Distinct pathogenic mechanisms of various RARS1 mutations in Pelizaeus-Merzbacher-like disease

Mutations of the genes encoding aminoacyl-tRNA synthetases are highly associated with various central nervous system disorders. Recurrent mutations, including c.5A>G, p.D2G; c.1367C>T, p.S456L; c.1535G>A, p.R512Q and c.1846_1847del, p. Y616Lfs*6 of RARS1 gene, which encodes two forms of human cytoplasmic arginyl-tRNA synthetase (hArgRS), are linked to Pelizaeus-Merzbacher-like disease (PMLD) with unclear pathogenesis. Among these mutations, c.5A>G is the most extensively reported mutation, leading to a p.D2G mutation in the N-terminal extension of the long-form hArgRS. Here, we showed the detrimental effects of R512Q substitution and ΔC mutations on the structure and function of hArgRS, while the most frequent mutation c.5A>G, p.D2G acted in a different manner without impairing hArgRS activity. The nucleotide substitution c.5A>G reduced translation of hArgRS mRNA, and an upstream open reading frame contributed to the suppressed translation of the downstream main ORF. Taken together, our results elucidated distinct pathogenic mechanisms of various RARS1 mutations in PMLD.