Analysis of gene mutation in a pedigree with autosomal dominant Charcot-Marie-Tooth disease / 南方医科大学学报

OBJECTIVE@#To investigate the molecular genetic mechanism of Charcot- Marie-Tooth (CMT) disease in a pedigree.@*METHODS@#Genomic DNA was extracted from the peripheral blood of the family members of a pedigree with autosomal dominant CMT disease, and 65 candidate genes of the proband were screened using target exon capture and the next generation sequencing, and the suspicious genes were verified using Sanger sequencing. PolyPhen-2, PROVEAN and SIFT software were used to predict the function of the mutant genes, and PyMOL-1 software was used to simulate the mutant protein structure.@*RESULTS@#A heterozygous missense mutation [c.371A>G (p.Y124C)] was detected in exon 3 of gene of the proband. This heterozygous mutation was also detected in both the proband's mother and her brother, but not in her father. Multiple sequence alignment analysis showed that tyrosine at codon 124 of GDAP1 protein was highly conserved. All the 3 prediction software predicted that the mutation was harmful. Molecular structure simulation showed a weakened interaction force between the amino acid residues at codon 124 and the surrounding amino acid residues to affect the overall stability of the protein.@*CONCLUSIONS@#The mutation of gene may be related to the pathogenesis of autosomal dominant AD-CMT in this pedigree. The newly discovered c.371A>G mutation (p.Y124C) expands the mutation spectrum of gene, but further study is needed to clarify the underlying pathogenesis.

Clinical features of autosomal recessive Charcot-Marie-Tooth disease 2K / 中华神经科杂志

Objective To report the clinical and peripheral neuropathological findings in two patients with autosomal recessive Charcot-Marie-Tooth disease 2K(AR-CMT2K).Methods Case one was a nine year-old girl.She had distal weakness of lower limbs for six years, with calf atrophy and contracture of Achilles tendon for three years.Case two was an eight year-old boy.He had distal weakness of lower limbs with contracture of Achilles tendon and calf muscle atrophy for three years, and proximal weakness of low limbs for two years.The motor nerve conduction velocities in median nerves were 48.1 m/s in case one and 47.6 m/s in case two.The compound motor action potential amplitude of median nerves decreased by 46% in case one and 69% in case two.Sural nerve biopsies and gene targeted next-generation sequencing were performed in both patients.Results Density of myelinated fibers was 8 407/mm2 in case one and 7 714/mm2 in case two.The ratio of myelinated fibers with diameter over 8 μm was 2.6% in case one and 0 in case two.Both patients had small regenerating cluster of myelinated fibers.Thin myelinated fibers appeared in case one.In case two, atypical onion bulb formations with focal folded myelin appeared, and electromicroscopy revealed mitochondrial aggregate in axons.Compound heterozygous mutations of ganglioside-induced differentiation associated protein 1 gene were detected in both patients, including c.767A>G(p.H256R) and c.466G>A (p.A156T) in case one and c.767A>G and 845G>A(p.R282H) in case two.Conclusions Contracture of Achilles tendon may appear in early childhood of AR-CMT2K patients.The main pathological changes in sural nerve are loss of large myelinated fibers, mitochondrial aggregate in axons and myelin abnormalities.