DNA methylation and alternative splicing modulate FBXW11 gene expression in Holstein bull testis and are correlated with sperm quality

摘要

F-box and WD-40 domain protein 11 (FBXW11) is an important component of the E3 ubiquitin-ligase enzyme that plays a key role in the ubiquitin-dependent regulation of spermatogenesis. In our previous research, the mRNA expression of FBXW11 in bull sperm with high motility is significantly higher than that with low motility. In the present study, the protein expression levels of FBXW11 in bull testicular tissues with low-performance sperm quality groups were significantly higher than those in normal performance groups. The immunohistochemistry result demonstrated that FBXW11 protein was located in the periphery of Leydig cells and seminiferous tubules. Three splice variants of the FBXW11 gene, namely, FBXW11-tv1, FBXW11-tv2, and FBXW11-tv3, were identified in testicular tissues. The splicing patterns of the three variants are exon skipping. The transcript FBXW11-tv2 expressions were the highest in each sample. The low-performance groups displayed higher FBXW11-tv1 and FBXW11-tv2 transcript expressions than the normal performance groups. Two CpG islands were located within the 5’ UTR and exon 1-2 region of the FBXW11 gene. Bisulfite sequencing PCR results demonstrated that the methylation levels of 11 methylation sites in the CpG island 2 from ?99 to ?43 in the normal performance groups were significantly lower than those in the low-performance groups. Pearson correlation analysis suggested that the CpG island 2 methylation level was negatively correlated with sperm motility and the transcript FBXW11-tv2 expression level. Our data revealed that alternative splicing and DNA methylation jointly regulated FBXW11 gene expression and were correlated with sperm quality traits during spermatogenesis in Holsteins.