NAT10-mediated mRNA N4-acetylcytidine Modifications in Mouse Oocytes Constitute a Checkpoint of Ovarian Follicle Development [NAT10-smart-seq2]

During mammalian follicular development, the correct establishment of the epitranscriptome in oocytes is essential for precise gene repression and the acquisition of developmental competence. N4-acetylcytidine (ac4C) is a conserved posttranscriptional RNA modification catalyzed by the only known “writer”, N-acetyltransferase 10 (NAT10). NAT10-targeted transcripts in oocytes and their functions in supporting folliculogenesis are poorly understood. In this study, we showed that oocyte-specific knockout of Nat10 resulted in retardation of oocyte growth with defective follicular development, premature ovarian failure, and female sterility. We profiled the ac4C landscape in the ovarian transcriptome and identified many folliculogenesis-related oocyte genes with ac4C modifications. Loss of Nat10 in oocytes eliminated ac4C signals, resulting in the downregulation of numerous oocyte-derived transcripts with reduced stability. Moreover, Nat10-deletion in oocytes or mutations in these ac4C sites led to decreased levels of protein translation, whereas the introduction of ac4C into these mRNAs increased their translational efficiencies. In addition, our data showed that the distinct gene expression patterns in granulosa cells within arrested secondary follicles were disrupted, and the identity of granulosa cells was altered by Nat10 deletion in oocytes. Taken together, these findings provide evidence that NAT10-mediated ac4C modification is a crucial regulatory factor in the maintenance of oocyte competence and that it constitutes a checkpoint for ovarian folliculogenesis beyond the secondary follicle stage.