Detection of aberrant DNA methylation patterns in sperm of male recurrent spontaneous abortion patients.

Aberrant DNA methylation patterns in sperm are a cause of embryonic failure and infertility, and could be a critical factor contributing to male recurrent spontaneous abortion (RSA). The purpose of this study was to reveal the potential effects of sperm DNA methylation levels in patients with male RSA. We compared sperm samples collected from fertile men and oligoasthenospermia patients. Differentially methylated sequences were identified by reduced representation bisulfite sequencing (RRBS) methods. The DNA methylation levels of the two groups were compared and qRT-PCR was used to validate the expression of genes showing differential methylation. The results indicated that no difference in base distribution was observed between the normal group and the patient group. However, the chromosome methylation in these two groups was markedly different. One site was located on chromosome 8 and measured 150 bp, while the other sites were on chromosomes 9, 10, and X and measured 135 bp, 68 bp, and 136 bp, respectively. In particular, two genes were found to be hypermethylated in these patients, one gene was DYDC2 (placed in the differential methylation region of chromosome 10), and the other gene was NXF3 (located on chromosome X). Expression levels of DYDC2 and NXF3 in the RSA group were significantly lower than those in the normal group (P < 0.05). Collectively, these results demonstrated that changes in DNA methylation might be related to male RSA. Our findings provide important information regarding the potential role of sperm DNA methylation in human development.

Paternal hypoxia exposure impairs fertilization process and preimplantation embryo development.

Environmental hypoxia exposure causes fertility problems in human and animals. Compelling evidence suggests that chronic hypoxia impairs spermatogenesis and reduces sperm motility. However, it is unclear whether paternal hypoxic exposure affects fertilization and early embryo development. In the present study, we exposed male mice to high altitude (3200 m above sea level) for 7 or 60 days to evaluate the effects of hypoxia on sperm quality, zygotic DNA methylation and blastocyst formation. Compared with age-matched controls, hypoxia-treated males exhibited reduced fertility after mating with normoxic females as a result of defects in sperm motility and function. Results of in vitro fertilization (IVF) experiments revealed that 60 days' exposure significantly reduced cleavage and blastocyst rates by 30% and 70%, respectively. Immunohistochemical staining of pronuclear formation indicated that the pronuclear formation process was disturbed and expression of imprinted genes was reduced in early embryos after paternal hypoxia. Overall, the findings of this study suggested that exposing male mice to hypoxia impaired sperm function and affected key events during early embryo development in mammals.

Function and transcriptomic dynamics of Sertoli cells during prospermatogonia development in mouse testis.

In mammals, spermatogonial stem cells (SSCs) arise from a subpopulation of prospermatogonia during neonatal testis development. Currently, molecular mechanisms directing the prospermatogonia to spermatogonial transition are not well understood. In the study, we found that reducing Sertoli cells number by Amh-cre mediated expression of diphtheria toxin (AC;DTA) in murine fetal testis caused defects in prospermatogonia fate decisions. Histological and immunohistochemical analyses confirmed that Sertoli cells loss occurred at embryonic day (E) 14.5. Prospermatogonia maintained mitotic arrest at E16.5 in control animals, in contrast, 13.4% of germ cells in AC;DTA testis reentered cell cycle and expressed gH2A.X and Sycp3, indicating the commitment to meiosis. After birth, the number of prospermatogonia resuming mitosis was significantly affected by Sertoli cell loss in AC;DTA animals. Lastly, we isolated primary Sertoli cells using a Sertoli cell specific GFP reporter line and showed dynamics of Sertoli cell transcriptomes at E12.5, E13.5, E16.5 and P1. By further analysis, we revealed unique gene expression patterns and potential candidate genes regulating Sertoli cell development and likely mediating interactions between Sertoli cells, prospermatogonia and other testicular cells.

[Association of abnormal length of Y chromosome with semen quality and outcome of assisted reproductive technology in humans].

OBJECTIVE: To investigate the association of the abnormal length of human Y chromosome with semen quality and the outcome of assisted reproductive technology (ART). METHODS: Based on the karyotype, we assigned the patients undergoing ART to a normal control, a long Y chromosome (Y>18), and a short Y chromosome group (Y<22). We compared the semen parameters and numbers of embryos and high-quality embryos among the three groups of patients and performed statistical analysis of the obtained data using Chi-square distribution and t-test. RESULTS: Compared with the control, the Y>18 group showed a significantly lower incidence rate of asthenozoospermia (31.03% vs 8.33%, P <0.05) and a larger number of high-quality embryos (5.46 ± 4.54 vs 7.40 ± 5.49, P<0.05). Both the incidence rate of azoospermia and number of total embryos were remarkably lower in the control than in the Y<22 group (1.87% vs 16.47%, P <0.05; 8.60 ± 7.03 vs 10.00 ± 6.58, P<0.05). No statistically significant differences were found in the pregnancy rate between the Y>18 and Y<22 groups (P>0.05). CONCLUSIONS: Short Y chromosome may affect spermatogenesis, but the length of Y chromosome does not negatively influence the outcome of ART.