Implication of the SH3TC2 gene in Charcot-Marie-Tooth disease associated with deafness and/or scoliosis: Illustration with four new pathogenic variants.

The autosomal recessive demyelinating form of Charcot-Marie-Tooth can be due to SH3TC2 gene pathogenic variants (CMT4C, AR-CMTde-SH3TC2). We report on a series of 13 patients with AR-CMTde-SH3TC2 among a French cohort of 350 patients suffering from all type of inheritance peripheral neuropathy. The SH3TC2 gene appeared to be the most frequently mutated gene for demyelinating neuropathy in this series by NGS. Four new pathogenic variants have been identified: two nonsense variants (p.(Tyr970*), p.(Trp1199*)) and two missense variants (p.(Leu1126Pro), p.(Ala1206Asp)). The recurrent variant p.Arg954* was present in 62%, and seems to be a founder mutation. The phenotype is fairly homogeneous, as all these patients, except the youngest ones, presented scoliosis and/or hearing loss.

Is troponin I gene therapy effective for osteosarcoma treatment? Study on a human-like orthotopic rat model.

BACKGROUND: An anti-angiogenesis strategy has been widely recognized as a viable approach to fight cancer and more and more anti-angiogenic factors are continually being identified. Among them, the muscular isoform of Troponin I (TnI) has been described as being a powerful anti-angiogenic agent in vitro as well as in vivo. We investigated the therapeutic efficacy of TnI gene therapy in a human-like orthotopic rat osteosarcoma model. MATERIALS AND METHODS: In this tumor model, we evaluated whether the administration of the secreted TnI coding sequence complexed to cationic liposomes (named TnITag cDNA/lCLP) could induce a delay in tumor growth and reduce tumor vasculature. RESULTS: Although TnI specifically inhibited endothelial cell growth in vitro, we were not able to demonstrate any therapeutic efficacy of TnI in the transplantable osteosarcoma model. CONCLUSION: This lack of efficacy probably resulted from the rapid degradation of recombinant TnI by matrix metalloproteinases, especially MMP2, which are present in large amounts in tumors.

[Hereditary motor and sensory neuropathy of Charcot-Marie-Tooth disease]. / La neuropathie héréditaire sensitivomotrice de Charcot-Marie-Tooth.

Charcot-Marie-Tooth disease (Hereditary Motor and Sensory Neuropathy) sometimes begins during childhood and can lead to learning and/or orthopedic disabilities. Due to the genetic and clinical heterogeneity of the disease, the diagnosis is based on a familial study of clinical, electromyographic and pathological abnormalities. Two major types of Charcot-Marie-Tooth disease have been described. Type 1 is characterized by a decrease in nerve conduction velocities and by a peripheral nerve hypertrophy due to myelinic alterations, while type 2 is the consequence of axonal alterations. Although type 1 and type 2 patients share similar clinical symptoms, type 2 patients have normal nerve conduction velocities and histological signs of axonal damage. Several genes involved in this disease have been recently located, and, in certain cases, an individual and direct diagnosis is available if the familial abnormality is related to chromosome 17.

Charcot-Marie-Tooth disease from first description to genetic localization of mutations.

Charcot-Marie-Tooth disease is a hereditary motor and sensory neuropathy first described in 1886. Our increasing knowledge of this disease correlates well with the development of methods used in neurology over the past 100 years. Although its physiopathology and treatment is still not fully understood, current developments in techniques are opening the way to future discoveries. We have divided its history into three theoretical periods: the first from 1886 to 1956, which was devoted to clinical and pathological study of the disease; the second from 1956 to 1982, which saw the development of electromyography in the investigation of neuromuscular diseases; and the last and current period based upon genetic research, using the methods of molecular biology.

Autosomal recessive forms of Charcot-Marie-Tooth disease.

In some countries with a high prevalence of consanguineous marriages, autosomal recessive inheritance is likely to account for the great majority of all forms of Charcot-Marie-Tooth (CMT) disease. As with the dominant forms, it is usual to differentiate the demyelinating forms (autosomal recessive -CMT1 or AR-CMT4) from the axonal forms (AR-CMT2). Genetic analysis of large families with recessive transmission has proved to be an efficient mean of discovering novel CMT genotypes (eg, the genes GDAP1, MTMR2, MTMR13, KIAA1985, NDGR1, periaxin, and lamin). Because of the clinical, electrophysiologic, and histologic heterogeneity of these patients, it is likely that there are numerous genes that remain to be discovered, which will probably make classification even more complex. Clinical, and especially histologic, phenotypes often lead to a suspicion that a specific gene is implicated. There is, therefore, an indication for nerve biopsy to orient diagnostic research in molecular biology, which is presently very time consuming and can only be performed in highly specialized laboratories.

Clinical and electrophysiological phenotype of a homozygously duplicated Charcot-Marie-Tooth (type 1A) disease.

Type 1A of Charcot-Marie-Tooth disease (CMT1A) is associated with a microduplication of chromosome 17 (region 17p11.2) which contains PMP22, an important gene for peripheral nerve myelination. Patients carrying two duplications are expected to have a more severe phenotype, close to the Dejerine-Sottas syndrome. In this article, we report a family of 5 CMT1A patients in whom the unrelated father and mother carry a 17p11.2 duplication. The 2 daughters carry only one duplication (one given by the father, the other given by the mother), but the son carries two 17p11.2 duplications. Interestingly, the clinical phenotype of the son is more severe (scoliosis) compared to those of his sisters, but his motor nerve conduction velocities are in the range of a heterozygote CMT1A patient. The mechanisms leading to a more severe phenotype for CMT1A are discussed and may not be strictly related to lower nerve conduction velocities.

Modelization of motor nerve conduction velocities for Charcot-Marie-Tooth (Type-1) patients. CMT-France Network.

Charcot-Marie-Tooth (CMT) type-1 (CMT1) neuropathy is characterized by peripheral nerve demyelination and has been divided into several subtypes. The most frequent among these, subtype 1A, is related to a microduplication of the region p11.2 of chromosome 17. This region contains the PMP-22 gene which is involved in peripheral nerve myelination. Since motor nerve conduction velocity (MNCV) is closely related to nerve myelination, we compared type-1A patient MNCVs versus non-A CMT1 patient MNCVs, in 57 CMT1A patients and 21 non-A type-1 patients. Patients with the 17p11.2 duplication have MNCVs that are significantly more reduced (about 20 m/s) compared to patients without the 17p11.2 duplication (about 30 m/s). This study also permits a model of the MNCV in the median nerve (MedMNCV) of CMT1 patients, with age, gender and molecular status as parameters. Furthermore, in order to help clinicians to diagnose subtypes of CMT1 patients, the probability for type 1A is modeled as a function of MedMNCV only.

Detection of deletion within 17p11.2 in 7 French families with hereditary neuropathy with liability to pressure palsies (HNPP).

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant peripheral neuropathy which is characterized by recurrent episodes of truncular palsies. We have analyzed the D17S122 locus in 7 French families, including 18 affected members, with microsatellite RM11GT and the RFLP probe VAW409R3a. Only one allele could be detected in all affected individuals with the highly polymorphic RM11GT marker. Allele segregation at D17S122 showed no contribution from the affected parent to the affected child, demonstrating that an interstitial deletion within the 17p11.2 region is associated with HNPP in the 7 families studied. This same region is duplicated, however, in another inherited neuropathy, Charcot-Marie-Tooth 1A disease. This would be the first example of two dominantly inherited diseases caused by a 'in mirror image' deletion/duplication mechanism where a gene dosage effect would be sufficient to produce two different phenotypes characterized by abnormal myelination of the peripheral nerves. The RM11GT microsatellite is an informative tool for the molecular diagnosis of HNPP.

X-linked dominant Charcot-Marie-Tooth neuropathy (CMTX): new mutations in the connexin32 gene.

X-linked dominant Charcot-Marie-Tooth (CMTX) neuropathy has been mapped to the Xq13 region. Subsequently, several mutations that could account for CMTX have been detected in the coding part of the connexin32 (Cx32) gene, which is located within this region. In order to develop more specific diagnostic tools, we have begun a systematic screening of families with dominant CMTX for mutations in the coding region of the Cx32 gene. This report describes a study of ten families and different mutations segregating with the disease were detected in five of them. In addition to the previously reported Arg22stop and Arg215Trp substitutions, three novel mutations are described, including two different missense mutations at codon Arg22 (Arg22Pro and Arg22Gly), and a nonsense mutation at codon Trp133. The identification of new CMTX-causing mutations is a critical step for carrier detection and presymptomatic diagnosis, and should provide essential information on the structure-function relationship of Cx32 in vitro as well as in vivo.

New mutations in the X-linked form of Charcot-Marie-Tooth disease.

Mutations in the gene for connexin 32 are associated with a chromosome X-linked form of Charcot-Marie-Tooth disease. The prevalence of this form is probably underestimated. We screened 12 candidate families and found 7 missense mutations of which 4 are new. These mutations are located in intra- and extramembraneous parts of the protein. Some mutations are probably present with a higher frequency. This study further confirms variation of connexin 32 mutations with scarcity in the second transmembrane domain and, so far, absence in the fourth transmembrane domain and in the carboxy-terminal region.