Methamphetamine-induced inhibition of Mettl21c in undifferentiated spermatogonia impairs male fertility in mice

Chronic methamphetamine (Meth) exposure has been recognized as a critical risk factor for male reproductive dysfunction, yet its mechanistic underpinnings remain elusive. This study elucidates the molecular pathways through which Meth compromises spermatogenesis in a murine model. Male mice subjected to 15 days of chronic Meth administration presented severe testicular atrophy, characterized by seminiferous epithelial disorganization and diminished sperm reserves in both the testes and epididymides. Quantitative assessments revealed marked reductions in sperm motility and increased tail abnormalities. Transcriptomic profiling revealed significant down-regulation of methyltransferase-like 21C (Mettl21c), an undifferentiated spermatogonial-enriched methyltransferase, within pathways governing germ cell differentiation. Immunofluorescence analysis revealed predominant Mettl21c colocalization with undifferentiated spermatogonial marker ubiquitin carboxyl-terminal hydrolase L1 (Uchl1), with minimal overlap in tyrosine-protein kinase Kit (Kit) positive differentiated populations. In vitro suppression of Mettl21c in C18-4 lines triggered proliferation arrest and increased apoptosis. These findings establish Mettl21c as a pivotal mediator of Meth-induced spermatogenic failure through spermatogonial maintenance pathways. Our work provides novel insights into the epigenetic regulation of drug-associated male infertility and identifies Mettl21c as a potential therapeutic target for preserving fertility in substance abuse cases.