The M6A Writer Mettl3 Regulates Mouse Placental Development

Placenta supports embryonic development in the uterus in mammal.N6methyladenosine(m6A)is involved in a variety of physical and pathological process.However,it is still not clarified whether m6A-modified RNA is involved in the development of the placenta.We report in the current research that Mettl3/14,the members of m6A writer complex,is involved in placental development.The specific knockout of Mettl3/14 in mouse trophoblast resulted in embryonic death in middle stage of pregnancy.The self-renew ability of trophoblast stem cell was compromised,with reduced proliferation and down-regulation of genes mastering trophoblast sternness.Besides,the Mettl3 conditional knockout(cKO)embryos cannot correctly develop into chorionic,spongy trophoblast precursor cells,and reduced primary trophoblast giant cells(p-TGC)at embryonic day 8.5(E8.5).Meanwhile,cKO of Mettl14 in trophoblast resulted in the lack of spongio-trophoblast and glycogen trophoblast and reduction of p-TGC.KO of Mettl3 in cultured in vitro mouse trophoblast stem cells(mTSCs)resulted in decrease of cell proliferation and down-regulation of sternness genes expression.KO of Cdkn1a could restore the ability of cell proliferation.KO of Mettl3 resulted in insufficient down-regulation of trophoblast stem genes and up-regulation of differentiation genes in mTSCs during differentiation.Restoring METTL3 with ectopic wild-type Mettl3 could rescue the phenotype,while enzymatic-mutant Mettl3 could not,indicating that Mettl3 was involved in the self-renewal and differentiation of mTSCs depending on the m6A modification function.m6A-RIP-Seq results showed that mRNA of mouse trophoblast related genes was m6A modified.However,m6A modification didnot affect the stability of these mRNA.In conclusion,this study found that Mettl3 participates in the development of placental trophoblasts by affecting the expression of trophoblast sternness related genes in an m6A modification dependent manner.