Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0031117 (peripheral neuropathy)
 10,577 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present work, we describe a large Turkish family (N=39) with Charcot-Marie-Tooth disease, which is the most commonly inherited peripheral neuropathy. The subjects were from four generations, including six hemizygote patients and nine heterozygote carrier females. Symptoms appeared in late childhood in males (mean age=13.5) but later in carrier females (mean age=33.5). The peripheral nerve conduction was more severely affected in males than females. Genomic DNA was isolated from peripheral white blood cells. Using SSCP technique (single strand conformation polymorphism analysis), abnormal patterns of migration were observed in 15 subjects: 6 of them were hemizygote males and 9 were heterozygote carrier females. We identified a mutation of the Cx32 gene, consisting of a guanine to adenine transition at position 271 (271G-A). The results suggested relations between degenerative processes and position of Cx32 mutations.
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PMID:Connexin 32 mutation in a Turkish family with X-linked Charcot-Marie-Tooth disease. 1277 42

X-linked Charcot-Marie-Tooth disease is an inherited peripheral neuropathy arising in patients with mutations in the gene encoding connexin 32 (Cx32). Cx32 is expressed at the paranodes and Schmidt-Lantermann incisures of myelinating Schwann cells in which it is believed to form a reflexive pathway between the abaxonal and adaxonal cytoplasmic domains. Patients with the Val181Ala (V181A) mutation have a severe peripheral neuropathy. Experiments using a nude mouse xenograft system show that Schwann cells expressing only this mutant form of Cx32 are profoundly impaired in their ability to support the earliest stages of regeneration of myelinated fibers. Coupling between paired Xenopus oocytes expressing V181A is reduced compared with the coupling between oocytes expressing wild-type human Cx32 (32WT), and protein levels assayed by Western blot are substantially lower. Immunocytochemisty shows that Neuro2a cells expressing the V181A mutant have very few gap junction plaques compared with cells expressing 32WT; Cx32 protein levels are lower in these cells than in those expressing 32WT. Because failure of normal regeneration is evident before formation of myelin, loss of function of Cx32 may impact on the function of precursors of the myelinating Schwann cell before the formation of the hypothesized reflexive pathway. The Glu102Gly (E102G) mutation leads to a milder phenotype. Early regeneration is normal in grafts with Schwann cells expressing the E102G mutant. The only abnormality detected in the behavior of its channel is increased sensitivity to acidification-induced closure, a property that may lead to reduced gap junction coupling during periods of metabolic stress. This restricted functional abnormality may explain the relatively mild phenotype seen in the xenograft model and in E102G patients.
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PMID:Pathogenesis of X-linked Charcot-Marie-Tooth disease: differential effects of two mutations in connexin 32. 1462 39

In addition to forming gap-junction channels, a subset of connexins (Cxs) also form functional hemichannels. Most hemichannels are activated by depolarization, and opening depends critically on the external Ca2+ concentration. Here we describe the mechanisms of action and the structural determinants underlying the Ca2+ regulation of Cx32 hemichannels. At millimolar calcium concentrations, hemichannel voltage gating to the full open state of approximately 90 pS is inhibited, and ion conduction at negative voltages of the partially open hemichannels ( approximately 18 pS) is blocked. Thus, divalent cation blockage should be considered as a physiological mechanism to protect the cell from the potentially adverse effects of leaky hemichannels. A ring of 12 Asp residues within the external vestibule of the pore is responsible for the binding of Ca2+ that accounts for both pore occlusion and blockage of gating. The residue Asp-169 of one subunit and the Asp-178 of an adjacent subunit must be arranged precisely to allow interactions with Ca2+ to occur. Interestingly, a naturally occurring mutation (D178Y) that causes an inherited peripheral neuropathy induces a complete Ca2+ deregulation of Cx32 hemichannel activity, suggesting that this dysfunction may be involved in the pathogenesis of the neuropathy.
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PMID:Molecular basis of calcium regulation in connexin-32 hemichannels. 1466 44

Charcot-Marie-Tooth type X1 disease (CMTX1) is an X-dominant peripheral neuropathy caused by mutations in the GJB1 gene. Molecular genetic analysis of the GJB1 gene is crucial for CMTX1 diagnosis and for genetic counselling. To date, molecular genetic analysis of the GJB1 gene revealed 264 mutations in the GJB1 gene. In spite of the rising number of GJB1 gene mutations, family history was documented in only a few CMTX1 cases. The aim of this study was a molecular genetic analysis of the GJB1 gene in 7 families, performed in 19 CMTX1-affected patients and 13 healthy family members. Moreover, we attempted to report evidence of effects of 6 amino-acid substitutions described in this study. To the best of our knowledge, the G110D, V152D and K167E mutations are novel substitutions, which have not been reported so far.
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PMID:Molecular genetic analysis of the GJB1 gene: a study of six mutations. 1496 Jul 72

To investigate the pathogenic role of connexin-32 (Cx32) mutation in X-linked dominant Charcot-Marie-Tooth disease (CMTX), dual whole-cell voltage-clamp recordings and tracer coupling were performed to investigate functional properties of wild-type and 22 CMTX mutant Cx32 proteins expressed in N2A cells. Ten mutant Cx32 proteins either formed defective junctional channels (Y65C, V95M, R107W, L156R, R164W and G199R) or failed to form gap junctions (G12S, S182T, E208K and Y211stop). Except (G12S) and (E208K) mutants, other mutant Cx32 proteins were localized in the cell membrane despite their impaired ability to form functional gap junctions. Twelve CMTX mutations (V13L, R15Q, R22Q, I30N, V35M, V63I, R75Q, Q80R, W133R, P158A, P172S and N205S) did not affect the ability of Cx32 to form homotypic gap junctions in N2A cells. Our results indicate that 10 of 22 CMTX Cx32 mutations studied in the present investigation could lead to the assembly of defective Cx32 gap junctions, which in turn may result in peripheral neuropathy. However, further studies are required to elucidate the exact mechanism by which CMTX mutant Cx32 proteins, which retain the ability to form homotypic junctional channels, damage Schwann cells and cause demyelinating neuropathy.
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PMID:Functional analysis of connexin-32 mutants associated with X-linked dominant Charcot-Marie-Tooth disease. 1500 6

Urinary bladder dysfunction is a major complication in diabetes mellitus and its mechanism has been attributed to altered neurological function (autonomic and/or peripheral neuropathy). Previous studies have demonstrated impaired nerve deficiencies, including either loss of nerve function and/or anatomical loss of neuromuscular nerve terminals. While the phenomenon of diabetes-related neurological injury is well recognised, its pathogenesis is not well understood. Using a well established rat model of diabetes (streptozotocin model), we investigated the prevalence of sympathetic and parasympathetic nerves and relative prevalence of connexin isoforms (gap junction proteins) during diabetes-related bladder dysfunction. Immunohistochemistry and digital image analysis was used to detect the prevalence of postsynaptic neuronal markers, NOS1 and connexin isoform expressions. Immunohistochemistry showed significant increases in tyrosine hydroxylase (marker of sympathetic innervation) and decreased vesicular acetylcholine transporter (marker of parasympathetic innervation), predominantly in the smooth muscle layer, 3 days after diabetes induction, when compared to age-matched controls. Time-dependent and cell-specific decreases in the connexin 43 isoform, but transient increases in connexin 32 and 26, were also observed in diabetic rats vs. controls (p<0.05). These data suggest that selective and time-dependent expression of gap junction proteins and altered prevalence of sympathetic/parasympathetic innervation are early events during diabetes-related bladder dysfunction and remodelling.
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PMID:Innervation and connexin isoform expression during diabetes-related bladder dysfunction: early structural vs. neuronal remodelling. 1625 38

Mutations in GJB1, the gene encoding the gap junction protein connexin32 (Cx32), cause X-linked Charcot-Marie-Tooth disease, an inherited demyelinating peripheral neuropathy. We generated transgenic mice that express the R142W mutation in myelinating Schwann cells. The R142W mutant protein was aberrantly localized to the Golgi, indicating that it does not traffic properly, but the molecular organization of the myelin sheath, including the localization of Cx29, another connexin expressed by myelinating Schwann cells, was not disrupted. In a wild type background, this mutation dramatically decreased the level of wild type mouse Cx32 in immunoblots of sciatic nerve and caused demyelination. The expression of wild type human Cx32 with the same transgenic construct had different effects-increased amounts of Cx32, normal localization of Cx32 at nodes and incisures, and split myelin sheaths. Thus, the R142W mutant protein has dominant effects that are distinct from overexpression.
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PMID:The effects of a dominant connexin32 mutant in myelinating Schwann cells. 1679 Mar 56

From 1995 to 2004, 979 families with hereditary peripheral neuropathy were referred to the Genetic Diagnosis Center. Using single-strand conformation analysis (SSCA), the connexin 32 gene was analysed in all the patients from 498 families with sporadic or dominant inheritance with no male-to-male transmission and absence of the 17p2 duplication or deletion. Affected males had pes cavus, distal leg weakness, muscular distal atrophy, areflexia and distal sensory loss. The 106 families in which SSCA revealed abnormal migration electrophoresis were directly sequenced. We found 34 families (59 patients) with mutations in connexin 32 gene. In electrophysiological studies, 58.8% families presented slow and 14.7% intermediate nerve conduction velocities. Molecular findings revealed that codon 164 (29.4 +/- 15.3%) and the second extracellular (EC2) domain (44.1 +/- 16.6%) were the most frequently affected codon and domain of the connexin 32. Six novel mutations, Leu39fs, Glu47Gly, His153fs, Cys179Tyr, Cys201Phe and Ser211fs, were found in our study.
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PMID:Clinical and molecular analysis of X-linked Charcot-Marie-Tooth disease type 1 in Spanish population. 1710 Sep 97

Charcot-Marie-Tooth (CMT) disease is the most common inherited peripheral neuropathy. Administration of vinca alkaloids is considered contraindicated in CMT because of the risk of life threatening acute neuropathy. We describe a 5-year-old patient with a family history of X-linked CMT1 who presented with Wilms tumour. Despite confirmation of a connexin 32 point mutation, the patient was treated with 40.5 mg/m(2) of vincristine with no clinical evidence of drug-related neuropathy. This case describes vincristine being safely administered to a patient with molecularly proven type CMT 1X, but in type 1A CMT vincristine is still contraindicated. An extensive literature review revealed no other series of cases in which vincristine administration in molecularly proven CMT 1X had been described. CMT should be excluded in any patient who develops a profound, acute neuropathy following vincristine, as many patients in the cases reviewed were asymptomatic prior to treatment.
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PMID:Uneventful administration of vincristine in Charcot-Marie-Tooth disease type 1X. 1751 37

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.
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PMID:Gap junction beta 1 (GJB1) gene mutations in Italian patients with X-linked Charcot-Marie-Tooth disease. 1837 23


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