Identification of novel and differentially expressed micro RNAs in ovine ovary and testis tissues using Solexa sequencing and bioinformatics

Micro RNAs（mi RNAs） are small, single stranded, non-coding RNA molecules, about 19–25 nucleotides in length, which regulate the development and functions of reproductive system of mammal.To discover novel mi RNAs and identify the differential expression of them in ovine ovary and testis tissues, the study constructed two libraries by using next-generation sequencing technologies（Solexa high-throughput sequencing technique）.As a result, 9 321 775 and 9 511 538 clean reads were obtained from the ovary and testis separately, which included 130 562（90 genes of ovary） and 56 272（85 genes of testis） of known mi RNAs and 486 potential novel mi RNAs reads.In this study, a total of 65 conserved mi RNAs were significantly differentially expressed（P〈0.01） between the two samples.Among them, 28 mi RNAs were up-regulated and 3 mi RNAs were down-regulated on ovary compared with testis.In addition, the known mi RNAs with the highest expression level（5 mi RNAs） and 30 novel mi RNAs with the functions related to reproduction were validated using the real-time quantitative RT-PCR.Moreover, the gene ontology（GO） annotation and Kyoto encyclopedia of genes and genomes（KEGG） pathway analysis showed that differentially expressed mi RNAs were involved in ovary and testis physiology, including signal transduction, gonad development, sex differentiation, gematogenesis, fertilization and embryo development.The results will be helpful to facilitate studies on the regulation of mi RNAs during ruminant reproduction.