Enhancing METTL3-mediated m6A modification of Fzd3 mRNA exhibits neuroprotection in amyotrophic lateral sclerosis

Abstract Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder characterized by progressive loss of motor neurons (MNs). N 6 -methyladenosine (m 6 A) is the most abundant mRNA modification, yet its role in ALS MNs degeneration remains poorly understood. In this study we observed a significant decrease in global m 6 A levels in the spinal cords of hSOD1 G93A transgenic ALS mouse model and hSOD1 G93A NSC34 cells, accompanied by reduced expression of the methyltransferase METTL3. Knocking down Mettl3 in the ALS MN model further impaired neurite outgrowth and acetylcholine release in an m 6 A-dependent manner. AAV-mediated Mettl3 overexpression attenuated MN loss, improved motor ability and extended survival in ALS mice. Integrated analysis based on m 6 A-methylome and transcriptome identified Fzd3 , a WNT signaling pathway receptor gene, as a key m 6 A-modified target. Mechanistically, METTL3 promotes the expression of FZD3 by enhancing the stability of its mRNA through IGF2BP3. Knockdown of Fzd3 abolished the protective effects of METTL3 on neurite outgrowth and acetylcholine release in ALS MNs. Collectively, our research reveals that METTL3-mediated m 6 A modification on Fzd3 mRNA plays a critical role in ALS pathogenesis and highlights METTL3 as a promising therapeutic target for ALS.