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PubMed2001

Episodes of generalized weakness in two sibs with the C164T mutation of the connexin 32 gene.

Two sibs with Charcot-Marie-Tooth disease had repeated episodes of generalized weakness. The patients had distal weakness and atrophy as well as findings of CNS involvement on brain MRI. Both patients bear the C164T mutation of the connexin 32 gene but no mutations of the genes responsible for hyper- or hypokalemic periodic paralysis. It is possible that both patients have one disease with complex phenotype due to abnormal expression of the connexin 32 gene.

Adult↗
PubMed1994

Deletion in the CMT1A locus on chromosome 17p11.2 in hereditary neuropathy with liability to pressure palsies.

Hereditary neuropathy with liability to pressure palsies (NHPP) is an autosomal dominant disease of peripheral nerves, characterized by recurrent focal neuropathies often with an underlying asymptomatic polyneuropathy. We report the clinical, electrophysiological, and histopathological findings in three families with HNPP and confirm the presence of a deletion on chromosome 17p11.2, including all the markers known to be duplicated in Charcot-Marie-Tooth disease type 1A. This deletion appears to be the underlying molecular deficit in this disease and provides additional evidence for the importance of this locus for peripheral nerve function.

Adolescent↗
PubMed1995

[Diagnostic studies in patients and relatives with hereditary neuromuscular diseases].

Preclinical and prenatal diagnosis as well as detection of healthy carriers is now theoretically possible for more than 200 monogenic inherited neurological and neuromuscular diseases and practically performed in many of them. However, it has to be made a condition, that the diagnosis in the index patient is secured by all clinical and laboratory methods available today, and that the specific mutation has been localized or even sequenced, and of course the families must give their full consent to the examinations. It is important to submit material for the different laboratory investigations from patients and their relatives as early as possible [biopsies, blood samples for DNA, etc.], at least for rapidly progressive diseases with a poor prognosis. In order to obtain very high probabilities in diagnostic predictions a family has to be examined either with mutation-specific DNA-probes and/or with probes for closely linked polymorphic DNA-markers. This requires a close cooperation between genetic services and DNA-laboratories on the one hand and the family doctors, specialists and clinics on the other. Specific strategies are discussed for hereditary sensory and motor neuropathy [HMSN la or Charcot-Marie-Tooth disease], Duchenne und Becker muscular dystrophy and childhood spinal muscular atrophies.

Charcot-Marie-Tooth Disease↗
PubMed1993

Structure and chromosomal localization of the gene encoding the human myelin protein zero (MPZ).

We describe the cloning, characterization, and chromosomal mapping of the human myelin protein zero (MPZ) gene. The gene is about 7 kb long and consists of six exons corresponding to the functional domains. All exon-intron junction sequences conform to the GT/AG rule. The 5'-flanking region of the gene has a TA-rich element (TATA-like box), two CAAT boxes, and a single defined transcription initiation site detected by the primer extension method. The gene for human MPZ was assigned to chromosome 1q22-q23 by spot blot hybridization of flow-sorted human chromosomes and fluorescence in situ hybridization. The localization of the MPZ gene coincides with the locus for Charcot-Marie-Tooth disease type 1B, determined by linkage analysis.

Base Sequence↗
PubMed1979

Homozygous expression of a dominant gene for Charcot-Marie-Tooth neuropathy.

A kindred of 68 French Acadians who were heterozygous for a dominant gene of Charcot-Marie-Tooth disease associated with peripheral nerve hypertrophy are described. Marriage between 2 heterozygotes resulted in 2 homozygous offspring. Clinical features of the homozygotes were similar to the classic description of Dejerine-Sottas disease. Laboratory studies in this family revealed no chemical, metabolic, or chromosomal abnormalities in either the homozygotes or the heterozygotes.

Adult↗
PubMed1978

Computed tomography in hereditary ataxias.

Cranial CT in 39 patients (23 belonged to 8 families) with four different groups of hereditary ataxia (HA) showed mainly three combinations of atrophic findings: (1) cerebellar ataxia (CA, n = 17) had marked atrophy of the cerebellum and/or the brain stem combined with moderate cerebral atrophy; (2) an intermediate group consisting of hereditary spastic paraplegia (HSP, n = 10) and Friedreich's ataxia (FA, n = 7), both with moderate infra- and supratentorial atrophy; (3) atrophy was hardly demonstrated in the group of Charcot-Marie-Tooth disease (CMT, n = 5). HA cases with atrophy could be distinguished from multiple sclerosis (MS) by CT.

Adolescent↗
PubMed2005

Emerging pathways for hereditary axonopathies.

Motor neurons are affected in a number of neurological diseases. Their unifying pathological signature is degeneration of extended projecting axons and loss of motor neurons in the prefrontal cortex and/or the spinal cord. Based on clinical criteria, hereditary forms have been traditionally divided into distinct entities, such as familial amyotrophic lateral sclerosis, hereditary motor neuropathy, spinal muscular atrophy, familial spinal paraplegia, and Charcot-Marie-Tooth disease type 2, also known as hereditary motor and sensory neuropathy II. Genetic research of the last decade has revealed remarkable heterogeneity within these disorders. Most of the identified genes to date cause disease in a classic Mendelian inheritance pattern with a high phenotypic penetrance. This rich source of molecular genetic data has already provided insight into the underlying major pathways of these diseases and should continue to do so in the future. This review attempts to cross the traditional clinical classifications in order to draw an emerging picture of common pathways between causative genes, providing a different perspective of this rapidly growing scientific field.

Amyotrophic Lateral Sclerosis↗
PubMed2001

Mutations of peripheral myelin protein 22 result in defective trafficking through mechanisms which may be common to diseases involving tetraspan membrane proteins.

Phenotypes of several heritable disorders including forms of hearing loss, myelin diseases, hypomagnesemia, and cataracts are linked to missense mutations in single alleles encoding membrane proteins having four transmembrane spans. In some cases, the mutant proteins exhibit dominant negative or gain-of-function behavior whereby heterozygous coexpression of mutant and wild-type genes leads to more serious pathology than is the case for individuals in which only a single wild-type allele is expressed. An example is found in the relationship of peripheral myelin protein 22 (PMP22) to Charcot-Marie-Tooth disease (CMTD) type 1A. A number of disease-linked PMP22 mutants fail to undergo normal trafficking beyond the endoplasmic reticulum or intermediate compartment to reach the cell surface. Moreover, recent evidence suggests that pathology resulting from this mistrafficking-based loss of function may also be augmented by the ability of some mutants to disrupt normal trafficking of the product of the wild-type PMP22 allele. The basis for this phenomenon appears to be the heterodimerization of trafficking-incompetent mutants with wild-type PMP22, such that both the wild-type protein and the mutant forms are retained early in the secretory pathway. The full cellular and structural biological details of these observations remain to be elucidated. However, the model suggested by the existing data regarding the relationship of PMP22 to CMTD may be useful to explain phenotypes of several other diseases involving other tetraspan membrane proteins and to facilitate predictions regarding previously undetected disease-protein linkages.

Amino Acid Sequence↗
PubMed1995

Inheritance of CMT1A duplication from a mosaic father.

We describe a case with molecular duplication of chromosome 17 (p11.2-p12) whose duplicated chromosome was inherited from a mosaic father. The patient has clinical manifestations consistent with Charcot-Marie-Tooth disease type 1A (CMT1A), while the mosaic father has minimal findings of CMT1A. The father was found to be homozygous with DNA markers VAW409R3A (D17S122) and p132G8RI (PMP-22) which are duplicated in CMT1A cases. Fluorescence in situ hybridisation (FISH) analysis with YAC clone 49H7 confirmed the duplication in the affected patient and diagnosed the mosaicism in his father. These findings based on clinical diagnosis and FISH analysis suggest that the mosaicism may have occurred early in embryogenesis leading to the disease in the father. This is the only reported case of CMT1A with transmission from a mildly affected mosaic father.

Blotting, Southern↗
PubMed1990

[Charcot-Marie-Tooth: a family case report].

Three cases in a Spanish family are presented, showing diagnosis criteria of hereditary motor-sensitive neuropathy (Charcot-Marie-Tooth disease) type I: suggestive symptoms, neurological and anatomopathological findings. The current classification of this pathology.

Adult↗
PubMed1997

Altered trafficking of mutant connexin32.

We examined the cellular localization of nine different connexin32 (Cx32) mutants associated with X-linked Charcot-Marie-Tooth disease (CMTX) in communication-incompetent mammalian cells. Cx32 mRNA was made, but little or no protein was detected in one class of mutants. In another class of mutants, Cx32 protein was detectable in the cytoplasm and at the cell surface, where it appeared as plaques and punctate staining. Cx32 immunoreactivity in a third class of mutants was restricted to the cytoplasm, where it often colocalized with the Golgi apparatus. Our studies suggest that CMTX mutations have a predominant effect on the trafficking of Cx32 protein, resulting in a potentially toxic cytoplasmic accumulation of Cx32 in these cells. These results and evidence of cytoplasmic accumulation of other mutated myelin proteins suggest that diseases affecting myelinating cells may share a common pathophysiology.

Amino Acid Sequence↗
PubMed2002

Anticipation in a unique family with Charcot-Marie-Tooth syndrome and deafness: delineation of the clinical features and review of the literature.

Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous group of polyneuropathies characterized by degeneration of peripheral nerves, resulting in distal muscle atrophy, sensory loss, and deformities of hands and feet. We have studied 34 individuals in a large 84-member four-generation central Illinois family with autosomal dominant Charcot-Marie-Tooth and deafness. Nerve conduction velocities are consistent with type 1 CMT. Audiological evaluation revealed both auditory neuropathy and cochlear involvement in affected individuals. There is increasing clinical severity and younger age of onset of CMT and deafness with each progressive generation, suggestive of anticipation (P < 0.05). The proband, a female diagnosed at birth with hypotonia, bilateral vocal cord palsy, swallowing incoordination, and hearing impairment, died at age 18 months. Another individual died at the age of 3 months from hypotonia later attributed to CMT. Genetic analysis indicated that affected individuals in this family do not have the common 1.4 Mb duplication associated with type 1A CMT; however, all affected individuals have a unique G to C transversion at position 248 in coding exon 3 of the peripheral myelin PMP22 gene located on chromosome 17p11.2-p12. This mutation is predicted to cause an Ala67Pro substitution in the second transmembrane domain of PMP22, consistent with the molecular cause of the CMT phenotype. However, it does not explain the cochlear component of the deafness, the clinical observation of anticipation, and other features in this family.

Adolescent↗
PubMed1996

A de novo duplication in 17p11.2 and a novel mutation in the Po gene in two Déjérine-Sottas syndrome patients.

Déjérine-Sottas syndrome (DSS), or hereditary motor and sensory neuropathy (HMSN) type III, is a severe hypertrophic demyelinating neuropathy with infantile onset. The clinical symptoms are similar to those found in Charcot-Marie-Tooth disease type 1 (CMT1) or HMSN type I patients, but they are more severe. DSS is genetically heterogeneous. Dominant mutations in two major peripheral myelin protein genes, PMP22 and Po, are associated with a DSS phenotype. Mutations in the same genes are also responsible for the CMT1 phenotype. A 1.5-Mb duplication in 17p11.2 is the major mutation found in familial and sporadic CMT1 patients. We studied two genetically sporadic DSS patients. The presence of a de novo duplication in one patient was revealed by Southern blot analysis, using polymorphic markers located in the duplicated area. The 17p11.2 allele segregation in this patient and in her parents suggests that the duplication is of maternal origin. In the other patient, single-strand conformation polymorphism (SSCP) analysis of the 6 exons of the Po gene revealed two additional bands in exon 3. Sequencing of this exon identified a novel dominant mutation replacing a sequence of 8 bp by a mutated sequence of 5 bp. The mutation apparently leads to the replacement of 4 amino acids at positions 86-89 by three different amino acids, in an area that is part of a predicted beta-strand. Our findings support the suggestion that DSS and CMT1 disease should not be considered as two different clinical entities.

Adult↗
PubMed2000

PMP22 Thr118Met is not a clinically relevant CMT1 marker.

It is controversial if peripheral myelin protein 22 gene (PMP22) Thr118Met represents a functionally irrelevant polymorphism or, since hemizygosity for this variant has been found in two patients with Charcot-Marie-Tooth disease type 1 (CMT1 patients), it can act as a recessive CMT1 mutation. To shed further light on this variant and its diagnostic value we searched for carriers in 1018 individuals from the German general population, in 104 probands with hereditary neuropathy with liability to pressure palsies (HNPP) who were carriers of the 1.5-Mb deletion frequently associated with this disorder, in 187 patients with the 1.5-Mb duplication, and in 22 patients with a CMT1 phenotype who did not have any detectable anomaly in the PMP22 gene. Using allele-specific PCR we identified 14 [allele frequency (AF)=0.007] in the German general population, one (AF=0.01) in the HNPP group and six (AF=0.016) and two (AF=0.05) carriers of the PMP22 Thr118Met mutation in the CMT1 groups with and without gene defect. Carriers from all groups showed nerve conduction velocities which did not differ from typical values for these groups. We conclude that the hemizygous occurrence of the 118Met allele does not usually cause CMT1. Because of previous reports on its association with disease, and because its allele product shows abnormalities in in vitro expression systems, it seems possible that this mutation, together with yet unidentified factors, predisposes to CMT1. Alternatively, previously reported disease associations occurred by chance, and the 118Met allele causes biochemical abnormalities irrelevant for CMT1 formation. In either case this mutation is not a clinically relevant disease marker.

Biomarkers↗
PubMed1975

F-wave conduction velocity in the central segment of the peroneal and tibial nerves.

A simple method was devised to measure the F-wave conduction velocity (FWCV) in the central segment (knee to spinal cord) of the peroneal and tibial nerves in contrast to the conventional motor nerve conduction velocity (MNCV) in the distal segment (knee to ankle). In 33 normal subjects, the FWCV in the central segment (56.3 +/- 4.9 meters/sec for peroneal nerve; 54.4 +/- 3.6 meters/sec for tibial nerve) was slightly faster than the MNCV in the distal segment (49.5 +/- 3.8 meters/sec; 46.8 +/- 3.4 meters/sec) as measured in the conventional manner. In 4 of 14 patients with the Guillain-Barrĕ syndrome, the F-wave was absent or slowed in the face of normal MNCV indicating more marked slowing of nerve conduction proximally. The average FWCV (36.8 +/- 13.6 meters/sec; 42.2 +/- 9.3 meters/sec) and MNCV (41.4 +/- 8.0 meters/sec; 39.0 +/- 5.6 meters/sec) were considerably decreased compared to the normal values. The F-wave could not be elicited in the lower extremities in 16 of 19 patients with Charcot-Marie-Tooth disease. The FWCV was normal in 10 patients with multiple sclerosis including 3 with clinical findings suggesting demyelination in the conus medullaris.

Adolescent↗
PubMed2000

Electrodiagnosis of demyelinating neuropathies.

The inflammatory demyelinating neuropathies constitute a significant proportion of the acquired polyneuropathies. Major progress in finding the causes and in the treatment of these neuropathies has been made over the last decade. Early recognition is of paramount importance, because timely and appropriate treatment can largely reduce morbidity and disability. Electrodiagnosis plays a key role in the detection and characterization of the inflammatory demyelinating neuropathies. Electrodiagnostic criteria for primary demyelination have therefore been developed. They are empirically based on changes of nerve conduction parameters in populations of patients with a confirmed clinical and laboratory diagnosis of inflammatory demyelinating neuropathy. The challenge consists of defining criteria sets that are highly specific but also as sensitive as possible. Most of the hereditary demyelinating neuropathies are part of Charcot-Marie-Tooth disease type 1. The pattern of nerve conduction abnormalities usually provides valuable clues for the distinction from chronic inflammatory demyelinating neuropathies.

Action Potentials↗
PubMed1992

Further evidence of a duplication in 17p11.2 in families with recurrence of HMSN Ia (Charcot-Marie-Tooth neuropathy type Ia).

Five Italian families with recurrence of cases of Charcot-Marie-Tooth disease (type Ia) were analysed using three closely linked DNA probes that detect polymorphisms in the region 17p11.2. The probe pVAW409R3 detected the presence of a duplication in all the affected subjects, but not in the subjects with normal electromyographic (EMG) findings. This observation confirms previous data indicating the association of the duplication with the disease, suggesting that, at least in populations of European origin, the duplication might be the molecular feature diagnostic of the pathological trait.

Charcot-Marie-Tooth Disease↗
PubMed1995

The prevention of neurogenetic disease.

A significant number of major neurogenetic diseases have been defined at the molecular level in recent years, making it possible to determine precisely the genotype for familial Alzheimer's disease, Huntington's disease, Machado-Joseph disease, dominantly inherited ataxia, Charcot-Marie-Tooth disease, myotonic muscular dystrophy, Duchenne-Becker muscular dystrophy, familial amyotrophic lateral sclerosis, and neurofibromatosis. This information has made it possible to identify the abnormal genotype of at-risk persons for these diseases and for at-risk pregnancies for several of them. Precise molecular diagnoses are thus possible using applied molecular markers. Prevention of disease can be achieved using these molecular markers with genetic counseling and appropriate family planning. Significant progress is being made in this regard with Tay-Sachs disease, Huntington's disease, the dominantly inherited ataxias, and the muscular dystrophies. Further, this molecular genotyping will be of indispensible value to families with these diseases when somatic cell gene therapy becomes available. The field of molecular neurogenetics is moving forward rapidly, and advances in gene identification for these diseases will lead in the near future to the means to prevent many of them.

Alzheimer Disease↗