Charcot-Marie-Tooth disease (CMT) is the commonest form of inherited neuropathy and has an incidence of 1/2500. CMT1A is the commonest subtype of CMT, which is caused by duplication of peripheral myelin protein 22 (PMP22) gene and accounts for approximately 50% of CMT diagnosed by genetic testing. Duplication of PMP22 may influence the production of PMP22 mRNA and protein, and interfere with the proliferation, differentiation and apoptosis of Schwann cells. In addition, deregulation of NRG1/ErbB pathway and lipid metabolism can also lead to dysfunction of Schwann cells. Such factors may disturb the myelination process, leading to axon degeneration, muscle weakness, and atrophy subsequently. Accordingly, drug therapies for CMT1A are developed by targeting such factors. PXT3003, antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) are supposed to down-regulate the level of PMP22 mRNA, while recombinant human NRG-1 (rhNRG1) and neurotrophin-3 (NT-3) may enhance Schwann cells survival and differentiation. In addition, lipid-supplemented diet may remedy the defect of lipid metabolism and maintain the proper structure of myelin. Other targeting drugs include ascorbic acid, progesterone antagonists, IFB-088, ADX71441, and ACE-083. This review is to sum up the pathogenesis of CMT1A and promising targeting drug therapies for further research.
Cell Differentiation ; Charcot-Marie-Tooth Disease ; genetics ; pathology ; therapy ; Genetic Testing ; Humans ; Schwann Cells ; cytology

OBJECTIVETo report a Chinese Charcot-Marie-Tooth disease type 2 (CMT2) family.

METHODSAll the members in the family were studied clinically,and 6 patients were studied electrophysiologically. Sural nerve biopsy was performed in the proband. PMP22 gene duplications were detected by highly polymorphic short tandem repeat. Point mutation analysis of PMP22, MPZ and NEFL gene was screened by PCR-SSCP combined with DNA direct sequencing. A genome-wide screening was carried out to the family.

RESULTExcept 2 who had weakness and atrophy in both proximal and distal muscles of the lower limbs, all patients presented muscle wasting and a predominating weakness of distal parts of the lower limbs, and mild to moderate sensory impairments. In 6 patients who were subjected to elctrophysiological examinations, median-nerve conduction velocity (NCV) of the median nerve was normal. Electromyograms (EMGs) revealed signs of denervation with large motor unit potentials, fibrillation potentials and positive sharp waves. Sural nerve biopsy of the proband confirmed the presence of axonal neuropathy with an important loss of large myelinating fibers and a large number of clusters with mostly thinly myelinated axons. PMP22, MPZ and NEFL gene mutations were not found. The results of genome-wide screening revealed a linkage of CMT2 to a locus at chromosome 12q24.

CONCLUSIONThe results are consistent with the diagnosis of CMT2. This family represents a rare genetic type of CMT2 which can be designated as CMT2L.

Adolescent ; Adult ; Asian Continental Ancestry Group ; Charcot-Marie-Tooth Disease ; genetics ; pathology ; Chromosomes, Human, Pair 12 ; genetics ; Electromyography ; Female ; Humans ; Male ; Pedigree

OBJECTIVETo analyze the phenotype and genotype of CMTX1 patients with episodic transient reversible white matter involvement, and delineate the features of brain MRI in the episode and the possible mechanisms.

METHODThree Chinese probands and their family members were sequenced in the coding regions of GJB1. With the other 16 reported CMTX1 patients with episodic transient reversible white matter involvement, the clinical feature of the episodic central nervous system symptoms and the genotypes were reviewed.

RESULTMissense mutations in GJB1 were identified in all 3 probands. In 19 patients with transient reversible white matter involvement, the episodes were manifested as weakness of the limbs, dysarthria, and dysphagia, without disturbance of consciousness or seizures. The episodes lasted for 13 hours (10 min-72 hours) with complete remission in all patients; There were multiple episodes in 9 patients. During the episode, brain MRI showed symmetrical high signals in T2 weighted, Flair and DWI images in periventricular white matter, with predominance in posterior region including splenium of corpus callosum. These changes in imaging were most prominent during or within 1 week after the clinical episode.Significant improvements occurred within 1 month, with complete remission within 4-6 months.No specific locations of mutant amino acids in GJB1 protein were found in these patients with episodic transient reversible white matter involvement.

CONCLUSIONEpisodic transient reversible white matter involvement may present in a small number of patients with CMTX1. Transient edema of oligodendrocytes due to the dysfunction of gap junction may be involved in the pathogenesis. There is no correlation between the location of the mutant amino acids in GJB1 and the occurrence of the episodes.

Adolescent ; Brain ; diagnostic imaging ; pathology ; Brain Diseases ; diagnostic imaging ; etiology ; pathology ; Central Nervous System ; pathology ; Charcot-Marie-Tooth Disease ; complications ; genetics ; pathology ; Child ; Connexins ; genetics ; Corpus Callosum ; pathology ; Genetic Linkage ; Humans ; Magnetic Resonance Imaging ; Male ; Mutation, Missense ; Pedigree ; Phenotype ; Radiography

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.
Cell Death ; Cell Survival ; Charcot-Marie-Tooth Disease* ; Endoplasmic Reticulum ; Endoplasmic Reticulum Stress ; Genotype ; Mass Screening* ; Mutant Proteins ; Myelin P0 Protein ; Myelin Sheath ; Pathology, Molecular ; Peripheral Nervous System Diseases ; Phenotype ; Schwann Cells ; Thapsigargin

BACKGROUNDX-linked Charcot-Marie-Tooth type 1 (CMT1X) disease is one of the most common forms of inherited neuropathy caused by mutations in the gap junction beta-1 protein (GJB1) gene (also known as connexin 32). This study presented the clinical and genetic features of a series of Chinese patients with GJB1 gene mutations.

METHODSA total of 22 patients from unrelated families, who were referred to Department of Neurology, Peking University First Hospital from January 2005 to January 2016, were identified with GJB1 mutations. Their clinical records and laboratory findings were retrospectively collected and reviewed. Mutations in the GJB1 gene were analyzed by targeted next-generation sequencing (NGS). Nucleotide alternations were confirmed with Sanger sequencing.

RESULTSThe CMT1X patients predominantly showed distal muscle weakness of lower limbs with mild sensory disturbance. The mean age of onset was 15.6 ± 8.7 years (ranging from 1 year to 42 years). The sudden onset of cerebral symptoms appeared in four patients (18.2%); two were initial symptoms. One case had constant central nervous system (CNS) signs. There were 19 different heterozygous mutations, including 15 known mutations and four novel mutations (c.115G>T, c.380T>A, c.263C>A, and c.818_819insGGGCT). Among the 22 Chinese patients with CMT1X, the frequency of the GJB1 mutation was 4.5% in transmembrane domain 1 (TM1), 4.5% in TM2, 22.7% in TM3, 9.1% in TM4, 4.5% in extracellular 1 (EC1), 27.3% in EC2, 9.1% in intracellular loop, 13.6% in the N-terminal domain, and 4.5% in the C-terminal domain. CMT1X with CNS impairment appeared in five (22.7%) of these patients.

CONCLUSIONSThis study indicated that CNS impairment was not rare in Chinese CMT1X patients. Mutations in the EC2 domain of the GJB1 gene were hotspot in Chinese CMT1X patients.

Adolescent ; Adult ; Central Nervous System ; metabolism ; Charcot-Marie-Tooth Disease ; genetics ; pathology ; Child ; Child, Preschool ; Connexins ; genetics ; DNA Mutational Analysis ; Electrophysiology ; Female ; Genotype ; Humans ; Infant ; Male ; Mutation ; Phenotype ; Retrospective Studies ; Young Adult

We reviewed dinical, histological and ultrastructural findings of 124 cases of sural nerve biopsy specimens to delineate the trends of peripheral nerve diseases in our institute. Eighty-one were men and 43 were women. We categorized them into five groups: specific diagnosis (66 cases, 53.2%), axonal degeneration type (47 cases, 37.9%), demyelinating type (4 cases, 3.2%), mixed axonal degeneration-demyelinating type (6 cases, 4.8%) and normal (1 case, 0.9%). Cases with specific diagnosis included 21 inflammatory demyelinating polyneuropathy (15 chronic inflammatory demyelinating polyradiculoneuropathy, 6 Guillain-Barre disease), 13 hereditary motor and sensory neuropathy (7 Charcot-Marie-Tooth type I, 6 Charcot-Marie-Tooth type II), 10 vasculitis, 6 toxic neuropathy, 4 leprosy, 3 diabetic neuropathy, 2 alcoholic neuropathy, 1 Fabry's disease and other specific diseases (5 cases). In our cases, the proportion of specific diagnoses was higher, while the proportion of demyelinating peripheral neuropathies and normal were lower than those of Western series. The results of this study indicate that 1) a dose clinicopathologic correlation is important to make a precise diagnosis of peripheral nerve biopsy, 2) Biopsy under strict indication may reduce unnecessary histologic examination, 3) There is no difference in disease pattern of peripheral neuropathy between Western people and Koreans.
Adult ; Biopsy ; Charcot-Marie-Tooth Disease/pathology ; Demyelinating Diseases/pathology ; Fabry Disease/pathology ; Female ; Hereditary Motor and Sensory Neuropathies/pathology ; Human ; Korea ; Leprosy/pathology ; Male ; Microscopy, Electron ; Nerve Fibers, Myelinated/pathology ; Peripheral Nerves/ultrastructure ; Peripheral Nerves/pathology ; Peripheral Nervous System Diseases/pathology* ; Peripheral Nervous System Diseases/microbiology ; Polyradiculoneuropathy, Chronic Inflammatory Demyelinating/pathology ; Sural Nerve/ultrastructure ; Sural Nerve/pathology*

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant inherited disorder characterized by recurrent pressure palsies. Most HNPP patients have a 1.5 mb deletion in chromosome 17p11.2-p12. The present study aimed at evaluating the deletion of the 17p11.2-p12 region in Korean subjects with families exhibiting HNPP phenotype, and to determine the clinical, electrophysiological and morphological aspects specifically associated with this deletion in HNPP patients. By genotyping six microsatellite markers (D17S921, D17S955, D17S1358, D17S839, D17S122 and D17S261), HNPP with the deletion was observed in 79% (19 of 24) of HNPP families. Nerve conduction studies were performed in 35 HNPP patients from these 19 families. The observed HNPP deletion frequency in Koreans is consistent with findings in other populations. Disease onset occurred at a significantly earlier age in patients with recurrent pressure palsies than in those with a single attack (P<0.01). Nerve conduction studies demonstrated diffuse mild to moderate slowing of nerve conduction velocities that were worse over the common entrapment sites, regardless of the clinical manifestations. A long duration of compound muscle action potentials without a conduction block or a temporal dispersion is a characteristic of this disease. A sural nerve biopsy with teasing was performed in four patients, and tomacula of the myelin sheath was found in 56.4%. Our findings appear to support the existence of a phenotype/genotype correlation in HNPP patients of Korean ancestry with the deletion, and suggest that HNPP patients with earlier symptom onset face an increased chance of having recurrent attacks.
Adolescent ; Adult ; Age of Onset ; Aged ; Charcot-Marie-Tooth Disease/genetics ; Child ; Child, Preschool ; *Chromosome Deletion ; *Chromosomes, Human, Pair 17 ; DNA Mutational Analysis ; Electrophysiology ; Female ; Genotype ; Hereditary Motor and Sensory Neuropathies/*genetics/pathology/physiopathology ; Humans ; Korea ; Male ; Microsatellite Repeats ; Middle Aged ; Paralysis/*genetics/pathology/physiopathology ; Pedigree ; Phenotype ; Research Support, Non-U.S. Gov't ; Sural Nerve/pathology/physiopathology

We identified Charcot-Marie-Tooth disease type 1A (CMT1A) in a family with schwannomas in the spinal cord and median nerve. The CMT1A in this family showed an autosomal dominant pattern, like other CMT patients with PMP22 duplication, and the family also indicated a possible genetic predisposition to schwannomas by 'mother-to-son' transmission. CMT1A is mainly caused by duplication of chromosome 17p11.2-p12 (PMP22 gene duplication). A schwannoma is a benign encapsulated tumor originating from a Schwann cell. A case of hereditary neuropathy with liability to pressure palsies (HNPP) concurrent with schwannoma has been previously reported. Although it seems that the co-occurrence of CMT1A and schwannomas in a family would be the result of independent events, we could not completely ignore the possibility that the coincidence of two diseases might be due to a shared genetic background.
Adolescent ; Adult ; Charcot-Marie-Tooth Disease/complications/*diagnosis/genetics ; Chromosomes, Human, Pair 17 ; Female ; Genetic Predisposition to Disease ; Humans ; Magnetic Resonance Imaging ; Male ; Median Neuropathy/*diagnosis/genetics ; Myelin Proteins/genetics ; Neurilemmoma/complications/*diagnosis/pathology ; Pedigree ; Peripheral Nervous System Neoplasms/*diagnosis/genetics ; Spinal Cord Neoplasms/*diagnosis/genetics

OBJECTIVETo study the possible mechanism of the intracellular aggregate formation of small heat shock protein HSPB8 (HSPB8)(K141N) mutation resulting in axonal Charcot-Marie-Tooth disease type 2L(CMT2L).

METHODSThe cell models which transiently expressed pEGFPN1-HSPB8 and pEGFPN1-(K141N)HSPB8 were established. The immunofluorescent co-location study of EGFP-(K141N)HSPB8 and HSPB1, EGFP-(K141N)HSPB8 and neurofilament light chain (NEFL) was carried out in the SHSY5Y cell models. The aggregate formation of EGFP-(K141N)HSPB8 in cell models was investigated and the possible mechanism of cellular aggregate formation was analyzed by t test and analysis of variance between group(ANOVA).

RESULTSEGFP-(K141N)HSPB8 formed large aggregate which predominantly located around the nucleus in cell models. EGFP-(K141N)HSPB8 co-localized perfectly with HSPB1 and NEFL in the SHSY5Y cell models. The aggregate formation was different in different cell types, there were fewer aggregates formed in an sHSPs deficient milieu than in HEK293T cells.

CONCLUSION(K141N)HSPB8 formed aggregates predominantly locate around the nucleus in cells. (K141N)HSPB8 co-localizes perfectly with HSPB1 and NEFL. The aggregate formation may be due to (K141N)HSPB8 conformational change leading to self aggregation and its abnormal interaction with other sHSPs such as HSPB1.

Cell Line ; Cell Line, Tumor ; Cell Nucleus ; metabolism ; Charcot-Marie-Tooth Disease ; genetics ; metabolism ; Green Fluorescent Proteins ; genetics ; metabolism ; HSP27 Heat-Shock Proteins ; HeLa Cells ; Heat-Shock Proteins ; genetics ; metabolism ; Humans ; Kidney ; cytology ; metabolism ; Microscopy, Confocal ; Neoplasm Proteins ; genetics ; metabolism ; Neuroblastoma ; genetics ; metabolism ; pathology ; Neurofilament Proteins ; genetics ; metabolism ; Point Mutation ; Protein-Serine-Threonine Kinases ; genetics ; metabolism ; Recombinant Fusion Proteins ; genetics ; metabolism ; Transfection