LRSAM1 variants and founder effect in French families with ataxic form of Charcot-Marie-Tooth type 2

Eur J Hum Genet. 2019 Sep;27(9):1406-1418. doi: 10.1038/s41431-019-0403-8. Epub 2019 Apr 17.

Abstract

Currently only 25-30% of patients with axonal forms of Charcot-Marie-Tooth disease (CMT) receive a genetic diagnosis. We aimed to identify the causative gene of CMT type 2 in 8 non-related French families with a distinct clinical phenotype. We collected clinical, electrophysiological, and laboratory findings and performed genetic analyses in four different French laboratories. Seventy-two patients with autosomal dominant inheritance were identified. The disease usually started in the fourth decade and the clinical picture was dominated by sensory ataxia (80%), neuropathic pain (38%), and length-dependent sensory loss to all modalities. Electrophysiological studies showed a primarily axonal neuropathy, with possible isolated sensory involvement in milder phenotypes. Disease severity varied greatly but the clinical course was generally mild. We identified 2 novel variants in LRSAM1 gene: a deletion of 4 amino acids, p.(Gln698_Gln701del), was found in 7 families and a duplication of a neighboring region of 10 amino acids, p.(Pro702_Gln711dup), in the remaining family. A common haplotype of ~450 kb suggesting a founder effect was noted around LRSAM1 in 4 families carrying the first variant. LRSAM1 gene encodes for an E3 ubiquitin ligase important for neural functioning. Our results confirm the localization of variants in its catalytic C-terminal RING domain and broaden the phenotypic spectrum of LRSAM1-related neuropathies, including painful and predominantly sensory ataxic forms.

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Alleles
  • Amino Acid Sequence
  • Biopsy
  • Cell Cycle Proteins / genetics
  • Charcot-Marie-Tooth Disease / diagnosis*
  • Charcot-Marie-Tooth Disease / genetics*
  • Family*
  • Founder Effect*
  • France
  • Genetic Testing
  • Genetic Variation*
  • Humans
  • Nuclear Proteins / genetics
  • Pedigree
  • Phenotype*
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics*

Substances

  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • MAD2L1BP protein, human
  • Nuclear Proteins
  • LRSAM1 protein, human
  • Ubiquitin-Protein Ligases