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mitosis , meiosis

Delphine Mieulet, Sylvie Jolivet, Maud Rivard, Laurence Cromer, Aurore Vernet, Pauline Mayonove, Lucie Pereira, Gaëtan Droc, Brigitte Courtois, Emmanuel Guiderdoni, Raphael Mercier
Introduction of clonal reproduction through seeds (apomixis) in crops has the potential to revolutionize agriculture by allowing self-propagation of any elite variety, in particular F1 hybrids. In the sexual model plant Arabidopsis thaliana synthetic clonal reproduction through seeds can be artificially implemented by (i) combining three mutations to turn meiosis into mitosis (MiMe) and (ii) crossing the obtained clonal gametes with a line expressing modified CENH3 and whose genome is eliminated in the zygote...
October 21, 2016: Cell Research
Suzanne Vigneron, Perle Robert, Khaled Hached, Lena Sundermann, Sophie Charrasse, Jean-Claude Labbé, Anna Castro, Thierry Lorca
Entry into mitosis requires the coordinated activation of various protein kinases and phosphatases that together activate sequential signaling pathways allowing entry, progression and exit of mitosis. The limiting step is thought to be the activation of the mitotic Cdk1-cyclin B kinase. However, this model has recently evolved with new data showing that in addition to the Cdk1-cyclin B complex, Greatwall (Gwl) kinase is also required to enter into and maintain mitosis. This new concept proposes that entry into mitosis is now based on the combined activation of both kinases Cdk1-cyclin B and Gwl, the former promoting massive phosphorylation of mitotic substrates and the latter inhibiting PP2A-B55 phosphatase responsible for dephosphorylation of these substrates...
2016: International Journal of Developmental Biology
Zhanzhan Xu, Yu Zhou, Yexuan Cao, Thi Lan Anh Dinh, Jing Wan, Min Zhao
Ovarian cancer is the first leading cause of mortality in gynecological malignancies. To identify key genes and microRNAs in ovarian cancer, mRNA microarray dataset GSE36668, GSE18520, GSE14407 and microRNA dataset GSE47841 were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and microRNAs (DEMs) were obtained using GEO2R. Functional and pathway enrichment analysis were performed for DEGs using DAVID database. Protein-protein interaction (PPI) network was established by STRING and visualized by Cytoscape...
November 2016: Medical Oncology
Maryam Ataeian, Justus Tegha-Dunghu, Donna G Curtis, Ellen M E Sykes, Ashkan Nozohourmehrabad, Megha Bajaj, Karen Cheung, Martin Srayko
In most animals, female meiosis completes only after fertilization. Sperm entry has been implicated in providing a signal for the initiation of the final meiotic processes, however, a maternal component required for this process has not been previously identified. We report the characterization of a novel family of three highly similar paralogs (memi-1, memi-2, memi-3) that encode oocyte-specific proteins. A hypermorphic mutation memi-1(sb41) results in failure to exit female meiosis II properly, however, loss of all three paralogs results in a "skipped meiosis II" phenotype...
October 11, 2016: Genetics
Stephen D Thorpe, Myriam Charpentier
The last decade has seen rapid advances in our understanding of the proteins of the nuclear envelope, which have multiple roles including positioning the nucleus, maintaining its structural organisation, and in events ranging from mitosis and meiosis to chromatin positioning and gene expression. Diverse new and stimulating results relating to nuclear organisation and genome function from across kingdoms were presented in a session stream entitled "Dynamic Organisation of the Nucleus" at this year's Society of Experimental Biology (SEB) meeting in Brighton, UK (July 2016)...
October 7, 2016: Nucleus
Aimee Jaramillo-Lambert, Amy S Fabritius, Tyler J Hansen, Harold E Smith, Andy Golden
Topoisomerase II alleviates DNA entanglements that are generated during mitotic DNA replication, transcription, and sister chromatid separation. In contrast to mitosis, meiosis has two rounds of chromosome segregation following one round of DNA replication. In meiosis II, sister chromatids segregate from each other similar to mitosis. Meiosis I, on the other hand, segregates homologs, which requires pairing, synapsis, and recombination. The exact role that topoisomerase II plays during meiosis is unknown. In a screen re-examining Caenorhabditis elegant legacy mutants isolated thirty years ago, we identified a novel allele of the gene encoding topoisomerase II, top-2(it7) In this study, we demonstrate that top-2(it7) males produce dead embryos, even when fertilizing wild-type oocytes...
October 5, 2016: Genetics
HaiYang Wang, Yu-Jin Jo, Tian-Yi Sun, Suk Namgoong, Xiang-Shun Cui, Jeong Su Oh, Nam-Hyung Kim
To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) delays anaphase onset by preventing the premature activation of anaphase-promoting complex/cyclosome (APC/C) until all kinetochores are attached to the spindle. Although an escape from mitosis in the presence of unsatisfied SAC has been shown in several cancer cells, it has not been reported in oocyte meiosis. Here, we show that CDK7 activity is required to prevent a bypass of SAC during meiosis I in mouse oocytes. Inhibition of CDK7 using THZ1 accelerated the first meiosis, leading to chromosome misalignment, lag of chromosomes during chromosome segregation, and a high incidence of aneuploidy...
October 1, 2016: Biochimica et Biophysica Acta
Xiaoxin Dai, Mianqun Zhang, Yajuan Lu, Yilong Miao, Changyin Zhou, Bo Xiong
The Cullin9 gene encodes a putative E3 ligase that serves a wide variety of biological functions in mitosis, whereas its roles in meiosis have not yet clearly defined. Here, we report that Cullin9 accumulates on the spindle apparatus and colocalizes with the microtubule fibers during mouse oocyte meiotic maturation. Depletion of Cullin9 by morpholino microinjection results in a remarkably higher rate of disorganized spindles and misaligned chromosomes in oocytes, which is coupled with the impaired kinetochore-microtubule attachments...
September 24, 2016: Biochimica et Biophysica Acta
Kyeoung-Hwa Kim, Ji-Hoon Park, Eun-Young Kim, Jung-Jae Ko, Kyung-Soon Park, Kyung-Ah Lee
Rad51 is a conserved eukaryotic protein that mediates the homologous recombination repair of DNA double-strand breaks that occur during mitosis and meiosis. In addition, Rad51 promotes mitochondrial DNA synthesis when replication stress is increased. Rad51 also regulates cell cycle progression by preserving the G2/M transition in embryonic stem cells. In this study, we report a novel function of Rad51 in regulating mitochondrial activity during in vitro maturation of mouse oocytes. Suppression of Rad51 by injection of Rad51 dsRNA into germinal vesicle-stage oocytes resulted in arrest of meiosis in metaphase I...
September 28, 2016: Scientific Reports
William D Gilliland, Dennis P May, Eileen M Colwell, James A Kennison
Drosophila stocks bearing compound chromosomes, single molecules of DNA that carry the genomic complement of two chromosomes, are useful tools for studying meiosis and mitosis. However, these stocks cannot easily be crossed to stocks with regular chromosomes, due to the lethality of the resulting whole-chromosome aneuploidy. This prevents the examination of interesting genetic variants in a compound chromosome background. Methods to circumvent this difficulty have included the use of triploid females or nondisjunction (caused by either cold-induced microtubule depolymerization or meiotic mutants...
September 26, 2016: G3: Genes—Genomes—Genetics
Juan Liu, Yan Sun, Chunhong Yang, Yan Zhang, Qiang Jiang, Jinming Huang, Zhihua Ju, Xiuge Wang, Jifeng Zhong, Changfa Wang
Inner centromere protein (INCENP) plays an important role in mitosis and meiosis as the main member of chromosomal passenger protein complex (CPC). To investigate the functional markers of the INCENP gene associated with semen quality, the single nucleotide polymorphisms (SNPs) g.19970 A>G and g.34078 T>G were identified and analyzed. The new splice variant INCENP-TV is characterized by the deletion of exon 12. The g.19970 A>G in the exonic splicing enhancer (ESE) motif region results in an aberrant splice variant by constructing two minigene expression vectors using the pSPL3 exon capturing vector and transfecting vectors into MLTC-1 cells...
2016: PloS One
Elena Morelli, Valeria Mastrodonato, Galina V Beznoussenko, Alexandre A Mironov, Emiliana Tognon, Thomas Vaccari
The kinetochore is an essential structure that mediates accurate chromosome segregation in mitosis and meiosis. While many of the kinetochore components have been identified, the mechanisms of kinetochore assembly remain elusive. Here, we identify a novel role for Snap29, an unconventional SNARE, in promoting kinetochore assembly during mitosis in Drosophila and human cells. Snap29 localizes to the outer kinetochore and prevents chromosome mis-segregation and the formation of cells with fragmented nuclei. Snap29 promotes accurate chromosome segregation by mediating the recruitment of Knl1 at the kinetochore and ensuring stable microtubule attachments...
September 19, 2016: EMBO Journal
Mahesh Chemudupati, Aysha H Osmani, Stephen A Osmani
During Aspergillus nidulans mitosis peripheral nuclear pore complex (NPC) proteins (Nups) disperse from the core NPC structure. Unexpectedly, one predicted peripheral Nup, Gle1, remains at the mitotic NE via an unknown mechanism. Gle1 affinity purification identified MtgA ( M: itotic T: ether for G: le1), which tethers Gle1 to the NE during mitosis, but not during interphase when Gle1 is at NPCs. MtgA is the ortholog of the Schizosaccharomyces pombe telomere-anchoring inner nuclear membrane protein Bqt4. Like Bqt4, MtgA has meiotic roles but is functionally distinct from Bqt4 as MtgA is not required for tethering telomeres to the NE...
September 14, 2016: Molecular Biology of the Cell
Neil Hattersley, Dhanya Cheerambathur, Mark Moyle, Marine Stefanutti, Amelia Richardson, Kian-Yong Lee, Julien Dumont, Karen Oegema, Arshad Desai
During M-phase entry in metazoans with open mitosis, the concerted action of mitotic kinases disassembles nuclei and promotes assembly of kinetochores-the primary microtubule attachment sites on chromosomes. At M-phase exit, these major changes in cellular architecture must be reversed. Here, we show that the conserved kinetochore-localized nucleoporin MEL-28/ELYS docks the catalytic subunit of protein phosphatase 1 (PP1c) to direct kinetochore disassembly-dependent chromosome segregation during oocyte meiosis I and nuclear assembly during the transition from M phase to interphase...
September 12, 2016: Developmental Cell
Jianhui Ji, Ding Tang, Yi Shen, Zhihui Xue, Hongjun Wang, Wenqing Shi, Chao Zhang, Guijie Du, Yafei Li, Zhukuan Cheng
The human mitotic arrest-deficient 2 (Mad2) binding protein p31(comet) participates in the spindle checkpoint and coordinates cell cycle events in mitosis although its function in meiosis remains unknown in all organisms. Here, we reveal P31(comet) as a synaptonemal complex (SC) protein in rice (Oryza sativa L.). In p31(comet), homologous pairing and synapsis are eliminated, leading to the homologous nondisjunction and complete sterility. The failure in loading of histone H2AX phosphorylation (γH2AX) in p31(comet), together with the suppressed chromosome fragmentation in rice completion of meiotic recombination 1 (com1) p31(comet) and radiation sensitive 51c (rad51c) p31(comet) double mutants, indicates that P31(comet) plays an essential role in double-strand break (DSB) formation...
September 20, 2016: Proceedings of the National Academy of Sciences of the United States of America
Yasuharu Kushida, Masak Takaine, Kentaro Nakano, Toshiro Sugai, Krishna Kumar Vasudevan, Mayukh Guha, Yu-Yang Jiang, Jacek Gaertig, Osamu Numata
Ciliates such as Tetrahymena thermophila have two distinct nuclei within one cell: the micronucleus that undergoes mitosis and meiosis and the macronucleus that undergoes amitosis, a type of nuclear division that does not involve a bipolar spindle, but still relies on intranuclear microtubules. Ciliates provide an opportunity for the discovery of factors that specifically contribute to chromosome segregation based on a bipolar spindle, by identification of factors that affect the micronuclear but not the macronuclear division...
September 6, 2016: Journal of Eukaryotic Microbiology
Jennifer N Cech, Catherine L Peichel
Having one and only one centromere per chromosome is essential for proper chromosome segregation during both mitosis and meiosis. Chromosomes containing two centromeres are known as dicentric and often mis-segregate during cell division, resulting in aneuploidy or chromosome breakage. Dicentric chromosome can be stabilized by centromere inactivation, a process which reestablishes monocentric chromosomes. However, little is known about this process in naturally occurring dicentric chromosomes. Using a combination of fluorescence in situ hybridization (FISH) and immunofluorescence combined with FISH (IF-FISH) on metaphase chromosome spreads, we demonstrate that centromere inactivation has evolved on a neo-Y chromosome fusion in the Japan Sea threespine stickleback fish (Gasterosteus nipponicus)...
August 23, 2016: Chromosome Research
Yuko Murakami-Tonami, Haruna Ikeda, Ryota Yamagishi, Mao Inayoshi, Shiho Inagaki, Satoshi Kishida, Yosuke Komata, Jan Koster, Ichiro Takeuchi, Yutaka Kondo, Tohru Maeda, Yoshitaka Sekido, Hiroshi Murakami, Kenji Kadomatsu
Shugoshin 1 (SGO1) is required for accurate chromosome segregation during mitosis and meiosis; however, its other functions, especially at interphase, are not clearly understood. Here, we found that downregulation of SGO1 caused a synergistic phenotype in cells overexpressing MYCN. Downregulation of SGO1 impaired proliferation and induced DNA damage followed by a senescence-like phenotype only in MYCN-overexpressing neuroblastoma cells. In these cells, SGO1 knockdown induced DNA damage, even during interphase, and this effect was independent of cohesin...
2016: Scientific Reports
Walter W Steiner, Chelsea L Recor, Bethany M Zakrzewski
The M26 hotspot of the fission yeast Schizosaccharomyces pombe is one of the best-characterized eukaryotic hotspots of recombination. The hotspot requires a seven bp sequence, ATGACGT, that serves as a binding site for the Atf1-Pcr1 transcription factor, which is also required for activity. The M26 hotspot is active in meiosis but not mitosis and is active in some but not all chromosomal contexts and not on a plasmid. A longer palindromic version of M26, ATGACGTCAT, shows significantly greater activity than the seven bp sequence...
November 15, 2016: Gene
André Marques, Andrea Pedrosa-Harand
The centromere is the chromosomal site of kinetochore assembly and is responsible for the correct chromosome segregation during mitosis and meiosis in eukaryotes. Contrary to monocentrics, holocentric chromosomes lack a primary constriction, what is attributed to a kinetochore activity along almost the entire chromosome length during mitosis. This extended centromere structure imposes a problem during meiosis, since sister holocentromeres are not co-oriented during first meiotic division. Thus, regardless of the relatively conserved somatic chromosome structure of holocentrics, during meiosis holocentric chromosomes show different adaptations to deal with this condition...
September 2016: Chromosoma
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