NSUN2 suppresses ferroptosis via the KLF4/GPX4 axis to preserve stem cells and tissues.

RNA 5-methylcytosine (m5C) methylation has emerged as an important epitranscriptomic regulator of gene expression, yet its role in stem cell maintenance remains not well understood. Here we identify a previously unrecognized function of the m5C methyltransferase NSUN2 in protecting stem cells from ferroptosis and promoting tissue regeneration. NSUN2 deletion reduced GPX4 expression, decreased intracellular GSH levels, increased Fe2+ accumulation, and enhanced lipid peroxidation in stem cells, leading to ferroptotic cell death, loss of tissue stem cells and impaired tissue regeneration across multiple organs. Mechanistically, NSUN2 catalyzed m5C methylation of Klf4 mRNA, thereby increasing KLF4 expression and transcriptionally promoting GPX4 to suppress ferroptosis in stem cells. Importantly, KLF4 restoration in vivo rescued NSUN2 deficiency-induced stem cell defects and impaired tissue regeneration. Furthermore, NSUN2 gene therapy significantly bolstered tissue stem cells with superior tissue regeneration and repair in multiple tissues. These findings highlight the NSUN2/KLF4/GPX4 axis in safeguarding stem cells against ferroptosis for tissue repair and a promising therapeutic value of NSUN2 in regenerative medicine.