Abstract
8-Hydroxyguanine (8-oxoG) is the most common oxidative DNA lesion and unrepaired 8-oxoG is associated with DNA fragmentation in sperm. However, the molecular effects of 8-oxoG on spermatogenesis are not entirely understood. Here, we identified one infertile bull (C14) due to asthenoteratozoospermia. We compared the 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 the expression of sperm proteins by 2-dimensional polyacrylamide gel electrophoresis followed by peptide mass fingerprinting (2D-PAGE/PMF) in the sperm of C14 with those of a fertile bull (C13). We found that the average levels of 8-oxoG in C13 and C14 sperm were 0.027% and 0.044% of the total dG and it was significantly greater in infertile sperm DNA (p = 0.0028). Over 81% of the 8-oxoG loci were distributed around the transcription start site (TSS) and 165 genes harboring 8-oxoG were exclusive to infertile sperm. Functional enrichment and network analysis revealed that the Golgi apparatus was significantly enriched with the products from 8-oxoG genes of infertile sperm (q = 2.2 × 10−7). Proteomic analysis verified that acrosome-related proteins, including acrosin-binding protein (ACRBP), were downregulated in infertile sperm. These preliminary results suggest that 8-oxoG formation during spermatogenesis dysregulated the acrosome-related gene network, causing structural and functional defects of sperm and leading to infertility.
Highlights
In beef production in Korea, more than 90% of the beef is bred by artificial insemination (AI); the ability to predict the fertility of bulls before AI has been a long-term objective of the animal breeding industry
The analysis indicated that the percentage of motile sperm with standard deviation (SD)
We found an infertile bull with asthenoteratozoospermia, which had a significantly higher level of 8-oxoG formation in its sperm DNA
Summary
In beef production in Korea, more than 90% of the beef is bred by artificial insemination (AI); the ability to predict the fertility of bulls before AI has been a long-term objective of the animal breeding industry. The reproductive soundness of the selected bulls should be managed. The evolutional conservation of spermatogenesis is reported in the mammalian species. The irregularity of spermatogenic gene expression reduces the quality of semen and may lead to the failure of fertilization both in cattle and humans [1]. Environmental and genetic effects have been associated with decreased male fertility, which is known to contribute to a dysregulated spermatogenic gene network, abnormal spermatogenesis, and eventually, impaired sperm fertility [2]. The molecular basis for the cause of poor sperm quality has not been studied in detail
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