Mettl1-mediated internal mG methylation of Sptbn2 mRNA elicits neurogenesis and anti-alzheimer's disease.

Background: N-methylguanosine (mG) is one of the most conserved modifications in nucleosides impacting mRNA export, splicing, and translation. However, the precise function and molecular mechanism of internal mRNA mG methylation in adult hippocampal neurogenesis and neurogenesis-related Alzheimer's disease (AD) remain unknown.

Results: We profiled the dynamic Mettl1/Wdr4 expressions and mG modification during neuronal differentiation of neural stem cells (NSCs) in vitro and in vivo. Adult hippocampal neurogenesis and its molecular mechanisms were examined by morphology, biochemical methods and biological sequencing. The translation efficiency of mRNA was detected by polysome profiling. The stability of Sptbn2 mRNA was constructed by RNA stability assay. APPswe/PS1ΔE9 (APP/PS1) double transgenic mice were used as model of AD. Morris water maze was used to detect the cognitive function.

Methods: We found that mG methyltransferase complex Mettl1/Wdr4 as well as mG was significantly elevated in neurons. Functionally, silencing Mettl1 in neural stem cells (NSCs) markedly decreased mG modification, neuronal genesis and proliferation in addition to increasing gliogenesis, while forced expression of Mettl1 facilitated neuronal differentiation and proliferation. Mechanistically, the mG modification of Sptbn2 mRNA by Mettl1 enhanced its stability and translation, which promoted neurogenesis. Importantly, genetic defciency of Mettl1 reduced hippocampal neurogenesis and spatial memory in the adult mice. Furthermore, Mettl1 overexpression in the hippocampus of APP/PS1 mice rescued neurogenesis and behavioral defects.

Conclusion: Our findings unravel the pivotal role of internal mRNA mG modification in Sptbn2-mediated neurogenesis, and highlight Mettl3 regulation of neurogenesis as a novel therapeutic target in AD treatment.