Dysregulation of acrosome formation network by 8-oxoguanine (8-oxoG) in infertile sperm

Various environmental factors contribute to dysregulated spermatogenic gene network, abnormal spermatogenesis, and eventually impaired sperm fertility. 8-hydroxyguanine (8-oxoG) is the most common and well-studied oxidative DNA lesion of the four DNA bases and unrepaired 8-oxoG modifications are associated with DNA fragmentation in sperms. However, the molecular effects of 8-oxoG generated in sperm DNA by oxidative stress on spermatogenesis are not entirely understood. Here, we identified one infertile Korean native striped cattle at 6-year old (C14) due to asthenozoospermia and teratozoospermia. We compared global concentration of 8-oxoG by reverse-phase liquid chromatography/mass spectrometry (RP-LC/MS), the genomic distribution of 8-oxoG by next-generation sequencing (OG-seq), and expression of sperm proteins by 2-dimensional electrophoresis followed by mass spectrometry (2D/MS) in sperms of C14 with those of normal counterpart (C13). We found that averaged levels of 8-oxoG in C13 and C14 sperms were 0.027% and 0.044% of total dG and 8-oxoG was significantly greater in infertile sperm DNA (p = 0.0028). More than 81% of the 8-oxoG loci were distributed around the transcription start site (TSS) and 8-oxoG harboring 165 genes, including phospholipases, were annotated exclusively into infertile sperm DNA. Gene set enrichment analysis (GSEA) and the protein-protein interaction networking revealed that the Golgi apparatus was significantly enriched with the 8-oxoG genes of infertile sperm (q = 2.20E-07). Proteomic analysis verified that acrosome-related proteins including Acrosin-binding protein (ACRBP) and Sperm equatorial segment protein 1 (SPESP1) were 1.6-fold and 2.6-fold down-regulated in infertile sperm, respectively. These results suggest that 8-oxoG formation during spermatogenesis would dysregulate the acrosome-related gene network, causing structural and functional defects of sperm, leading to infertility. We identified one infertile Korean native striped cattle at 6-year old (C14) due to asthenozoospermia and teratozoospermia. We compared global concentration of 8-oxoG by reverse-phase liquid chromatography/mass spectrometry (RP-LC/MS), the genomic distribution of 8-oxoG by next-generation sequencing (OG-seq), and expression of sperm proteins by 2-dimensional electrophoresis followed by mass spectrometry (2D/MS) in sperms of C14 with those of normal counterpart (C13)