Zeitschriftenartikel: „Prophase I“

1

Rieder, Conly L., und Richard W. Cole. „Entry into Mitosis in Vertebrate Somatic Cells Is Guarded by a Chromosome Damage Checkpoint That Reverses the Cell Cycle When Triggered during Early but Not Late Prophase“. Journal of Cell Biology 142, Nr. 4 (24.08.1998): 1013–22. http://dx.doi.org/10.1083/jcb.142.4.1013.

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When vertebrate somatic cells are selectively irradiated in the nucleus during late prophase (<30 min before nuclear envelope breakdown) they progress normally through mitosis even if they contain broken chromosomes. However, if early prophase nuclei are similarly irradiated, chromosome condensation is reversed and the cells return to interphase. Thus, the G2 checkpoint that prevents entry into mitosis in response to nuclear damage ceases to function in late prophase. If one nucleus in a cell containing two early prophase nuclei is selectively irradiated, both return to interphase, and prophase cells that have been induced to returned to interphase retain a normal cytoplasmic microtubule complex. Thus, damage to an early prophase nucleus is converted into a signal that not only reverses the nuclear events of prophase, but this signal also enters the cytoplasm where it inhibits e.g., centrosome maturation and the formation of asters. Immunofluorescent analyses reveal that the irradiation-induced reversion of prophase is correlated with the dephosphorylation of histone H1, histone H3, and the MPM2 epitopes. Together, these data reveal that a checkpoint control exists in early but not late prophase in vertebrate cells that, when triggered, reverses the cell cycle by apparently downregulating existing cyclin-dependent kinase (CDK1) activity.

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2

Wang, Tianzuo, Mengya Xue, Peng Sha, Fei Xue und Linxiang Wang. „Study on the Influence of Different Prophase Stress Levels on the Fatigue Damage Characteristics of Granite“. Shock and Vibration 2021 (05.06.2021): 1–12. http://dx.doi.org/10.1155/2021/5513910.

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In order to reveal the influence of prophase stress levels on the fatigue damage characteristics of granite, uniaxial fatigue tests of granite with different prophase stress levels were carried out on the basis of the MTS 815.04 rock mechanics test system. The results show that, under the same number of cycles, the failure degree increases with the increase of the prophase stress level. Under the low upper limit of cyclic stress, the tangent modulus and dissipated energy increase significantly with the increase of prophase stress level at the early stage of the cycle loading, while the increasing trend is not obvious with the increase of prophase stress level at the late stage. Under the high upper limit of cyclic stress, the tangent modulus and dissipated energy are less affected by the prophase stress level. The development trend of elastic release energy is not obvious with the increase of prophase stress level, which is less affected by the number of cycles. From the damage parameters defined by dissipative energy, under the low upper limit of cyclic stress, the initial damage is less affected by the prophase stress level. With the increase of the number of cycles, the influence of the prophase stress level on the development trend of the damage variable increases gradually. And the development trend of damage variables shows “C-shaped” damage.

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3

Fellmeth, Jessica E., Janet K. Jang, Manisha Persaud, Hannah Sturm, Neha Changela, Aashka Parikh und Kim S. McKim. „A dynamic population of prophase CENP-C is required for meiotic chromosome segregation“. PLOS Genetics 19, Nr. 11 (29.11.2023): e1011066. http://dx.doi.org/10.1371/journal.pgen.1011066.

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The centromere is an epigenetic mark that is a loading site for the kinetochore during meiosis and mitosis. This mark is characterized by the H3 variant CENP-A, known as CID in Drosophila. In Drosophila, CENP-C is critical for maintaining CID at the centromeres and directly recruits outer kinetochore proteins after nuclear envelope break down. These two functions, however, happen at different times in the cell cycle. Furthermore, in Drosophila and many other metazoan oocytes, centromere maintenance and kinetochore assembly are separated by an extended prophase. We have investigated the dynamics of function of CENP-C during the extended meiotic prophase of Drosophila oocytes and found that maintaining high levels of CENP-C for metaphase I requires expression during prophase. In contrast, CID is relatively stable and does not need to be expressed during prophase to remain at high levels in metaphase I of meiosis. Expression of CID during prophase can even be deleterious, causing ectopic localization to non-centromeric chromatin, abnormal meiosis and sterility. CENP-C prophase loading is required for multiple meiotic functions. In early meiotic prophase, CENP-C loading is required for sister centromere cohesion and centromere clustering. In late meiotic prophase, CENP-C loading is required to recruit kinetochore proteins. CENP-C is one of the few proteins identified in which expression during prophase is required for meiotic chromosome segregation. An implication of these results is that the failure to maintain recruitment of CENP-C during the extended prophase in oocytes would result in chromosome segregation errors in oocytes.

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4

Walters, Marta Sherman. „Meiosis readiness in Lilium“. Canadian Journal of Genetics and Cytology 27, Nr. 1 (01.02.1985): 33–38. http://dx.doi.org/10.1139/g85-007.

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It was observed in five cultivars and two hybrids of Lilium that premeiotic prophase is retarded in anthers approaching meiosis. The occurrence of premeiotic despiralization was related to the degree of retardation of premeiotic prophase. It is proposed that meiosis is initiated by stimuli arising outside the premeiotic cells. It is suggested that an accumulation of meiosis-inducing substances in the cytoplasm of the premeiotic cells causes prophase to slow down; when a critical level ("meiosis readiness") is reached, mitotic division is no longer possible and cells in premeiotic prophase despiralize to interphase.Key words: meiotic prophase, Lilium, meiotic readiness, premeiotic despiralization.

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Kireeva, Natashe, Margot Lakonishok, Igor Kireev, Tatsuya Hirano und Andrew S. Belmont. „Visualization of early chromosome condensation“. Journal of Cell Biology 166, Nr. 6 (07.09.2004): 775–85. http://dx.doi.org/10.1083/jcb.200406049.

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Current models of mitotic chromosome structure are based largely on the examination of maximally condensed metaphase chromosomes. Here, we test these models by correlating the distribution of two scaffold components with the appearance of prophase chromosome folding intermediates. We confirm an axial distribution of topoisomerase IIα and the condensin subunit, structural maintenance of chromosomes 2 (SMC2), in unextracted metaphase chromosomes, with SMC2 localizing to a 150–200-nm-diameter central core. In contrast to predictions of radial loop/scaffold models, this axial distribution does not appear until late prophase, after formation of uniformly condensed middle prophase chromosomes. Instead, SMC2 associates throughout early and middle prophase chromatids, frequently forming foci over the chromosome exterior. Early prophase condensation occurs through folding of large-scale chromatin fibers into condensed masses. These resolve into linear, 200–300-nm-diameter middle prophase chromatids that double in diameter by late prophase. We propose a unified model of chromosome structure in which hierarchical levels of chromatin folding are stabilized late in mitosis by an axial “glue.”

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Hajeri, Vinita A., Brent A. Little, Mary L. Ladage und Pamela A. Padilla. „NPP-16/Nup50 Function and CDK-1 Inactivation Are Associated with Anoxia-induced Prophase Arrest in Caenorhabditis elegans“. Molecular Biology of the Cell 21, Nr. 5 (März 2010): 712–24. http://dx.doi.org/10.1091/mbc.e09-09-0787.

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Oxygen, an essential nutrient, is sensed by a multiple of cellular pathways that facilitate the responses to and survival of oxygen deprivation. The Caenorhabditis elegans embryo exposed to severe oxygen deprivation (anoxia) enters a state of suspended animation in which cell cycle progression reversibly arrests at specific stages. The mechanisms regulating interphase, prophase, or metaphase arrest in response to anoxia are not completely understood. Characteristics of arrested prophase blastomeres and oocytes are the alignment of condensed chromosomes at the nuclear periphery and an arrest of nuclear envelope breakdown. Notably, anoxia-induced prophase arrest is suppressed in mutant embryos lacking nucleoporin NPP-16/NUP50 function, indicating that this nucleoporin plays an important role in prophase arrest in wild-type embryos. Although the inactive form of cyclin-dependent kinase (CDK-1) is detected in wild-type–arrested prophase blastomeres, the inactive state is not detected in the anoxia exposed npp-16 mutant. Furthermore, we found that CDK-1 localizes near chromosomes in anoxia-exposed embryos. These data support the notion that NPP-16 and CDK-1 function to arrest prophase blastomeres in C. elegans embryos. The anoxia-induced shift of cells from an actively dividing state to an arrested state reveals a previously uncharacterized prophase checkpoint in the C. elegans embryo.

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Wang, Jianyue, und Feixiong Zhang. „Nucleolus disassembly and distribution of segregated nucleolar material in prophase of root-tip meristematic cells in Triticum aestivum L.“ Archives of Biological Sciences 67, Nr. 2 (2015): 405–10. http://dx.doi.org/10.2298/abs140810007w.

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This paper presents details of the process of nucleolar disassembly, studied by conventional transmission electron microscopy (TEM) in wheat root cells. In early prophase, chromatin condensation and irregular nucleolar morphology are observed, with many small particles appearing around the nucleolus. In middle prophase, the nucleolus radiates outwards; in late prophase, the fine structure of the nucleolus disappears and nucleolar material diffuses away. Using ?en bloc? silver-staining to distinguish between nucleoli and chromatin, we observed that the dispersed nucleolar material aggregates around the chromatin, forming a sheath-like perichromosomal structure that coats the chromosomes in late prophase.

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Láscarez-Lagunas, Laura, Marina Martinez-Garcia und Mónica Colaiácovo. „SnapShot: Meiosis – Prophase I“. Cell 181, Nr. 6 (Juni 2020): 1442–1442. http://dx.doi.org/10.1016/j.cell.2020.04.038.

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9

Fan, Xueying, Ioannis Moustakas, Vanessa Torrens-Juaneda, Qijing Lei, Geert Hamer, Leoni A. Louwe, Gonneke S. K. Pilgram et al. „Transcriptional progression during meiotic prophase I reveals sex-specific features and X chromosome dynamics in human fetal female germline“. PLOS Genetics 17, Nr. 9 (09.09.2021): e1009773. http://dx.doi.org/10.1371/journal.pgen.1009773.

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During gametogenesis in mammals, meiosis ensures the production of haploid gametes. The timing and length of meiosis to produce female and male gametes differ considerably. In contrast to males, meiotic prophase I in females initiates during development. Hence, the knowledge regarding progression through meiotic prophase I is mainly focused on human male spermatogenesis and female oocyte maturation during adulthood. Therefore, it remains unclear how the different stages of meiotic prophase I between human oogenesis and spermatogenesis compare. Analysis of single-cell transcriptomics data from human fetal germ cells (FGC) allowed us to identify the molecular signatures of female meiotic prophase I stages leptotene, zygotene, pachytene and diplotene. We have compared those between male and female germ cells in similar stages of meiotic prophase I and revealed conserved and specific features between sexes. We identified not only key players involved in the process of meiosis, but also highlighted the molecular components that could be responsible for changes in cellular morphology that occur during this developmental period, when the female FGC acquire their typical (sex-specific) oocyte shape as well as sex-differences in the regulation of DNA methylation. Analysis of X-linked expression between sexes during meiotic prophase I suggested a transient X-linked enrichment during female pachytene, that contrasts with the meiotic sex chromosome inactivation in males. Our study of the events that take place during meiotic prophase I provide a better understanding not only of female meiosis during development, but also highlights biomarkers that can be used to study infertility and offers insights in germline sex dimorphism in humans.

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Jessus, C., C. Thibier und R. Ozon. „Levels of microtubules during the meiotic maturation of the Xenopus oocyte“. Journal of Cell Science 87, Nr. 5 (01.06.1987): 705–12. http://dx.doi.org/10.1242/jcs.87.5.705.

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The total level of tubulin and the ratio of polymeric tubulin to tubulin dimer were measured by a colchicine filter-binding assay during meiotic maturation of the Xenopus oocyte. Although the total level of tubulin remains unchanged (0.12 +/− 0.03 micrograms/oocyte), the level of polymeric tubulin decreases during maturation (25% in prophase oocytes versus 20% in metaphase oocytes). The percentage of polymerized tubulin was estimated after drug (nocodazole and taxol) treatments and cold treatment in prophase and progesterone-matured oocytes; in all cases the microtubules present in mature oocyte are less stable than prophase microtubules. The presence of the nucleus modifies neither the level nor the stability of prophase microtubules. Our quantitative results as well as cytological arguments suggest that full-grown Xenopus oocytes may contain a cortical microtubular array.

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11

Stringer, Jessica M., Amy Winship, Nadeen Zerafa, Matthew Wakefield und Karla Hutt. „Oocytes can efficiently repair DNA double-strand breaks to restore genetic integrity and protect offspring health“. Proceedings of the National Academy of Sciences 117, Nr. 21 (07.05.2020): 11513–22. http://dx.doi.org/10.1073/pnas.2001124117.

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Female fertility and offspring health are critically dependent on an adequate supply of high-quality oocytes, the majority of which are maintained in the ovaries in a unique state of meiotic prophase arrest. While mechanisms of DNA repair during meiotic recombination are well characterized, the same is not true for prophase-arrested oocytes. Here we show that prophase-arrested oocytes rapidly respond to γ-irradiation–induced DNA double-strand breaks by activating Ataxia Telangiectasia Mutated, phosphorylating histone H2AX, and localizing RAD51 to the sites of DNA damage. Despite mobilizing the DNA repair response, even very low levels of DNA damage result in the apoptosis of prophase-arrested oocytes. However, we show that, when apoptosis is inhibited, severe DNA damage is corrected via homologous recombination repair. The repair is sufficient to support fertility and maintain health and genetic fidelity in offspring. Thus, despite the preferential induction of apoptosis following exogenously induced genotoxic stress, prophase-arrested oocytes are highly capable of functionally efficient DNA repair. These data implicate DNA repair as a key quality control mechanism in the female germ line and a critical determinant of fertility and genetic integrity.

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12

Gabrielli, B. G., C. P. De Souza, I. D. Tonks, J. M. Clark, N. K. Hayward und K. A. Ellem. „Cytoplasmic accumulation of cdc25B phosphatase in mitosis triggers centrosomal microtubule nucleation in HeLa cells“. Journal of Cell Science 109, Nr. 5 (01.05.1996): 1081–93. http://dx.doi.org/10.1242/jcs.109.5.1081.

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The formation of the mitotic spindle is an essential prerequisite for successful mitosis. The dramatic changes in the level of microtubule (Mt) nucleation at the centrosomes and Mt dynamics that occur in prophase are presumed to be initiated through the activity of cdc2/cyclin B. Here we present data that the cdc25B isoform functions to activate the cytoplasmic pool of cdc2/cyclin B responsible for these events. In contrast to cdc25C, cdc25B is present at low levels in HeLa cells during interphase, but sharply increases in prophase, when cdc25B accumulation in the cytoplasm correlates with prophase spindle formation. Overexpression of wild type and dominant negative mutants of cdc25B and cdc25C shows that prophase Mt nucleation is a consequence of cytoplasmic cdc25B activity, and that cdc25C regulates nuclear G2/M events. Our data also suggest that the functional status of the centrosome can regulate nuclear mitotic events.

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13

Bednara, Józef, Mieczysław Kuraś und Bohdan Rodkiewicz. „Ultrastructural changes during megasporogenesis in Epipactis (Orchidaceae)“. Acta Societatis Botanicorum Poloniae 50, Nr. 1-2 (2014): 127–30. http://dx.doi.org/10.5586/asbp.1981.017.

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Plastids were temporarily localized within the micropylar portion of the early first prophase Epipactis meiocyte. Some of these plastids were observed in close proximity to the nuclear envelope. With the exception of this short period plastids were distributed randomly in the meiocyte. During late prophase, starch-containing plastids become cup-shaped and depleted of starch. Plastids were found within both dyad cells and all cells of the tetrad. Elongated segments of ER cisternae in various configurations were present. The chalazal wall of the prophase meiocyte differed from other walls in the presence of the ingrowths and plasmodesmata. The micropylar portion of the nuclear envelope at some stages of the I prophase seemed to be devoid of pores whereas the chalazal part contained numerous pores. These structural characters reflect a polar differentiation of the meiocyte along a micropylar-chalazal axis.

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Castro, A., und T. Lorca. „Arpp19 in prophase I resumption“. Cell Cycle 16, Nr. 17 (10.08.2017): 1564–65. http://dx.doi.org/10.1080/15384101.2017.1348069.

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15

Jones, G. H., und J. E. Vincent. „Meiosis in allopolyploid Crepis capillaris. II. Autotetraploids“. Genome 37, Nr. 3 (01.06.1994): 497–505. http://dx.doi.org/10.1139/g94-069.

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Meiotic chromosome pairing of autotetraploid Crepis capillaris was analysed by electron microscopy of surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I chromosome configurations. Prophase I quadrivalent frequencies are high in all three tetrasomes. (A, D, and C) and partially dependent on chromosome size. At metaphase I quadrivalent frequencies are much lower and strongly dependent on chromosome size. There is no evidence for multivalent elimination during prophase I in this system, and the reduction in multivalent frequency at metaphase I can be explained by an insufficiency of appropriately placed chiasmata. The high frequencies of prophase I quadrivalents far exceed the two-thirds expected on a simple model with two terminal independent pairing initiation sites per tetrasome, suggesting that multiple pairing initiation occurs. Direct observations reveal relatively high frequencies of pairing partner switches (PPSs) at prophase I, which confirms this suggestion. The numbers of PPSs per tetrasome show a good fit to the Poisson distribution, and their positional distribution along chromosomes is random and nonlocalized. These observations favour a model of pairing initiation based on a large number of evenly distributed autonomous pairing sites each with a uniform and low probability of generating a PPS.Key words: autotetraploid, meiosis, Crepis capillaris, multivalent, pairing partner switch.

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Matveevsky, Sergey, Nikolay Tropin, Aleksandr Kucheryavyy und Oxana Kolomiets. „The First Analysis of Synaptonemal Complexes in Jawless Vertebrates: Chromosome Synapsis and Transcription Reactivation at Meiotic Prophase I in the Lamprey Lampetra fluviatilis (Petromyzontiformes, Cyclostomata)“. Life 13, Nr. 2 (11.02.2023): 501. http://dx.doi.org/10.3390/life13020501.

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Transcription is known to be substage-specific in meiotic prophase I. If transcription is reactivated in the mid pachytene stage in mammals when synapsis is completed, then this process is observed in the zygotene stage in insects. The process of transcriptional reactivation has been studied in a small number of different taxa of invertebrates and vertebrates. Here, for the first time, we investigate synapsis and transcription in prophase I in the European river lamprey Lampetra fluviatilis (Petromyzontiformes, Cyclostomata), which is representative of jawless vertebrates that diverged from the main branch of vertebrates between 535 and 462 million years ago. We found that not all chromosomes complete synapsis in telomeric regions. Rounded structures were detected in chromatin and in some synaptonemal complexes, but their nature could not be determined conclusively. An analysis of RNA polymerase II distribution led to the conclusion that transcriptional reactivation in lamprey prophase I is not associated with the completion of chromosome synapsis. Monomethylated histone H3K4 is localized in meiotic chromatin throughout prophase I, and this pattern has not been previously detected in animals. Thus, the findings made it possible to identify synaptic and epigenetic patterns specific to this group and to expand knowledge about chromatin epigenetics in prophase I.

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17

Hebbar, Sachin, Mariano T. Mesngon, Aimee M. Guillotte, Bhavim Desai, Ramses Ayala und Deanna S. Smith. „Lis1 and Ndel1 influence the timing of nuclear envelope breakdown in neural stem cells“. Journal of Cell Biology 182, Nr. 6 (22.09.2008): 1063–71. http://dx.doi.org/10.1083/jcb.200803071.

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Lis1 and Ndel1 are essential for animal development. They interact directly with one another and with cytoplasmic dynein. The developing brain is especially sensitive to reduced Lis1 or Ndel1 levels, as both proteins influence spindle orientation, neural cell fate decisions, and neuronal migration. We report here that Lis1 and Ndel1 reduction in a mitotic cell line impairs prophase nuclear envelope (NE) invagination (PNEI). This dynein-dependent process facilitates NE breakdown (NEBD) and occurs before the establishment of the bipolar spindle. Ndel1 phosphorylation is important for this function, regulating binding to both Lis1 and dynein. Prophase cells in the ventricular zone (VZ) of embryonic day 13.5 Lis1+/− mouse brains show reduced PNEI, and the ratio of prophase to prometaphase cells is increased, suggesting an NEBD delay. Moreover, prophase cells in the VZ contain elevated levels of Ndel1 phosphorylated at a key cdk5 site. Our data suggest that a delay in NEBD in the VZ could contribute to developmental defects associated with Lis1–Ndel1 disruption.

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Drouin, R., und C. L. Richer. „Analysis of high-resolution R-bands, obtained by heat-denaturation and Giemsa staining, on human prophase chromosomes“. Canadian Journal of Genetics and Cytology 27, Nr. 1 (01.02.1985): 83–91. http://dx.doi.org/10.1139/g85-014.

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RHG-bands (heat-denatured Giemsa R-bands) of human prophase chromosomes were analyzed at high resolution, and the banding patterns at prophase and metaphase are presented. The bands were compared with those of the International Standard Cytogenetic Nomenclature idiograms and of the G-band idiograms proposed by J. J. Yunis. The number, size, and position of the RHG-bands correspond rather well with their equivalent G-negative bands, but some differences were noted in the zones of preferential stretching, the juxtacentromeric regions, and the telomeres. Variations in the centromere index and the banding pattern in heterochromatin were also discussed.Key words: human prophase chromosomes, RHG-bands, high-resolution chromosomes.

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Nadarajan, Saravanapriah, Elisabeth Altendorfer, Takamune T. Saito, Marina Martinez-Garcia und Monica P. Colaiácovo. „HIM-17 regulates the position of recombination events and GSP-1/2 localization to establish short arm identity on bivalents in meiosis“. Proceedings of the National Academy of Sciences 118, Nr. 17 (21.04.2021): e2016363118. http://dx.doi.org/10.1073/pnas.2016363118.

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The position of recombination events established along chromosomes in early prophase I and the chromosome remodeling that takes place in late prophase I are intrinsically linked steps of meiosis that need to be tightly regulated to ensure accurate chromosome segregation and haploid gamete formation. Here, we show that RAD-51 foci, which form at the sites of programmed meiotic DNA double-strand breaks (DSBs), exhibit a biased distribution toward off-centered positions along the chromosomes in wild-type Caenorhabditis elegans, and we identify two meiotic roles for chromatin-associated protein HIM-17 that ensure normal chromosome remodeling in late prophase I. During early prophase I, HIM-17 regulates the distribution of DSB-dependent RAD-51 foci and crossovers on chromosomes, which is critical for the formation of distinct chromosome subdomains (short and long arms of the bivalents) later during chromosome remodeling. During late prophase I, HIM-17 promotes the normal expression and localization of protein phosphatases GSP-1/2 to the surface of the bivalent chromosomes and may promote GSP-1 phosphorylation, thereby antagonizing Aurora B kinase AIR-2 loading on the long arms and preventing premature loss of sister chromatid cohesion. We propose that HIM-17 plays distinct roles at different stages during meiotic progression that converge to promote normal chromosome remodeling and accurate chromosome segregation.

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Masruroh, Faridatul, und Esty Saraswati Nurhatiningrum. „Peran Algoritma Julia Set Dalam Mengkonstruksi Pembelahan Sel Mitosis“. Al-Khwarizmi: Jurnal Pendidikan Matematika dan Ilmu Pengetahuan Alam 4, Nr. 2 (08.09.2018): 173–84. http://dx.doi.org/10.24256/jpmipa.v4i2.261.

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Fractal geometry is a structure that is constructed of an element geometry (points, lines, areas, and space) and these elements are experiencing faults equation is not continuous, monotonous go up or down the course, the graph circular, blending and converging to the center, and size scale in each substructure same. This is similar to the principle of cell division, mitosis is the process of cell division that splits into two cells, and each cell has the same chromosomes as their parent. Mitosis is usually followed by cytokinesis, the division of the cytoplasm to two identical daughter cells. The stages of mitotic division consists of prophase, metafese, anaphase, telophase and interphase. Of the five stages only obtained three stages which can be searched equation through the Julia set algorithm, namely prophase, telophase, and interphase. The mathematical equation for prophase and interphase are the same, namely , the difference is the position x. At prophase position x is -0,9 ? x ? 0,1 while at the interphase stage position x is -0,9 ? x ? 0,9. The mathematical equation for telophase stage is .

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Guo, Yuxuan, und Yixian Zheng. „Lamins position the nuclear pores and centrosomes by modulating dynein“. Molecular Biology of the Cell 26, Nr. 19 (Oktober 2015): 3379–89. http://dx.doi.org/10.1091/mbc.e15-07-0482.

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Lamins, the type V nuclear intermediate filament proteins, are reported to function in both interphase and mitosis. For example, lamin deletion in various cell types can lead to an uneven distribution of the nuclear pore complexes (NPCs) in the interphase nuclear envelope, whereas deletion of B-type lamins results in spindle orientation defects in mitotic neural progenitor cells. How lamins regulate these functions is unknown. Using mouse cells deleted of different combinations or all lamins, we show that lamins are required to prevent the aggregation of NPCs in the nuclear envelope near centrosomes in late G2 and prophase. This asymmetric NPC distribution in the absence of lamins is caused by dynein forces acting on NPCs via the dynein adaptor BICD2. We further show that asymmetric NPC distribution upon lamin depletion disrupts the distribution of BICD2 and p150 dynactin on the nuclear envelope at prophase, which results in inefficient dynein-driven centrosome separation during prophase. Therefore lamins regulate microtubule-based motor forces in vivo to ensure proper NPC distribution in interphase and centrosome separation in the mitotic prophase.

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Seluja, G. A., L. Roche und A. J. Solari. „Male meiotic prophase in Didelphis albiventris“. Journal of Heredity 78, Nr. 4 (Juli 1987): 218–22. http://dx.doi.org/10.1093/oxfordjournals.jhered.a110369.

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23

Kaul, M. L. H., und Jaswinder Kaur. „Checkered Prophase I in Crown Daisy.“ CYTOLOGIA 60, Nr. 2 (1995): 195–203. http://dx.doi.org/10.1508/cytologia.60.195.

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SORSA, VEIKKO. „Condensation of chromosomes during meiotic prophase“. Hereditas 72, Nr. 2 (12.02.2009): 215–22. http://dx.doi.org/10.1111/j.1601-5223.1972.tb01045.x.

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SORSA, VEIKKO. „Condensation of chromosomes during mitotic prophase“. Hereditas 75, Nr. 1 (12.02.2009): 101–8. http://dx.doi.org/10.1111/j.1601-5223.1973.tb01146.x.

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Tsubouchi, Hideo, Bilge Argunhan und Tomomi Tsubouchi. „Exiting prophase I: no clear boundary“. Current Genetics 64, Nr. 2 (25.10.2017): 423–27. http://dx.doi.org/10.1007/s00294-017-0771-y.

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27

Sager, P. R., N. L. Rothfield, J. M. Oliver und R. D. Berlin. „A novel mitotic spindle pole component that originates from the cytoplasm during prophase.“ Journal of Cell Biology 103, Nr. 5 (01.11.1986): 1863–72. http://dx.doi.org/10.1083/jcb.103.5.1863.

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Several unique aspects of mitotic spindle formation have been revealed by investigation of an autoantibody present in the serum of a patient with the CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, schlerodacytyly, and telangiectasias) syndrome. This antibody was previously shown to label at the spindle poles of metaphase and anaphase cells and to be absent from interphase cells. We show here that the serum stained discrete cytoplasmic foci in early prophase cells and only later localized to the spindle poles. The cytoplasmic distribution of the antigen was also seen in nocodazole-arrested cells and prophase cells in populations treated with taxol. In normal and taxol-treated cells, the microtubules appeared to emanate from the cytoplasmic foci and polar stain, and in cells released from nocodazole block, microtubules regrew from antigen-containing centers. This characteristic distribution suggests that the antigen is part of a microtubule organizing center. Thus, we propose that a prophase originating polar antigen functions in spindle pole organization as a coalescing microtubule organizing center that is present only during mitosis. Characterization of the serum showed reactions with multiple proteins at 115, 110, 50, 36, 30, and 28 kD. However, affinity-eluted antibody from the 115/110-kD bands was shown to specifically label the spindle pole and cytosolic foci in prophase cells.

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Mu, Xiaomin, Yi-Fen Lee, Ning-Chun Liu, Yei-Tsung Chen, Eungseok Kim, Chih-Rong Shyr und Chawnshang Chang. „Targeted Inactivation of Testicular Nuclear Orphan Receptor 4 Delays and Disrupts Late Meiotic Prophase and Subsequent Meiotic Divisions of Spermatogenesis“. Molecular and Cellular Biology 24, Nr. 13 (01.07.2004): 5887–99. http://dx.doi.org/10.1128/mcb.24.13.5887-5899.2004.

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ABSTRACT Testicular orphan nuclear receptor 4 (TR4) is specifically and stage-dependently expressed in late-stage pachytene spermatocytes and round spermatids. In the developing mouse testis, the highest expression of TR4 can be detected at postnatal days 16 to 21 when the first wave of spermatogenesis progresses to late meiotic prophase. Using a knockout strategy to delete TR4 in mice, we found that sperm production in TR4−/− mice is reduced. The comparison of testes from developing TR4+/+ and TR4−/− mice shows that spermatogenesis in TR4−/− mice is delayed. Analysis of the first wave of spermatogenesis shows that the delay can be due to delay and disruption of spermatogenesis at the end of late meiotic prophase and subsequent meiotic divisions. Seminiferous tubule staging shows that stages X to XII, where late meiotic prophase and meiotic divisions take place, are delayed and disrupted in TR4−/− mice. Histological examination of testis sections from TR4−/− mice shows degenerated primary spermatocytes and some necrotic tubules. Testis-specific gene analyses show that the expression of sperm 1 and cyclin A1, which are genes expressed at the end of meiotic prophase, was delayed and decreased in TR4−/− mouse testes. Taken together, results from TR4+/+ and TR4−/− mice indicate that TR4 is essential for normal spermatogenesis in mice.

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Bellani, Marina A., Kingsley A. Boateng, Dianne McLeod und R. Daniel Camerini-Otero. „The Expression Profile of the Major Mouse SPO11 Isoforms Indicates that SPO11β Introduces Double Strand Breaks and Suggests that SPO11α Has an Additional Role in Prophase in both Spermatocytes and Oocytes“. Molecular and Cellular Biology 30, Nr. 18 (20.07.2010): 4391–403. http://dx.doi.org/10.1128/mcb.00002-10.

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ABSTRACT Both in mice and humans, two major SPO11 isoforms are generated by alternative splicing: SPO11α (exon 2 skipped) and SPO11β. Thus, the alternative splicing event must have emerged before the mouse and human lineages diverged and was maintained during 90 million years of evolution, arguing for an essential role for both isoforms. Here we demonstrate that developmental regulation of alternative splicing at the Spo11 locus governs the sequential expression of SPO11 isoforms in male meiotic prophase. Protein quantification in juvenile mice and in prophase mutants indicates that early spermatocytes synthesize primarily SPO11β. Estimation of the number of SPO11 dimers (ββ/αβ/αα) in mutants in which spermatocytes undergo a normal number of double strand breaks but arrest in midprophase due to inefficient repair argues for a role for SPO11β-containing dimers in introducing the breaks in leptonema. Expression kinetics in males suggested a role for SPO11α in pachytene/diplotene spermatocytes. Nevertheless, we found that both alternative transcripts can be detected in oocytes throughout prophase I, arguing against a male-specific function for this isoform. Altogether, our data support a role for SPO11α in mid- to late prophase, presumably acting as a topoisomerase, that would be conserved in male and female meiocytes.

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Asakawa, Haruhiko, Aki Hayashi, Tokuko Haraguchi und Yasushi Hiraoka. „Dissociation of the Nuf2-Ndc80 Complex Releases Centromeres from the Spindle-Pole Body during Meiotic Prophase in Fission Yeast“. Molecular Biology of the Cell 16, Nr. 5 (Mai 2005): 2325–38. http://dx.doi.org/10.1091/mbc.e04-11-0996.

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In the fission yeast Schizosaccharomyces pombe, centromeres remain clustered at the spindle-pole body (SPB) during mitotic interphase. In contrast, during meiotic prophase centromeres dissociate from the SPB. Here we examined the behavior of centromere proteins in living meiotic cells of S. pombe. We show that the Nuf2-Ndc80 complex proteins (Nuf2, Ndc80, Spc24, and Spc25) disappear from the centromere in meiotic prophase when the centromeres are separated from the SPB. The centromere protein Mis12 also dissociates during meiotic prophase; however, Mis6 remains throughout meiosis. When cells are induced to meiosis by inactivation of Pat1 kinase (a key negative regulator of meiosis), centromeres remain associated with the SPB during meiotic prophase. However, inactivation of Nuf2 by a mutation causes the release of centromeres from the SPB in pat1 mutant cells, suggesting that the Nuf2-Ndc80 complex connects centromeres to the SPB. We further found that removal of the Nuf2-Ndc80 complex from the centromere and centromere-SPB dissociation are caused by mating pheromone signaling. Because pat1 mutant cells also show aberrant chromosome segregation in the first meiotic division and this aberration is compensated by mating pheromone signaling, dissociation of the Nuf2-Ndc80 complex may be associated with remodeling of the kinetochore for meiotic chromosome segregation.

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Marcet-Ortega, Marina, Andros Maldonado-Linares, Maria López-Panadés und Ignasi Roig. „p53 Controls Meiotic Prophase Progression and Crossover Formation“. International Journal of Molecular Sciences 23, Nr. 17 (29.08.2022): 9818. http://dx.doi.org/10.3390/ijms23179818.

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Meiosis initiates with the formation of double strand breaks (DSBs) throughout the genome. To avoid genomic instability, these DSBs need to be correctly repaired by homologous recombination. Surveillance mechanisms involving the DNA damage response (DDR) pathway ATM-CHK2-p53 can detect the persistence of unrepaired DBSs and activate the recombination-dependent arrest at the pachytene stage. However, a complete understanding of p53 functions under normal physiological conditions remains lacking. Here, we report a detailed analysis of the p53 role during meiotic prophase in mice spermatocytes. We show that the absence of p53 regulates prophase progression by slowing down the pachytene stage when the recombination-dependent arrest occurs. Furthermore, our results show that p53 is necessary for proper crossover (CO) formation and localization. Our study contributes to a deeper understanding of p53 roles during the meiotic prophase.

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Mukai, Y., und B. S. Gill. „Detection of barley chromatin added to wheat by genomic in situ hybridization“. Genome 34, Nr. 3 (01.06.1991): 448–52. http://dx.doi.org/10.1139/g91-067.

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A technique for in situ hybridization is reported that can be used to detect barley chromatin in wheat background using total genomic DNA as a probe. A 1:2 ratio of biotin-labeled genomic DNA of barley to blocking (unlabeled, sheared) DNA of wheat was sufficient to reveal brownish labeled barley chromosome domains against bluish background of unlabeled wheat chromatin in metaphase, prophase, and interphase nuclei of wheat-barley addition lines. Using this procedure, the behavior of specific barley chromosomes was analyzed in interphase and prophase cells. In prophase cells, the 6H chromosome was always associated with a nucleolus. A genomic clone of α-amylase gene (gRAmy56) that contains a barley-specific dispersed repeat sequence was also used to detect barley chromosomes in a wheat background.Key words: Hordeum vulgare, Triticum aestivum, genomic in situ hybridization, biotin, nucleolar organizing region.

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Martínez, M., C. Cuadrado, J. Sybenga und C. Romero. „Differences in the synaptic pattern in two autotetraploid cultivars of rye with different quadrivalent frequencies at metaphase I“. Genome 42, Nr. 4 (01.08.1999): 662–67. http://dx.doi.org/10.1139/g99-009.

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Synaptic behaviour of the two tetraploids rye cultivars Gigantón (G) and Tetrapico (T) displaying significant differences in their quadrivalent frequencies at metaphase I was analyzed by electron microscopy in surface-spread prophase I nuclei. A different behaviour was observed between the two cultivars; the synaptonemal complex (SC) quadrivalents frequency being significantly higher in G than in T at prophase I. Moreover, the G SC quadrivalents had more synaptic partner exchanges (SPEs) and their location was more distal than the T SC quadrivalents. However, inverse findings were found at metaphase I, the quadrivalent frequency was higher in T than in G. The role that different factors, mainly the number and location of the SPEs and the frequency and distribution of chiasmata, could play in the evolution from prophase I to metaphase I in both cultivars is discussed.Key words: autotetraploid rye, synaptonemal complex, spreading.

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López Ruiz, Luz María, Dominic Johnson, William H. Gittens, George G. B. Brown, Rachal M. Allison und Matthew J. Neale. „Meiotic prophase length modulates Tel1-dependent DNA double-strand break interference“. PLOS Genetics 20, Nr. 3 (01.03.2024): e1011140. http://dx.doi.org/10.1371/journal.pgen.1011140.

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During meiosis, genetic recombination is initiated by the formation of many DNA double-strand breaks (DSBs) catalysed by the evolutionarily conserved topoisomerase-like enzyme, Spo11, in preferred genomic sites known as hotspots. DSB formation activates the Tel1/ATM DNA damage responsive (DDR) kinase, locally inhibiting Spo11 activity in adjacent hotspots via a process known as DSB interference. Intriguingly, in S. cerevisiae, over short genomic distances (<15 kb), Spo11 activity displays characteristics of concerted activity or clustering, wherein the frequency of DSB formation in adjacent hotspots is greater than expected by chance. We have proposed that clustering is caused by a limited number of sub-chromosomal domains becoming primed for DSB formation. Here, we provide evidence that DSB clustering is abolished when meiotic prophase timing is extended via deletion of the NDT80 transcription factor. We propose that extension of meiotic prophase enables most cells, and therefore most chromosomal domains within them, to reach an equilibrium state of similar Spo11-DSB potential, reducing the impact that priming has on estimates of coincident DSB formation. Consistent with this view, when Tel1 is absent but Ndt80 is present and thus cells are able to rapidly exit meiotic prophase, genome-wide maps of Spo11-DSB formation are skewed towards pericentromeric regions and regions that load pro-DSB factors early—revealing regions of preferential priming—but this effect is abolished when NDT80 is deleted. Our work highlights how the stochastic nature of Spo11-DSB formation in individual cells within the limited temporal window of meiotic prophase can cause localised DSB clustering—a phenomenon that is exacerbated in tel1Δ cells due to the dual roles that Tel1 has in DSB interference and meiotic prophase checkpoint control.

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Baarends, Willy M., Evelyne Wassenaar, Roald van der Laan, Jos Hoogerbrugge, Esther Sleddens-Linkels, Jan H. J. Hoeijmakers, Peter de Boer und J. Anton Grootegoed. „Silencing of Unpaired Chromatin and Histone H2A Ubiquitination in Mammalian Meiosis“. Molecular and Cellular Biology 25, Nr. 3 (01.02.2005): 1041–53. http://dx.doi.org/10.1128/mcb.25.3.1041-1053.2005.

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ABSTRACT During meiotic prophase in male mammals, the X and Y chromosomes are incorporated in the XY body. This heterochromatic body is transcriptionally silenced and marked by increased ubiquitination of histone H2A. This led us to investigate the relationship between histone H2A ubiquitination and chromatin silencing in more detail. First, we found that ubiquitinated H2A also marks the silenced X chromosome of the Barr body in female somatic cells. Next, we studied a possible relationship between H2A ubiquitination, chromatin silencing, and unpaired chromatin in meiotic prophase. The mouse models used carry an unpaired autosomal region in male meiosis or unpaired X and Y chromosomes in female meiosis. We show that ubiquitinated histone H2A is associated with transcriptional silencing of large chromatin regions. This silencing in mammalian meiotic prophase cells concerns unpaired chromatin regions and resembles a phenomenon described for the fungus Neurospora crassa and named meiotic silencing by unpaired DNA.

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Marciniak, C. „Cytochemical investigations of the megasporocyte and embryo sac in Lilium regale at various stages of development“. Acta Societatis Botanicorum Poloniae 44, Nr. 3 (2015): 335–47. http://dx.doi.org/10.5586/asbp.1975.030.

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During megasporocyte and embryo sac development in Lilium regale, characteristic changes were noted within the cytoplasm. In the course of prophase I there appear parallel systems of endoplasmic reticulum cisternae which further transform to cytoplasmic bodies built of protein and different-sized lipid inclusions. During maturation of the embryo sac the cytoplasmic bodies and lipid inclusions synthesized during prophase I undergo hydrolysis and constitute storage material utilized during maturation of the embryo sac.

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cormier, Patrick, Odile Mulner-Lorillon, René Ozon und Robert Bellé. „Involvement of protein kinase A and casein kinase II in the in vivo protein kinase activities in prophase arrested Xenopus oocytes“. Bioscience Reports 9, Nr. 3 (01.06.1989): 351–58. http://dx.doi.org/10.1007/bf01114688.

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In vivo β casein phosphorylation was analysed in Xenopus full-grown oocytes arrested in the prophase of the meiotic cell division. The phosphorylation was inhibited by the protein kinase inhibitor (PKI) and also by heparin (3 μg/ml; final concentration). β casein phosphorylation was increased by spermine (2 mM). Therefore, protein kinase A and casein kinase II are both active in vivo in full-grown oocytes and may be involved in the prophase arrest of meiotic cell division.

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Wolf, Klaus Werner, und Bryan M. Turner. „The pattern of histone H4 acetylation on the X chromosome during spermatogenesis of the desert locust Schistocerca gregaria“. Genome 39, Nr. 5 (01.10.1996): 854–65. http://dx.doi.org/10.1139/g96-108.

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We have used antibodies directed against histone H4 acetylated at lysine residue 5, 8, 12, or 16 and indirect immunofluorescence microscopy to probe chromosomes from spermatogonia and spermatocytes of the desert locust, Schistocerca gregaria. The autosomes showed bright overall fluorescence, indicative of high levels of H4 acetylation. In contrast, the X chromosome, which is facultatively heterochromatic during spermatogenesis of the locust, remained completely unstained in spermatogonia and secondary spermatocytes and showed only a small terminal fluorescent band in primary spermatocytes. This band probably corresponds to centromere-associated constitutive heterochromatin. Thus, underacetylation is a cytogenetic marker for facultative heterochromatin, but not necessarily constitutive heterochromatin, during spermatogenesis of the locust. Scanning electron microscopy of chromosomes from prophase spermatogonia and prophase I spermatocytes revealed that underacetylation of histone H4 in the X chromosome was not accompanied by a chromatin organization visibly different from that of the autosomes. Transmission electron microscopy of mitotic spermatogonia showed that the X chromosome is separated from the autosomes in a small nuclear compartment of its own in prophase and telophase and associated with membranes in metaphase. In prophase I spermatocytes, autosomes and the sex univalent were in the same compartment. This compartmentalization may be responsible for the underacetylation and (or) transcriptional silencing of the X chromosome in spermatogonial mitosis. Key words : histone acetylation, chromosomes, meiosis, heterochromatin, desert locust.

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Bardhan, Amit, und T. Sharma. „Sequential meiotic prophase development in the pubertal Indian pygmy field mouse: Synaptic progression of the XY chromosomes, autosomal heterochromatin, and pericentric inversions“. Genome 43, Nr. 1 (01.02.2000): 172–80. http://dx.doi.org/10.1139/g99-080.

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Sequential meiotic prophase development has been followed in the pubertal male pygmy mouse Mus terricolor, with the objective to identify early meiotic prophase stages. The pygmy mouse differs from the common mouse by having large heterochromatic blocks in the X and Y chromosomes. These mice also show various chromosomal mutations; for example, fixed variations of autosomal short arms heterochromatin among different chromosomal species and pericentric inversion polymorphism. Identification of prophase stages was crucial to analyzing effects of heterozygosity for these chromosomal changes on the process of homologous synapsis. Here we describe identification of the prophase stages in M. terricolor, especially the pachytene substages, on the basis of morphology of the XY bivalent. Based on this substaging, we show delayed pairing of the heterochromatic short arms, which may be the reason for their lack of chiasmata. The identification of precise pachytene substages also reveals an early occurrence of "synaptic adjustment" in the pericentric inversion heterobivalents, a mechanism that would prevent chiasma formation in the inverted segment and thereby would abate adverse effects of such heterozygosity. The identification of pachytene substages would serve as the basis to analyze the nature of synaptic anomalies met in M. terricolor hybrids (which will be the basis of a subsequent paper). Key words: Mus terricolor, meiotic synapsis, sex chromosomes, pericentric inversion, heterochromatin.

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Rodkiewicz, Bohdan, und Ewa Duda. „Aggregations of organelles in meiotic cells of higher plants“. Acta Societatis Botanicorum Poloniae 57, Nr. 4 (2014): 637–54. http://dx.doi.org/10.5586/asbp.1988.058.

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During early prophase I in microsporocytes and sporocytes of various plants all mitochondria and plastids aggregate in a group, where some plastids seem to undergo division. This group desintegrates by middle prophase I. Further aggregations of plastids and mitochondria occur in microsporogenesis and sporogenesis is of a simultaneous type. Organelles aggregate the second time at the end of prophase 1 and during or after telophase I they form a dense equatorial plate which lasts until telophase IL Since the phragmoplast is dismantled after telophase I and there is no cytokinesis, organelles aggregated in the plate apparently prevent merging of the nuclei and spindles of meiosis II, thus taking over a role of a phragmoplast and cell wall. In some plants after telophase II organelle aggregation changes shape and occupies the planes where cell walls will be built in simultaneous cytokinesis. Positioning of plastids and mitochondria along these planes may facilitate their equal apportionment among the postmeiotic cells.

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Yang, Hui-Ju, Haruhiko Asakawa, Tokuko Haraguchi und Yasushi Hiraoka. „Nup132 modulates meiotic spindle attachment in fission yeast by regulating kinetochore assembly“. Journal of Cell Biology 211, Nr. 2 (19.10.2015): 295–308. http://dx.doi.org/10.1083/jcb.201501035.

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During meiosis, the kinetochore undergoes substantial reorganization to establish monopolar spindle attachment. In the fission yeast Schizosaccharomyces pombe, the KNL1–Spc7-Mis12-Nuf2 (KMN) complex, which constitutes the outer kinetochore, is disassembled during meiotic prophase and is reassembled before meiosis I. Here, we show that the nucleoporin Nup132 is required for timely assembly of the KMN proteins: In the absence of Nup132, Mis12 and Spc7 are precociously assembled at the centromeres during meiotic prophase. In contrast, Nuf2 shows timely dissociation and reappearance at the meiotic centromeres. We further demonstrate that depletion of Nup132 activates the spindle assembly checkpoint in meiosis I, possibly because of the increased incidence of erroneous spindle attachment at sister chromatids. These results suggest that precocious assembly of the kinetochores leads to the meiosis I defects observed in the nup132-disrupted mutant. Thus, we propose that Nup132 plays an important role in establishing monopolar spindle attachment at meiosis I through outer kinetochore reorganization at meiotic prophase.

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Marcon, Edyta. „Hendrik Peter Bernelot Moens (1931–2008)“. Genome 51, Nr. 12 (Dezember 2008): 1063–67. http://dx.doi.org/10.1139/g08-075.

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The synaptonemal complex (SC) is a proteinaceous structure that physically holds the two homologous chromosomes together during meiotic prophase. First observed in 1956 by Montrose J. Moses (Duke University, Durham, North Carolina) in meiotic prophase spermatocytes of crayfish, the SC was found in many other species. Initially, the research into the SC focused on its structural characteristics, but with the availability of antibodies, the focus shifted to the protein components of the complex, and later, attention was diverted to the proteins associated with this structure at different time points during meiotic prophase. Various possible roles of this meiotic-specific structure have been debated since the discovery of the SC structure but consensus has yet to be reached. Dr. Peter Moens has been an internationally recognized expert on the SC, being involved in all of the steps and characterizing many of the structural and functional components of the complex mainly in mice but also in other species.

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Gaillard, Jérémie, Emmanuelle Neumann, Daniel Van Damme, Virginie Stoppin-Mellet, Christine Ebel, Elodie Barbier, Danny Geelen und Marylin Vantard. „Two Microtubule-associated Proteins of Arabidopsis MAP65s Promote Antiparallel Microtubule Bundling“. Molecular Biology of the Cell 19, Nr. 10 (Oktober 2008): 4534–44. http://dx.doi.org/10.1091/mbc.e08-04-0341.

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The Arabidopsis MAP65s are a protein family with similarity to the microtubule-associated proteins PRC1/Ase1p that accumulate in the spindle midzone during late anaphase in mammals and yeast, respectively. Here we investigate the molecular and functional properties of AtMAP65-5 and improve our understanding of AtMAP65-1 properties. We demonstrate that, in vitro, both proteins promote the formation of a planar network of antiparallel microtubules. In vivo, we show that AtMAP65-5 selectively binds the preprophase band and the prophase spindle microtubule during prophase, whereas AtMAP65-1-GFP selectively binds the preprophase band but does not accumulate at the prophase spindle microtubules that coexists within the same cell. At later stages of mitosis, AtMAP65-1 and AtMAP65-5 differentially label the late spindle and phragmoplast. We present evidence for a mode of action for both proteins that involves the binding of monomeric units to microtubules that “zipper up” antiparallel arranged microtubules through the homodimerization of the N-terminal halves when adjacent microtubules encounter.

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Freudzon, Leon, Rachael P. Norris, Arthur R. Hand, Shigeru Tanaka, Yoshinaga Saeki, Teresa L. Z. Jones, Mark M. Rasenick, Catherine H. Berlot, Lisa M. Mehlmann und Laurinda A. Jaffe. „Regulation of meiotic prophase arrest in mouse oocytes by GPR3, a constitutive activator of the Gs G protein“. Journal of Cell Biology 171, Nr. 2 (24.10.2005): 255–65. http://dx.doi.org/10.1083/jcb.200506194.

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The arrest of meiotic prophase in mouse oocytes within antral follicles requires the G protein Gs and an orphan member of the G protein–coupled receptor family, GPR3. To determine whether GPR3 activates Gs, the localization of Gαs in follicle-enclosed oocytes from Gpr3+/+ and Gpr3−/− mice was compared by using immunofluorescence and GαsGFP. GPR3 decreased the ratio of Gαs in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Gαs in the oocyte. Both of these properties indicate that GPR3 activates Gs. The follicle cells around the oocyte are also necessary to keep the oocyte in prophase, suggesting that they might activate GPR3. However, GPR3-dependent Gs activity was similar in follicle-enclosed and follicle-free oocytes. Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity.

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Chikashige, Yuji, Miho Yamane, Kasumi Okamasa, Chihiro Tsutsumi, Tomoko Kojidani, Mamiko Sato, Tokuko Haraguchi und Yasushi Hiraoka. „Membrane proteins Bqt3 and -4 anchor telomeres to the nuclear envelope to ensure chromosomal bouquet formation“. Journal of Cell Biology 187, Nr. 3 (02.11.2009): 413–27. http://dx.doi.org/10.1083/jcb.200902122.

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In many organisms, telomeres cluster to form a bouquet arrangement of chromosomes during meiotic prophase. Previously, we reported that two meiotic proteins, Bqt1 and -2, are required for tethering telomeres to the spindle pole body (SPB) during meiotic prophase in fission yeast. This study has further identified two novel, ubiquitously expressed inner nuclear membrane (INM) proteins, Bqt3 and -4, which are required for bouquet formation. We found that in the absence of Bqt4, telomeres failed to associate with the nuclear membranes in vegetative cells and consequently failed to cluster to the SPB in meiotic prophase. In the absence of Bqt3, Bqt4 protein was degraded during meiosis, leading to a phenotype similar to that of the bqt4-null mutant. Collectively, these results show that Bqt4 anchors telomeres to the INM and that Bqt3 protects Bqt4 from protein degradation. Interestingly, the functional integrity of telomeres is maintained even when they are separated from the nuclear envelope in vegetative cells.

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Kalaev, V. N., I. V. Ignatova, N. N. Kharchenko und S. S. Karpova. „CYTOGENETIC MARKERS FOR SELECTION MATERNAL TREES OF SCOTS PINE AND WHITE SPRUCE PRODUCING SEED OFFSPRING WITH CERTAIN LEVEL OF GENETIC STABILITY“. Scientific Notes of V.I. Vernadsky Crimean Federal University. Biology. Chemistry 7 (73), Nr. 3 (2022): 55–67. http://dx.doi.org/10.37279/2413-1725-2021-7-3-55-67.

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Currently, the depletion of the gene pool of forest woody plants is observed due to the fact that in the course of selective felling, specimens valuable for economic characteristics were destroyed and seeds from the remaining specimens were used, which did not have the best qualities. It was noted that a high level of genetic heterogeneity allows the population to adapt to changing environmental conditions, ensures the stability of the population and is a resource for breeding. The selection of valuable genotypes in the creation of forest seed plantations, which is carried out according to the phenotype, is based on the heterogeneity of populations. Meanwhile, studies show that phenotypically normal trees do not always produce good offspring. The cytogenetic method allows assessing the offspring. With its help, it is possible to distinguish among the seed offspring the mother trees of the group with different levels of stability of the genetic material. The aim of the work was to identify markers among cytogenetic parameters for the selection of trees producing seed offspring with different stability of the genetic material. The objects of the study were seedlings of seeds of phenotypically normal Scots pine trees growing in the Khopersky State Nature Reserve (51°10’56.9″N 41°44’17.2″E), and white spruce growing in the Botanical Garden. prof. B.M. Kozo-Polyansky Voronezh State University (51°42’41.57 «N 39°12’17.57″E). The trees had no visible pest damage. The method of preparation and analysis of preparations of seed sprouts is described in the work of Butorina A.K. (2000). In the course of the study, 20 cytogenetic parameters were determined: the mitotic index (counted with and without taking into account cells at the prophase of mitosis), the level of mitotic pathologies (counted with and without taking into account cells at the prophase of mitotic), the proportions of cells at the stages of prophase, metaphase, anaphase , the proportions of cells with 1–10 nucleoli in the nucleus of interphase cells, the proportion of cells with micronuclei, the proportion of cells with residual nucleoli in interphase and mitosis. Statistical processing of the study results was carried out using the STADIA 7.0 and MedCalc 17.5.3 software. The diagnostic value of the indicator is characterized by the area under the ROC-curve: 0.9–1.0 – excellent; 0.8–0.9 – very good; 0.7–0.8 – good, 0.6–0.7 – average, 0.6 and less – unsatisfactory. Among the cytogenetic indicators, there are those that are suitable for separating the mutable group from the weakly mutable and intermediate, as well as the weakly mutable from the intermediate. In pine, these include the proportion of cells at the prophase stage and the average number of nucleoli in the nucleus, in spruce – the mitotic index without taking into account cells at the prophase stage, the level of mitotic pathologies with and without taking into account cells at the prophase stage and the proportion of cells at the metaphase stage. There are indicators that make it possible to distinguish the mutable group from the weakly mutable and from the intermediate, but are not suitable for separating the weakly mutable group from the intermediate. These include the mitotic index, calculated taking into account cells at the prophase stage in pine, and the proportion of cells at the metaphase and ana-telophase stages in spruce. According to some indicators, it is possible to distinguish the intermediate group from the mutable and the weakly mutable, but it is impossible to distinguish the mutable group from the weakly mutable. In pine, such indicators are the proportion of cells in the metaphase, and in spruce, the proportion of cells with residual nucleoli in the interphase and meta-telophase. Indicators have been identified that make it possible to distinguish only mutable group from weakly mutable (in pine, the proportion of cells at the ana-telophase stage), and weakly mutable group from intermediate (in pine, the mitotic index taking into account cells at the prophase stage, the level of mitotic pathologies with and without taking into account cells at prophase stage, in spruce – mitotic index, taking into account cells at the prophase stage, the proportion of cells with micronuclei).

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Sedwick, Caitlin. „Needhi Bhalla: Chromosomes do the most amazing things“. Journal of Cell Biology 212, Nr. 3 (01.02.2016): 260–61. http://dx.doi.org/10.1083/jcb.2123pi.

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48

Su, Yongchun, Yunfei Li und Ping Ye. „Mammalian meiosis is more conserved by sex than by species: conserved co-expression networks of meiotic prophase“. REPRODUCTION 142, Nr. 5 (November 2011): 675–87. http://dx.doi.org/10.1530/rep-11-0260.

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Despite the importance of meiosis to human reproduction, we know remarkably little about the genes and pathways that regulate meiotic progression through prophase in any mammalian species. Microarray expression profiles of mammalian gonads provide a valuable resource for probing gene networks. However, expression studies are confounded by mixed germ cell and somatic cell populations in the gonad and asynchronous germ cell populations. Further, widely used clustering methods for analyzing microarray profiles are unable to prioritize candidate genes for testing. To derive a comprehensive understanding of gene expression in mammalian meiotic prophase, we constructed conserved co-expression networks by linking expression profiles of male and female gonads across mouse and human. We demonstrate that conserved gene co-expression dramatically improved the accuracy of detecting known meiotic genes compared with using co-expression in individual studies. Interestingly, our results indicate that meiotic prophase is more conserved by sex than by species. The co-expression networks allowed us to identify genes involved in meiotic recombination, chromatin cohesion, and piRNA metabolism. Further, we were able to prioritize candidate genes based on quantitative co-expression links with known meiotic genes. Literature studies of these candidate genes suggest that some are human disease genes while others are associated with mammalian gonads. In conclusion, our co-expression networks provide a systematic understanding of cross-sex and cross-species conservations observed during meiotic prophase. This approach further allows us to prioritize candidate meiotic genes for in-depth mechanistic studies in the future.

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49

Gautier, T., M. Robert-Nicoud, M. N. Guilly und D. Hernandez-Verdun. „Relocation of nucleolar proteins around chromosomes at mitosis. A study by confocal laser scanning microscopy“. Journal of Cell Science 102, Nr. 4 (01.08.1992): 729–37. http://dx.doi.org/10.1242/jcs.102.4.729.

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The behaviour of nucleolar antigens known to associate with chromosomes at mitosis was investigated in mammalian cells (HeLa, HEp-2, PtK1, CHO) by immunofluorescence and confocal laser scanning microscopy. Serial optical sections through mitotic cells, from prophase to telophase, were used to generate three-dimensional images of the antigen distribution. Our results indicate that, at the onset of mitosis, these antigens leave the nucleoli in a highly ordered manner to form a network extending from the nucleoli towards the nuclear envelope. The migration begins at very early prophase, when the condensation of the chromosomes is not yet visible. After completion of the migration at late prophase, the labelling is found at the chromosome periphery. The antigens remain distributed as a sheath surrounding the chromosomes from prophase to telophase. Therefore, the proteins involved in the formation of this perichromosomal layer have different behaviour than those of the prenucleolar bodies. The antigens appear to interact strongly with chromosomes, since they are not lost during chromosome isolation in hypotonic buffer. Each chromosome is entirely covered from one telomere to the other, except in the centromeric region. Thus the relocation of these nucleolar proteins does not appear to be the result of a passive accumulation at the chromosome periphery, but seems rather to be due to an active targeting to specific sites. Consequently, these proteins may have a determining function in the progression of the cells through mitosis, possibly by participating in the protection and stabilization of the chromosomes.

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Kwiatkowska, Maria. „PCC-like induction of mitosis in Chara vulgaris antheridia initiating differentiation of spermatozoids in the darkness“. Acta Societatis Botanicorum Poloniae 66, Nr. 1 (2014): 33–39. http://dx.doi.org/10.5586/asbp.1997.005.

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The objects of this research were the antheridial filament cells of Chara vulgaris which after 5-day mitodepressing treatment of the darkness reactivated mitosis (without light stimulation) in the result of the physiological state evocing the initiation of spermiogenesis in the antheridium. The course of these divisions was observed in relation to control cells cultivated in the natural photoperiod L:D = 14:10. It was shown that the passage of dark-arrested cells from early G2 (VII stage) to the early prophase in the cells linked to the base of filaments by plasmodesmata with spermatids initiating spermiogenesis, resembles the prematuraly condensed chromosomes (PCC). In this way a by-pass of the cells in the stage VII to early prophase occurs without reconstruction of granular components of nucleoli and with condensed stage of mitochondria characterising the dark-arrested cells. In opposition to this phenomenon in the control cell cycle and in light-induced reactivation of mitosis in the dark-arrested cells, initiation of the prophase follows the series of changes of the nuclear ultrastructure (VIII stage - decondensation of chromatin, IX and X stages nuclei with reticulate chromatin). At the early prophase, irrespective of the physiological conditions, the electron-transparent space appears between nuclear envelope and the chromatin as the effect of solublisation of lamins. The fine fibrils pass this space and link chromatin to the inner nuclear membrane.

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