Humans ; Meiosis/physiology* ; Mitosis/physiology*

The synaptonemal complex (SC) is a meiosis-specific proteinaceous macromolecular structure that assembles between paired homologous chromosomes during meiosis in various eukaryotes. The SC has a highly conserved ultrastructure and plays critical roles in controlling multiple steps in meiotic recombination and crossover formation, ensuring accurate meiotic chromosome segregation. Recent studies in different organisms, facilitated by advances in super-resolution microscopy, have provided insights into the macromolecular structure of the SC, including the internal organization of the meiotic chromosome axis and SC central region, the regulatory pathways that control SC assembly and dynamics, and the biological functions exerted by the SC and its substructures. This review summarizes recent discoveries about how the SC is organized and regulated that help to explain the biological functions associated with this meiosis-specific structure.
Animals ; Chromosome Segregation ; Meiosis/physiology* ; Synaptonemal Complex/physiology*

OBJECTIVETo reveal the mechanism of sterility of Liriope spicata var. prolifera.

METHODMeiotic behavior and pollen development of L. spicata var. prolifera were described in detail. Its proto-variety L. spicata was also investigated for comparison.

RESULTDuring the meiosis of microspore mother cells (MMC), most of cells displayed normally in L. spicata, but abnormally in L. spicata var. prolifera. The abnormity was showed that: some chromosomes or their fragments moved out of the spindle of the cell at metaphase; some chromosome bridges, fragments and lagging ones were formed at anaphase; and many microspores displayed the micronucleus at the telophase. The pollen development was abnormal in L. spicata var. prolifera and normal in L. spicata, with the aberration rate of pollen was 95.81% and 3.44% separately.

CONCLUSIONThese results indicate that some abnormalities of meiotic behavior and pollen development are main reasons for inducing microspore abortion during its development.

Liriope Plant ; cytology ; physiology ; Meiosis ; physiology ; Plants, Medicinal ; cytology ; physiology ; Pollen ; physiology

The present experiments were conducted to evaluate the effects of follicular fluid on maturation of bovine follicular oocytes. TC medium 199 seemed to be in adequate for this purpose since a high proportion (ranging 84.1. to 97.0%) of the oocytes were able to resume meiotic division in both media-with or without the addition of follicular fluid. This implies a possible similarity between TC medium 199 and follicular fluid with regard to the components initiating meiosis. Actually, TC medium 199 contains amino acids, vitamins and carbohydrates most of which are also found in follicular fluid. For this reason, the effect of follicular fluid on the ovum maturation was investigated by applying Krebs-Ringer bicarbonate solution (SECM), which was main1y composed of the salts, pyruvate and lactate. When the oocytes were cultured in SECM without the addition of follicular fluid, only 7-14% of them resumed meiotic division within 30 hours. However, when follicular fluid was added, the proportion of oocytes undergoing maturation was sharply increased to about 70%. Among the groups cultured in media containing different concentrations of follicular fluid, the proportion of the oocytes in meiosis remained constant, In pure follicular fluid, 87-89% of the oocytes showed enhancement of meiotic division. The presence of the follicular fluid contributed to a decrease in the production of degenerative oocytes. As a consequence it has been noted that addition of follicular fluid to the culture medium provides a more beneficial environment for cow oocytes. Meiotic division is initiated and production of degenerative oocytes is inhibited.
Animal ; Cattle ; Cells, Cultured ; Culture Media ; Female ; Meiosis ; Oocytes/physiology* ; Ovarian Follicle/physiology* ; Ovum/physiology*

Repairing DNA double-strand breaks (DSBs) with homologous chromosomes as templates is the hallmark of meiosis. The critical outcome of meiotic homologous recombination is crossovers, which ensure faithful chromosome segregation and promote genetic diversity of progenies. Crossover patterns are tightly controlled and exhibit three characteristics: obligatory crossover, crossover interference, and crossover homeostasis. Aberrant crossover patterns are the leading cause of infertility, miscarriage, and congenital disease. Crossover recombination occurs in the context of meiotic chromosomes, and it is tightly integrated with and regulated by meiotic chromosome structure both locally and globally. Meiotic chromosomes are organized in a loop-axis architecture. Diverse evidence shows that chromosome axis length determines crossover frequency. Interestingly, short chromosomes show different crossover patterns compared to long chromosomes. A high frequency of human embryos are aneuploid, primarily derived from female meiosis errors. Dramatically increased aneuploidy in older women is the well-known "maternal age effect." However, a high frequency of aneuploidy also occurs in young women, derived from crossover maturation inefficiency in human females. In addition, frequency of human aneuploidy also shows other age-dependent alterations. Here, current advances in the understanding of these issues are reviewed, regulation of crossover patterns by meiotic chromosomes are discussed, and issues that remain to be investigated are suggested.
Cell Division/physiology* ; Chromosome Segregation/physiology* ; Humans ; Meiosis/genetics* ; Recombination, Genetic

This study evaluated the meiotic competence of buffalo oocytes with different layers of cumulus cells. A total of 588 oocytes were collected from 775 ovaries averaging 0.78 oocytes per ovary. Oocytes with homogenous cytoplasm (n = 441) were selected for in vitro maturation (IVM) and divided into four groups based on their cumulus morphology: a) oocytes with > or == 3 layers of cumulus cells, b) 1-2 layers of cumulus cells and oocytes with partial remnants or no cumulus cells to be cocultured c) with or d) without cumulus cells. Oocytes in all four groups were matured in 100 microL drop of TCM-199 supplemented with 10microgram/mL follicle stimulating hormone (FSH), 10microgram/mL luteinizing hormone (LH), 1.5microgram/mL estradiol, 75microgram/mL streptomycin, 100 IU/mL penicillin, 10 mM Hepes and 10% FBS at 39degrees C and 5% CO2 for 24 hours. After IVM, cumulus cells were removed from oocytes using 3 mg/mL hyaluronidase, fixed in 3% glutaraldehyde, stained with DAPI and evaluated for meiotic competence. The oocytes with > or ==3 layers of cumulus cells showed higher maturation rates (p <0.05: 64.5%) than oocytes with partial or no cumulus cells (8.6%) and oocytes co-cultured with cumulus cells (34.5%) but did not differ from oocytes having 1-2 layers of cumulus cells (51.4%). The degeneration rates were higher (p < 0.05) for oocytes with partial or no cumulus cells (51%) than rest of the groups (range: 13.8% to 17.4%). These results suggest that buffalo oocytes with intact layers of cumulus cells show better IVM rates than oocytes without cumulus cells and the co-culture of poor quality oocytes with cumulus cells improves their meiotic competence.
Animals ; Buffaloes/*physiology ; Female ; Fluorescent Dyes/chemistry ; Indoles/chemistry ; Meiosis/*physiology ; Microscopy, Fluorescence/veterinary ; Oocytes/cytology/growth&development/*physiology

Meiosis is an essential step in gametogenesis which is the key process in sexually reproducing organisms as meiotic aberrations may result in infertility. In meiosis, programmed DNA double-strand break (DSB) formation is one of the fundamental processes that are essential for maintaining homolog interactions and correcting segregation of chromosomes. Although the number and distribution of meiotic DSBs are tightly regulated, still abnormalities in DSB formation are known to cause meiotic arrest and infertility. This review is a detailed account of molecular bases of meiotic DSB formation, its evolutionary conservation, and variations in different species. We further reviewed the mutations of DSB formation genes in association with human infertility and also proposed the future directions and strategies about the study of meiotic DSB formation.
DNA Breaks, Double-Stranded ; DNA Repair/genetics* ; Humans ; Infertility/genetics* ; Meiosis/physiology*

Male meiosis is a complex process whereby spermatocytes undergo cell division to form haploid cells. This review focuses on the role of retinoic acid (RA) in meiosis, as well as several processes regulated by RA before cell entry into meiosis that are critical for proper meiotic entry and completion. Here, we discuss RA metabolism in the testis as well as the roles of stimulated by retinoic acid gene 8 (STRA8) and MEIOSIN, which are responsive to RA and are critical for meiosis. We assert that transcriptional regulation in the spermatogonia is critical for successful meiosis.
Animals ; Cell Differentiation/genetics* ; Humans ; Meiosis/drug effects* ; Spermatogenesis/physiology* ; Tretinoin/metabolism*

Adult ; Chromatids/genetics* ; Chromosome Aberrations ; Humans ; Infertility, Male/genetics* ; Male ; Meiosis ; Metaphase/genetics* ; Spermatocytes/physiology*

Tubulin is the major protein of microtubule. alpha- and beta- tubulins form heterodimers, while gamma-tubulin regulates microtubule organization. The present study aimed to observe the dynamic changes of gamma-tubulin in preimplantation development of parthenogenetic mouse embryos. Immunofluorescence and laser confocal microscopy were used to detect the location of gamma-tubulin in preimplantation parthenogenetic embryos activated by SrCl2. The oocytes were collected at 13-14 h after hCG injection, and then activated with 10 mmol/L SrCl2 in Ca(2+)-free CZB medium with 5 mmol/L cytochalasin B (CB), fixed at 1 h intervals until 6 h after activation. The results showed that spindle was paralleled with the cell membrane all the time, when the meiosis of MII mouse oocytes resumed. The rotation of spindle was inhibited, but karyokinesis was not influenced. At 0 h after activation, i.e. at metaphase, gamma-tubulin was distributed mainly on the two poles of spindle. At 1 h after activation, i.e. at anaphase, following the separation of chromosomes, gamma-tubulin was transformed from dense to disperse. At 2 h after activation, gamma-tubulin was localized between the segregated sister chromatids at telophase. However, at 3-6 h after activation, gamma-tubulin concentrated around the two female pronuclei during their formation and juxtaposition. Moreover, another group of MII oocytes were activated for 6 h and cultured in droplets of KSOM medium under mineral oil in 5% CO2 in air at 37 degrees C to permit parthenogenetic development. The embryos were collected and fixed at 3 h, 14 h, 16 h, and 18 h of culture. At 3 h after culture, i.e. at mitotic interphase, it was shown that amorphous gamma-tubulin distributed around the nuclei of early parthenogenetic embryos. At 24 h after culture, i.e. at prometaphase, gamma-tubulin migrated along the spindle microtubule to the two poles. Our results showed that gamma-tubulin had similar location patterns at metaphase, anaphase and telophase in meiosis and mitosis. It was concluded that gamma-tubulin assembly in parthenogenetically activated oocytes facilitated the formation of negative pole cap and the stabilization of microtubule, thus promoting the spindle formation at meiosis and mitosis. The relocation of gamma-tubulin at anaphase and telophase might be induced by the event of segregation of homologous chromosome being pulled away by the spindle. gamma-tubulin might contribute to the migration and juxtaposition of the two female pronuclei as well.
Animals ; Embryo, Mammalian ; Embryonic Development ; Female ; Meiosis ; Mice ; Mitosis ; Oocytes ; cytology ; Parthenogenesis ; Spindle Apparatus ; physiology ; Tubulin ; physiology