Destabilization of mRNAs enhances competence to initiate meiosis in mouse spermatogenic cells.

The specialized cell cycle of meiosis transforms diploid germ cells into haploid gametes. In mammals, diploid spermatogenic cells acquire the competence to initiate meiosis in response to retinoic acid. Previous mouse studies revealed that MEIOC interacts with RNA-binding proteins YTHDC2 and RBM46 to repress mitotic genes and to promote robust meiotic gene expression in spermatogenic cells that have initiated meiosis. Here, we have used the enhanced resolution of scRNA-seq and bulk RNA-seq of developmentally synchronized spermatogenesis to define how MEIOC molecularly supports early meiosis in spermatogenic cells. We demonstrate that MEIOC mediates transcriptomic changes before meiotic initiation, earlier than previously appreciated. MEIOC, acting with YTHDC2 and RBM46, destabilizes its mRNA targets, including the transcriptional repressors E2f6 and Mga, in mitotic spermatogonia. MEIOC thereby derepresses E2F6- and MGA-repressed genes, including Meiosin and other meiosis-associated genes. This confers on spermatogenic cells the molecular competence to, in response to retinoic acid, fully activate the transcriptional regulator STRA8-MEIOSIN, which is required for the meiotic G1/S phase transition and for meiotic gene expression. We conclude that, in mice, mRNA decay mediated by MEIOC-YTHDC2-RBM46 enhances the competence of spermatogenic cells to initiate meiosis.