examine more closely the expression patterns of GCNF in germ cells to begin to define spatio-temporal domains of its activity. In situ hybridization showed that GCNF messenger RNA (mRNA) is lacking in the testis of hypogonadal mutant mice, which lack developed spermatids, but is present in the wild-type testis. Thus, GCNF is, indeed, germ cell specific in the adult male. Quantitation of the specific in situ hybridization signal in wild-type testis reveals that GCNF mRNA is most abundant in stage VII round spermatids. Similarly, Northern analysis and specific in situ hybridization show that GCNF expression first occurs in testis of 20-day-old mice, when round spermatids first emerge. Therefore, in the male, GCNF expression occurs postmeiotically and may participate in the morphological changes of the maturing spermatids. In contrast, female expression of GCNF is shown in growing oocytes that have not completed the first meiotic division. Thus, GCNF in the female is expressed before the completion of meiosis. Finally, the nature of the two different mRNAs that hybridize to the GCNF complementary DNA was studied. Although both messages contain the DNA binding domain, only the larger message is recognized by a probe from the extreme 3' untranslated region. In situ hybridization with these differential probes demonstrates that both messages are present in growing oocytes. In addition, the coding region and portions of the 3' untranslated region of the GCNF complementary DNA are conserved in the rat.

  8. Nuclear blackmail and nuclear balance

    International Nuclear Information System (INIS)

    Betts, R.K.

    1987-01-01

    This book raises pointed questions about nuclear saber rattling. More than a dozen cases since the bombing of Hiroshima and Magasaki in which some sort of nuclear threat was used as a sparring technique in tense confrontations are cited. Each incident is described and analyzed. Two theories offered to explain America's use of nuclear threats, the balance of interest theory and the balance of power theory, are contrasted throughout the book. This book helps to fill the gap in the understanding of nuclear weapons and their uses, while pointing out that nuclear bravado could lead to an unintended unleashing of these weapons

  9. The meiosis-specific nuclear passenger protein is required for proper assembly of forespore membrane in fission yeast.

    Science.gov (United States)

    Takaine, Masak; Imada, Kazuki; Numata, Osamu; Nakamura, Taro; Nakano, Kentaro

    2014-10-15

    Sporulation, gametogenesis in yeast, consists of meiotic nuclear division and spore morphogenesis. In the fission yeast Schizosaccharomyces pombe, the four haploid nuclei produced after meiosis II are encapsulated by the forespore membrane (FSM), which is newly synthesized from spindle pole bodies (SPBs) in the cytoplasm of the mother cell as spore precursors. Although the coordination between meiosis and FSM assembly is vital for proper sporulation, the underlying mechanism remains unclear. In the present study, we identified a new meiosis-specific protein Npg1, and found that it was involved in the efficient formation of spores and spore viability. The accumulation and organization of the FSM was compromised in npg1-null cells, leading to the error-prone envelopment of nuclei. Npg1 was first seen as internuclear dots and translocated to the SPBs before the FSM assembled. Genetic analysis revealed that Npg1 worked in conjunction with the FSM proteins Spo3 and Meu14. These results suggest a possible signaling link from the nucleus to the meiotic SPBs in order to associate the onset of FSM assembly with meiosis II, which ensures the successful partitioning of gametic nuclei. © 2014. Published by The Company of Biologists Ltd.

  10. Nuclear energy and nuclear weapons

    International Nuclear Information System (INIS)

    Robertson, J.A.L.

    1983-06-01

    We all want to prevent the use of nuclear weapons. The issue before us is how best to achieve this objective; more specifically, whether the peaceful applications of nuclear energy help or hinder, and to what extent. Many of us in the nuclear industry are working on these applications from a conviction that without peaceful nuclear energy the risk of nuclear war would be appreciably greater. Others, however, hold the opposite view. In discussing the subject, a necessary step in allaying fears is understanding some facts, and indeed facing up to some unpalatable facts. When the facts are assessed, and a balance struck, the conclusion is that peaceful nuclear energy is much more part of the solution to preventing nuclear war than it is part of the problem

  11. Nuclear materials

    International Nuclear Information System (INIS)

    1996-01-01

    In 1998, Nuclear Regulatory Authority of the Slovak Republic (NRA SR) performed 38 inspections, 25 of them were performed in co-operation with IAEA inspectors. There is no fresh nuclear fuel at Bohunice A-1 NPP at present. Fresh fuel of Bohunice V-1 and V-2 NPPs is inspected in the fresh fuel storage.There are 327 fresh fuel assemblies in Mochovce NPP fresh fuel storage. In addition to that, are also 71 small users of nuclear materials in Slovakia. In most cases they use: covers made of depleted uranium for non-destructive works, detection of level in production plants, covers for therapeutical sources at medical facilities. In. 1995, NRA SR issued 4 new licences for nuclear material withdrawal. In the next part manipulation with nuclear materials, spent fuel stores and illegal trafficking in nuclear materials are reported

  12. Nuclear Law

    International Nuclear Information System (INIS)

    Wiesbauer, Bruno

    1978-01-01

    This book is the first attempt of a comprehensive compilation of national Austrian Nuclear Law (Nuclear Liability Act; Radiation protection Act, Radiation Protection Ordinance, Security Control Act, Act on the uses of Nuclear Energy - Zwentendorf Nuclear Power Plant) and the most important international agreements to which Austria is a party. Furthermore, the book contains the most important Nuclear Liability Conventions to which Austria is not yet a party, but which are applicable in neighbouring; the Paris Convention served as a model for the national Nuclear Liability Act and may be used for its interpretation. The author has translated a number of international instruments into German, such as the Expose des Motifs of the Paris Convention. (NEA) [fr

  13. Nuclear nonproliferation

    International Nuclear Information System (INIS)

    Neubert, M.

    1992-01-01

    The following motion was put before the United Kingdom House of Commons on 3rd February 1992 and agreed; that this House, recognising the potential dangers of the rapidly changing world order, welcomes the recent proposals for substantial reductions in nuclear weaponry, the growing support for the non-proliferation treaty and progress in the implementation of the United Nations Security Council Resolutions concerning the dismantling of Iraqi nuclear, chemical and biological capabilities; urges the Government to play their full part in helping the relevant authorities in the Commonwealth of Independent States to dismantle their nuclear devices, to safeguard their nuclear components and to discourage the proliferation of nuclear expertise; and believes it is of the first importance that Britain retains an effective and credible minimum nuclear deterrent as security in a world where there remain many sources of instability. The record of arguments for and against the motion in the debate is presented. (author)

  14. Nuclear energy

    International Nuclear Information System (INIS)

    Panait, A.

    1994-01-01

    This is a general report presenting the section VII entitled Nuclear Power of the National Conference on Energy (CNE '94) held in Neptun, Romania, on 13-16 June 1994. The problems addressed were those relating to electric power produced by nuclear power plant, to heat secondary generation, to quality assurance, to safety, etc. A special attention was paid to the commissioning of the first Romanian nuclear power unit, the Cernavoda-1 reactor of CANDU type. The communications were grouped in four subsections. These were: 1. Quality assurance, nuclear safety, and environmental protection; 2. Nuclear power plant, commissioning, and operation; 3. Nuclear power plant inspection, maintenance, and repairs, heavy water technology; 4. Public opinion education. There were 22 reports, altogether

  15. Nuclear power

    International Nuclear Information System (INIS)

    King, P.

    1990-01-01

    Written from the basis of neutrality, neither for nor against nuclear power this book considers whether there are special features of nuclear power which mean that its development should be either promoted or restrained by the State. The author makes it dear that there are no easy answers to the questions raised by the intervention of nuclear power but calls for openness in the nuclear decision making process. First, the need for energy is considered; most people agree that energy is the power to progress. Then the historicalzed background to the current position of nuclear power is given. Further chapters consider the fuel cycle, environmental impacts including carbon dioxide emission and the greenhouse effect, the costs, safety and risks and waste disposal. No conclusion either for or against nuclear power is made. The various shades of opinion are outlined and the arguments presented so that readers can come to their own conclusions. (UK)

  16. Nuclear power

    International Nuclear Information System (INIS)

    Porter, Arthur.

    1980-01-01

    This chapter of the final report of the Royal Commission on Electric Power Planning in Ontario updates its interim report on nuclear power in Ontario (1978) in the light of the Three Mile Island accident and presents the commission's general conclusions and recommendations relating to nuclear power. The risks of nuclear power, reactor safety with special reference to Three Mile Island and incidents at the Bruce generating station, the environmental effects of uranium mining and milling, waste management, nuclear power economics, uranium supplies, socio-political issues, and the regulation of nuclear power are discussed. Specific recommendations are made concerning the organization and public control of Ontario Hydro, but the commission concluded that nuclear power is acceptable in Ontario as long as satisfactory progress is made in the disposal of uranium mill tailings and spent fuel wastes. (LL)

  17. Nuclear astrophysics

    International Nuclear Information System (INIS)

    Haxton, W.C.

    1992-01-01

    The problem of core-collapse supernovae is used to illustrate the many connections between nuclear astrophysics and the problems nuclear physicists study in terrestrial laboratories. Efforts to better understand the collapse and mantle ejection are also motivated by a variety of interdisciplinary issues in nuclear, particle, and astrophysics, including galactic chemical evolution, neutrino masses and mixing, and stellar cooling by the emission of new particles. The current status of theory and observations is summarized

  18. Nuclear physics

    International Nuclear Information System (INIS)

    Patel, S.B.

    1991-01-01

    This book is a simple and direct introduction to the tools of modern nuclear physics, both experimental and mathematical. Emphasizes physical intuition and illuminating analogies, rather than formal mathematics. Topics covered include particle accelerators, radioactive series, types of nuclear reactions, detection of the neutrino, nuclear isomerism, binding energy of nuclei, fission chain reactions, and predictions of the shell model. Each chapter contains problems and illustrative examples. Pre-requisites are calculus and elementary vector analysis

  19. Nuclear energy

    International Nuclear Information System (INIS)

    Hesketh, Ross.

    1985-01-01

    The subject is treated under the headings: nuclear energy -what is it; fusion (principles; practice); fission (principles); reactor types and systems (fast (neutron) reactors as breeders; fast reactors; thermal reactors; graphite-moderated thermal reactors; the CANDU reactor; light water reactors - the BWR and the PWR); the nuclear fuel cycle (waste storage; fuel element manufacture; enrichment processes; uranium mining); safety and risk assessment; the nuclear power industry and the economy (regulating authorities; economics; advantages and disadvantages). (U.K.)

  20. Nuclear Asia

    National Research Council Canada - National Science Library

    Ferguson, Joseph; Tarleton, Gael

    2004-01-01

    .... This event was an opportunity for policy makers, security analysts, nuclear scientists and engineers, regional experts, and military planners to share perspectives and identify those issues requiring...

  1. Nuclear cardiology

    International Nuclear Information System (INIS)

    Fish, M.B.

    2002-01-01

    Recent advances in nuclear medicine instrumentation and software, including myocardial perfusion imaging, offer increased accuracy in the detection, diagnosis and prognosis of coronary artery disease. (orig.)

  2. Nuclear medicine

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    The area of nuclear medicine, the development of artificially produced radioactive isotopes for medical applications, is relatively recent. Among the subjects covered in a lengthy discussion are the following: history of development; impact of nuclear medicine; understanding the most effective use of radioisotopes; most significant uses of nuclear medicine radioimmunoassays; description of equipment designed for use in the field of nuclear medicine (counters, scanning system, display systems, gamma camera); description of radioisotopes used and their purposes; quality control. Numerous historical photographs are included. 52 refs

  3. Nuclear Law

    International Nuclear Information System (INIS)

    Pascal, Maurice.

    1979-01-01

    This book on nuclear law is the first of a series of analytical studies to be published by the French Energy Commission (CEA) concerning all the various nuclear activities. It describes national and international legislation applicable in France covering the following main sectors: the licensing procedure for nuclear installations, the law of the sea and nuclear law, the legal system governing radioisotopes, the transport of radioactive materials, third party liability and insurance and radiation protection. In each chapter, the overall analysis is supplemented by the relevant regulatory texts and by organisation charts in annex. (NEA) [fr

  4. Nuclear Safety

    Energy Technology Data Exchange (ETDEWEB)

    Silver, E G [ed.

    1989-01-01

    This document is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated.

  5. Nuclear power

    International Nuclear Information System (INIS)

    Bupp, I.C.

    1991-01-01

    Is a nuclear power renaissance likely to occur in the United States? This paper investigates the many driving forces that will determine the answer to that question. This analysis reveals some frequently overlooked truths about the current state of nuclear technology: An examination of the issues also produces some noteworthy insights concerning government regulations and related technologies. Public opinion will play a major role in the unfolding story of the nuclear power renaissance. Some observers are betting that psychological, sociological, and political considerations will hod sway over public attitudes. Others wager that economic and technical concerns will prevail. The implications for the nuclear power renaissance are striking

  6. Meiosis gene inventory of four ciliates reveals the prevalence of a synaptonemal complex-independent crossover pathway.

    Science.gov (United States)

    Chi, Jingyun; Mahé, Frédéric; Loidl, Josef; Logsdon, John; Dunthorn, Micah

    2014-03-01

    To establish which meiosis genes are present in ciliates, and to look for clues as to which recombination pathways may be treaded by them, four genomes were inventoried for 11 meiosis-specific and 40 meiosis-related genes. We found that the set of meiosis genes shared by Tetrahymena thermophila, Paramecium tetraurelia, Ichthyophthirius multifiliis, and Oxytricha trifallax is consistent with the prevalence of a Mus81-dependent class II crossover pathway that is considered secondary in most model eukaryotes. There is little evidence for a canonical class I crossover pathway that requires the formation of a synaptonemal complex (SC). This gene inventory suggests that meiotic processes in ciliates largely depend on mitotic repair proteins for executing meiotic recombination. We propose that class I crossovers and SCs were reduced sometime during the evolution of ciliates. Consistent with this reduction, we provide microscopic evidence for the presence only of degenerate SCs in Stylonychia mytilus. In addition, lower nonsynonymous to synonymous mutation rates of some of the meiosis genes suggest that, in contrast to most other nuclear genes analyzed so far, meiosis genes in ciliates are largely evolving at a slower rate than those genes in fungi and animals.

  7. Influence of serotonin on the action of melatonin in MIH-induced meiotic resumption in the oocytes of carp Catla catla.

    Science.gov (United States)

    Chattoraj, Asamanja; Seth, Mohua; Maitra, Saumen Kumar

    2008-07-01

    The influences of serotonin (5-hydroxytryptamine) on the action of melatonin (N-acetyl-5-methoxytryptamine) in MIH (maturation inducing hormone)-induced meiotic resumption were evaluated in the oocytes of carp Catla catla using an in vitro model. Oocytes from gravid female carp were isolated and incubated separately in Medium 199 containing either (a) only melatonin (MEL; 100 pg/mL), or (b) only serotonin (SER; 100 pg/mL), or (c) only MIH (1 microg/mL), or (d) MEL and MIH (e) or MEL (4 h before) and MIH, or (f) MEL and SER, (g) or SER and MIH, or (h) SER (4 h before) and MIH, or (i) luzindole (L-antagonist of MEL receptors; 10 microM) and MEL, or (j) MEL, L and MIH, or (k) MEL (4 h before), L and MIH, or (l) metoclopramide hydrochloride (M-antagonist of SER receptors; 10 microM) and SER, or (m) M, MEL, SER, or (n) M, SER and MIH, or (o) M, SER (4 h before) and MIH, or (p) M, MEL SER and MIH, or (q) MEL, L, SER and M, or (r) MEL, L, SER, M, and MIH, or (s) MEL, SER, L and MIH. Control oocytes were incubated in the medium alone. Oocytes were incubated for 4, or 8, or 12, or 16 h and effects were evaluated by considering the rate (%) of germinal vesicle breakdown (GVBD). At the end of 16 h incubation, 93.24+/-1.57% oocytes underwent GVBD following incubation with only MIH, while incubation with only MEL or only SER resulted in 77.15+/-1.91% or 14.42+/-0.43% GVBD respectively. Interestingly, incubation with MEL 4 h prior to addition of MIH in the medium, led to an accelerated rate of GVBD (92.58+/-1.10% at 12 h). In contrast, SER, irrespective of its time of application in relation to MIH, resulted in a maximum of 64.57+/-0.86% GVBD. While L was found to reduce the stimulatory actions of melatonin, M suppressed the inhibitory actions of serotonin. In each case, both electrophoretic and immunoblot studies revealed that the rate of GVBD was associated with the rate of formation of maturation promoting factor (a complex of two proteins: a regulatory component--cyclin B

  8. The Meiotic Recombination Activator PRDM9 Trimethylates Both H3K36 and H3K4 at Recombination Hotspots In Vivo.

    Science.gov (United States)

    Powers, Natalie R; Parvanov, Emil D; Baker, Christopher L; Walker, Michael; Petkov, Petko M; Paigen, Kenneth

    2016-06-01

    In many mammals, including humans and mice, the zinc finger histone methyltransferase PRDM9 performs the first step in meiotic recombination by specifying the locations of hotspots, the sites of genetic recombination. PRDM9 binds to DNA at hotspots through its zinc finger domain and activates recombination by trimethylating histone H3K4 on adjacent nucleosomes through its PR/SET domain. Recently, the isolated PR/SET domain of PRDM9 was shown capable of also trimethylating H3K36 in vitro, raising the question of whether this reaction occurs in vivo during meiosis, and if so, what its function might be. Here, we show that full-length PRDM9 does trimethylate H3K36 in vivo in mouse spermatocytes. Levels of H3K4me3 and H3K36me3 are highly correlated at hotspots, but mutually exclusive elsewhere. In vitro, we find that although PRDM9 trimethylates H3K36 much more slowly than it does H3K4, PRDM9 is capable of placing both marks on the same histone molecules. In accord with these results, we also show that PRDM9 can trimethylate both K4 and K36 on the same nucleosomes in vivo, but the ratio of K4me3/K36me3 is much higher for the pair of nucleosomes adjacent to the PRDM9 binding site compared to the next pair further away. Importantly, H3K4me3/H3K36me3-double-positive nucleosomes occur only in regions of recombination: hotspots and the pseudoautosomal (PAR) region of the sex chromosomes. These double-positive nucleosomes are dramatically reduced when PRDM9 is absent, showing that this signature is PRDM9-dependent at hotspots; the residual double-positive nucleosomes most likely come from the PRDM9-independent PAR. These results, together with the fact that PRDM9 is the only known mammalian histone methyltransferase with both H3K4 and H3K36 trimethylation activity, suggest that trimethylation of H3K36 plays an important role in the recombination process. Given the known requirement of H3K36me3 for double strand break repair by homologous recombination in somatic cells, we

  9. Nuclear stress test

    Science.gov (United States)

    ... Persantine stress test; Thallium stress test; Stress test - nuclear; Adenosine stress test; Regadenoson stress test; CAD - nuclear stress; Coronary artery disease - nuclear stress; Angina - nuclear ...

  10. Nuclear physics for nuclear fusion

    International Nuclear Information System (INIS)

    Li Xingzhong; Liu Bin; Wei Qingming; Ren Xianzhe

    2004-01-01

    The D-T fusion cross-section is calculated using quantum mechanics with the model of square nuclear potential well and Coulomb potential barrier. The agreement between ENDF data and the theoretically calculated results is well in the range of 0.2-280 keV. It shows that the application of Breit-Wigner formula is not suitable for the case of the light nuclei fusion reaction. When this model is applied to the nuclear reaction between the charged particles confined in a lattice, it explains the 'abnormal phenomena'. It implies a prospect of nuclear fusion energy without strong nuclear radiations

  11. Nuclear installations

    International Nuclear Information System (INIS)

    2001-01-01

    This document presents the fulfilling of the Brazilian obligations under the Convention on Nuclear Safety. The Chapter 2 of the document contains some details about the existing Brazilian nuclear installations. Also, safety improvements at Angra 1 and aspects of Angra 2 and 3 are reported

  12. Nuclear safety

    International Nuclear Information System (INIS)

    1991-02-01

    This book reviews the accomplishments, operations, and problems faced by the defense Nuclear Facilities Safety Board. Specifically, it discusses the recommendations that the Safety Board made to improve safety and health conditions at the Department of Energy's defense nuclear facilities, problems the Safety Board has encountered in hiring technical staff, and management problems that could affect the Safety Board's independence and credibility

  13. Nuclear violence

    International Nuclear Information System (INIS)

    Mullen, R.K.

    1987-01-01

    A great deal of attention has been paid in the past decade or so to the characteristics of terrorists and their apparent goals and objectives, capabilities, and evolving strategy and tactics with respect to nuclear terrorism. In contrast, little has been said about the procedural aspects of nuclear terrorism, and even less about the way in which such endeavors can fail. This latter omission is important because it bears directly on the ability to evaluate credibly the potential for nuclear terrorism. Here, the author addresses the requirements inherent in acquiring a nuclear explosive capability by three routes: separation of plutonium from irradiated light or heavy water reactor (LWR or HWR) fuel, processing, or use of separated fissile material, and theft of a nuclear weapon. In addition, he deals with other potential acts of nuclear terrorism: sabotage of power reactors, uranium enrichment facilities and spent nuclear fuel in transport, and dispersal of radioactive materials, in particular, plutonium. He specifically does not look at the design or production of a nuclear weapon. Finally, the discussion here assumes that the terrorist is subnational; that is, a nation is not involved. Also, the discussion of subnational participation does not address the possibility of collusion with insiders

  14. Nuclear installations

    International Nuclear Information System (INIS)

    1998-01-01

    This document presents the fulfilling of the Brazilian obligations under the Convention on Nuclear Safety. The Chapter 2 of the document contains some details about the existing Brazilian nuclear installations. Also, safety improvements at Angra 1 and aspects of Angra 2 and 3 are reported

  15. Nuclear power

    International Nuclear Information System (INIS)

    Abd Khalik Wood

    2003-01-01

    This chapter discuss on nuclear power and its advantages. The concept of nucleus fission, fusion, electric generation are discussed in this chapter. Nuclear power has big potential to become alternative energy to substitute current conventional energy from coal, oil and gas

  16. Nuclear energy

    International Nuclear Information System (INIS)

    1978-01-01

    This brochure is intended as a contribution to a better and more general understanding of one of the most urgent problems of present society. Emphasis is laid on three issues that are always raised in the nuclear debate: 1) Fuel cycle, 2) environmental effects of nuclear power plants, 3) waste disposal problems. (GL) [de

  17. Nuclear pollution

    International Nuclear Information System (INIS)

    Ramade, Francois

    1979-01-01

    In this chapter devoted to nuclear pollution the following topics were studied: fundamentals of radiobiology (ecological importance of the various radioisotopes, biological effects of ionizing radiations); ecological effects of radioactive fallout (contamination of atmosphere, terrestrial ecosystems, oceans). The electronuclear industry and its environmental impact. PWR type reactors, fuel reprocessing plants, contamination of trophic chains by radionuclides released in the environment from nuclear installations [fr

  18. Nuclear lifetimes

    International Nuclear Information System (INIS)

    Caraca, J.M.G.

    1976-01-01

    The importance of the results obtained in experiments of measurement of lifetimes for a detailed knowledge of nuclear structure is referred. Direct methods of measurement of nuclear lifetimes are described, namely, electronic methods, recoil-distance method, doppler shift atenuation method and blocking-method. A brief reference is made to indirect methods for measurement of life-times

  19. Nuclear facts

    International Nuclear Information System (INIS)

    1982-01-01

    The subject is discussed as follows: the case for using nuclear energy (Britain's energy needs; energy policy); safety; transport of spent fuel; radiation (natural radioactivity); environment (land use of nuclear power plants; storage and disposal of radioactive wastes). (U.K.)

  20. Nuclear measurements

    International Nuclear Information System (INIS)

    Schenkel, R.

    2005-01-01

    Nuclear measurements play a fundamental role in the development of nuclear technology and the assurance of its peaceful use. They are also required in many non-power nuclear applications such as in nuclear medicine, agriculture, environmental protection, etc. This presentation will show examples of most recent advances in measurement methodology or technology in the areas described below. The Generation IV International Forum has selected six innovative reactor systems as candidates for a next generation of sustainable, economic and safe nuclear energy systems. The choice of the best options relies heavily on the availability of accurate nuclear data that can only be obtained, in an international effort, using highly specialised facilities. Significant efforts are being directed towards the partitioning and transmutation of highly active nuclear waste. Different concepts involving fast reactors or accelerator-driven systems are being studied in view of their transmutation capabilities. State of the art equipment has been developed to assess basic properties of nuclear fuel at very high burn-up; some fine examples of this work will be shown. Physical and chemical methods play a crucial role in the detection and identification of radioisotopes used in various stages of the nuclear fuel cycle. Radiation measurement techniques are used, for example, to monitor the quantities of uranium, plutonium and other actinide elements in fuel enrichment and reprocessing facilities. Another field of application of physical and chemical methods is the characterisation of nuclear material seized from illicit trafficking. Seized material has to be analysed in order to obtain clues on its origin and intended use and to prevent diversion of nuclear material from the same source in the future. A recent highlight in basic physics relates to nuclear fission and transmutation with high intensity lasers. Ultra-fast high intensity lasers can produce high energy (tens of MeV) photons through