Ythdf2-mediated m6A mRNA clearance modulates neural development in mice

Background: N-6-methyladenosine (m(6)A) modification in mRNAs was recently shown to be dynamically regulated, indicating a pivotal role in multiple developmental processes. Most recently, it was shown that the Mettl3-Mettl14 writer complex of this mark is required for the temporal control of cortical neurogenesis. The m(6)A reader protein Ythdf2 promotes mRNA degradation by recognizing m(6)A and recruiting the mRNA decay machinery. Results: We show that the conditional depletion of the m(6)A reader protein Ythdf2 in mice causes lethality at late embryonic developmental stages, with embryos characterized by compromised neural development. We demonstrate that neural stem/progenitor cell (NSPC) self-renewal and spatiotemporal generation of neurons and other cell types are severely impacted by the loss of Ythdf2 in embryonic neocortex. Combining in vivo and in vitro assays, we show that the proliferation and differentiation capabilities of NSPCs decrease significantly in Ythdf2(-/-) embryos. The Ythdf2(-/-) neurons are unable to produce normally functioning neurites, leading to failure in recovery upon reactive oxygen species stimulation. Consistently, expression of genes enriched in neural development pathways is significantly disturbed. Detailed analysis of the m(6)A-methylomes of Ythdf2(-/-) NSPCs identifies that the JAK-STAT cascade inhibitory genes contribute to neuroprotection and neurite outgrowths show increased expression and m(6)A enrichment. In agreement with the function of Ythdf2, delayed degradation of neuron differentiation-related m(6)A-containing mRNAs is seen in Ythdf2(-/-) NSPCs. Conclusions: We show that the m(6)A reader protein Ythdf2 modulates neural development by promoting m(6)A-dependent degradation of neural development-related mRNA targets.