METTL14 Drives Neuronal Ferroptosis in Spinal Cord Injury by Inducing m6A Methylation of USP7

Background: Spinal cord injury (SCI) is a devastating disorder in which ferroptosis drives secondary neuronal degeneration. However, whether m6A epitranscriptomic regulation modulates neuronal ferroptosis via specific downstream pathways remains unclear. Methods: A rat model of SCI and erastin-induced neuronal ferroptosis in vitro were employed. Methyltransferase-like 14 (METTL14) expression and global N6-methyladenosine (m6A) levels were assessed, along with ferroptosis-related markers, including glutathione peroxidase 4 (GPX4), acyl-CoA synthetase long-chain family member 4 (ACSL4), iron accumulation, lipid peroxidation, and mitochondrial ultrastructure. Loss-and gain-of-function approaches were used to evaluate the functional role of METTL14 and ubiquitin-specific protease 7 (USP7). Methylated RNA immunoprecipitation (MeRIP), RNA stability assays, and molecular analyses were conducted to determine m6A modification of USP7 mRNA and its regulatory consequences. Behavioral assessments were performed to evaluate locomotor recovery after SCI. Results: We observed a significant increase in METTL14 and m6A levels post-SCI, concomitant with key ferroptotic alterations (reduced GPX4, elevated ACSL4, iron accumulation, lipid peroxidation). METTL14 knockdown alleviated these pathological features and improved motor function. In neuronal cells, METTL14 inhibition reversed erastin-induced ferroptosis hallmarks and restored USP7/stearoyl-CoA desaturase (SCD) expression. Mechanistic studies revealed that METTL14 mediated m6A-dependent degradation of USP7 mRNA, thereby suppressing the USP7-SCD pathway—a conclusion substantiated by the rescue effect of USP7 overexpression on METTL14-induced ferroptosis. Conclusions: This study reveals that METTL14 promotes neuronal ferroptosis after SCI by degrading USP7 mRNA via m6A modification, thereby suppressing the USP7-SCD axis. This is the first systematic demonstration that the METTL14–USP7–SCD axis drives neuronal ferroptosis in a SCI model and highlights this pathway as a promising therapeutic target for SCI.