Identification and functional characterization of two missense mutations in NDRG1 associated with Charcot‐Marie‐Tooth disease type 4D

Charcot‐Marie‐Tooth disease type 4D (CMT4D) is an autosomal‐recessive demyelinating form of CMT characterized by a severe distal motor and sensory neuropathy. NDRG1 is the causative gene for CMT4D. To date, only four mutations in NDRG1 —c.442C>T (p.Arg148*), c.739delC (p.His247Thrfs*74), c.538‐1G>A, and duplication of exons 6–8—have been described in CMT4D patients. Here, using targeted next‐generation sequencing examination, we identified for the first time two homozygous missense variants in NDRG1, c.437T>C (p.Leu146Pro) and c.701G>A (p.Arg234Gln), in two Chinese CMT families with consanguineous histories. Further functional studies were performed to characterize the biological effects of these variants. Cell culture transfection studies showed that mutant NDRG1 carrying p.Leu146Pro, p.Arg148*, or p.Arg234Gln variant degraded faster than wild‐type NDRG1, resulting in lower protein levels. Live cell confocal microscopy and coimmunoprecipitation analysis indicated that these variants did not disrupt the interaction between NDRG1 and Rab4a protein. However, NDRG1‐knockdown cells expressing mutant NDRG1 displayed enlarged Rab4a‐positive compartments. Moreover, mutant NDRG1 could not enhance the uptake of DiI‐LDL or increase the fraction of low‐density lipoprotein receptor on the cell surface. Taken together, our study described two missense mutations in NDRG1 and emphasized the important role of NDRG1 in intracellular protein trafficking.     

High frequency of SH3TC2 mutations in Czech HMSN I patients

La??uthová P, Mazanec R, Vondrá?ek P, ?i?ková D, Haberlová J, Sabová J, Seeman P. High frequency of SH3TC2 mutations in Czech HMSN I patients. Charcot–Marie–Tooth (CMT) neuropathy type 4C (CMT4C) is an autosomal recessive (AR), demyelinating neuropathy with early spine deformities caused by mutations in the SH3TC2 gene. To determine the spectrum of SH3TC2 mutations in the Czech population, the entire coding region of SH3TC2 was sequenced in 60 unrelated Czech patients. The prevalent mutation was shown to be the p.Arg954Stop. Therefore, 412 additional patients referred for CMT testing were tested for the presence of p.Arg954Stop only. Of 60 patients in whom the SH3TC2 gene was sequenced, at least one mutation was detected in 13 (21.7%) patients and biallelic pathogenic mutations were detected in 7 (11.6%) patients. Of the 412 patients tested for p.Arg954Stop, the mutation was found in 8 patients (1.94%), 6 were homozygous and 2 were heterozygous. The second causative mutation was detected by sequencing in one of the patients but not in the other. Nine novel sequence variants were detected. Their pathogenicity was further tested in silico and in control samples. Mutations in the SH3TC2 gene are a frequent cause of demyelinating hereditary neuropathy among Czech patients. In total, at least one mutation was found in 21 unrelated patients. CMT4C seems to be the most frequent type of AR CMT and one of the most frequent of all CMT types. Mutation p.Arg954Stop is highly prevalent in the Czech population. Patients with demyelinating neuropathy along with non‐dominant mode of inheritance and negative for CMT1A/hereditary neuropathy with liability to pressure palsy should be tested for the presence of the p.Arg954Stop mutation or other mutations in the SH3TC2 gene.     

Inherited neuropathies: from gene to disease

Inherited disorders of peripheral nerves represent a common group of neurologic diseases. Charcot-Marie-Tooth neuropathy type 1 (CMT1) is a genetically heterogeneous group of chronic demyelinating polyneuropathies with loci mapping to chromosome 17 (CMT1A), chromosome 1 (CMT1B) and to another unknown autosome (CMT1C). CMT1A is most often associated with a tandem 1.5-megabase (Mb) duplication in chromosome 17p11.2-12, or in rare patients may result from a point mutation in the peripheral myelin protein-22 (PMP22) gene. CMT1B is associated with point mutations in the myelin protein zero (P0 or MPZ) gene. The molecular defect in CMT1C is unknown. X-linked Charcot-Marie-Tooth neuropathy (CMTX), which has clinical features similar to CMT1, is associated with mutations in the connexin32 gene. Charcot-Marie-Tooth neuropathy type 2 (CMT2) is an axonal neuropathy, also of undetermined cause. One form of CMT2 maps to chromosome 1p36 (CMT2A), another to chromosome 3p (CMT2B) and another to 7p (CMT2D). Dejerine-Sottas disease (DSD), also called hereditary motor and sensory neuropathy type III (HMSNIII), is a severe, infantile-onset demyelinating polyneuropathy syndrome that may be associated with point mutations in either the PMP22 gene or the P0 gene and shares considerable clinical and pathological features with CMT1. Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder that results in a recurrent, episodic demyelinating neuropathy. HNPP is associated with a 1.5-Mb deletion in chromosome 17p11.2-12 and results from reduced expression of the PMP22 gene. CMT1A and HNPP are reciprocal duplication/deletion syndromes originating from unequal crossover during germ cell meiosis. Other rare forms of demyelinating peripheral neuropathies map to chromosome 8q, 10q and 11q. Hereditary neuralgic amyotrophy (familial brachial plexus neuropathy) is an autosomal dominant disorder causing painful, recurrent brachial plexopathies and maps to chromosome 17q25.     

Spectrum of mutations in Finnish patients with Charcot-Marie-Tooth disease and related neuropathies

Our patient material included families and sporadic patients of Finnish origin with the diagnosis of Charcot-Marie-Tooth (CMT) disease types 1 and 2, Déjérine-Sottas syndrome (DSS), and hereditary neuropathy with liability to pressure palsies (HNPP). We screened for mutations in the peripheral myelin protein genes connexin 32 (Cx32), myelin protein zero (P₀) and peripheral myelin protein 22 (PMP22) by direct sequencing. All patients chosen for mutation screening were negative for the 1.5 Mb duplication/deletion at 17p11.2-p12. Eleven Cx32 mutations were found in 12 families, six with a CMT2 diagnosis, three with a CMT1 diagnosis and three with unclassified CMT. The total number of patients in these 12 CMTX families was 61, giving a minimum prevalence of 1.2/100,000 for CMTX in Finland. Four of the mutations, Pro58Arg, Pro172Leu, Asn175Asp and Leu204Phe, have not been previously reported. One male patient with an early onset CMT had a double Cx32 mutation, Arg22Gln and Val63Ile. The double de novo mutation was found to be of maternal grandpaternal origin. In the P₀ gene a Ser78Leu mutation was found in one family with severe CMT1 and a de novo Tyr82Cys mutation was found in one DSS patient. Both mutations have been previously reported in other CMT1 families. A novel PMP22 mutation, deletion of Phe84, was found in one sporadic DSS patient. Our mutation screening results show the necessity of molecular diagnosis, in addition to clinical and electrophysiological evaluation, for proper subtyping of the disease and for accurate genetic counseling. Hum Mutat 12:59–68, 1998. © 1998 Wiley-Liss, Inc.     

Mitochondrial GTPase mitofusin 2 mutations in Korean patients with Charcot-Marie-Tooth neuropathy type 2

Charcot-Marie-Tooth disease (CMT) is classified into two types, the demyelinating (CMT1) and axonal forms (CMT2). CMT2 is further subdivided by linkage analysis into eight subgroups. Recently, mutations in the MFN2 gene, which encodes the mitochondrial GTPase mitofusin 2 (Mfn2) that regulates the mitochondrial network architecture by fusing the mitochondria, were identified in CMT2A patients. This study carried out mutation analysis of the MFN2 gene in 12 unrelated Korean patients suspected of having CMT2 and identified four mutations (Arg94Trp, His165Arg, Ser263Pro, and Ser350Pro). Three mutations were found within the highly conserved GTPase domain that is essential for the function of Mfn2, and one mutation (Ser350Pro) was observed between the GTPase domain and the downstream coiled-coil domain. This suggests that mutations in the MFN2 gene are an important causative gene underlying Korean patients with CMT2, and screening for a mutation in the MFN2 gene is strongly recommended for making a molecular diagnosis of CMT2.     

A novel GDAP1 Q218E mutation in autosomal dominant Charcot-Marie-Tooth disease

A wide range of phenotypes have been reported in autosomal recessive (AR) Charcot-Marie-Tooth disease (CMT) patients carrying mutations in the ganglioside-induced differentiation-associated protein 1 (GDAP1) gene, such as axonal, demyelinating, and intermediate forms of AR CMT. There have been very few reports of GDAP1 mutations in autosomal dominant (AD) CMT. Here, we report an AD CMT family with a novel Q218E mutation in the GDAP1 gene. The mutation was located within the well-conserved glutathione S-transferase (GST) core region and co-segregated with the affected members in the pedigree. The affected AD CMT individuals had a later disease onset and much milder phenotypes than the AR CMT patients, and the histopathologic examination revealed both axonal degeneration and demyelination.     

Periaxin mutation causes early-onset but slow-progressive Charcot-Marie-Tooth disease

Periaxin (PRX) plays a significant role in the myelination of the peripheral nerve. To date, seven non-sense or frameshift PRX mutations have been reported in six pedigrees with Dejerine-Sottas neuropathy or severe Charcot-Marie-Tooth neuropathy (CMT). We detected a PRX mutation in three patients in the screening of 66 Japanese demyelinating CMT patients who were negative for the gene mutation causing dominant or X-linked demyelinating CMT. Three unrelated patients were homozygous for a novel R1070X mutation and presented early-onset but slowly progressive distal motor and sensory neuropathies. Mutations lacking the carboxyl-terminal acidic domain may show loss-of-function effects and cause severe demyelinating CMT.     

Diagnostic algorithms in Charcot–Marie–Tooth neuropathies: experiences from a German genetic laboratory on the basis of 1206 index patients

We present clinical features and genetic results of 1206 index patients and 124 affected relatives who were referred for genetic testing of Charcot–Marie–Tooth (CMT) neuropathy at the laboratory in Aachen between 2001 and 2012. Genetic detection rates were 56% in demyelinating CMT (71% of autosomal dominant (AD) CMT1/CMTX), and 17% in axonal CMT (24% of AD CMT2/CMTX). Three genetic defects (PMP22 duplication/deletion, GJB1/Cx32 or MPZ/P0 mutation) were responsible for 89.3% of demyelinating CMT index patients in whom a genetic diagnosis was achieved, and the diagnostic yield of the three main genetic defects in axonal CMT (GJB1/Cx32, MFN2, MPZ/P0 mutations) was 84.2%. De novo mutations were detected in 1.3% of PMP22 duplication, 25% of MPZ/P0, and none in GJB1/Cx32. Motor nerve conduction velocity was uniformly <38 m/s in median or ulnar nerves in PMP22 duplication, >40 m/s in MFN2, and more variable in GJB1/Cx32, MPZ/P0 mutations. Patients with CMT2A showed a broad clinical severity regardless of the type or position of the MFN2 mutation. Out of 75 patients, 8 patients (11%) with PMP22 deletions were categorized as CMT1 or CMT2. Diagnostic algorithms are still useful for cost‐efficient mutation detection and for the interpretation of large‐scale genetic data made available by next generation sequencing strategies.     

Charcot‐Marie‐Tooth Disease Type 4H Resulting from Compound Heterozygous Mutations in FGD4 from Nonconsanguineous Korean Families

Charcot‐Marie‐Tooth disease type 4H (CMT4H) is an autosomal recessive demyelinating subtype of peripheral enuropathies caused by mutations in the FGD4 gene. Most CMT4H patients are in consanguineous Mediterranean families characterized by early onset and slow progression. We identified two CMT4H patients from a Korean CMT cohort, and performed a detailed genetic and clinical analysis in both cases. Both patients from nonconsanguineous families showed characteristic clinical manifestations of CMT4H including early onset, scoliosis, areflexia, and slow disease progression. Exome sequencing revealed novel compound heterozygous mutations in FGD4 as the underlying cause in both families (p.Arg468Gln and c.1512‐2A>C in FC73, p.Met345Thr and c.2043+1G>A (p.Trp663Trpfs*30) in FC646). The missense mutations were located in highly conserved RhoGEF and PH domains which were predicted to be pathogenic in nature by in silico modeling. The CMT4H occurrence frequency was calculated to 0.7% in the Korean demyelinating CMT patients. This study is the first report of CMT4H in Korea. FGD4 assay could be considered as a means of molecular diagnosis for sporadic cases of demyelinating CMT with slow progression.     

Gap junction beta 1 (<Emphasis Type="Italic">GJB1</Emphasis>) gene mutations in Italian patients with X-linked Charcot-Marie-Tooth disease

X-linked Charcot-Marie-Tooth disease (CMT1X) is a peripheral neuropathy transmitted in a dominant manner and caused by mutations in the Connexin 32 (Cx32) gene (GJB1, gap junction beta 1). Here we report the mutation analysis of the GJB1 gene in 76 subjects with possible CMT1 and absence of 17p11.2 duplication, and in 38 CMT2 patients without mutations in CMT2-associated-genes, selected from a cohort of 684 patients with peripheral sensory-motor neuropathy. The analysis was performed by direct sequencing of the coding sequence and exon/intron boundaries of the GJB1 gene. The mutation screening identified 22 mutations in GJB1, eight of which have not been previously published: six point mutations (c.50C > G, c.107T > A, c.545C > T, c.545C > G, c.548G > C, c.791G > T) and two deletions (c.84delC, c.573_581delCGTCTTCAT). The GJB1 mutation frequency (19.3%) and the clinical heterogeneity of our patients suggest searching for GJB1 mutations in all CMT cases without the 17p11.2 duplication, regardless of the gender of the proband, as well as in CMT2 patients with possible X-linked inheritance.     

Myelin protein zero (MPZ) gene mutations in nonduplication type 1 Charcot-Marie-Tooth disease

The myelin protein zero gene (MPZ) maps to chromosome 1q22-q23 and encodes the most abundant peripheral nerve myelin protein. The P_o protein functions as a homophilic adhesion molecule in myelin compaction. Mutations in the MPZ gene are associated with the demyelinating peripheral neuropathies Charcot-Marie-Tooth disease type 1B (CMT1B), and the more severe Dejerine-Sottas syndrome (DSS). We have surveyed a cohort of 70 unrelated patients with demyelinating polyneuropathy for additional mutations in the MPZ gene. The 1.5-Mb DNA duplication on chromosome 17p11.2-p12 associated with CMT type 1A (CMT1A) was not present. By DNA heteroduplex analysis, four base mismatches were detected in three exons of MPZ. Nucleotide sequence analysis identified a de novo mutation in MPZ exon 3 that predicts an Ile(135)Thr substitution in a family with clinically severe early-onset CMT1, and an exon 3 mutation encoding a Gly(137)Ser substitution was identified in a second CMT1 family. Each predicted amino acid substitution resides in the extracellular domain of the P_o protein. Heteroduplex analysis did not detect either base change in 104 unrelated controls, indicating that these substitutions are disease-associated mutations rather than common polymorphisms. In addition, two polymorphic mutations were identified in MPZ exon 5 and exon 6, which do not alter the codons for Gly(200) and Ser(228), respectively. These observations provide further confirmation of the role of MPZ in CMT1B and suggest that MPZ coding region mutations may account for a limited percentage of disease-causing mutations in nonduplication CMT1 patients. © 1996 Wiley-Liss, Inc.     

Comparison of a new pmp22 transgenic mouse line with other mouse models and human patients with CMT1A

Charcot-Marie-Tooth disease type 1A is a dominantly inherited demyelinating disorder of the peripheral nervous system. It is most frequently caused by overexpression of peripheral myelin protein 22 (PMP22), but is also caused by point mutations in the PMP22 gene. We describe a new transgenic mouse model (My41) carrying the mouse, rather than the human, pmp22 gene. The My41 strain has a severe phenotype consisting of unstable gait and weakness of the hind limbs that becomes obvious during the first 3 weeks of life. My41 mice have a shortened life span and breed poorly. Pathologically, My41 mice have a demyelinating peripheral neuropathy in which 75% of axons do not have a measurable amount of myelin. We compare the peripheral nerve pathology seen in My41 mice, which carry the mouse pmp22 gene, with previously described transgenic mice over-expressing the human PMP22 protein and Trembler-J (TrJ) mice which have a P16L substitution. We also look at the differences between CMT1A duplication patients, patients with the P16L mutation and their appropriate mouse models.     

Mutational analysis of PMP22, MPZ, GJB1, EGR2 and NEFL in Korean Charcot-Marie-Tooth neuropathy patients

We examined CMT1A duplication of 17p11.2-p12, mutations of PMP22, MPZ (P0), GJB1 (Cx32), EGR2 and NEFL genes in 57 Korean families with patients diagnosed as having Charcot-Marie-Tooth (CMT) disease. The CMT1A duplication was present in 53.6% of 28 CMT type 1 patients. In the 42 CMT families without CMT1A duplication, 10 pathogenic mutations were found in 9 families. The 10 mutations were not detected in 105 healthy controls. Seven mutations (c.318delT (p.Ala106fs) in PMP22, c.352G>A (p.Asp118Asn), c.449-1G>T (3'-splice site), c.706A>G (p.Lys236Glu) in MPZ, c.407T>C (p.Val136Ala)[corrected], c.502T>C (p.Cys168Arg) in GJB1, and c.1001T>C (p.Leu334Pro) in NEFL) were determined to be novel. The mutation frequencies of PMP22 and MPZ were similar to those found in several European populations, however, it appeared that mutations in GJB1 are less frequent in East Asian CMT patients than in Eur opean patients. We described the identified mutations and phenotype-genotype correlations based on nerve conduction studies.     

Coagulation Factor XIIIA Subunit Missense Mutations Affect Structure and Function at the Various Steps of Factor XIII Action

Inherited defects of coagulation Factor XIII (FXIII) can be categorized into severe and mild forms based on their genotype and phenotype. Heterozygous mutations occurring in F13A1 and F13B genes causing mild FXIII deficiency have been reported only in the last few years primarily because the mild FXIII deficiency patients are often asymptomatic unless exposed to some kind of a physical trauma. However, unlike mutations causing severe FXIII deficiency, many of these mutations have not been comprehensively characterized based on expression studies. In our current article, we have transiently expressed 16 previously reported missense mutations detected in the F13A1 gene of patients with mild FXIII deficiency and analyzed their respective expression phenotype. Complimentary to expression analysis, we have used in silico analysis to understand and explain some of the in vitro findings. The expression phenotype has been evaluated with a number of expression phenotype determining assays. We observe that the mutations influence different aspects of FXIII function and can be functionally categorized on the basis of their expression phenotype. We identified mutations which even in heterozygous form would have strong impact on the functional status of the protein (namely mutations p.Arg716Gly, p.Arg704Gln, p.Gln602Lys, p.Leu530Pro, p.His343Tyr, p.Pro290Arg, and p.Arg172Gln).     

MPZ mutation in an early-onset Charcot-Marie-Tooth disease type 1B family by genome-wide linkage analysis

Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous peripheral neuropathy. The objective of this study was to find the causative mutation(s) in a demyelinating autosomal dominant CMT family. A high density SNP-based genome-wide linkage scan was performed, and causative mutations were determined by sequencing of candidate genes in the linkage disequilibrium region. Linkage analysis mapped the underlying gene to a region on chromosome 1q22-q23 with a maximum two-point LOD score of 2.036. Sequencing analysis revealed a novel c.243C>G (His81Gln) mutation in the MPZ gene, which encodes the major integral membrane protein of the peripheral nerve system. MPZ is well known as a CMT-causative gene with wide phenotypic spectrum. The clinical symptoms were more similar to those of patients with the His81Arg than patients with the His81Tyr mutation. The novel mutation completely co-segregated with affected members, and was not found in controls. Therefore, we suggest that the identified mutation in MPZ is the underlying cause of CMT in the family. In addition, this study demonstrated that the clinical phenotypes may be variable with different mutations at the same site in the MPZ gene.     

Charcot-Marie-Tooth neuropathy type 2 and P0 point mutations: two novel amino acid substitutions (Asp61Gly; Tyr119Cys) and a possible "hotspot" on Thr124Met

Mutations in the gene for the major protein component of peripheral nerve myelin, myelin protein zero (MPZ, P0), cause hereditary disorders of Schwann cell myelin such as Charcot-Marie-Tooth neuropathy type 1B (CMT1B), Dejerine-Sottas syndrome (DSS), and congenital hypomyelinating neuropathy (CHN). More recently, P0 mutations were identified in the axonal type of CMT neuropathy, CMT2, which is different from the demyelinating variants with respect to electroneurography and nerve pathology. We screened 49 patients with a clinical and histopathological diagnosis of CMT2 for mutations in the P0 gene. Three heterozygous single nucleotide changes were detected: two novel missense mutations, Asp61Gly and Tyr119Cys, and the known Thr124Met substitution, that has already been reported in several CMT patients from different European countries. Haplotype analysis for the P0 locus proved that our patients with the 124Met allele were not related to a cohort of patients with the same mutation, all of Belgian descent and all found to share a common ancestor. Our data suggest that P0 mutations account for a detectable proportion of CMT2 cases with virtually every patient harbouring a different mutation but recurrence of the Thr124Met amino acid substitution. The high frequency of this peculiar genotype in the European CMT population is presumably not only due to a founder effect but Thr124Met might constitute a mutation hotspot in the P0 gene as well.     

ZNF687 mutations are frequently found in pagetic patients from South Italy: implication in the pathogenesis of Paget's disease of bone

Paget's disease of bone (PDB) is a skeletal disorder whose molecular basis is not fully elucidated. However, 10% of patients show a familial PDB and 35% of them carry mutations in the SQSTM1 gene. We recently reported a founder mutation (p.Pro937Arg) in the ZNF687 gene, underlying PDB complicated by giant cell tumor (GCT/PDB) and rarely occurring in PDB patients without neoplastic degeneration. Since 80% of Italian GCT/PDB patients derive from Avellino, we hypothesized that ZNF687 mutation rate was higher in this region than elsewhere. Interestingly, our molecular analysis on 30 PDB patients showed that 33% hosted ZNF687 mutations, with the p.Pro937Arg identified in 8 familial cases. Two novel ZNF687 mutations (p.Pro665Leu and p.Gln784Glu) were detected in 2 sporadic patients. Only 2 subjects were positive for the p.Pro392Leu mutation in SQSTM1. ZNF687‐mutated patients showed a severe PDB, with a remarkable number of affected sites. in vitro studies revealed that the ZNF687‐mutant osteoclasts appeared as giant sized with up to 150 nuclei, never described in PDB. Finally, we also confirmed the causality of the p.Pro937Arg mutation in 4 additional GCT/PDB cases deriving from the same geographic area, indicating that PDB and GCT/PDB represent 2 sides of the same coin.     

Genetics of the Charcot‐Marie‐Tooth disease in the Spanish Gypsy population: the hereditary motor and sensory neuropathy‐Russe in depth

Four private mutations responsible for three forms demyelinating of Charcot‐Marie‐Tooth (CMT) or hereditary motor and sensory neuropathy (HMSN) have been associated with the Gypsy population: the NDRG1 p.R148X in CMT type 4D (CMT4D/HMSN‐Lom); p.C737_P738delinsX and p.R1109X mutations in the SH3TC2 gene (CMT4C); and a G>C change in a novel alternative untranslated exon in the HK1 gene causative of CMT4G (CMT4G/HMSN‐Russe). Here we address the findings of a genetic study of 29 Gypsy Spanish families with autosomal recessive demyelinating CMT. The most frequent form is CMT4C (57.14%), followed by HMSN‐Russe (25%) and HMSN‐Lom (17.86%). The relevant frequency of HMSN‐Russe has allowed us to investigate in depth the genetics and the associated clinical symptoms of this CMT form. HMSN‐Russe probands share the same haplotype confirming that the HK1 g.9712G>C is a founder mutation, which arrived in Spain around the end of the 18th century. The clinical picture of HMSN‐Russe is a progressive CMT disorder leading to severe weakness of the lower limbs and prominent distal sensory loss. Motor nerve conduction velocity was in the demyelinating or intermediate range.     

GDAP1, the protein causing Charcot-Marie-Tooth disease type 4A, is expressed in neurons and is associated with mitochondria

Mutations in GDAP1, the ganglioside-induced differentiation-associated protein 1 gene, cause Charcot-Marie-Tooth (CMT) type 4A, a severe autosomal recessive form of neuropathy associated with either demyelinating or axonal phenotypes. Here, we demonstrate that GDAP1 has far greater expression in neurons than in myelinating Schwann cells. We investigated cell localization of GDAP1 in a human neuroblastoma cell line by means of transient overexpression and co-localization with organelle markers in COS-7 cells and by western blot analysis of subcell fractions with anti-GDAP1 polyclonal antibodies. We observed that GDAP1 is localized in mitochondria. We also show that C-terminal transmembrane domains are necessary for the correct localization in mitochondria; however, missense mutations do not change the mitochondrial pattern of the wild-type protein. Our findings suggest that CMT4A disease is in fact a mitochondrial neuropathy mainly involving axons and represents a disease belonging to the new category of mitochondrial disorders caused by mutations in nuclear genes. We postulate that GDAP1 may be related to the maintenance of the mitochondrial network.     

Characteristics of demyelinating Charcot-Marie-Tooth disease with concurrent diabetes mellitus

Purpose: Charcot-Marie-Tooth disease (CMT) is the most common type of inherited peripheral neuropathy and has a high degree of genetic heterogeneity. CMT with concurrent diabetes mellitus (DM) is rare. The purpose of this study is to explore the genetic, clinical and pathological characteristics of the patients with CMT and concurrent DM. Methods: We investigated gene mutations (the peripheral myelin protein 22 gene, myelin protein zero gene, lipopolysaccharide-induced tumor necrosis factor-α factor gene, early growth response gene and the neurofilament light chain gene loci) of a relatively large and typical Chinese family with CMT1 and concurrent DM2. From the literature, we also retrieved all reported families and single cases with CMT and concurrent DM. We comprehensively analyzed the characteristics of total 33 patients with CMT and concurrent DM, and further compared these characteristics with those of patients of diabetic peripheral neuropathy (DPN). Results: Patients with CMT and concurrent DM had some relatively independent characteristics and pathogenic mechanisms. So we designated that kind of characteristic demyelinating CMT which accompanies DM as Yu-Xie syndrome (YXS), a new specific clinical subtype of CMT. Conclusion: CMT is an etiologic factor of DM, even though the intrinsic association between CMT and DM still remains further exploration.