• Journal of Genetic Medicine
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• 제17권2호
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• pp.89-91
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• 2020

Charcot-Marie-Tooth (CMT) disease can be divided mainly into demyelination and axonopathy based on the results of the electrophysiological study. Mitofusin 2, encoded by MFN2 gene, has a crucial role in the fusion of mitochondria, which is known to associate with CMT type 2A as one of the axonal forms. We describe a 44-year-old man with progressive weakness on bilateral legs after noticing foot drop in his early teen. When we examined him at 45 years of age, he presented atrophy on entire legs and with distal muscle weakness on limbs. The nerve conduction study revealed severely decreased amplitude on motor nerve ranging from 0.2 to 4.5 mV, while conduction velocity remained more than 30.4 m/s. The whole-exome sequencing revealed a novel variant c.2228G>T in MFN2 by efficient genetic analysis tool, MutationDistiller. This report will not only expand the mutation spectrum of CMT2A but also introduce a time-saving genetic analysis tool.

• 생명과학회지
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• 제18권6호
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• pp.764-769
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• 2008

커넥신(connexin) 32 유전자의 돌연변이가 씨엠티엑스(CMTX, X-linked Charcot-Marie-Tooth) 질환과 관련이 있다. 현재까지 300여개 이상의 돌연변이가 보고가 되었으나 이 질환에 대한 상세한 분자병리학적 원인을 거의 알려져 있지 않고 있다. 여러 연구를 통해서 커넥신 세포막채널이 간극결합채널이 갖고 있는 대부분의 생물리학적 특성을 갖고 있는 것으로 판명되었다. 이번 연구에서는 씨엠티엑스 질환과 관련된 두 개의 돌연변이체를 선정하여 간극결합채녈 대신 돌연변이체로 구성된 커넥신 세포막채널을 이용하여 단일채널수준에서 이들 돌연변이체의 특성을 조사하였다. M34T 돌연변이 세포막채널의 생물리학적 특성은 이들로 구성된 돌연변이 간극결합채널의 특성과 거의 유사하였다. 더욱이, 돌연변이 세포막채널을 이용한 연구를 통해서 간극결합채널을 이용한 연구에서는 밝혀지지 않았던 개폐극성의 역전, 빠른 개폐의 소실과 느린 개폐의 생성과 같은 새로운 사실을 알게 되었다. T86C 돌연변이 세포막채널 또한 이의 모체가 되는 커넥신 32 세포막채널과 유사한 특성을 갖고 있음을 알게 되었다. 이상의 결과를 통해서 커넥신 세포막을 이용한 연구가 씨엠티엑스 질환의 돌연변이체를 연구하는데 매우 유용할 것으로 생각된다.

• Journal of Genetic Medicine
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• 제12권1호
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• pp.25-30
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• 2015

Purpose: Charcot-Marie-Tooth disease (CMT) is a peripheral neuropathy mainly divided into CMT type 1 (CMT1) and CMT2 according to the phenotype and genotype. Although molecular pathologies for each genetic causative have not been revealed in CMT2, the correlation between cell death and accumulation of misfolded proteins in the endoplasmic reticulum (ER) of Schwann cells is well documented in CMT1. Establishment of in vitro models of ER stress-mediated Schwann cell death might be useful in developing drug-screening systems for the treatment of CMT1. Materials and Methods: To develop high-throughput screening (HTS) systems for CMT1, we generated cell models using transient expression of mutant proteins and chemical induction. Results: Overexpression of wild type and mutant peripheral myelin protein 22 (PMP22) induced ER stress. Similar results were obtained from mutant myelin protein zero (MPZ) proteins. Protein localization revealed that expressed mutant PMP22 and MPZ proteins accumulated in the ER of Schwann cells. Overexpression of wild type and L16P mutant PMP22 also reduced cell viability, implying protein accumulation-mediated ER stress causes cell death. To develop more stable screening systems, we mimicked the ER stress-mediated cell death in Schwann cells using ER stress inducing chemicals. Thapsigargin treatment caused cell death via ER stress in a dose dependent manner, which was measured by expression of ER stress markers. Conclusion: We have developed genetically and chemically induced ER stress models using Schwann cells. Application of these models to HTS systems might facilitate the elucidation of molecular pathology and development of therapeutic options for CMT1.

• Molecules and Cells
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• 제39권5호
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• pp.382-388
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• 2016

Inherited peripheral neuropathies (IPN), which are a group of clinically and genetically heterogeneous peripheral nerve disorders including Charcot-Marie-Tooth disease (CMT), exhibit progressive degeneration of muscles in the extremities and loss of sensory function. Over 70 genes have been reported as genetic causatives and the number is still growing. We prepared a targeted gene panel for IPN diagnosis based on next generation sequencing (NGS). The gene panel was designed to detect mutations in 73 genes reported to be genetic causes of IPN or related peripheral neuropathies, and to detect duplication of the chromosome 17p12 region, the major genetic cause of CMT1A. We applied the gene panel to 115 samples from 63 non-CMT1A families, and isolated 15 pathogenic or likelypathogenic mutations in eight genes from 25 patients (17 families). Of them, eight mutations were unreported variants. Of particular interest, this study revealed several very rare mutations in the SPTLC2, DCTN1, and MARS genes. In addition, the effectiveness of the detection of CMT1A was confirmed by comparing five 17p12-nonduplicated controls and 15 CMT1A cases. In conclusion, we developed a gene panel for one step genetic diagnosis of IPN. It seems that its time- and cost-effectiveness are superior to previous tiered-genetic diagnosis algorithms, and it could be applied as a genetic diagnostic system for inherited peripheral neuropathies.

• Molecules and Cells
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• 제23권1호
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• pp.39-48
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• 2007

Charcot-Marie-Tooth (CMT) disease and hereditary neuropathy with liability to pressure palsies (HNPP) are frequent forms of genetically heterogeneous peripheral neuropathies. Reciprocal unequal crossover between flanking CMT1A-REPs on chromosome 17p11.2-p12 is a major cause of CMT type 1A (CMT1A) and HNPP. The importance of a sensitive and rapid method for identifying the CMT1A duplication and HNPP deletion is being emphasized. In the present study, we established a molecular diagnostic method for the CMT1A duplication and HNPP deletion based on hexaplex PCR of 6 microsatellite markers (D17S921, D17S9B, D17S9A, D17S918, D17S4A and D17S2230). The method is highly time-, cost- and sample-saving because the six markers are amplified by a single PCR reaction and resolved with a single capillary in 3 h. Several statistical and forensic estimates indicated that most of these markers are likely to be useful for diagnosing the peripheral neuropathies. Reproducibility, as determined by concordance between independent tests, was estimated to be 100%. The likelihood that genotypes of all six markers are homozygous in randomly selected individuals was calculated to be $1.6{\times}10^{-4}$, which indicates that the statistical error rate for this diagnosis of HNPP deletion is only 0.016%.

• 생명과학회지
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• 제29권7호
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• pp.800-808
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• 2019

샤르코-마리-투스병(Charcot-Marie-Tooth disease: CMT)은 희귀 말초신경병의 그룹으로, 진행성 근육 약화 및 위축, 감각 소실, 상지 및 하지의 무반사 증상을 나타낸다. CMT1A는 PMP22 유전자가 존재하는 17p12 지역의 직렬 중복으로 발병하는데, 유전자형-표현형의 상관성이 느슨하여 2차 유전적 요인의 존재를 암시한다. 최근 MIR149의 rs71428439 (n.83A>G)와 rs2292832 (n.86T>C) 변이가 후기 발병 및 가벼운 증상의 표현형과 연관성이 있는 것으로 보고되었다. 본 연구는 CMT1A 기계내 임상적 표현형의 이질성이 MIR149의 SNP과 연관성이 있는지를 규명하기 위해 수행하였으며, 조사 대상으로는 가계내 표현형의 차이가 심한 6 CMT1A 대 가계를 대상으로 하였다. 그 결과, MIR149의 rs71428439와 s2292832 유전자형은 가족내의 늦은 발병과 약한 중증도의 유전적 요인으로 작용할 수 있음을 제시하였다. 특히, AG+GG (n.83A>G)와 TC+CC 유전자형(n.86T>C)은 발병 시기가 늦고 경미한 증상을 보였다. 운동신경 전기전도도(MNCV)는 MIR149 유전형과 연관이 없는 것으로 보였는데, 이러한 결과는 이전 연구와 일치한다. 따라서 본 연구는 MIR149의 rs71428439와 rs2292832 변이는 CMT1A 가계내 표현형적 이질성의 원인 중 하나로 작용할 가능성을 제시한다. 본 연구는 가계 내 증상의 차이가 심한 6 대가족을 사용하여 연구를 수행한 것은 의미가 크다고 여겨지며, 이런 결과는 CMT1A 환자의 분자 진단과 치료에 도움을 줄 수 있을 것으로 기대된다.

• BMB Reports
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• 제41권12호
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• pp.868-874
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• 2008

Neurofilaments (NFs) are neuronal intermediate filaments composed of light (NF-L), middle (NF-M), and heavy (NF-H) subunits. NF-L self-assembles into a "core" filament with which NF-M or NF-H co-assembles to form the neuronal intermediate filament. Recent reports show that point mutations of the NF-L gene result in Charcot-Marie-Tooth disease (CMT). However, the most recently described rod domain mutant of human NF-L (A148V) has not been characterized in cellular level. We cloned human NF-L and used it to engineer the A148V. In phenotypic analysis using SW13 cells, A148V mutation completely abolished filament formation despite of presence of NF-M. Moreover, A148V mutation reduced the levels of in vitro self-assembly using GST-NF-L (H/R) fusion protein whereas control (A296T) mutant did not affect the filament formation. These results suggest that alanine at position 148 is essentially required for NF-L self-assembly leading to subsequent filament formation in neuronal cells.

• Molecules and Cells
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• 제43권10호
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• pp.880-888
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• 2020

Inherited peripheral neuropathy is a heterogeneous group of peripheral neurodegenerative disorders including Charcot-Marie-Tooth disease. Many peripheral neuropathies often accompany impaired axonal construction and function. To study the molecular and cellular basis of axon-defective peripheral neuropathy, we explore the possibility of using Caenorhabditis elegans, a powerful nematode model equipped with a variety of genetics and imaging tools. In search of potential candidates of C. elegans peripheral neuropathy models, we monitored the movement and the body posture patterns of 26 C. elegans strains with disruption of genes associated with various peripheral neuropathies and compiled a database of their phenotypes. Our assay showed that movement features of the worms with mutations in HSPB1, MFN2, DYNC1H1, and KIF1B human homologues are significantly different from the control strain, suggesting they are viable candidates for C. elegans peripheral neuropathy models.

• Annals of Clinical Neurophysiology
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• 제4권2호
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• pp.125-132
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• 2002

Objectives : Although the diagnosis of hereditary neuropathy with liability to pressure palsies (HNPP) is important for correct prognostic evaluation and genetic counseling, the diagnosis is frequently missed or delayed. Our main aim on undertaking this study was to characterize the electrodiagnostic features of HNPP. Material and Methods : Clinical, electrophysiologic and molecular studies were performed on Korean HNPP patients with 17p11.2 deletion. The results of electrophysiologic studies were compared with those of Charcot-Marie-Tooth disease type 1A (CMT1A) patients carrying 17p11.2 duplication. Results : Eight HNPP (50 motor, 39 sensory nerves) and six CMT1A (28 motor, 16 sensory nerves) patients were included. The slowing of sensory conduction in nearly all nerves and the distal accentuation of motor conduction abnormalities are the main features of background polyneuropathy in HNPP. In contrast to CMT1A, where severity of nerve conduction slowing was not different among nerve groups, HNPP sensory nerve conduction was more slowed in the median and ulnar nerves than in the sural nerve (p<0.01), and DML was more prolonged in the median nerve than in the other motor nerves (p<0.01). TLIs were significantly lower in HNPP than in the normal control and CMT1A patients for the median and ulnar nerves (p<0.01), and were also significantly reduced for the peroneal nerve (p<0.05) compared with those of the normal controls. Conclusion : The distribution and severity of the background electrophysiologic abnormalities are closely related to the topography of common entrapment or compression sites, which suggests the possible pathogenetic role of subclinical pressure injury at these sites in the development of the distinct background polyneuropathy in HNPP.

• Molecules and Cells
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• 제45권4호
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• pp.231-242
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• 2022

The neuromuscular junction (NMJ), which is a synapse for signal transmission from motor neurons to muscle cells, has emerged as an important region because of its association with several peripheral neuropathies. In particular, mutations in GARS that affect the formation of NMJ result in Charcot-Marie-Tooth disease and distal hereditary motor neuropathy. These disorders are mainly considered to be caused by neuronal axon abnormalities; however, no treatment is currently available. Therefore, in order to determine whether the NMJ could be targeted to treat neurodegenerative disorders, we investigated the NMJ recovery effect of HDAC6 inhibitors, which have been used in the treatment of several peripheral neuropathies. In the present study, we demonstrated that HDAC6 inhibition was sufficient to enhance movement by restoring NMJ impairments observed in a zebrafish disease model. We found that CKD-504, a novel HDAC6 inhibitor, was effective in repairing NMJ defects, suggesting that treatment of neurodegenerative diseases via NMJ targeting is possible.