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1.
A new technique was developed for a light microscopic analysis of meiosis in Drosophila oocytes. — When the nuclear envelope breaks down the bivalents, till then compressed into a karyosome, separate in early prometaphase. The homologues remain associated by chiasmata except for the fourth chromosomes which are no longer associated. Non-homologous chromosomes regularly segregating from each other in genetic experiments are also unconnected after karyosome disintegration but during metaphase I the fourth chromosomes and the heterologous pairs coorient on the same arc of the spindle and move precociously towards opposite poles. Nondisjunction and other irregularities are not infrequent in oocytes having an uneven number of achiasmatic elements. The fourth chromosomes and the Xs or the large autosomes, when lacking chiasmata, may be involved in non-homologous segregation. In c3G homozygotes all chromosomes appear as univalents in prometaphase. Segregation is variable but the observations suggest the polar distribution of equal numbers of chromosomes in variable combinations irrespective of the size. — Coorientation of univalents may be accounted for if the centromeres, whether homologous or non-homologous, are associated in pairs during early meiotic prophase, and that in the karyosome these pairing relationships are preserved until spindle organization at the onset of prometaphase. 相似文献
2.
The influence of trisomy on meiotic chromosome association and synapsis was studied in oocytes of two trisomy 21 fetuses. The patterns of association of the three chromosomes 21 were determined by analysis of late zygotene to early diplotene fetal oocytes after immunofluorescent staining of synaptonemal complexes. The identity of chromosome 21 was confirmed using FISH with either a whole chromosome 21 paint or an alpha-satellite DNA repeat probe. In both fetuses, a wide variety of configurations was present at pachytene. The most common configurations were a trivalent (35.5% and 51.6% of analyzable cells) and a bivalent plus univalent (62.9% and 45.2%). These different frequencies between the fetuses were not significant. Trivalents showed either triple synapsis or double synapsis with pairing-partner switches. The extent of triple synapsis varied from a short segment, either terminal or interstitial, to the whole chromosome length. Through use of immunofluorescent staining of the centromeres, we identified novel types of abnormal chromosome behavior in trisomy 21 fetal oocytes. Thus, we found that 6/41 trivalents had one of the chromosomes associated "out of register," i.e., in a nonhomologous fashion, with its two homologs. Likewise, we found three cells with bivalent plus univalent configurations, in which the univalent showed self-synapsis. The presence of three copies of chromosome 21 therefore results not only in the formation of complex and highly variable synaptic associations but also causes a significant increase in the occurrence of nonhomologous synapsis in human fetal oocytes. 相似文献
3.
During plant cytokinesis, kinesin-related motor proteins are believed to play critical roles in microtubule organization and vesicle transport in the phragmoplast. Previously, we reported that the motor AtPAKRP1 was associated with the plus end of phragmoplast microtubules in Arabidopsis thaliana [Lee Y-RJ, Liu B (2000) Curr Biol 10:797–800]. In this paper, we report a full-length cDNA from the same organism, which encodes a polypeptide 74% identical to AtPAKRP1. This AtPAKRP1-like protein—AtPAKRP1L—and AtPAKRP1 share similar domain structures along the polypeptides. Peptide antibodies were raised and purified to distinguish the two polypeptides in vitro and in vivo. When monospecific anti-AtPAKRP1 and anti-AtPAKRP1L antibodies were used in immunofluorescence, they both decorated the plus end of phragmoplast microtubules at all stages of phragmoplast development. Their localization patterns were indistinguishable from each other. By using bacterially expressed fusion proteins of motor-less versions of both polypeptides, it was revealed that AtPAKRP1 and AtPAKRP1L were able to interact with themselves and with each other. Using T-DNA insertional mutants, it was also demonstrated that AtPAKRP1 and AtPAKRP1L were not required for each others localization. Our results therefore indicate that AtPAKRP1 and AtPAKRP1L are both expressed in the same cells, and likely have identical functions in the phragmoplast by forming either homodimers or heterodimers.Abbreviations AtPAKRP1 Arabidopsis thaliana phragmoplast-associated kinesin-related protein 1 - AtPAKRP1L A. thaliana phragmoplast-associated kinesin-related protein 1-like - GST Glutathione S-transferase - KRP Kinesin-related protein - 6×His Six-histidine tag 相似文献
4.
Annelise Fiil 《Chromosoma》1978,69(3):381-395
The synaptonemal complexes of the oocytes of the mosquito Culex pipiens quinquefasciatus have been reconstructed from serial sections. A diffuse structure, probably a chromocenter composed of centromeric heterochromatin, was present during pachytene. As no synaptonemal complexes were visible inside the chromocenter the continuity of the 2 arms of a bivalent was lost. The telomeric ends were clustered in a small area of the nuclear membrane in a bouquet arrangement; they were associated in pairs, and sometimes joined through a special structure. One pair was composed of the 2 telomeres of the shortest bivalent and a ring configuration was thus formed. The other 2 chromosomes may form one or two rings. During a short transitional stage, after the disappearence of the synaptonemal complexes, several thousand annuli, 1200–1500 A in diameter, were present in the nuclei. The annuli disappeared as material originating mainly from the transverse filaments of the synaptonemal complexes formed a capsule around the chromosomes during diplotene. 相似文献
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It was previously shown that more than half of the human oocytes obtained from IVF patients of advanced reproductive age are aneuploid, due to meiosis I and meiosis II errors. The present paper further confirms that 61.8% of the oocytes tested by fluorescent probes specific for chromosomes 13, 16, 18, 21 and 22 are abnormal, representing predominantly chromatid errors, which are the major source of aneuploidy in the resulting embryos. Almost half of the oocytes with meiosis I errors (49.3%) are prone to sequential meiosis II errors, which may lead to aneuploidy rescue in 30.8% of the cases. Half of the detected aneuploidies (49.8%) are of complex nature with involvement of two or more chromosomes, or the same chromosome in both meiotic divisions. The aneuploidy rates for individual chromosomes are different, with a higher prevalence of chromosome 21 and 22 errors. The origin of aneuploidy for the individual chromosomes is also not random, with chromosome 16 and 22 errors originating more frequently in meiosis II, and chromosome 18, 13 and 21 errors in meiosis I. There is an age dependence not only for the overall frequency of aneuploidies, but also for each chromosome error, aneuploidies originating from meiosis I, meiosis II, and both meiosis I and meiosis II errors, as well as for different types of aneuploidies. The data further suggest the practical relevance of oocyte aneuploidy testing for detection and avoidance from transfer of the embryos deriving from aneuploid oocytes, which should contribute significantly to the pregnancy outcomes of IVF patients of advanced reproduction age. 相似文献
8.
Meiotic recombination in Drosophila females depends on chromosome continuity between genetically defined boundaries 下载免费PDF全文
In the pairing-site model, specialized regions on each chromosome function to establish meiotic homolog pairing. Analysis of these sites could provide insights into the mechanism used by Drosophila females to form a synaptonemal complex (SC) in the absence of meiotic recombination. These specialized sites were first established on the X chromosome by noting that there were barriers to crossover suppression caused by translocation heterozygotes. These sites were genetically mapped and proposed to be pairing sites. By comparing the cytological breakpoints of third chromosome translocations to their patterns of crossover suppression, we have mapped two sites on chromosome 3R. We have performed experiments to determine if these sites have a role in meiotic homolog pairing and the initiation of recombination. Translocation heterozygotes exhibit reduced gene conversion within the crossover-suppressed region, consistent with an effect on the initiation of meiotic recombination. To determine if homolog pairing is disrupted in translocation heterozygotes, we used fluorescent in situ hybridization to measure the extent of homolog pairing. In wild-type oocytes, homologs are paired along their entire lengths prior to accumulation of the SC protein C(3)G. Surprisingly, translocation heterozygotes exhibited homolog pairing similar to wild type within the crossover-suppressed regions. This result contrasted with our observations of c(3)G mutant females, which were found to be defective in pairing. We propose that each Drosophila chromosome is divided into several domains by specialized sites. These sites are not required for homolog pairing. Instead, the initiation of meiotic recombination requires continuity of the meiotic chromosome structure within each of these domains. 相似文献
9.
Meiotic chromosome synapsis-promoting proteins antagonize the anti-crossover activity of sgs1 下载免费PDF全文
Sgs1, the budding yeast homolog of the mammalian BLM helicase, has been implicated in preventing excess recombination during both vegetative growth and meiosis. Most meiotic crossover (CO) recombination requires full function of a set of yeast proteins (Zip1, Zip2, Zip3, Zip4/Spo22, Mer3, Msh4, and Msh5, termed the SIC or ZMM proteins) that are also required for homologous chromosome synapsis. We report here genetic and molecular assays showing that sgs1 single mutants display relatively modest increases in CO recombination (less than 1.6-fold relative to wild-type). In contrast, a much greater CO increase is seen when an sgs1 mutation is introduced into the CO- and synapsis-deficient zip1, zip2, zip3, mer3, or msh4 mutants (2- to 8-fold increase). Furthermore, close juxtaposition of the axes of homologous chromosomes is restored. CO restoration in the mutants is not accompanied by significant changes in noncrossover (NCO) recombinant frequencies. These findings show that Sgs1 has potent meiotic anti-CO activity, which is normally antagonized by SIC/ZMM proteins. Our data reinforce previous proposals for an early separation of meiotic processes that form CO and NCO recombinants. 相似文献
10.
The number and location of crossovers across genomes are highly regulated during meiosis, yet the key components controlling them are fast evolving, hindering our understanding of the mechanistic causes and evolutionary consequences of changes in crossover rates. Drosophila melanogaster has been a model species to study meiosis for more than a century, with an available high-resolution crossover map that is, nonetheless, missing for closely related species, thus preventing evolutionary context. Here, we applied a novel and highly efficient approach to generate whole-genome high-resolution crossover maps in D. yakuba to tackle multiple questions that benefit from being addressed collectively within an appropriate phylogenetic framework, in our case the D. melanogaster species subgroup. The genotyping of more than 1,600 individual meiotic events allowed us to identify several key distinct properties relative to D. melanogaster. We show that D. yakuba, in addition to higher crossover rates than D. melanogaster, has a stronger centromere effect and crossover assurance than any Drosophila species analyzed to date. We also report the presence of an active crossover-associated meiotic drive mechanism for the X chromosome that results in the preferential inclusion in oocytes of chromatids with crossovers. Our evolutionary and genomic analyses suggest that the genome-wide landscape of crossover rates in D. yakuba has been fairly stable and captures a significant signal of the ancestral crossover landscape for the whole D. melanogaster subgroup, even informative for the D. melanogaster lineage. Contemporary crossover rates in D. melanogaster, on the other hand, do not recapitulate ancestral crossovers landscapes. As a result, the temporal stability of crossover landscapes observed in D. yakuba makes this species an ideal system for applying population genetic models of selection and linkage, given that these models assume temporal constancy in linkage effects. Our studies emphasize the importance of generating multiple high-resolution crossover rate maps within a coherent phylogenetic context to broaden our understanding of crossover control during meiosis and to improve studies on the evolutionary consequences of variable crossover rates across genomes and time. 相似文献
11.
The nature, intracellular distribution, and role of proteins synthesized during meiotic maturation of mouse oocytes in vitro have been examined. Proteins synthesized during the initial stages of maturation are concentrated within the nucleus (germinal vesicle) and become intimately associated with the condensing chromosomes. Inhibition of protein synthesis during this period does not prevent germinal vesicle dissolution or chromosome condensation, but meiotic progression is blocked reversibly at the circular bivalent stage. A protein is synthesized during meiotic maturation of the mouse oocyte which exhibits several of the characteristics of the very lysine-rich histone, FI; this and other histones are phosphorylated during the initial stages of maturation. These results are discussed in relation to studies of meiotic maturation of oocytes from non-mammalian species and chromosome condensation in both oocytes and mitotic cells. 相似文献
12.
Meiotic competence of prepubertal goat oocytes 总被引:3,自引:0,他引:3
The object of this work was to evaluate in vitro maturation of follicular oocytes from the ovaries of prepubertal goats obtained from the slaughterhouse. To obtain the oocytes, follicles were dissected and classified according to their diameters. In the first experiment, oocytes were matured in vitro with granulosa cells. No significant differences were detected in the percentages of maturation between adult and prepubertal goat oocytes recovered from follicles of 2.5 to 6.0 mm in diameter (81.82 vs 72.47%, respectively). The percentage of maturation increased to 88.0% in prepubertal goat oocytes from 3.0 to 6.0-mm follicles. In the second experiment, the percentage of maturation of prepubertal goat oocytes was greater after 27 than after 24 h. In the third experiment, the maturational capacity of prepubertal goat oocytes according to follicular diameter was evaluated. The percentages of maturation after 27 h of culture with no granulosa cells were 24.14, 56.60 and 74.78%, respectively, for follicles 1.0 to 1.9 mm, 2.0 to 2.9 mm, and 3.0 to 6.0 mm in diameter. As the follicular diameter increased, growth of the oocyte as well as a greater number of oocytes with more cumulus cell layers were observed. A correlation between the diamter of the oocyte and its competence to complete in vitro maturation was also observed. Oocytes with more cumulus cell layers showed only a slight superiority in their capacity for maturation in large-size follicles (3.0 to 6.0 mm), but the difference was not significant. In conclusion, oocytes from prepubertal goats complete their growth and reach meiotic competence in follicles larger than 3.0 mm. With these oocytes it is possible to obtain in vitro maturation results similar to those from adult goats. 相似文献
13.
Iftikhar Ali 《Cell Adhesion & Migration》2020,14(1):139-152
ABSTRACT Kinesins constitute a superfamily of ATP-driven microtubule motor enzymes that convert the chemical energy of ATP hydrolysis into mechanical work along microtubule tracks. Kinesins are found in all eukaryotic organisms and are essential to all eukaryotic cells, involved in diverse cellular functions such as microtubule dynamics and morphogenesis, chromosome segregation, spindle formation and elongation and transport of organelles. In this review, we explore recently reported functions of kinesins in eukaryotes and compare their specific cargoes in both plant and animal kingdoms to understand the possible roles of uncharacterized motors in a kingdom based on their reported functions in other kingdoms. 相似文献
14.
Meiotic cell cycle arrest in mammalian oocytes 总被引:1,自引:0,他引:1
Meiotic cell cycle in mammalian oocytes is a dynamic process that involves several stop/go channels. The cell cycle arrest in oocyte occurs at various stages such as diplotene, metaphase‐I (M‐I), metaphase‐II (M‐II), and so called metaphase‐like arrest (M‐III). Leutinizing hormone surge induces meiotic resumption from diplotene arrest in follicular microenvironment by overriding several factors responsible for the maintenance of meiotic arrest. The inhibitory factors are synthesized in oocyte or in the associated follicular somatic cells and transferred to the oocyte. The major factors include hypoxanthine, cyclic adenosine 3′, 5′‐monophosphate, cyclic guanosine 3′, 5′‐monophosphate, reactive oxygen species, protein kinase A, and protein kinase C. In the presence of active protein kinases, epidermal‐like growth factors are produced that activate mitogen‐activated protein kinase in cumulus granulosa cells. The maturation promoting factor, cytostatic factors, and spindle assembly checkpoint proteins are also involved in that maintenance of arrest at various stages of meiotic cell cycle in mammalian oocytes. In this review, we briefly summarize the role of these factors in the maintenance of meiotic cell cycle arrest in mammalian oocytes. J. Cell. Physiol. 223:592–600, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
15.
To investigate the chromosomal effects of topoisomerase II (topo-II)-interactive drugs on mammalian primary oocytes, female Chinese hamsters were treated with etoposide (VP-16) at various intervals pre- and post-human chorionic gonadotropin (hCG) injections. Chromosome analysis of oocytes at metaphase II (M II) showed that treatment with VP-16 at 50h pre-hCG had no effect, but the treatments between 24h pre-hCG and 2h post-hCG often caused structural chromosome aberrations. Although treatment at 4h post-hCG had no effect, subsequent treatments at 6 and 8h post-hCG produced a significant increase in structural chromosome aberrations. No effect was found following treatment at 10h post-hCG. The incidence of aneuploidy following exposure to VP-16 was also dependent on the time of hCG injection. Taking the time course of meiotic progression in primary oocytes following hCG injection and pharmacokinetics of VP-16 into consideration, it is likely that meiotic stages from late dictyate to diakinesis are highly sensitive to VP-16, while stages at dictyate and from metaphase I (M I) to telophase I (telo I) are relatively insensitive to the drug. Moreover, the effect of VP-16 on structural chromosome aberrations and aneuploidy was dose-dependent.Chromosome analysis at M I detected a frequent occurrence of structural chromosome aberrations in treated oocytes. This suggests that structural aberrations may be caused by disruption of cleavable complexes during chromosome condensation. Detection of chromosome bridges during anaphase I/telophase I (ana I/telo I) may support the hypothesis that induction of aneuploidy by VP-16 is due to failure in decatenation of recombinant homologous chromosomes. 相似文献
16.
Meiotic competence of in vitro grown goat oocytes 总被引:1,自引:0,他引:1
The objective of the present study was to grow meiotically incompetent goat oocytes from early antral follicles in vitro and to render them competent to undergo germinal vesicle breakdown. Cumulus-oocyte complexes with pieces of parietal granulosa cells were isolated from follicles 0.35-0.45 mm in diameter using both mechanical and enzymatic methods. The cumulus-oocyte complexes were divided into two groups according to oocyte diameter (group A: < 95 microm; group B: > 95 microm) and cultured for 8 or 9 days on granulosa cell monolayers. Within 8 days of culture, the mean oocyte diameter increased from 86 +/- 0.4 microm to 95 +/- 0.7 microm in group Aand from 106 +/- 0.2 microm to 109 +/- 0.5 microm in group B. After 9 days of culture, the mean diameter of oocytes from groups A and B were 99 +/- 0.5 microm and 112 +/- 0.4 microm, respectively. The meiotic competence of oocytes grown in vitro was evaluated by in vitro maturation. Within 8 days of culture, only 3% of oocytes from group A and 6% of oocytes from group B acquired the ability to undergo germinal vesicle breakdown. After 9 days of culture, 7% of group A oocytes and 42% of group B oocytes were competent to resume meiosis. The expression of p34(cdc2) in oocytes grown in vitro was analysed by the western blot technique. During 9 days of culture, p34(cdc2) accumulated in both groups of growing oocytes, but its concentration was lower than in fully grown oocytes used as controls. The results showed for the first time that goat oocytes from early antral follicles can grow, accumulate p34(cdc2) and acquire the ability to resume meiosis, when cultured for 9 days on granulosa cell monolayers. 相似文献
17.
Meiosis in triploidRhoeo spathacea (2n=3x=18) is characterized by multivalents composed of up to 16 chromosomes as well as bivalents and univalents. Forty-nine types of configurations were present in 113 completely analyzed cells. Univalents were present in 91.15% of the cells, ranging 0–8, mean 2.21±0.14 per cell. Bivalents were seen in 76.11% and trivalents in 69.03% of the cells with means of 1.58±0.12 (1.12±0.13 chains, 0.46±0.07 rings) and 1.33±0.12 respectively, per cell. As the size of the configurations increases, their mean decreases. There were 7.47±0.18 two-arm and 2.62±0.14 three-arm associations per cell. No 4-arm associations were observed. The theory of segmental interchange is consistent with all these data. The mean number of countable chiasmata per cell was 12.7±0.16, or 0.71 per chromosome. Preferential pairing of complex homologues occurred. 相似文献
18.
Nakaya M Fukui A Izumi Y Akimoto K Asashima M Ohno S 《Development (Cambridge, England)》2000,127(23):5021-5031
The asymmetric distribution of cellular components is an important clue for understanding cell fate decision during embryonic patterning and cell functioning after differentiation. In C. elegans embryos, PAR-3 and aPKC form a complex that colocalizes to the anterior periphery of the one-cell embryo, and are indispensable for anterior-posterior polarity that is formed prior to asymmetric cell division. In mammals, ASIP (PAR-3 homologue) and aPKCgamma form a complex and colocalize to the epithelial tight junctions, which play critical roles in epithelial cell polarity. Although the mechanism by which PAR-3/ASIP and aPKC regulate cell polarization remains to be clarified, evolutionary conservation of the PAR-3/ASIP-aPKC complex suggests their general role in cell polarity organization. Here, we show the presence of the protein complex in Xenopus laevis. In epithelial cells, XASIP and XaPKC colocalize to the cell-cell contact region. To our surprise, they also colocalize to the animal hemisphere of mature oocytes, whereas they localize uniformly in immature oocytes. Moreover, hormonal stimulation of immature oocytes results in a change in the distribution of XaPKC 2-3 hours after the completion of germinal vesicle breakdown, which requires the kinase activity of aPKC. These results suggest that meiotic maturation induces the animal-vegetal asymmetry of aPKC. 相似文献
19.
Drosophila: the genetics of two major larval proteins. 总被引:10,自引:0,他引:10
A series of irradiation-induced deficiencies covering 62 polytene chromosome bands in chromosome arm 3L of Drosophila melanogaster includes the loci of two abundant developmentally regulated larval proteins. The structural gene for larval serum protein 2 (LSP 2) lies at 68E3 or 4, and that for salivary glue secretion protein 3 between 68A8 and 68C11, coincident with a major intermoult puff active in the salivary gland at the time of glue synthesis. The structural genes for esterase 6 and four visible recessive loci lie within the same region. 相似文献
20.
We document the occurrence of ``sex ratio' meiotic drive in natural populations of Drosophila testacea. ``Sex ratio' males sire >95% female offspring. Genetic analysis reveals that this effect is due to a meiotically driven X chromosome, as in other species of Drosophila in which ``sex ratio' has been found. In contrast to other drosophilids, the ``sex ratio' and standard chromosomes of D. testacea do not differ in gene arrangement, implying that the effect may be due to a single genetic factor in this species. In all likelihood, the ``sex ratio' condition has evolved independently in D. testacea and in the Drosophila obscura species group, as the loci responsible for the effect occur on different chromosomal elements. An important ecological consequence of ``sex ratio' is that natural populations of D. testacea exhibit a strong female bias. Because D. testacea mates, oviposits, and feeds as adults and larvae on mushrooms, this species provides an excellent opportunity to study the selective factors in nature that prevent ``sex ratio' chromosomes from increasing to fixation and causing the extinction of the species. 相似文献