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Emily P Dawson, Denise G Lanza, Nicholas J Webster, Susan M Benton, Isao Suetake, Jason D Heaney
Testicular teratomas result from anomalies in embryonic germ cell development. In 129 inbred mice, teratoma initiation coincides with germ cell sex-specific differentiation and the mitotic-meiotic switch: XX and XY germ cells repress pluripotency, XX germ cells initiate meiosis, and XY germ cells activate male-specific differentiation and mitotic arrest. Here, we report that expression of Nanos2 , a gene that is crucial to male sex specification, is delayed in teratoma-susceptible germ cells. Decreased expression of Nanos2 was found to be due, in part, to the Nanos2 allele present in 129 mice...
March 15, 2018: Development
Sheena L P Regan, Phil G Knight, John L Yovich, Yee Leung, Frank Arfuso, Arun Dharmarajan
Primordial germ cells migrate to the fetal gonads and proliferate during gestation to generate a fixed complement of primordial follicles, the so-called ovarian reserve. Primordial follicles comprise an oocyte arrested at the diplotene stage of meiosis, surrounded by a layer of pregranulosa cells. Activation of primordial follicles to grow beyond this arrested stage is of particular interest because, once activated, they are subjected to regulatory mechanisms involved in growth, selection, maturation, and ultimately, ovulation or atresia...
2018: Vitamins and Hormones
Sabrina Z Jan, Aldo Jongejan, Cindy M Korver, Saskia K M van Daalen, Ans M M van Pelt, Sjoerd Repping, Geert Hamer
To prevent chromosomal aberrations to be transmitted to the offspring, strict meiotic checkpoints are in place to remove aberrant spermatocytes. However, in about 1% of all males these checkpoints cause complete meiotic arrest leading to azoospermia and subsequent infertility. We here unravel two clearly distinct meiotic arrest mechanisms that act during the prophase of human male meiosis. Type I arrested spermatocytes display severe asynapsis of the homologous chromosomes, disturbed XY-body formation and increased expression of the Y-chromosome encoded gene ZFY and seem to activate a DNA damage pathway leading to induction of p63, possibly causing spermatocyte apoptosis...
March 14, 2018: Development
Ganga Anil Kumar, Kuppuswamy Subramaniam
Pairing of homologous chromosomes is essential for genetic recombination during gametogenesis. In many organisms, chromosome ends are attached to cytoplasmic dynein, and dynein-driven chromosomal movements facilitate the pairing process. Factors that promote / control the cytoskeletal tethering of chromosomes are largely unknown. Here, we show that the conserved RNA-binding protein PUF-8 facilitates the tethering and pairing processes in the C. elegans germline by promoting proteasome activity. We have isolated a hypomorphic allele of pas-1 , which encodes a proteasome core subunit, and find that the homologous chromosomes fail to pair in the puf-8; pas-1 double mutant due to failure of chromosome tethering...
March 14, 2018: Development
Sona Gregorova, Vaclav Gergelits, Irena Chvatalova, Tanmoy Bhattacharyya, Barbora Valiskova, Vladana Fotopulosova, Petr Jansa, Diana Wiatrowska, Jiri Forejt
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 between two mouse subspecies. But within species Prdm9 determines the sites of programmed DNA double-strand breaks 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 rescue male fertility...
March 14, 2018: ELife
Diego Hojsgaard
Polyploid genomes evolve and follow a series of dynamic transfigurations along with adaptation and speciation. The initial formation of a new polyploid individual within a diploid population usually involves a triploid bridge, a two-step mechanism of cell fusions between ubiquitous (reduced) and rare (unreduced) gametes. The primary fusion event creates an intermediate triploid individual with unbalanced genome sets, a situation of genomic-shock characterized by gene expression dysregulation, high dosage sensitivity, disturbed cell divisions, and physiological and reproductive attributes drastically altered...
2018: Frontiers in Plant Science
Xiao Wang, Huarong Wang, Wei Liu, Zhiyuan Zhang, Yanhao Zhang, Wenqiang Zhang, Zijiang Chen, Guoliang Xia, Chao Wang
Polycystic ovary syndrome (PCOS), which is characterized by hyperandrogenism, is a complex endocrinopathy that affects the fertility of 9%-18% of reproductive-age women. However, the exact mechanism of PCOS, especially hyperandrogen-induced anovulation, is largely unknown to date. Physiologically, the natriuretic peptide type C/natriuretic peptide receptor 2 (CNP/NPR2) system is essential for sustaining oocyte meiotic arrest until the preovulatory luteinizing hormone (LH) surge. We therefore hypothesized that the CNP/NPR2 system is also involved in PCOS and contributes to arresting oocyte meiosis and ovulation...
March 13, 2018: Clinical Science (1979-)
Dal-Hoe Koo, William T Molin, Christopher A Saski, Jiming Jiang, Karthik Putta, Mithila Jugulam, Bernd Friebe, Bikram S Gill
Gene amplification has been observed in many bacteria and eukaryotes as a response to various selective pressures, such as antibiotics, cytotoxic drugs, pesticides, herbicides, and other stressful environmental conditions. An increase in gene copy number is often found as extrachromosomal elements that usually contain autonomously replicating extrachromosomal circular DNA molecules (eccDNAs). Amaranthus palmeri , a crop weed, can develop herbicide resistance to glyphosate [ N -(phosphonomethyl) glycine] by amplification of the 5-enolpyruvylshikimate-3-phosphate synthase ( EPSPS ) gene, the molecular target of glyphosate...
March 12, 2018: Proceedings of the National Academy of Sciences of the United States of America
Miriam Ratliff, Katherine L Hill-Harfe, Elizabeth J Gleason, Huiping Ling, Tim L Kroft, Steven W L'Hernault
Covalent attachment of ubiquitin to substrate proteins changes their function or marks them for proteolysis, and specificity of ubiquitin attachment is mediated by the numerous E3 ligases encoded by animals. Mind Bomb is an essential E3 ligase during Notch pathway signaling in insects and vertebrates. While C. elegans encodes a Mind Bomb homolog ( mib-1 ), it has never been recovered in the extensive Notch suppressor/enhancer screens that have identified numerous pathway components. Here, we show that C. elegans mib-1 null mutants have a spermatogenesis-defective phenotype that results in a heterogeneous mixture of arrested spermatocytes, defective spermatids and motility-impaired spermatozoa...
March 12, 2018: Genetics
Kyuha Choi, Xiaohui Zhao, Andrew J Tock, Christophe Lambing, Charles J Underwood, Thomas J Hardcastle, Heïdi Serra, Juhyun Kim, Hyun Seob Cho, Jaeil Kim, Piotr A Ziolkowski, Nataliya E Yelina, Ildoo Hwang, Robert A Martienssen, Ian R Henderson
Meiotic recombination initiates from DNA double-strand breaks (DSBs) generated by SPO11 topoisomerase-like complexes. Meiotic DSB frequency varies extensively along eukaryotic chromosomes, with hotspots controlled by chromatin and DNA sequence. To map meiotic DSBs throughout a plant genome, we purified and sequenced Arabidopsis thaliana SPO11-1-oligonucleotides. SPO11-1-oligos are elevated in gene promoters, terminators, and introns, which is driven by AT-sequence richness that excludes nucleosomes and allows SPO11-1 access...
March 12, 2018: Genome Research
Charles J Underwood, Kyuha Choi, Christophe Lambing, Xiaohui Zhao, Heïdi Serra, Filipe Borges, Joe Simorowski, Evan Ernst, Yannick Jacob, Ian R Henderson, Robert A Martienssen
Eukaryotic centromeres contain the kinetochore, which connects chromosomes to the spindle allowing segregation. During meiosis, centromeres are suppressed for inter-homolog crossover, as recombination in these regions can cause chromosome missegregation and aneuploidy. Plant centromeres are surrounded by transposon-dense pericentromeric heterochromatin that is epigenetically silenced by histone 3 lysine 9 dimethylation (H3K9me2), and DNA methylation in CG and non-CG sequence contexts. However, the role of these chromatin modifications in control of meiotic recombination in the pericentromeres is not fully understood...
March 12, 2018: Genome Research
Yong-Zhen Huang, Li-Na Qian, Jian Wang, Chun-Lei Zhang, Xing-Tang Fang, Chu-Zhao Lei, Xian-Yong Lan, Yun Ma, Yue-Yu Bai, Feng-Peng Lin, Hong Chen
The α-adducin (ADD1) is a subunit of adducin which is a cytoskeleton heterodimeric protein. Adducin participates in oocytes chromosome meiosis of mice, prompting adducin has an effect on embryonic development. Adducin gene mutation has significantly functional change. So the present study was to identify and characterize polymorphisms within the coding region of the bovine ADD1 gene among different cattle breeds. Here, 11 novel single nucleotide polymorphisms (SNPs 1-11) were identified by DNA sequencing and polymerase chain reaction-single stranded conformational polymorphism, there were one synonymous mutation in exon 1 (SNP1); four missense mutations in exons 4, 7, and 8 (SNPs 3-6); and six mutations in introns 4, 12, 13, and 14 (SNPs 2, 7-10)...
March 12, 2018: Animal Biotechnology
Kevin Brick, Florencia Pratto, Chi-Yu Sun, Rafael D Camerini-Otero, Galina Petukhova
The repair of programmed DNA double-strand breaks (DSBs) physically tethers homologous chromosomes in meiosis to allow for accurate segregation through meiotic cell divisions. This process, known as recombination, also results in the exchange of alleles between parental chromosomes and contributes to genetic diversity. In mammals, meiotic DSBs occur predominantly in a small fraction of the genome, at sites known as hotspots. Studies of the formation and repair of meiotic DSBs in mammals are challenging, because few cells undergo meiotic DSB formation at a given time...
2018: Methods in Enzymology
Hardeep Kaur, Jasvinder S Ahuja, Michael Lichten
Proteins with potential roles in meiotic recombination often have essential or important functions during the mitotic cell cycle. In addition, proteins may have different functions at different times during meiosis. In such cases, it can be challenging to precisely determine protein function during meiosis using null or hypomorphic mutants. One example is the Sgs1-Top3-Rmi1 helicase-decatenase complex, which is required for normal vegetative growth and genome stability. In such cases, conditional loss-of-function mutants can be useful...
2018: Methods in Enzymology
Eleni P Mimitou, Scott Keeney
During meiosis, the specialized cell division giving rise to gametes, numerous DNA double-strand breaks (DSBs) are introduced at multiple places throughout the genome by the topoisomerase-like protein Spo11. Homologous recombination, a highly conserved DSB repair pathway, is employed for their repair and ensures the formation of chiasmata and the proper segregation of homologous chromosomes. In the initial steps of recombination, end resection takes place, wherein Spo11 is endonucleolytically released and the 5'-terminal strands of each DSB are exonucleolytically processed, exposing the ssDNA necessary to identify a homologous repair template...
2018: Methods in Enzymology
Shannon Owens, Shangming Tang, Neil Hunter
Homologous recombination is fundamental to sexual reproduction, facilitating accurate segregation of homologous chromosomes at the first division of meiosis, and creating novel allele combinations that fuel evolution. Following initiation of meiotic recombination by programmed DNA double-strand breaks (DSBs), homologous pairing and DNA strand exchange form joint molecule (JM) intermediates that are ultimately resolved into crossover and noncrossover repair products. Physical monitoring of the DNA steps of meiotic recombination in Saccharomyces cerevisiae (budding yeast) cultures undergoing synchronous meiosis has provided seminal insights into the molecular basis of meiotic recombination and affords a powerful tool for dissecting the molecular roles of recombination factors...
2018: Methods in Enzymology
Liangyu Zhang, Simone Köhler, Regina Rillo-Bohn, Abby F Dernburg
During meiosis, each pair of homologous chromosomes typically undergoes at least one crossover (crossover assurance), but these exchanges are strictly limited in number and widely spaced along chromosomes (crossover interference). The molecular basis for this chromosome-wide regulation remains mysterious. A family of meiotic RING finger proteins has been implicated in crossover regulation across eukaryotes. Caenorhabditis elegans expresses four such proteins, of which one (ZHP-3) is known to be required for crossovers...
March 9, 2018: ELife
Ifeyinwa Onyemaobi, Habtamu Ayalew, Hui Liu, Kadambot H M Siddique, Guijun Yan
Grain number is a major trait for wheat yield under dryland farming. An International Triticeae Mapping Initiative (ITMI) mapping population comprising 105 recombinant inbred lines (RIL) developed from a cross between a Synthetic hexaploid wheat (Triticum aestivum) 'W7984' and a spring wheat variety 'Opata M85' was used to identify quantitative trait loci (QTL) associated with grain number per spike under two treatment conditions, normal watering and water stress during meiosis. Two major QTL for grain number per spike on the main stem Q...
2018: PloS One
Radka Symonová, Iva Vrbová, Dunja K Lamatsch, Jürgen Paar, Renate Matzke-Karasz, Olivier Schmit, Koen Martens, Stefan Müller
Transitions from sexual to asexual reproduction are often associated with polyploidy and increased chromosomal plasticity in asexuals. We investigated chromosomes in the freshwater ostracod species Eucypris virens (Jurine, 1820), where sexual, asexual and mixed populations can be found. Our initial karyotyping of multiple populations from Europe and North Africa, both sexual and asexual, revealed a striking variability in chromosome numbers. This would suggest that chromosomal changes are likely to be accelerated in asexuals because the constraints of meiosis are removed...
March 8, 2018: Genes
Arunika Das, Jeffry Cesario, Anna Maria Hinman, Janet K Jang, Kim S McKim
Bipolar spindle assembly occurs in the absence of centrosomes in the oocytes of most organisms. In the absence of centrosomes in Drosophila oocytes, we have proposed that the kinesin 6 Subito, a MKLP-2 homolog, is required for establishing spindle bipolarity and chromosome biorientation by assembling a robust central spindle during prometaphase I. Although the functions of the conserved motor domains of kinesins is well studied, less is known about the contribution of the poorly conserved N- and C- terminal domains to motor function...
March 7, 2018: G3: Genes—Genomes—Genetics
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