MiR-145-5p Affects Mouse Oocyte Maturation And Early Embryo Development By Regulating Ythdf2

N6-methyl-adenosine(m~6A)is one of the most common and abundant epigenetic modifications on RNA molecules present in eukaryotes.m~6A is a dynamic and reversible state due to its biological functions are regulated by methyltransferases,demethylases and recognition proteins.m~6A modification plays an important role in the maturation of mammalian oocytes and early embryonic development.Lack of the enzymes responsible for m~6A modification often causes oocyte developmental arrest and embryonic lethality,however,the regulatory mechanism of these enzymes are largely unknown.Therefore,the regulation of m~6A modification in oocyte and embryo development has become a hot topic in recent years.YTHDF2 is the first m6A binding protein to be discovered,and it can bind to m~6A to regulate mRNA stability and promote mRNA degradation.Ythdf2 affects oocyte developmental ability and the zygotic genome activation by regulating transcripts dosage.miRNA are small non-coding ribonucleic acids about 22 nucleotides in length and plays an important role in post-transcriptional regulation of genes.It has been reported that miRNAs regulate YTHDF2 to affect cell proliferation and migration in cancer.However,miRNA regulate Ythdf2 to affect gametogenesis and embryo development has not been reported yet.miR-145-5p is a 22-nucleotide miRNA located on human chromosome 5 and has been shown to be expressed in oocytes and embryos.It has been shown that miR-145-5p regulates YTHDF2 to inhibit the proliferation in liver cancer,but its regulatory function is still unknown in oocytes and embryos.In order to investigate whether miR-145-5p can regulate Ythdf2 to affect oocyte maturation,we injected siRNAs which interfere with Ythdf2 and miR-145-5p mimics and inhibitors into mouse GV stage oocytes.In our study,inhibiting Ythdf2 didn't affect the oocyte maturation rate,but reduced the oocyte development ability.miR-145-5p inhibited the expression of Ythdf2in oocytes.Moreover,inhibiting miR-145-5p reduced damage to oocytes when lack of Ythdf2.The function of Ythdf2 in zygotic genome activation and early embryonic development has not been reported in mouse.In order to investigate the role of Ythdf2and miR-145-5p in early embryonic development,we injected siRNAs which interfere with Ythdf2 and miR-145-5p mimics and inhibitors in mouse zygotes.In our study,inhibiting Ythdf2 significantly reduced the cleavage rate and blastocyst rate in mouse,and increases embryo apoptosis.miR-145-5p inhibited the expression of Ythdf2 during early embryonic development and increased the m~6A level in mouse blastocysts.Inhibiting miR-145-5p promoted the development of mouse early embryos and reduced apoptosis.In addition,miR-145-5p played an important role in mouse oocyte maturation and early embryonic development by regulating Ythdf2.