[Analysis of CX32 gene mutation and related clinical features in Chinese Han Charcot-Marie-Tooth families].

OBJECTIVE: To analyze the mutation of CX32 gene and related clinical features in Chinese Han patients with Charcot-Marie-Tooth (CMT) disease. METHODS: Thirty-four CMT families, from 2004 to 2011 at Departments of Neurology, Xiangya Hospital, Third Xiangya Hospital and National Key Laboratory of Medical Genetics, were selected for CX32 mutation screening after the exclusion of the PMP22 duplication and male-to-male transmission. Mutation analysis was carried out by polymerase chain reaction (PCR) plus direct sequencing. Analyses of clinical, electrophysiological and pathological features in 11 patients from 6 CMTX1 families were performed by 2 neurologists. RESULTS: Five CX32 gene mutations were detected in 6 CMT families: c.37G > A, c.65G > A, c.246C > G, c.256A > G and c.533A > G. Among them, c.246C > G and c.533A > G were firstly reported. The clinical manifestations included progressive distal muscle atrophy and weakness, areflexia, sensory abnormalities and pes vacus. Nerve conduction velocity ranged from 21.7 to 49.3 m/s. Both demyelination and axonal degeneration were detected in nerve biopsy. CONCLUSIONS: CMT1X has a frequency of around 9% in our study. The male patients tend to have more serious clinical features and their electrophysiological and pathological changes are intermediate. CX32 mutation analysis helps to confirm the genetic diagnosis of CMT so as to provide genetic counseling and reproductive guidance and elucidate its pathogenesis.

[Mutation analysis of LITAF, RAB7, LMNA and MTMR2 genes in Chinese Charcot-Marie-Tooth disease.].

The purpose of this study was to understand the mutation features of lipopolysaccharide-induced tumor necrosis factor-alpha factor (LITAF), ras-associated protein RAB7 (RAB7), lamin A/C (LMNA) and myotubularin-related protein 2 (MTMR2) genes in Chinese Charcot-Marie-Tooth disease (CMT) patients. Mutation analysis of LITAF gene was carried out using PCR combined with DNA sequencing, and mutation analysis of RAB7 gene by PCR-single strand conformation polymorphism (PCR-SSCP) combined with DNA sequencing in 33 CMT patients including 6 probands of autosomal domi-nated CMT families and 27 sporadic patients; mutation analysis of LMNA and MTMR2 genes was observed using PCR-SSCP combined with DNA sequencing in 41 CMT patients, including 14 probands of autosomal recessive CMT fami-lies and 27 sporadic patients. Two sequence variations c.269G-->A and c.274A-->G were detected in LITAF gene and two sequence variations c.1243G-->A and c.1910C-->T were detected in LMNA gene. No sequence variation was found in RAB7 and MTMR2 gene. Variations of c.269G-->A in LITAF gene and c.1243G-->A, c.1910C-->T in LMNA gene are newly found SNPs in this study. Variation of c.274A-->G in LITAF gene is known SNP reported in SNP database. Mutations in LITAF, RAB7, LMNA, and MTMR2 genes are rare in Chinese CMT patients.

[Mutation analysis of MFN2 gene in Chinese patients with Charcot-Marie-Tooth disease].

OBJECTIVE: To analyze MFN2 gene mutation in Chinese patients Charcot-Marie-Tooth disease (CMT) and to establish a quick and effective diagnostic method. METHODS: Through denaturing high-performance liquid chromatography (DHPLC) combined with DNA sequencing, MFN2 gene mutation analysis was carried out in 35 Chinese CMT2 patients including 9 probands of CMT2 pedigree and 26 sporadic CMT2 patients. RESULTS: The investigators found three abnormal sequence variations in MFN2 gene: c.281G-->A, c.395G-->A and c.408A-->T. c.395G-->A (C132T) was a novel causative missense mutation firstly reported while c.281G-->A (R94Q) a hotspot mutation and c.408A-->T (V136V) a single nucleotide polymorphism (SNP). The accuracy and specificity of DHPLC detection reached up to 100%. CONCLUSION: Through DHPLC combined with DNA sequencing, MFN2 mutations are detected in Chinese CMT2 patients. There are two causative missense mutations: c.395G-->A (C132T) and c.281G-->A (R94Q) and one SNP c.408A-->T (V136V). Such a method is an effective and economic diagnostic screening tool of MFN2 gene in CMT patients on a large scale.

Screening for SH3TC2, PMP2, and BSCL2 Variants in a Cohort of Chinese Patients with Charcot-Marie-Tooth.

BACKGROUND: SH3TC2, PMP2, and BSCL2 genes are related to autosomal recessive (AR) Charcot-Marie-Tooth (CMT) disease type 1, autosomal dominant (AD)-CMT1, and AD-CMT2, respectively. Pathogenic variants in these three genes were not well documented in Chinese CMT patients. Therefore, this study aims to detect SH3TC2, PMP2, and BSCL2 pathogenic variants in a cohort of 315 unrelated Chinese CMT families. METHODS: A total of 315 probands from 315 unrelated Chinese CMT families were recruited from the Department of Neurology of Third Xiangya Hospital and Xiangya Hospital. We screened for SH3TC2 pathogenic variants in 84 AR or sporadic CMT probands, PMP2 pathogenic variants in 39 AD or sporadic CMT1 probands, and BSCL2 pathogenic variants in 50 AD or sporadic CMT2 probands, using polymerase chain reaction and Sanger sequencing. All these patients were out of 315 unrelated Chinese CMT families and genetically undiagnosed after exclusion of pathogenic variants of PMP22, MFN2, MPZ, GJB1, GDAP1, HSPB1, HSPB8, EGR2, NEFL, and RAB7. Candidate variants were analyzed based on the standards and guidelines of American College of Medical Genetics and Genomics (ACMG). Clinical features were reevaluated. RESULTS: We identified three novel heterozygous variants such as p.L95V (c.283C>G), p.L1048P (c.3143T>C), and p.V1105M (c.3313G>A) of SH3TC2 gene and no pathogenic variants of PMP2 and BSCL2 genes. Although evaluation in silico and screening in the healthy control revealed that the three SH3TC2 variants were likely pathogenic, no second allele variants were discovered. According to the standards and guidelines of ACMG, the heterozygous SH3TC2 variants such as p.L95V, p.L1048P, and p.V1105M were considered to be of uncertain significance. CONCLUSIONS: SH3TC2, PMP2, and BSCL2 pathogenic variants might be rare in Chinese CMT patients. Further studies to confirm our findings are needed.

[Cloning to rule out 10 candidate genes located in chromosome 12q24 for Charcot-Marie-Tooth disease type 2L].

OBJECTIVE: To clone the disease-causing genes possibly existing in 6.8 cM distance between microsatellite markers D12S1720 and D12S1611 in chromosome 12q24 for Charcot-Marie-Tooth disease type 2L (CMT2L). METHODS: Ten positional and functional candidate genes were chosen among all known genes in this locus region by bioinformatics inqury. Mutation detection was performed by sequencing the exons and intron-exon junctions of the candidate genes. RESULTS: Eleven sequence variations, that included 5 heterozygous and 6 homozygous variations, were detected in the exons and flanking areas of the 10 candidate genes. All the variations showed no co-segregation with disease phenotype. CONCLUSION: Ten candidate genes(TAOK3, RAB35, RPLP0, PXN, RNF10, RHOF, VPS33A, RSN, DENR, RNP24) were ruled out as the disease-causing gene for CMT2L. Ten single nucleotide polymorphisms (SNP) were reported for the first time.

Mutation analysis of small heat-shock protein 22 gene in Chinese patients with Charcot-Marie-Tooth disease.

OBJECTIVE: To study the characteristics of the mutation of small heat-shock protein 22 (HSP22) gene in Chinese patients with Charcot-Marie-Tooth (CMT) disease. METHODS: A CMT2L proband with 423(G--> T) mutation in HSP22 gene had been studied and reported by the present authors. In this study, mutation analysis of HSP22 gene was performed using polymerase chain reaction and DNA direct sequencing in 114 CMT probands. RESULTS: In the 114 CMT probands, a 582(C--> T)(T194T)samesense mutation was found in two unrelated families. CONCLUSION: The rate of HSP22 gene mutation in Chinese patients with CMT is as low as 0.87%(1/115).

[Mutation analysis of small heat shock protein 27 gene in Chinese patients with Charcot-Marie-Tooth disease].

OBJECTIVE: To investigate the features of small heat shock protein 27 (HSP27) gene mutation in Chinese patients with Charcot-Marie-Tooth disease (CMT). METHODS: DNA samples from 114 CMT probands were screened for mutations in HSP27 gene by polymerase chain reaction and direct sequencing, and haplotype analysis was further carried out on the mutation detected families. RESULTS: One missense mutation C379T was detected in 4 autosomal dominant CMT2 families. Haplotype analysis indicated that the 4 families probably had a common ancestor. CONCLUSION: To the authors' knowledge, this is the first report of HSP27 gene mutation in Chinese patients with CMT, but it may be not common(0.90%). The C379T mutation in HSP27 gene also causes CMT2 except for distal hereditary motor neuropathy, thus providing further evidence that even the same mutation in the same gene may lead to distinct phenotypes.

[Mutation analysis of ganglioside-induced differentiation associated protein-1 gene in Chinese Charcot-Marie-Tooth disease].

OBJECTIVE: To study the mutation feature of ganglioside-induced differentiation associated protein-1 (GDAP1) gene in Chinese Charcot-Marie-Tooth disease(CMT) patients. METHODS: Mutation analysis was carried out by use of polymerase chain reaction-single strand conformation polymorphism(PCR-SSCP) combined with DNA direct sequencing of the six exons and their flanking regions of GDAP1 gene in twenty-three CMT patients, including 8 probands of autosomal recessive CMT families and 15 sporadic patients. RESULTS: A compound heterozygous mutation A533G and A767G were unveiled in one autosomal recessive CMT kindred. The homozygous and heterozygous T507G were common SNPs in Chinese population. CONCLUSION: A533G and A767G of GDAP1 gene were new mutations firstly reported.