人精子DNA损伤是引起男性不育的常见原因。多种环境压力都可导致精子DNA损伤增加，但损伤机制并不清楚，其中表观遗传作用引人关注。叶酸作为甲基基团供体，影响DNA甲基化过程。前期我们在198名不育男性中证实叶酸浓度与精子DNA损伤程度相关，进一步对低叶酸者进行全基因组甲基化测序，筛查到Rad54启动子区甲基化显著升高，并在小鼠模型中验证，而Rad54在DNA双键断裂(DSB)修复通路发挥重要作用。因此我们提出假设：男性叶酸缺乏会增强生精细胞Rad54启动子甲基化而抑制其基因表达，通过阻碍DNA双键断裂修复通路而造成精子DNA损伤增加。为证明此，本课题拟在小鼠中检测不同叶酸摄入对DNA甲基化影响，再分离精母细胞研究Rad54对DSB修复通路影响，并通过构建GC-2细胞模型进行基因功能和保护机制的研究。本研究的完成，不仅拓宽表观遗传调控精子DNA损伤机制的认识，还对临床提高男性生育力有借鉴意义。

Human sperm DNA damage is a common cause of male infertility. A variety of environmental stress can lead to sperm DNA damage, but the mechanism of sperm damage is not clear. Researchers pay attention to the epigenetic effects. As a methyl group donor, Folic acid regulates the process of DNA methylation. In the early we confirmed that folic acid concentration was associated with sperm DNA damage in 198 infertile males, and the whole genome methylation sequencing of the patients of low folic acid was performed. We found that the methylation of the Rad54 promoter region was significantly increased and the result was proved in mice model. Rad54 plays an important role in DNA double bond cleavage (DSB) repair pathway. Therefore, we hypothesize that male folic acid deficiency enhances the methylation of the spermatogenic cells and inhibits the gene expression, then increases the sperm DNA damage by blocking the DNA double bond cleavage pathway. In order to prove this, firstly we will detect the effect of different folic acid uptake on DNA methylation in mice. The effect of Rad54 on DSB repair pathway will be studied in spermatocytes. Finally, the mechanism of gene function and protection will be studied in GC-2 cell model. The completion of this study not only broaden the knowledge of epigenetic regulation of sperm DNA damage, but also give clinical reference to improve the male fertility.