Deep sequencing reveals microRNA signature is altered in the rat epididymis following bilateral castration

Background In the epididymis of bilateral castrated male rat, gene expression profile changed significantly. However, up to date, no study has investigated how these genes were regulated by microRNAs (miRNAs). Objective We investigated the alterations in the miRNA signature of the epididymis from sham-operated and bilaterally castrated rats. Methods By employing deep sequencing technology and qPCR, the global alterations of epididymal miRNA signature between sham-operated (Con-EP library) and bilaterally castrated rats (Cas-EP library) were explored. MiRNA-target interaction networks were annotated by GO and KEGG enrichment. Results We identified 313 and 306 known miRNAs as well as 152 and 114 novel miRNAs in the Con-EP and Cas-EP libraries, respectively. 59 miRNAs were differentially expressed, including 24 up-regulated and 35 down-regulated miRNAs, among which two up-regulated and three down-regulated ones were validated using qPCR. The expression of these miRNAs in the epididymides of rats at different postnatal ages showed regular changes from birth to adult, suggesting they were androgen-regulated. GO analysis showed that many of the miRNA targets were enriched in metabolic processes. KEGG analysis demonstrated that the targets mainly participated in the mitogen-activated protein kinase (MAPK) pathway. Moreover, 3 and 6 functional modules were detected among the up- and down-regulated miRNA target interaction networks, respectively, and these modules were involved in various biological processes. Conclusion This study represents the first systematic investigation of alterations in the miRNA signature of the epididymis from bilaterally castrated rats and will provide useful resources for functional studies of the miRNAs in the male reproductive system.