人类生精细胞在培养过程中的分化与变形

目的 探讨体外培养条件下生精细胞向单倍体精子细胞分化以及精子细胞变形为精子的可能性.方法 对11例非梗阻性无精子症患者行睾丸活检,将其中9份具有生精细胞的活检标本在终浓度为50 U/L卵泡刺激素和1μmol/L睾酮的改良人输卵管液培养液中进行体外培养,对培养前及培养后24h标本中精子及其他细胞进行计数,计算各种细胞的比例.应用流式细胞仪对2例患者培养前和培养后24 h的细胞进行细胞倍体分析.结果 9例标本培养前精子比例为(17.7±8.9)％,培养24h后为(25.6±10.3)％,培养前后差异有统计学意义(P=0.004).2例细胞倍体分析结果显示,培养前可见4、2和1 n波峰,培养后4 n波峰消失,1 n波峰显著增宽和增高.结论 生精细胞体外培养可使生精细胞发生减数分裂,并使精子细胞向精子变形.     

Deleterious mutation in SYCE1 is associated with non-obstructive azoospermia

Purpose

To determine the molecular basis of familial, autosomal-recessive, non-obstructive azoospermia in a consanguineous Iranian Jewish family.

Methods

We investigated the genetic cause of non-obstructive azoospermia in two affected siblings from a consanguineous family. Homozygosity mapping in the DNA samples of the patients and their normospermic brother was followed by exome analysis of one of the patients. Other family members were genotyped for the mutation by Sanger sequencing. The mutation effect was demonstrated by immunostaining of the patients’ testicular tissue.

Results

The two patients were homozygous for a splice site mutation in SYCE1 which resulted in retention of intron three in the cDNA and premature stop codon. SYCE1 encodes a Synaptonemal Complex protein which plays an essential role during meiosis. Immunostaining of patient’s testicular tissue with anti-Syce1 antibody revealed an undetectable level of Syce1. Histological examination of the patients’ tissue disclosed immature-stages spermatocytes without mature forms, indicating maturation arrest.

Conclusion

The significance of most synaptonemal complex proteins was previously demonstrated in a mutant mouse model. The present report underscores the importance of synaptonemal complex proteins in spermatogenenesis in humans. Our new approach, combining homozygosity mapping and exome sequencing, resulted in one of the first reports of an autosomal-recessive form of NOA.     

The association between the oocyte pool and aneuploidy: a comparative study of the reproductive potential of young and aged mice

Purpose

The present study examined the effect of aging on female reproductive potential.

Methods

Six-week-old and 9-month-old CD1 mice were referred to as the ‘young’ and ‘aged’ groups, respetively. Oocytes were collected after superovulation, and their viability were compared using parthenogenetic activation. The aneuploidy of the oocytes (MII) was assessed using chromosome spread, and the whole ovarian follicle number was counted using an unbiased stereological method. Serum hormone levels were measured using the radio-immunity method, and the expression of the Cohesin subunit genes in the oocytes (GV) were assessed using RT-PCR.

Results

The mean number of recovered (25.8 vs. 16.2; P < 0.05) and live oocytes (24.0 vs. 11.73; P <0.01) per head in the young-mice group (6-week-old) was significantly higher than that of the aged group (9-month-old). The aneuploidy rate of the ovulated oocytes in the aged group was significantly higher than that of the young group (36.8 % vs. 10 %; P < 0.01), and the rate of blastocyst formation in the young group (85.23 %) was significantly higher than that of the aged group (81.2 %; P <0.05). The number of primordial follicles (the oocyte pool) per ovary in the aged group was significantly decreased compared with the young group (330 ± 33.51 vs. 2079.6 ± 420.70; P < 0.01), and the level of AMH in the aged group was significantly higher than that of the young group (4.66 ± 0.11 ng/ml vs. 4.07 ± 0.18 ng/ml; P < 0.01).

Conclusions

We propose that maternal aging significantly reduces the oocyte pool, superovulation efficiency and developmental potential and increases the oocyte aneuploidy rate.

Electronic supplementary material

The online version of this article (doi:10.1007/s10815-013-0160-5) contains supplementary material, which is available to authorized users.     

甲苯对小鼠睾丸精母细胞减数分裂的影响

目的探讨甲苯对小鼠精母细胞减数分裂的影响。方法采用哺乳动物生殖细胞减数分裂制片技术,观察小鼠精母细胞减数分裂相的变化。结果甲苯低、中、高浓度实验组与对照组相比,差异程度分别为P>0.05、P<0.01、P<0.01。结论甲苯中、高浓度抑制小鼠睾丸精母细胞减数分裂。     

双酚A对诱导型一氧化氮合酶基因缺失鼠卵母细胞染色体不分离的影响

目的：研究双酚Ａ（ｂｉｓｐｈｅｎｏｌ Ａ,ＢＰＡ）暴露对诱导型一氧化氮合酶（ｉｎｄｕｃｉｂｌｅ ｎｉｔｒｉｃ ｏｘｉｄｅ ｓｙｎｔｈａｓｅ,ｉＮos）基因缺失（ｉＮos－／－）的实验鼠卵母细胞染色体不分离的影响。方法：给野生型雌鼠（ｉNos+/+）和iNos基因敲除（iNos-/-）的雌鼠强饲（oral gavage） BPA 100 μg/（kg·d）或200 μg/（kg·d）连续13 d。结果：在iNos+/+组实验鼠卵细胞MⅡ期非整倍体卵母细胞数量没有显著增加。在iNos-/-组实验鼠卵母细胞染色体分离错误和染色单体提前分离增加。基因表达的特性表明polo样激酶1（PLK1）和RAN GTPase蛋白（RAN）水平在iNos-/-组实验鼠卵细胞的细胞周期和纺锤体的调控大幅下降。结论：iNos可能通过维持蛋白PLK1和蛋白RAN在哺乳类动物卵细胞稳定地表达,直接或间接地保护染色体减数分裂中精确分离;低水平的BPA暴露可能引起具有iNos-/-遗传背景卵细胞染色体畸变。     

The T657C polymorphism on the SYCP3 gene is associated with recurrent pregnancy loss

SYCP3 (Sinaptonemal complex protein 3) plays a critical role in pairing and recombination of homologous chromosomes in meiosis 1. It has been shown that lack of this gene leads to infertility in male and weakened fertility in female mice. In a case–control study, we investigated the SYCP3T657C polymorphism in the genome of 100 Iranian women with recurrent pregnancy losses of unknown causes as well as 100 control samples of normal fertile women having at least one healthy child. The general aim of our study was to determine whether there is a relationship between genetic changes in the SYCP3 gene and recurrent pregnancy loss in human or not. Frequency of the heterozygous genotype and mutated allele C were significantly higher in women with recurrent pregnancy losses (P-value < 0.005). Our findings suggest that the T657C polymorphism of the SYCP3 gene is possibly associated with recurrent pregnancy loss of unknown cause in human.     

Distribution of ultraviolet light irradiated mitochondrial genomes during meiosis in yeast

Summary Clones derived from ascospores from ultraviolet irradiated diploid cells were examined for the genetic determinants or respiratory properties. Approximately 10% of the cells produced petites of mitochondrial origin at the dose applied. Among 13 asci which produced mitochondrial petites with high frequencies, 6 asci of uniparental type, 0 grandes : 4 petites, were observed. Furthermore, most of the petite spore clones from each individual uniparental ascus showed similar levels of suppressiveness and of mitochondrial gene retention. From these results it is suggested that a single mitochondrial genome participates meiosis in yeast.     

Sensitivity to ethidium bromide during meiosis in Saccharomyces cerevisiae

Summary Ethidium bromide was found to inhibit nuclear and mitochondrial DNA synthesis during meiosis which resulted in the inhibition of meiotic gene conversion and sporulation and was also lethal. Protection from the effects of ethidium bromide on meiotic gene conversion and survival was found to coincide with DNA synthesis, but it is possible that protection from sporulation inhibition occurs only later in meiosis.     

Mouse germ cell development: From specification to sex determination

Primordial germ cells (PGCs) are embryonic progenitors for the gametes. In the gastrulating mouse embryo, a small group of cells begin expressing a unique set of genes and so commit to the germline. Over the next 3–5 days, these PGCs migrate anteriorly and increase rapidly in number via mitotic division before colonizing the newly formed gonads. PGCs then express a different set of unique genes, their inherited epigenetic imprint is erased and an individual methylation imprint is established, and for female PGCs, the silent X chromosome is reactivated. At this point, germ cells (GCs) commit to either a female or male sexual lineage, denoted by meiosis entry and mitotic arrest, respectively. This developmental program is determined by cues emanating from the somatic environment.     

RAN1 + controls the transition from mitotic division to meiosis in fission yeast

Summary We have investigated the genetic and physiological control of meiosis in fission yeast. Nutritionally depleted h ⁺/h ^– diploid cells become irreversibly commited to meiosis immediately prior to the initiation of premeiotic S phase. Premeiotic DNA synthesis requires matP ⁺, matM ⁺, mei2 ⁺ and mei3 ⁺ but not the mitotic cell cycle control gene, cdc2 ⁺, ran1 ⁺ is an essential gene, loss of which provokes sexual conjugation, premeiotic DNA synthesis, pseudo-meiosis and the sporulation of haploid cells. Our experiments suggest that sexual differentiation is achieved physiologically by the inhibition of ran1 ⁺ activity in a two-step process. In the first step, partial inhibition of ran1 ⁺ in starved haploid cells, leads to cell cycle arrest in G₁ followed by sexual conjugation. In the second step, a pathway requiring the matP ⁺, matM ⁺ and mei3 ⁺ genes of the newly-formed zygote, further inhibits ran1 ⁺ and thereby commits the cell to meiosis. mei2 ⁺ is required for meiotic commitment after full inhibition of ran1 ⁺. ran1 ⁺ is normally essential for vegetative cell reproduction but is inessential in cells which have abnormally high levels of cAMP-dependent protein kinase. We propose that the ran1 ⁺ gene encodes a highly controlled protein kinase which shares key substrates with cAMP-dependent protein kinase.