Pathogenic missense variants altering codon 336 of GARS1 lead to divergent dominant phenotypes.

ABSTRACT

Heterozygosity for missense variants and small in-frame deletions in GARS1 has been reported in patients with a range of genetic neuropathies including Charcot-Marie-Tooth disease type 2D (CMT2D), distal hereditary motor neuropathy type V (dHMN-V), and infantile spinal muscular atrophy (iSMA). We identified two unrelated patients who are each heterozygous for a previously unreported missense variant modifying amino-acid position 336 in the catalytic domain of GARS1. One patient was a 20-year-old woman with iSMA, and the second was a 41-year-old man with CMT2D. Functional studies using yeast complementation assays support a loss-of-function effect for both variants; however, this did not reveal variable effects that might explain the phenotypic differences. These cases expand the mutational spectrum of GARS1-related disorders and demonstrate phenotypic variability based on the specific substitution at a single residue.