Two new miRNAs identified in bovine ovary

Abstract

The microRNAs (miRNAs) that participate in regulating oocyte growth and oocyte-embryo transition must be identified and characterised to understand maturation, fertilization and embryo development mechanisms in bovine reproduction. With the purpose of identifying new miRNAs that may play a role in oocyte maturation and early embryogenesis, a miRNAs genome library from bovine ovarian was developed. After analysing concatamers from 40 clones, two new miRNAs were identified and labeled bta-mir-8548 and bta-mir-8549. These miRNAs showed a stable stem-loop structure in accordance with established miRBase parameters. bta-mir-8548 was found at chromosome 8 in an intronic region between exons 1 and 2 of the MRSA gene (methionine sulfoxide reductase) suggesting that it may play a role in regulating oxidative stress during oocyte maturation. In the same way, bta-mir-8549 was found at chromosome 7 in the intergenic region between genes tRNA-Cys and GBPg5. The mature form of bta-mir-8549 showed the conserved sequence of the bta-let-7 family, which is associated with oocyte maturation. With the purpose of locate the correct place of bta-mir-8549 into the family of miRNA bta-let-7 a phylogenetic study was conducted. The cladogram generated from genetic distances between the various bta-let-7miRNAs showed that bta-mir-8549 was located monophyletically with bta-lec-7c, while the rest of the bta-let-7miRNAs were located in different clades. It was concluded that bta-mir-8548 and bta-mir-8549 are new bovine ovarian miRNAs that may act on the mechanisms regulating oocyte maturation and embryonic development.