Essential role of METTL3 in mitochondrial function and epigenetic regulation during preimplantation development in...

In brief: The m6A RNA modifications can affect mammalian preimplantation development. This study reveals that m6A methyltransferase METTL3 is crucial for mouse preimplantation development with proper mitochondrial homeostasis and epigenetic regulations. Abstract: Methyltransferase-like 3 (METTL3) is a key enzyme involved in N6-methyladenosine (m6A) RNA modification. METTL3 affects mitochondrial function via its well-known contribution to RNA translation and stability. Since METTL3 is essential for proper gene expression and mitochondrial function, we hypothesized that METTL3 plays a role in mouse preimplantation development via mitochondrial function and RNA metabolism. Mettl3-targeting antisense oligonucleotides were introduced to one-cell stage embryos to knock down its expression in mouse embryos. The resultant embryos were subjected to the detection analysis of m6A, Hippo signaling, histone methylation, mitochondrial reactive oxygen species, mitochondrial DNA copy number, and membrane potential at the morula stage. RNA sequencing was also conducted to identify differentially expressed genes in Mettl3 knockdown embryos. Mettl3 knockdown resulted in significant developmental impairments, including decreased blastocyst formation, reduced cell number, elevated mitochondrial reactive oxygen species levels, and increased mitochondrial DNA copy number. Histone H3 lysine 27 trimethylation levels, a repressive histone mark, were also altered in the nuclei of knockdown embryos. Reanalysis of public RNA immunoprecipitation sequencing data revealed that METTL3 inhibition alters m6A in transcripts of Hippo signaling key components and H3K27me3 modifiers in mouse preimplantation embryos. Additionally, Mettl3 knockdown altered the expression of genes related to RNA metabolism, mitochondrial activity, and protein folding. Our findings highlight the essential role of METTL3 in preimplantation development by influencing cell proliferation, mitochondrial function, and epigenetic regulation.