Identification and profiling of microRNAs from ovary of estrous Kazakh sheep induced by nutritional status in the anestrous season

Abstract Estrous regulation in sheep has an important role in the sheep industry in improving production of meat and wool. It has been reported that an enhanced nutritional status can induce estrus resulting in an end of the anestrous season earlier than occurs in ewes with a lesser nutritional status. However, the endocrine and physiological mechanisms that induce the increased incidence of estrus remains unclear. In the present study, the differences in amounts and characteristics of miRNAs in ewes at estrus or during the anestrous season were screened by using the Illumina HiSeq sequencing technology. In total, 294 miRNAs, including 174 novel miRNA candidates, were identified in ewes with an enhanced nutritional status (OEN) through assessment of the OEN library for this group and 307 miRNAs including 186 novel miRNA candidates were identified in the ewes with a lesser nutritional status (OAN) through assessing the OAN library, among which there were nine conserved and 104 novel miRNAs in differential amounts between the two libraries. Based on poly (A) q-PCR, six miRNAs were assessed to verify the accuracy of the library database. Furthermore, the family of the known miRNAs, the target genes and related pathways were also analyzed. The results indicated that the nutritional status had important roles in estrous regulation in sheep. The PLA2G4D can directly regulate ovarian follicle development, or indirectly influence leptin secretion involved in the regulation of the reproductive endocrine and physiological systems during the anestrous season. The identification of significantly different miRNAs expanded the repertoire of sheep miRNAs that have been examined and could contribute to further studies on the molecular mechanism of regulation of initiation of estrous cycles in previously anestrous ewes as influenced by different nutritional status.