Assessment of Targeted Next-Generation Sequencing as a Tool for the Diagnosis of Charcot-Marie-Tooth Disease and Hereditary Motor Neuropathy

Abstract

Charcot-Marie-Tooth disease is characterized by broad genetic heterogeneity with >50 known disease-associated genes. Mutations in some of these genes can cause a pure motor form of hereditary motor neuropathy, the genetics of which are poorly characterized. We designed a panel comprising 56 genes associated with Charcot-Marie-Tooth disease/hereditary motor neuropathy. We validated this diagnostic tool by first testing 11 patients with pathological mutations. A cohort of 33 affected subjects was selected for this study. The DNAJB2 c.352+1G>A mutation was detected in two cases; novel changes and/or variants with low frequency (<1%) were found in 12 cases. There were no candidate variants in 18 cases, and amplification failed for one sample. The DNAJB2 c.352+1G>A mutation was also detected in three additional families. On haplotype analysis, all of the patients from these five families shared the same haplotype; therefore, the DNAJB2 c.352+1G>A mutation may be a founder event. Our gene panel allowed us to perform a very rapid and cost-effective screening of genes involved in Charcot-Marie-Tooth disease/hereditary motor neuropathy. Our diagnostic strategy was robust in terms of both coverage and read depth for all of the genes and patient samples. These findings demonstrate the difficulty in achieving a definitive molecular diagnosis because of the complexity of interpreting new variants and the genetic heterogeneity that is associated with these neuropathies.

Recent advances in the genetic neuropathies

“…Disease-specific panels restricted to known CMT genes are currently the preferred method for employing NGS in clinical practice [4,5]. Whilst some groups have proposed disease-specific panels based on the phenotype (i.e.…”

“…Whilst some groups have proposed disease-specific panels based on the phenotype (i.e. CMT1 and CMT2) [2], others have proposed a broader CMT panel incorporating all genes [4,5]. In two separate studies employing either a 56 or 70 gene CMT panel in patients negative for the common CMT mutations, diagnostic rates of 12 and 27% were reported [4,5].…”

“…CMT1 and CMT2) [2], others have proposed a broader CMT panel incorporating all genes [4,5]. In two separate studies employing either a 56 or 70 gene CMT panel in patients negative for the common CMT mutations, diagnostic rates of 12 and 27% were reported [4,5]. To date, diagnostic algorithms for CMT1 have proposed using multiplex ligation probe amplification (MLPA) for the detection of duplications and deletions of the short arm of chromosome 17 before proceeding to disease-specific panels or WES [2].…”

Chaperonopathies: Spotlight on Hereditary Motor Neuropathies

“…These Spanish families were investigated by haplotype analysis and they carried the same homozygous haplotype. Hence, the DNAJB2 c.352+1G>A mutation appears to be a founder event (Lupo et al, 2016), and it is shared with a family reported elsewhere (Blumen et al, 2012). The patients in Spain displayed a dHMN or CMT2 phenotype and, in some cases, initial clinical manifestations that were consistent with dHMN and that subsequently evolved to CMT2 (Frasquet et al, 2016).…”

“…To date, the remaining known patients with mutations in the DNAJB2 gene carry the c.352+1G>A mutation in homozygosis: 5 families from Spain (Frasquet et al, 2016; Lupo et al, 2016) and one from Brazil (Teive et al, 2015). These Spanish families were investigated by haplotype analysis and they carried the same homozygous haplotype.…”