Expression profile analysis of microRNAs during the oestrous cycle of Qira black sheep
Ovarian follicular development is closely regulated by a multitude of genes and specific non-coding RNAs (ncRNAs), which are typically altered during the oestrous cycle. Identification of the microRNAs (miRNA) expression profiles in sheep ovaries during the oestrous cycle is a prerequisite to further understanding their functional status. This study presents a genome-wide analysis of miRNAs from three groups of Qira black sheep: oestrus (day 0), dioestrus (day 10) and pro-oestrus (day 14). A total of 545 conserved miRNAs and 206 novel miRNAs were identified. Furthermore, 229 differentially expressed miRNAs were screened in three comparisons and 16 miRNAs were found to be differentially expressed in all three different ovarian phases. 63 and 60 miRNAs were downregulated and 46 and 69 miRNAs were upregulated in dioestrus and pro-oestrus ovarian phases compared with the oestrus phase, respectively. Luciferase reporter assays indicated that ovine STAT3 was a target of miR-125b with two binding sites in the 3ˊUTR. In summary, the miRNA profiles show the dynamic nature of ovarian miRNAs during the oestrous cycle and will help to further understand the role of miRNAs in the regulation of the oestrous cycle, follicular development and ovarian function in sheep.