Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The X-linked dominant form of Charcot-Marie-Tooth syndrome (CMTX) is a clinically and genetically heterogeneous hereditary disorder of the peripheral nerves caused by mutations in the GJB1 gene that encodes a gap junction protein named connexin 32 (Cx32). Clinically, CMTX is characterized by peripheral motor and sensory deficit with muscle atrophy. A couple with a previous history of pregnancy termination after being diagnosed positive for CMTX by chorionic villus sampling, was referred for preimplantation genetic diagnosis (PGD). The female partner carried the causative H94Q, characterized by a C-->G substitution in codon 94 of exon 2 of the GJB1 gene. Embryos obtained after intracytoplasmic sperm injection (ICSI) were evaluated for the presence of the mother's mutation using polymerase chain reaction (PCR), followed by mutation analysis performed using the minisequencing method. Amelogenin sequences on the X and Y chromosomes were also co-amplified to provide a correlation between embryo gender and mutation presence. A single PGD cycle was performed, involving nine fertilized oocytes, five of which developed into good quality embryos useful for biopsy. Two unaffected embryos were transferred, resulting in a singleton pregnancy followed by the birth of a healthy female.
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PMID:Birth of a healthy female after preimplantation genetic diagnosis for Charcot-Marie-Tooth type X. 1468 May 48

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

During the last decade, molecular biology has demonstrated the extraordinary heterogeneity of genetic abnormalities in Charcot-Marie-Tooth disease (CMT). The main phenotypes are either of the demyelinating or axonal type, transmitted with dominant or recessive autosomal inheritance. X-linked CMT is less rare than it was initially described and is often misdiagnosed as autosomal dominant type. Linked phenotypes are Dejerine-Sottas disease, congenital hypomyelinization and hereditary neuropathy with susceptibility to pressure palsies. Each phenotype can be due to different genotypes and concerned genes are numerous. Conversely, each genotype can express different phenotypes. Molecular diagnostic strategy of CMT is mainly baised on three elements: - phenotypic expertise which is based on the analysis of the inheritance mode and on electrophysiological data, which are peculiar in CMTX - knowledge of respective occurrence of the different genotypes and phenotypes which is increasing - technical feasibility of molecular biology methods which is important to consider, even though progress are fastly coming. According to these considerations, a strategy is proposed for molecular diagnosis of CMT.
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PMID:[Molecular diagnosis of hereditary neuropathies such as Charcot-Marie-Tooth disease]. 1503 75

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.
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PMID:X-linked Charcot-Marie-Tooth disease: phenotypic expression of a novel mutation Ile127Ser in the GJB1 (connexin 32) gene. 1546 13

Charcot-Marie-Tooth disease is a clinically and genetically heterogeneous group of inherited neuropathies. The common clinical symptoms include distal muscle weakness, wasting and impaired distal sensation, more in the legs than in the arms, and reduced or absent reflexes. Moreover, foot and hand deformities are often encountered. A distinction between a primarily demyelinating or axonal neuropathy is often possible by means of nerve conduction studies. The major groups of inheritance are the autosomal dominant CMT1 (demyelinating), CMT2 (axonal) and the X-linked type (CMTX), but there are also autosomal recessive demyelinating (CMT4) and axonal (AR-CMT2) forms. The number of genes and loci is steadily increasing, with genes encoding proteins involved in myelin maintenance and axonal function, but also with genes encoding proteins, the function of which in peripheral nerve maintenance is notyet clear. Despite the increase in the number of known genes, especially for CMT2, there are many patients in whom no mutation can yet be found.
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PMID:[From gene to disease; Charcot-Marie-Tooth disease or the hereditary motor and sensory neuropathies]. 1603 95

In X-linked hereditary demyelinating neuropathies (CMTX), caused by mutations in Connexin 32, mild subclinical CNS involvement is not unusual. We present a young male patient suffering from genetically proven CMTX who presented with permanent bilateral corticospinal tract hyperintensities in cranial MRI -- a finding previously described to be characteristic for amyotrophic lateral sclerosis. MRI seems to be able to visualize corticospinal tract abnormalities, even if subclinical, in CMTX.
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PMID:Corticospinal tract MRI hyperintensity in X-linked Charcot-Marie-Tooth Disease. 1605 Oct 98

The X-linked form of Charcot-Marie-Tooth disease (CMTX) is caused by mutations in connexin32 (Cx32), a gap junction protein expressed by Schwann cells where it forms reflexive channels that allow the passage of ions and signaling molecules across the myelin sheath. Although most mutations result in loss of function, several studies have reported that some retain the ability to form homotypic intercellular channels. To gain insight into the molecular defect of three functional CMTX variants, S26L, Delta111-116 and R220stop, we have used several fluorescent tracers of different size and ionic charge to compare their permeation properties to those of wild-type Cx32. Although all mutations allowed the passage of the dye with the smallest molecular mass, they exhibited a clear reduction in the permeability of either one or all of the probes with respect to wild-type channels, as assessed by the percentage of injections showing dye coupling. These data reveal that a lower size cutoff distinguishes these functional CMTX variants from wild-type channels and suggest that this defect may be of pathophysiological relevance.
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PMID:Selective defects in channel permeability associated with Cx32 mutations causing X-linked Charcot-Marie-Tooth disease. 1644 4

Inherited neuropathies are clinically and genetically heterogeneous. At least 28 genes and 12 loci have been associated with Charcot-Marie-Tooth disease (CMT) and related inherited neuropathies. Most causes of inherited neuropathy have been discovered by positional cloning technique and in the past two years, the pace of CMT gene discovery has accelerated. Genetic studies have revealed the following gene mutations as the causes of inherited neuropathies; PMP22, MPZ, EGR2, SOX10, SIMPLE/LITAF, ARHGEF10 for CMT1 (autosomal dominant demyelinating form); GDAP1, MTMR2, SBF2/MTMR13, KIAA1985, NDRG1 PRX for CMT4 (autosomal recessive demyelinating form), MFN2, KIF1B, RAB7, GARS, NEFL, HSPB1, HSPB8 for CMT2 (autosomal dominant axonal form); LMNA, GAN1, KCC3, TDP1, APTX, SETX for AR-CMT2 (autosomal recessive axonal form); GIB1 for CMTX (X-linked CMT); DNM2 for CMT-DI (autosomal dominant CMT with intermediate nerve conduction velocities); and DHH for minifascicular neuropathy. These discovered CMT causing genes/proteins include those which show unpredictable correlations with the peripheral nervous system. However, these genes/proteins are definitely important for the peripheral nerve, and their discovery should pave the way for dramatic progress in the understanding of peripheral nerve biology. On the other hand, genotype-phenotype correlations of these genes are also important in order to understand the pathomechanisms of inherited neuropathy. Because, based on mutation studies, a large number of genes associated with both the CMT1/4 and CMT2 forms have been identified, it is usually difficult to predict the causative gene based on clinical information from patients without specific complications. To clarify the specific features and molecular mechanisms of five diseases that we previously reported, we reviewed recent progress in HMSN-P linked to chromosome 3, CMT4F caused by PRX, CMT4A caused by GDAP1, CMT4B2 caused by SBF2/MTMR13, and SCAN1 caused by TDP1. HMSN-P is characterized by late onset, proximal dominant severe muscle weakness, fasciculations, muscle cramp and sensory involvement. HMSN-P is a primary neuronopathy. Mutations in periaxin are associated with a broad spectrum of demyelinating neuropathies including DSS, a sensory dominant form and early onset slowly progressive CMT. Pathologically, loss of myelinated fibers, demyelination, small onion bulb formations, tomacula formation and myelin foldings were seen in sural nerves. Absence of septate like junction in the paranodal loop suggests that periaxin could be required for the adhesion complex. GDAP1 is a relatively common cause of CMT4. Half of reported patients showed the demyelinating form, while the rest showed the axonal form. The typical feature of CMT4A is paresis of the vocal cords and diaphragm. CMT4B2 is characterized by autosomal recessive, juvenile onset glaucoma and focally folded myelin in sural nerves. SBF2/MTMR13 mutations cause CMT4B2. Early onset glaucoma was seen in patients with nonsense mutations. SBF2/MTMR13 and MTMR2, which is the cause of CMT4B1, could be acting on the same 3-phosphoinositide signaling pathway. Clinical phenotypes of patients with TDP1, APTX, or SETX mutations share common clinical findings, namely cerebellar ataxia and axonal neuropathy. TDP1 and aprataxin both act on the single strand break repair pathway, with TDP1 working specifically on topoisomerase I related SSBR. Senataxin is a RNA helicase acting on RNA maturation and termination in yeast. Since these three proteins share a common pathway, disruption in any of them could induce a delay in the transcription process. The low rate of protein supply could lead to deaths of large neuronal cells.
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PMID:[Molecular genetics of inherited neuropathies]. 1654 90

Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous group of disorders sharing the same clinical phenotype, characterized by distal limb muscle wasting and weakness, usually with skeletal deformities, distal sensory loss, and abnormalities of deep tendon reflexes. Mutations of genes involved in different functions eventually lead to a length-dependent axonal degeneration, which is the likely basis of the distal predominance of the CMT phenotype. Nerve conduction studies are important for classification, diagnosis, and understanding of pathophysiology. The subdivision into demyelinating CMT1 and axonal CMT2 types was a milestone and is still valid for the majority of patients. However, exceptions to this partition are increasing. Intermediate conduction velocities are often found in males with X-linked CMT (CMTX), and different intermediate CMT types have been identified. Moreover, for some genes, different mutations may result either in demyelinating CMT with slow conduction, or in axonal CMT. Nerve conduction slowing is uniform and diffuse in the most common CMT1A associated with the 17p12 duplication, whereas it is often asymmetric and nonhomogeneous in CMTX, sometimes rendering difficult the differential diagnosis with acquired inflammatory neuropathies. The demyelinating recessive forms, termed CMT4, usually have early onset and run a more severe course than the dominant types. Pure motor CMT types are now classified as distal hereditary motor neuronopathy. The diagnostic approach to the identification of the CMT subtype is complex and cannot be based on the clinical phenotype alone, as different forms are often clinically indistinguishable. However, there are features that may be of help in addressing molecular investigation in a single patient. Late onset, prominent or peculiar sensory manifestations, autonomic nervous system dysfunction, cranial nerve involvement, upper limb predominance, subclinical central nervous system abnormalities, severe scoliosis, early-onset glaucoma, neutropenia are findings helpful for diagnosis.
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PMID:Clinical and electrophysiological aspects of Charcot-Marie-Tooth disease. 1677 64

X-linked Charcot-Marie-Tooth disease is the second most common variant of CMT. CMTX1 is caused by mutations in the GJB1 gene encoding for connexin 32. We describe an Italian family with an intermediate CMTX phenotype with late onset. Mutation screening of the GJB1 gene revealed a 9-bp duplication leading to the insertion of three aminoacids (Thr-Val-Phe) between the end of the second extracellular domain and the beginning of the fourth transmembrane domain. This is the third in-frame insertion in the GJB1 gene identified so far and, like the previous ones, it consists in the duplication of the flanking sequence which is repeated in tandem in the wild-type gene.
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PMID:A novel 9-bp insertion in the GJB1 gene causing a mild form of X-linked CMT with late onset. 1705 5


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