Superficial stromal cell population in the mouse uterus require METTL14 for development and functional competence to support embryo implantation

Uterine stromal cells are critical for pregnancy, coordinating embryo implantation, placental development, and maintenance of gestation. Single-cell RNA-seq analyses have identified two distinct stromal cell populations in the mouse uterus: superficial and deep stromal cells. However, their functional specialization remains unresolved. Here, we show that mice lacking methyltransferase-like 14 (METTL14), a core enzyme of the m6A methyltransferase complex, exhibit a selective depletion of superficial stromal cells while preserving deep stromal cells. This genetic model allowed us to investigate the physiological role of superficial stromal cells in uterine function. Paralleled by the aberrant development and loss of superficial stromal cells, Mettl14 deletion impaired embryo implantation and decidualization. Transcriptomic profiling revealed that Mettl14 deficiency disrupts hormonal signaling by upregulating estrogen (E2)-responsive genes and downregulating progesterone (P4)-responsive genes, resulting in aberrant development and loss of superficial stromal cells. Mechanistically, Mettl14 ablation reduces m6A methylation in the 3'-UTR of Esr1 mRNA, thereby impairing m6A-dependent mRNA degradation and elevating ESR1 expression, which amplifies E2 signaling. This study underscores the essential role of METTL14 in maintaining the superficial stromal cell population required for embryo implantation by regulating Esr1 mRNA stability through m6A modification.