METTL3-mediated m6 A modification is required for cerebellar development

N-6-methyladenosine (\m(6)A) RNA methylation is the most abundant modification on mRNAs and plays important roles in various biological processes. The formation of m(6)A is catalyzed by a methyltransferase complex including methyltransferase-like 3 (\METTL3) as a key factor. However, the in vivo functions of METTL3 and m(6)A modification in mammalian development remain unclear. Here, we show that specific inactivation of Mettl3 in mouse nervous system causes severe developmental defects in the brain. Mettl3 conditional knockout (\cKO) mice manifest cerebellar hypoplasia caused by drastically enhanced apoptosis of newborn cerebellar granule cells (\CGCs) in the external granular layer (\EGL). METTL3 depletion +/- induced loss of m(6)A modification causes extended RNA half-lives and aberrant splicing events, consequently leading to dysregulation of transcriptome-wide gene expression and premature CGC death. Our findings reveal a critical role of METTL3-mediated m(6)A in regulating the development of mammalian cerebellum.