Identification and differential expression of microRNAs in the testis of chicken with high and low sperm motility.

Sperm motility is one of the most important indicators for evaluating roosters' fecundity. However, molecular regulation underlying chickens' sperm motility remains to be understood. MicroRNA (miRNA) plays an epigenetic role in reproduction. In this study, we compared the testicular miRNAs of Beijing-you roosters with high (HS) and low (LS) sperm motility using Illumina sequencing to try to understand the associated molecular regulation. Length distribution analysis showed that the dominant size of small RNAs detected in the testes of the chicken samples was 24-28 nt. In total, 518 known and 106 novel miRNAs were identified. A total of 23 miRNAs were found differentially expressed (P < 0.05, |logfold change| ≥ 1) between the HS and LS groups, including 18 known and 5 novel miRNAs. Functional enrichment of the predicted target genes of the differentially expressed miRNAs indicated that these miRNAs were involved in the pathways of GnRH, MAPK and Wnt signaling. The miRNA-gene interaction network revealed two key candidate miRNA-gene pairs that might affect chicken sperm motility, viz, gga-miR-155/KCNA1 and gga-miR-7480-5p/AHI1. qPCR was then used to further validate their expressions. The results here provided a deep insight into the expressions of the miRNAs in the testes of chickens and suggested their roles in sperm motility regulation.