Single-nucleotide Resolution Epitranscriptomic Profiling Uncovers Dynamic m ⁶ A Regulation in Bovine Preimplantation Development

RNA N ⁶ -methyladenosine (m ⁶ A) plays a crucial role in regulating gene expression during early embryonic development. However, the m ⁶ A dynamics at single-nucleotide resolution in preimplantation development remain uncharacterized, and the functional significance of site specific m ⁶ A modifications in key developmental regulators is largely unknown. Here, using SAC-seq, a single-base resolution, antibody-independent m ⁶ A profiling method, we generate the first comprehensive m ⁶ A landscape in bovine oocytes and preimplantation embryos. We identify a previously uncharacterized m ⁶ A site in RPL12 transcript that is essential for embryonic development. Loss of m ⁶ A 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 m ⁶ A regulation extends beyond transcript abundance. Our findings provide a valuable resource of m ⁶ A at single-nucleotide resolution in mammalian embryogenesis and uncover a critical mechanism by which precise, site-specific m ⁶ A regulates translation and developmental competence in early embryos.