High-throughput sequencing reveals differential expression of miRNAs in yak and cattleyak epididymis.

Cattleyaks (CY) are interspecific hybrids between cattle (Bos taurus) and yak (Bos gruniens, YK) exhibiting the same prominent adaptability and higher performances than YK. The main problem of this crossbreeding is that the males are sterile. Different series of events of spermatogenesis coordinate to regulate gene expressing, involving microRNAs (miRNAs). As non-coding ribonucleic acids (ncRNAs), miRNAs predominantly facilitate the regulation of gene expression at post-transcriptional stages and play important roles in the acquisition and maintenance of male fertility in reproduction. The function of miRNA in the male reproductive system extends from the testis into the epididymis, regulating gene expression and contributing to regional gene expression variations. RNA sequencing on biological replicates, we described differentially expressed miRNAs profiles for tissue from epididymis of YK and CY. In the present study, High-throughput sequencing analysis showed that 55 differentially expressed (DE) miRNAs were identified in the epididymis of YK and CY. Among these, 43 DE miRNAs were upregulated while the remaining 12 DE miRNAs were downregulated between epididymis of YK and CY. In addition, we identified that the top most important DE miRNAs, bta-miR-449c, bta-miR-539, bta- miR-136, bta-miR-504, bta-miR-31 and bta-miR-222 were involved in the process of sperm maturation in epididymis CY. It was identified that the bta-miR-449c and bta-miR-222 may play major roles in the process of sperm maturation, sperm quality, sperm count, sperm production and male infertility of CY. Furthermore, GO and KEGG analyses were performed to classify the functions of target genes for DE miRNAs. In addition, RT-qPCR validation of the DE miRNAs and its targeted genes revealed that putative miRNAs are involved in the male CY infertility by altering the gene expression. Present findings may not only increase our understanding of the molecular mechanisms regulated by the miRNAs in epididymis, but also provide a valuable information to understand the male infertility mechanism of CY.

Comparative rna-seq analysis of region-specific miRNA expression in the epididymis of cattleyak.

The epididymis is the site of post-testicular sperm maturation, which constitutes the acquisition of sperm motility and the ability to recognize and fertilize oocytes. The role of miRNA in male reproductive system, including the control of different steps leading to proper fertilization such as gametogenesis, sperm maturation and maintenance of male fertility where the deletion of Dicer in mouse germ cells led to infertility, has been demonstrated. The identification of miRNA expression in a region-specific manner will therefore provide valuable insight into the functional differences between the regions of the epididymis. In this study, we employed RNA-seq technology to explore the expression pattern of miRNAs and establish some miRNAs of significant interest with regard to epididymal sperm maturation in the CY epididymis. We identified a total of 431 DE known miRNAs; 119, 185 and 127 DE miRNAs were detected for caput versus corpus, corpus versus cauda and caput versus cauda region pairs, respectively. Our results demonstrate region-specific miRNA expression in the CY epididymis. The GO and KEGG enrichment for the predicted target genes indicated the functional values of miRNAs. Furthermore, we observed that the expression of miR-200a was downregulated in the caput, compared with cauda. Since the family of miR-200 has previously been suggested to contribute to the distinct physiological function of sperm maturation in epididymis of adult rat, we speculate that the downregulation of miR-200a in CY caput epididymis may play an important role of sperm maturation in the epididymis of CY. Therefore, our findings may not only increase our understanding of the molecular mechanisms regulated by the miRNA functions in region-specific miRNA expression in the CY epididymis, it could provide a valuable information to understand the mechanism of male infertility of CY.