Dataset Information

GJB1/Connexin 32 whole gene deletions in patients with X-linked Charcot-Marie-Tooth disease.

ABSTRACT: The X-linked form of Charcot-Marie-Tooth disease (CMTX) is the second most common form of this genetically heterogeneous inherited peripheral neuropathy. CMT1X is caused by mutations in the GJB1 gene. Most of the mutations causative for CMT1X are missense mutations. In addition, a few disease causative nonsense mutations and frameshift deletions that lead to truncated forms of the protein have also been reported to be associated with CMT1X. Previously, there have been reports of patients with deletions of the coding sequence of GJB1; however, the size and breakpoints of these deletions were not assessed. Here, we report five patients with deletions that range in size from 12.2 to 48.3 kb and that completely eliminate the entire coding sequence of the GJB1 gene, resulting in a null allele for this locus. Analyses of the breakpoints of these deletions showed that they are nonrecurrent and that they can be generated by different mechanisms. In addition to PMP22, GJB1 is the second CMT gene for which both point mutations and genomic rearrangements can cause a neuropathy phenotype, stressing the importance of CMT as a genomic disorder.

SUBMITTER: Gonzaga-Jauregui C

PROVIDER: S-EPMC4222676 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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GJB1/Connexin 32 whole gene deletions in patients with X-linked Charcot-Marie-Tooth disease.

Gonzaga-Jauregui Claudia C Zhang Feng F Towne Charles F CF Batish Sat Dev SD Lupski James R JR

Neurogenetics 20100609 4

The X-linked form of Charcot-Marie-Tooth disease (CMTX) is the second most common form of this genetically heterogeneous inherited peripheral neuropathy. CMT1X is caused by mutations in the GJB1 gene. Most of the mutations causative for CMT1X are missense mutations. In addition, a few disease causative nonsense mutations and frameshift deletions that lead to truncated forms of the protein have also been reported to be associated with CMT1X. Previously, there have been reports of patients with de ...[more]

PMID: 20532933

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Project description:Charcot-Marie-Tooth disease (CMT) due to GJB1 variants (CMTX1) is the second most common form of CMT. It is an X-linked disorder characterized by progressive sensory and motor neuropathy with males affected more severely than females. Many reported GJB1 variants remain classified as variants of uncertain significance (VUS). In this large, international, multicentre study we prospectively collected demographic, clinical and genetic data on patients with CMT associated with GJB1 variants. Pathogenicity for each variant was defined using adapted American College of Medical Genetics criteria. Baseline and longitudinal analyses were conducted to study genotype-phenotype correlations, to calculate longitudinal change using the CMT Examination Score (CMTES), to compare males versus females, and pathogenic/likely pathogenic (P/LP) variants versus VUS. We present 387 patients from 295 families harbouring 154 variants in GJB1. Of these, 319 patients (82.4%) were deemed to have P/LP variants, 65 had VUS (16.8%) and three benign variants (0.8%; excluded from analysis); an increased proportion of patients with P/LP variants compared with using ClinVar's classification (74.6%). Male patients (166/319, 52.0%, P/LP only) were more severely affected at baseline. Baseline measures in patients with P/LP variants and VUS showed no significant differences, and regression analysis suggested the disease groups were near identical at baseline. Genotype-phenotype analysis suggested c.-17G>A produces the most severe phenotype of the five most common variants, and missense variants in the intracellular domain are less severe than other domains. Progression of disease was seen with increasing CMTES over time up to 8 years follow-up. Standard response mean (SRM), a measure of outcome responsiveness, peaked at 3 years with moderate responsiveness [change in CMTES (ΔCMTES) = 1.3 ± 2.6, P = 0.00016, SRM = 0.50]. Males and females progressed similarly up to 8 years, but baseline regression analysis suggested that over a longer period, females progress more slowly. Progression was most pronounced for mild phenotypes (CMTES = 0-7; 3-year ΔCMTES = 2.3 ± 2.5, P = 0.001, SRM = 0.90). Enhanced variant interpretation has yielded an increased proportion of GJB1 variants classified as P/LP and will aid future variant interpretation in this gene. Baseline and longitudinal analysis of this large cohort of CMTX1 patients describes the natural history of the disease including the rate of progression; CMTES showed moderate responsiveness for the whole group at 3 years and higher responsiveness for the mild group at 3, 4 and 5 years. These results have implications for patient selection for upcoming clinical trials.

Dataset Information

GJB1/Connexin 32 whole gene deletions in patients with X-linked Charcot-Marie-Tooth disease.

Publications

GJB1/Connexin 32 whole gene deletions in patients with X-linked Charcot-Marie-Tooth disease.

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