Mettl8 Regulates Hippocampal Neural Stem Cell Proliferation and Neurogenesis via mTOR/4E-BP1 Signaling

Aims: Hippocampal neural stem cells (NSCs) proliferation and differentiation are crucial for neuroregeneration, but their regulation remains unclear. This study investigates the role of the RNA methyltransferase Mettl8 in NSCs' fate determination.

Materials and methods: Stable Mettl8-knockdown and overexpressing NSCs lines were generated via lentiviral transduction. Gene/protein expression was analyzed by qRT-PCR, WB, and immunofluorescence. Proliferation and cell cycle were assessed using EdU assays and flow cytometry. Transcriptomic profiling was performed via RNA-seq, and mechanistic validation was conducted with the mTOR Inhibitor Rapamycin.

Results: Mettl8 expression was higher in differentiated neurons and astrocytes than in NSCs. Functionally, Mettl8 knockdown induced G0/G1 arrest, reduced Cyclin E, and suppressed proliferation, while its overexpression promoted proliferation. Conversely, Mettl8 loss increased neuronal (βIII-Tubulin) and astrocytic (GFAP) marker expression, whereas overexpression impaired differentiation. Mechanistically, Mettl8 negatively regulated the Akt/mTOR/4E-BP1 pathway. Knockdown activated this pathway, and Rapamycin reversed the enhanced mTOR/4E-BP1 phosphorylation and neuronal differentiation caused by Mettl8 loss.

Conclusion: Mettl8 maintains NSCs' proliferative homeostasis and suppresses differentiation by fine-tuning mTOR/4E-BP1 signaling, revealing a potential therapeutic target for neuroregeneration.