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PubMed2006

Periaxin mutation in Japanese patients with Charcot-Marie-Tooth disease.

Periaxin (PRX) plays an important role in the myelination of the peripheral nerve and consequently in the pathogenesis of Charcot-Marie-Tooth disease (CMT). To date, nine nonsense or frameshift PRX mutations have been reported in eight families with CMT. The patients with PRX mutations appeared to show characteristic clinical features with early onset but slow or no progression, a common result of mutations that lead to missing a C-terminal acidic domain. Here, we report a Japanese CMT patient with these characteristic clinical features, who was a compound heterozygote for PRX R1070X and L132FsX153 mutations. We previously reported that three Japanese isolated families also had the homozygous R1070X mutation. To examine the potential founder effect of the R1070X mutation in the Japanese population, we performed haplotype analysis and found that each R1070X allele lay on a different haplotype background in these four families. Therefore, the high frequency of the R1070X mutation among the Japanese population is not likely the consequence of a founder effect, but probably a result of a mutation hot spot.

Adult↗

PubMed2002

Footdrop, foot rotation, and plantarflexor failure in Charcot-Marie-Tooth disease.

OBJECTIVE: To evaluate the frequency of occurrence of the main causes of poor stance and gait in patients with Charcot-Marie-Tooth disease (footdrop graded as mild or severe, rotation, and plantarflexor failure) both as single and associated problems. DESIGN: Observational. SETTING: A neuromuscular disorders department in a specialized Italian rehabilitation hospital. PARTICIPANTS: One hundred twenty-six nonoperated lower limbs from 64 outpatients. INTERVENTIONS: Ankle angle during active dorsiflexion and heel angle in stance were measured in a photograph; the ability to raise the heel at least 2cm was evaluated. MAIN OUTCOME MEASURES: Frequency of mild footdrop (ankle angle < or =100 degrees ), severe footdrop (ankle angle >100 degrees ), and rotation and plantarflexor failure singularly and in association. RESULTS: Mild footdrop was present in 47.6% of examined limbs and was associated with rotation in 39.7% of limbs; severe footdrop was present in 52.4% of limbs and was associated with rotation in 28.6% of limbs, with rotation plus plantarflexor failure in 21.4% of limbs. CONCLUSIONS: We recommend categorizing problems in the lower limbs into 4 levels of increasing symptom severity, starting with mild footdrop and graduating to the instance where the 3 problems are associated.

Charcot-Marie-Tooth Disease↗

PubMed2001

Phenotypes of X-linked Charcot-Marie-Tooth disease and altered trafficking of mutant connexin 32 (GJB1).

To clarify the pathomechanism in three patients with X-linked Charcot-Marie-Tooth disease (CMTX) and unique clinical features, we studied three connexin (Cx) 32 (GJB1) mutants with respect to cellular localization in cultured cells. Wild-type Cx32 and three Cx32 mutants (Va163Ile and Glu186Lys, obtained from CMTX patients with hearing impairment; and Arg22Gln, obtained from a CMTX patient with a fair number of onion-bulb formations) were transfected to rat pheochromocytoma cells (PC12). We investigated the expression of Cx32 protein in each clone by immunoblotting and immunohistochemical staining. While Cx32 protein with the Arg22Gln mutation was detectable immunohistochemically only in the cytoplasm, Cx32 protein with the Va163Ile or Glu186Lys mutation was detected in both the plasma membrane and the cytoplasm. Cx32 protein with the wild-type sequence was detected mostly in the plasma membrane, with plaques indicating the existence of active gap junction formation. These three Cx32 mutations associated with CMTX patients with unique clinical and pathological findings caused altered trafficking of the Cx32 protein. These altered expressions indicated loss of active gap junction formation with different expression abnormalities in these CMTX patients.

Animals↗

PubMed2000

[A patient of Charcot-Marie-tooth disease with rigid spine and respiratory failure].

This report describes a case of a 17-year-old girl with Charcot-Marie-Tooth disease (CMT) representing rigid spine and respiratory failure. At age 11, she tended to walk on her toes and had difficulty in getting up from the floor without support. She became aware of flexion limitation of the neck at the age of 12. At 15 years of age, She began to have dyspnea on effort. When she was 17 years old, neurological examination revealed mild weakness of the upper extremities and severe weakness of the distal lower extremities, generalized wasting and areflexia. Superficial sensation was mildly impaired distally, and vibration sensation was severely impaired in the lower extremities. Motor and sensory nerve conduction velocities were mildly reduced, and compound muscle action potential of the tibial and peroneal nerves and sensory nerve action potential on ulnar and sural nerves were absent. Electromyography showed neurogenic changes with denervation potentials. Sural nerve biopsy revealed severe loss of myelinated fibers without any onion-bulb formation. As for family history, her elder sister showed moderate loss of vibration sensation in the lower extremities. On the basis of these findings, she was diagnosed as having CMT type 2, though a mode of inheritance was uncertain. She also had peculiar findings of flexion limitation of the spine (rigid spine), contracture of the hip joint, and fatty degeneration of paraspinal muscles on CT. Percent vital capacity (VC) was 22.5%, and arterial blood gas analysis showed PaO2 of 60.5 mmHg and PaCO2 65.0 mmHg. To our knowledge, this is the first case of CMT accompanied by rigid spine and respiratory failure. Motor and sensory neuropathy combined with rigid spine also have not been reported previously. The relationship between rigid spine syndrome with neurogenic muscular atrophy and CMT type 2C with the clinical characteristics of diaphragm and vocal cord paresis is discussed.

Adolescent↗

PubMed2002

Identification of novel sequence variants in the neurofilament-light gene in a Japanese population: analysis of Charcot-Marie-Tooth disease patients and normal individuals.

Mutations of the neurofilament-light (NEFL/NF-L) gene were examined in 124 unrelated Japanese patients with Charcot-Marie-Tooth disease (CMT) without known gene mutations, and 248 normal Japanese individuals. A new method, which can detect basepair mismatches with RNase cleavage on agarose gel electrophoresis, coupled with DNA sequencing, identified 8 novel sequence variations in the NF-L gene. In these sequence variants, 5 variants were polymorphisms, including 3 single nucleotide polymorphisms (SNPs), and 3 other missense mutations (Pro22Thr, Asn97Ser and Ala148Val) were found in the patients with CMT phenotype. The variant alleles in the NF-L gene could influence the developing process of CMT phenotype and also might cause CMT phenotype.

Adult↗

PubMed1976

Spinal deformity associated with heritable neurological conditions: spinal muscular atrophy, Friedreich's ataxia, familial dysautonomia, and Charcot-Marie-Tooth disease.

Children with progressive neurological conditions such as spinal muscular atrophy, Friedreich's ataxia, familial dysautonomia (Riley-Day syndrome), and Charcot-Marie-Tooth disease have a significant risk of acquiring a serious spinal deformity. As with paralytic scoliosis following poliomyelitis, the curves are difficult to control with bracing, and progression does not cease with maturation. An increasing spinal curvature may lead to loss of ambulation or, for the wheelchair-bound patient, loss of sitting balance. The curvature may further compromise pulmonary function that may already be compromised by the neurological deficit. Twenty patients are reported with an average follow-up of six years (range, one to fourteen years). For the properly selected patient, surgical stabilization of the spine arrested the progress of the curve and improved function. Complications were few; however, pseudarthrosis was more common than in patients with non-neurological problems.

Charcot-Marie-Tooth Disease↗

PubMed1999

Charcot-marie-tooth disease and related neuropathies: molecular basis for distinction and diagnosis.

Great advances have been made in understanding the molecular basis of Charcot-Marie-Tooth disease (CMT) and related neuropathies, namely Dejerine-Sottas disease (DSD), hereditary neuropathy with liability to pressure palsies (HNPP) and congenital hypomyelination (CH). The number of newly uncovered mutations and identified genetic loci is rapidly increasing, and, as a consequence, the classification of these disorders is becoming more complicated. Molecular genetics, animal models, and transfected cell studies are shedding light on function and dysfunction of proteins involved in hereditary myelinopathies-peripheral myelin protein 22 (PMP22), myelin protein zero (PO), connexin 32 (Cx32), and early growth response 2 (EGR2). Gene dosage effect, loss of function, gain of toxic function, and dominant negative effect are possible mechanisms whereby different gene mutations may exert their detrimental action on peripheral nerves. A tentative rational approach to clinical and molecular diagnosis based on genotype-phenotype correlation analysis is described.

Animals↗

PubMed1992

Charcot-Marie-Tooth disease type 1a (CMT1a): evidence for trisomy of the region p11.2 of chromosome 17 in south Wales families.

The gene for Charcot-Marie-Tooth disease type 1a (CMT1a) has been localised to chromosome 17p11.2. Locus D17S122 is recognised by the DNA probe pVAW409R3 which detects an MspI polymorphism with three alleles in the normal population. Subjects with CMT1a show evidence of trisomy for this region of chromosome 17 by displaying either all three alleles or a dosage effect when only two alleles are present. This phenomenon was seen in 10 out of 11 families with type I hereditary motor and sensory neuropathy (HMSN) where affected subjects were heterozygous for the MspI polymorphisms. This mutation is likely to have arisen from a non-reciprocal recombination event between non-sister chromatids of homologous chromosomes at meiosis I. The detection of this partial trisomy offers a rapid method for the diagnosis of CMT1a in families not suitable for linkage analysis.

Alleles↗

PubMed1992

A yeast artificial chromosome contig spanning the Charcot-Marie-Tooth disease type 1A duplication region.

A contiguous set of 43 overlapping yeast artificial chromosome (YAC) clones has been developed for the Charcot-Marie-Tooth disease type 1A (CMT1A) duplication region of chromosome 17p11.2. The contig spans approximately 2.0 Mb and can be represented in a minimum of five overlapping YACs. The YAC clones were isolated from two total human genomic YAC libraries and from YAC libraries made from rodent-human hybrid cell lines. YAC clones were isolated from the libraries by polymerase chain reaction (PCR) technique. Localization to chromosome 17p11.2 was confirmed by fluorescence in situ hybridization. Overlap between the YAC clones was detected by inter-Alu PCR amplification of the YACs and by cross hybridization of the YACs with YAC insert ends obtained by Vectorette PCR. This YAC contig is a useful resource for analyzing and mapping all the genes contained within the CMT1A duplication.

Base Sequence↗

PubMed1999

The role of the gap junction protein connexin32 in the pathogenesis of X-linked Charcot-Marie-Tooth disease.

Mutations in the gene encoding the gap junction protein connexin32 (Cx32; beta 1) cause the X-linked form of Charcot-Marie-Tooth disease (CMTX), a common form of inherited demyelinating neuropathy. Cx32 is localized to the paranodes and incisures of myelinating Schwann cells, and probably participates in the formation of gap junctions at these locations, thereby allowing the diffusion of ions and small molecules directly across the myelin sheath. In transfected cells different CMTX mutations have different effects on the ability of the mutant protein to form functional gap junctions; some mutant proteins cannot be detected within the cell, other mutant proteins accumulate within the cell but do not reach the cell membrane, while other mutants reach the cell membrane and some of these form functional gap junctions. In transgenic mice two mutants, R142W and 175 frameshift, have similar effects on protein trafficking as in transfected cells: the R142W mutant protein remains in the perinuclear region and does not reach the paranodes or incisures, and the 175 frameshift protein cannot be detected. Thus, different CMTX mutations have different effects on Cx32 protein, and these differences may help to explain the phenotypic differences seen in CMTX kindreds.

Amino Acid Sequence↗

PubMed2001

Histopathological features of X-linked Charcot-Marie-Tooth disease in 8 patients from 6 families with different connexin32 mutations.

There is still confusion as to whether X-linked Charcot-Marie-Tooth disease (CMTX) is primarily an axonal disorder or is primarily demyelinating. Eight symptomatic patients, 7 males and 1 female, from 6 families with identified connexin32 mutations underwent a superficial peroneal nerve biopsy. Quantitative and ultrastructural studies were performed, and histopathological lesions in these 8 patients proved to be quite homogeneous. The myelinated fiber count was within normal values or only moderately decreased. In 7 cases, the distribution of myelinated fibers was unimodal due to a loss of large fibers, coexisting with numerous clusters of small regenerating fibers. At ultrastructural level, these clusters were often surrounded by flattened Schwann cell processes giving an aspect of "pseudo-onion bulb" formation. There was no "naked axon" (ie, demyelinated axon), and real "onion bulb" formations composed of flattened Schwann cell processes surrounding an isolated myelinated fiber were discrete and not numerous. Macrophages laden with myelin debris were scarce or absent in the endoneurium. Several fibers appeared discretely hypomyelinated and the calculated g-ratio was scarcely higher than the mean control value. Lesions of unmyelinated fibers were absent in 7 cases and mild in one. Given that the primary defect concerns connexin32, we think that the histopathological features observed in our patients correspond to primary hypomyelination rather than to ongoing demyelination. The associated axonal degeneration might be secondary to defective axon-Schwann cell interactions.

Adolescent↗

PubMed2005

SIMPLE mutations in Charcot-Marie-Tooth disease and the potential role of its protein product in protein degradation.

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous group of inherited peripheral neuropathies characterized by progressive weakness and atrophy of distal limb muscles. Recently, SIMPLE/LITAF was shown to be responsible for an autosomal dominant demyelinating form of CMT linked to 16p (CMT1C). Although two transcripts encoding different proteins (SIMPLE and LITAF) have been reported from the same gene, we could not confirm the existence of LITAF. Here we show that the LITAF transcript appears to result from a DNA sequencing error. We screened the SIMPLE gene for mutations in a cohort of 192 patients with CMT or related neuropathies, each of whom tested negative for other known genetic causes of CMT. In 16 unrelated CMT families we identified nine different nucleotide variations in SIMPLE that were not detected in control chromosomes. SIMPLE mutations can occur de novo, associated with sporadic CMT1 and may convey both demyelinating and axonal forms. Bioinformatics analyses and other observations of SIMPLE suggest that 1) it could be a member of the RING finger motif-containing subfamily of E3 ubiquitin ligases that are associated with the ubiquitin-mediated proteasome processing pathway, 2) it could interact through its PPXY motifs with a WW domain containing protein, for instance with NEDD4, an E3 ubiquitin ligase, and 3) it could interact through the PSAP motif with TSG10, a protein associated with endosomal multivesicular protein sorting. Since both SIMPLE and Hrs are endosomal proteins and have both PPXY and P(S/T)AP motifs, we hypothesize that SIMPLE, like Hrs, is potentially a clathrin adaptor aiding in the retention of ubiquitinated proteins on to the endosomes. Thus the potential E3 ubiquitin ligase activity of SIMPLE, alteration in its interactions with NEDD4 or TSG101, or changes in its properties as a clathrin coat adaptor may underlie the pathogenesis of Charcot-Marie-Tooth disease.

Adult↗

PubMed1990

Charcot-Marie-Tooth disease and nephropathy in a mother and daughter with a review of the literature.

We report a mother-and-child combination of Charcot-Marie-Tooth disease and nephropathy. The mother received a cadaveric renal transplant, and the daughter has heavy proteinuria with normal glomerular filtration rate. There have been 7 single case reports of both disease entities and 1 report of 3 patients which includes the only sib pair. The related literature is reviewed.

Adolescent↗

PubMed2003

Molecular mechanisms, diagnosis, and rational approaches to management of and therapy for Charcot-Marie-Tooth disease and related peripheral neuropathies.

During the last decade, 18 genes and 11 additional loci harboring candidate genes have been associated with Charcot-Marie-Tooth disease (CMT) and related peripheral neuropathies. Ten of these 18 genes have been identified in the last 2 years. This phenomenal pace of CMT gene discovery has fomented an unprecedented explosion of information regarding peripheral nerve biology and its pathologic manifestations in CMT. This review integrates molecular genetics with the clinical phenotypes and provides a flowchart for molecular-based diagnostics. In addition, we discuss rational approaches to molecular therapeutics, including novel biologic molecules (eg, small interfering ribonucleic acid [siRNA], antisense RNA, and ribozymes) that potentially could be used as drugs in the future. These may be applicable in attempts to normalize gene expression in cases of CMT type 1A, wherein a 1.5 Mb genomic duplication causes an increase in gene dosage that is associated with the majority of CMT cases. Aggresome formation by the PMP22 gene product, the disease-associated gene in the duplication cases, could thus be avoided. We also discuss alternative therapeutics, in light of other neurodegenerative disorders, to disrupt such aggresomes. Finally, we review rational therapeutic approaches, including the use of antioxidants such as vitamin E, coenzyme Q10, or lipoic acid to relax potential oxidative stress in peripheral nerves, for CMT management.

Charcot-Marie-Tooth Disease↗

PubMed1988

Audiologic evaluation in Charcot-Marie-Tooth disease.

We have carried out a hearing study with pure tone audiometry and ABR of 39 patients affected by hereditary motor and sensory neuropathy or Charcot-Marie Tooth disease. We have noticed a hearing deficiency in a significant percentage of cases (28%). We attribute the abnormalities to disorders in the area of the VIIIth nerve and of the brainstem. No significant differences appear in the results obtained between patients belonging to type I and patients belonging to type II of this disease.

Adolescent↗

PubMed1987

The hypertrophic forms of hereditary motor and sensory neuropathy. A study of hypertrophic Charcot-Marie-Tooth disease (HMSN type I) and Dejerine-Sottas disease (HMSN type III) in childhood.

The clinical and histopathological features in sural nerve biopsies from 10 cases of dominantly inherited hypertrophic Charcot-Marie-Tooth disease (hereditary motor and sensory neuropathy (HMSN), type I) presenting in childhood are contrasted with those of 6 cases of Dejerine-Sottas disease (HMSN type III). There was a significantly greater incidence of ataxia, areflexia and clinical nerve enlargement in HMSN type III. In HMSN type III, there was also a significantly lower density of myelinated fibres 8 microns or more in diameter, a greater frequency of onion bulbs, more lamellae per onion bulb and, a higher ratio of mean axon diameter to fibre diameter. The functional severity of the HMSN type III cases was not markedly worse than those with HMSN type I. Using these parameters, it was possible to attempt classification of sporadic cases of hereditary motor and sensory neuropathy. Cerebrospinal fluid protein levels were unreliable in distinguishing the two types of neuropathy.

Action Potentials↗

PubMed2005

X-linked Charcot-Marie-Tooth disease: phenotypic expression of a novel mutation Ile127Ser in the GJB1 (connexin 32) gene.

We report a family with X-linked dominant Charcot-Marie-Tooth disease (CMTX1). Three affected family members are described, who underwent detailed clinical, electrophysiological, molecular genetic, and histopathological studies. A novel isoleucine at position 127 with serine (Ile127Ser) mutation in the gap junction protein beta 1 (GJB1) gene was detected. The electrophysiological findings were consistent with a primary demyelinating neuropathy with secondary axonal loss and support this model of disease progression. All patients having the CMT phenotype and intermediate conduction velocities who are negative for CMT1A duplication/hereditary neuropathy with liability to pressure palsies (HNPP) deletion, and whose family shows a dominant trait without male-to-male transmission, should be screened for CMTX1.

Adolescent↗

PubMed1992

Molecular genetics and neuropathology of Charcot-Marie-Tooth disease type 1A.

Charcot-Marie-Tooth (CMT) syndrome describes a genetically and clinically heterogeneous group of polyneuropathies. Electrophysiologically, at least two types of CMT can be distinguished; CMT1 which has decreased nerve conduction velocities (NCV) and CMT2 which has normal or near normal NCV with decreased amplitudes. For CMT1, three gene loci (on chromosomes 1, 17 and the X chromosome) have been mapped. The locus on chromosome 17, CMT type 1A (CMT1A), is responsible for the most common form of CMT which has recently been shown to be associated with a large DNA duplication. Recent data demonstrates that the CMT1A phenotype results from an inherited DNA rearrangement and a gene dosage effect. The trembler (Tr) and allelic tremblerJ (TrJ) mice have been proposed as animal models for CMT. Tr has similar electrophysiological and neuropathological features to CMT1 patients and maps to mouse chromosome 11 in a region of conserved synteny with human chromosome 17p. Tr and TrJ have recently been shown to have different point mutations in regions encoding putative transmembrane domains of the myelin specific protein PMP-22. The human peripheral nerve-specific PMP-22 gene maps within the CMT1A duplication. PMP-22 is thus a candidate gene for CMT1A. This paper describes the molecular genetics of CMT1A and sural nerve pathology in CMT1A patients with the CMT1A duplication.

Adult↗