Iyyappan, R.; Niu, Y.; Ming, H.; Pajdzik, K.; Rakestraw, N. R.; Jain, P. K.; He, C.; Zong, C.; Jiang, Z.

RNA N6-methyladenosine (m6A) plays a crucial role in regulating gene expression during early embryonic development. However, the m6A dynamics at single-nucleotide resolution in preimplantation development remain uncharacterized, and the functional significance of site specific m6A modifications in key developmental regulators is largely unknown. Here, using SAC-seq, a single-base resolution, antibody-independent m6A profiling method, we generate the first comprehensive m6A landscape in bovine oocytes and preimplantation embryos. We identify a previously uncharacterized m6A site in RPL12 transcript that is essential for embryonic development. Loss of m6A at this site leads to reduced protein synthesis, disrupted expression of translation-related genes, and impaired zygotic genome activation and blastocyst formation. Notably, supplementation with wild-type RPL12 mRNA fails to rescue the developmental arrest, indicating that m6A regulation extends beyond transcript abundance. Our findings provide a valuable resource of m6A at single-nucleotide resolution in mammalian embryogenesis and uncover a critical mechanism by which precise, site-specific m6A regulates translation and developmental competence in early embryos.