TRMT1 gene encodes a methyltransferase enzyme that acts on tRNA. This enzyme, which consists of a zinc finger motif and an arginine/proline rich region at its C-terminus, is responsible for catalyzing the dimethylation of a guanine residue located at position 26 of most tRNAs. TRMT1 uses S-adenosyl-L-methionine as a substrate and has both mono and dimethylase activity.     

Recent studies have suggested a possible link between TRMT1 gene mutations and Autosomal Recessive Intellectual Disability (ARID). Patients with TRMT1 mutations have been reported to suffer from moderate to severe intellectual disability, mild facial dysmorphia, progressive spasticity of the upper and lower limbs and pes planus. These findings are further bolstered by the fact that mutations in two other RNA-methyltransferase genes, NSUN2 and FTSJ1, have been associated with intellectual disability.