METTL3 is essential for normal progesterone signaling during embryo implantation via mA-mediated translation control of progesterone receptor.

Embryo implantation, a crucial step in human reproduction, is tightly controlled by estrogen and progesterone (P) via estrogen receptor alpha and progesterone receptor (PGR), respectively. Here, we report that -methyladenosine (mA), the most abundant mRNA modification in eukaryotes, plays an essential role in embryo implantation through the maintenance of P signaling. Conditional deletion of methyltransferase-like 3 (), encoding the mA writer METTL3, in the female reproductive tract using a Cre mouse line with promoter () resulted in complete implantation failure due to pre-implantation embryo loss and defective uterine receptivity. Moreover, the uterus of null mice failed to respond to artificial decidualization. We further found that deletion was accompanied by a marked decrease in PGR protein expression. Mechanistically, we found that mRNA is a direct target for METTL3-mediated mA modification. A luciferase assay revealed that the mA modification in the 5' untranslated region (5'-UTR) of mRNA enhances PGR protein translation efficiency in a YTHDF1-dependent manner. Finally, we demonstrated that METTL3 is required for human endometrial stromal cell decidualization in vitro and that the METTL3-PGR axis is conserved between mice and humans. In summary, this study provides evidence that METTL3 is essential for normal P signaling during embryo implantation via mA-mediated translation control of mRNA.