A previously unreported NARS1 variant causes dominant distal hereditary motor neuropathy in a French family

Background and Aims

Pathogenic variants in the NARS1 gene, which encodes for the asparaginyl-tRNA synthetase1 (NARS1) enzyme, were associated with complex central and peripheral nervous system phenotypes. Recently, Charcot–Marie–Tooth (CMT) disease has been linked to heterozygous pathogenic variants in NARS1 in nine patients. Here, we report two brothers and their mother from a French family with distal hereditary motor neuropathy (dHMN) carrying a previously unreported NARS1 variant.

Methods

The NARS1 variant (c.1555G>C; p.(Gly519Arg)) was identified through whole-genome sequencing (WGS) performed on the family members. Clinical findings, nerve conduction studies (NCS), needle electromyography (EMG), and functional assays in yeast complementation assays are reported here.

Results

The family members showed symptoms of dHMN, including distal weakness and osteoarticular deformities. They also exhibited brisk reflexes suggestive of upper motor neuron involvement. All patients were able to walk independently at the last follow-up. NCS and EMG confirmed pure motor neuropathy. Functional assays in yeast confirmed a loss-of-function effect of the variant on NARS1 activity.

Interpretation

Our findings expand the clinical spectrum of NARS1-associated neuropathies, highlighting the association of NARS1 mutations with dHMN. The benign disease course observed in our patients suggests a slowly progressive phenotype. Further reports could contribute to a more comprehensive understanding of the spectrum of NARS1-associated neuropathies.