Polymorphisms of nucleotide-excision repair genes may contribute to sperm DNA fragmentation and male infertility.

The nucleotide-excision repair (NER) system is crucial for the removal of bulky DNA adducts during spermatogenesis. Dysfunction of its repair capacity is likely related to the increased susceptibility to DNA damage. In this study, four polymorphisms in NER pathway (XPA(-4) G/A, ERCC1 C8092A, XPD Lys751Gln and XPF Ser835Ser) were selected to evaluate their potential impact on sperm DNA damage and male infertility. Genotypes were determined by PCR-restriction fragment length polymorphism. Sperm DNA damage was evaluated by TdT-mediated dUDP nick-end labelling assay. A case-only study of 620 infertile men found a significant association between XPA(-4) G/A polymorphism and sperm DNA damage. Individuals with the XPA(-4) A allele showed more sperm DNA damage and lower sperm concentration than G allele carriers. Further analysis, including 620 patients and 385 controls, revealed a 1.52-fold risk (95% CI 1.08-2.02) of developing male infertility in the XPA(-4) AA carriers compared with noncarriers. Luciferase assay verified that the promoter with the XPA(-4) A allele had a lower transcriptional activity than that with the G allele. These data provide the first evidence that -4 G/A polymorphism in XPA promoter alters its transcriptional activity and, thus, might contribute to sperm DNA damage and male infertility. Sperm DNA integrity is essential for the accurate transmission of genetic information. To our knowledge, few studies have elucidated the effect of DNA repair gene single-nucleotide polymorphisms on sperm DNA integrity, although the DNA repair system is indispensable in maintaining genetic stability and normal spermatogenesis. In this original study, we evaluated the potential impact of the polymorphisms in the nucleotide-excision repair pathway on the risk of sperm DNA damage based on 620 infertile patients and 385 controls, and provided the first evidence that -4 G/A polymorphism in the promoter for the xeroderma pigmentosum group A gene altered its transcriptional activity, which might contribute to sperm DNA damage and male infertility.