A recurrent GARS mutation causes distal hereditary motor neuropathy

Abstract

We found a p.Gly327Arg mutation in GARS in two unrelated women, both of whom had a similar phenotype - motor weakness that began in late childhood, distal weakness in the arms and legs, a motor greater than sensory neuropathy with slowing of motor and not sensory conduction velocities. A de novo mutation was proven in one patient and suspected in the other. The p.Gly327Arg GARS variant did not support yeast growth in a complementation assay, showing that this variant severely impairs protein function. Thus, the p.Gly327Arg GARS mutation causes a distal motor neuropathy.

Keywords: CMT; Charcot-Marie-Tooth disease; HMN; aminoacyl transferase.

Figure 1:

Pedigrees of patients 1 and 2. Segregation analysis is noted on the pedigree by (+) indicating the variant is present and (−) variant is not present. The individuals in the brackets were adopted into the family.

Figure 2:

The p.Gly327Arg GARS variant is a loss-of-function allele in yeast complementation assays. Haploid yeast lacking the endogenous GRS1 were transformed with an empty expression construct, an expression construct with wild-type human ΔMTSΔWHEP GARS, or an expression construct with p.Gly327Arg ΔMTSΔWHEP GARS. After transformants were selected using plasmid markers, colonies were grown to saturation in 2 mL selective media. Subsequently, 1 mL of saturated culture was concentrated into 50 ul water, spotted (undiluted or diluted 1:10) on media containing 5-FOA to assess yeast growth in the absence of a URA3-bearing maintenance vector. Four independently generated p.Gly327Arg GARS expression clones were tested (A-D) and two independent colonies were evaluated per transformation (Set 1 and Set 2).