Exome sequencing identifies a significant variant in methionyl-tRNA synthetase (MARS) in a family with late-onset CMT2

Abstract

Charcot-Marie-Tooth (CMT) disease is a genetically heterogeneous condition with >50 genes now being identified. Thanks to new technological developments, namely, exome sequencing, the ability to identify additional rare genes in CMT has been drastically improved. Here we present data suggesting that MARS is a very rare novel cause of late-onset CMT2. This is supported by strong functional and evolutionary evidence, yet the absence of additional unrelated cases warrant future studies to substantiate this conclusion.

Keywords: Charcot-Marie-Tooth disease; Exome sequencing; tRNA synthases.

Figure 1

(A) Pedigree of dominant CMT2 family displaying segregation of Arg618Cys. Two affected male individuals were analysed by exome sequencing (circles). (B) Sequence alignment of the MetRS proteins from becteria to human showing that Arg618 is a strictly conserved residue during evolution. (C) Structural model of human MetRS showing that Arg618 is located at the interface of the catalytic domain (blue) and the anticodon-binding domain (yellow), with the guanidinium side chain forming a strong salt-bridge with the side chain of Asp292 from the catalytic domain, and extensive hydrogen-bonding interactions with the backbone carbonly oxygens of Phe347 and Asn348 from the catalytic domain and of Pro758 and Tyr759 from the anticodon-binding domain. (D) Three representative cultures of each yeast strain (indicated along the top of each panel) were inoculated and grown on solid growth medium containing 5-FOA (see Methods for details). Each strain was previously transfected with a vector containing no insert (pRS315), wild-type MES1 (wt MES1) or the indicated variant form of MES1. Two independently generated mutant-bearing constructs were analysed (DNA Set 1 and DNA Set 2). Before inoculating on 5-FOA-containing medium, each strain was resuspended in 100 μl water, then diluted 1:10.