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Desai M, Kaur N, Hu J. Ectopic expression of the RING domain of the Arabidopsis peroxin2 protein partially suppresses the phenotype of the photomorphogenic mutant de-etiolated1. PLoS One 2014; 9:e108473. [PMID: 25248106 PMCID: PMC4172754 DOI: 10.1371/journal.pone.0108473] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 08/27/2014] [Indexed: 11/25/2022] Open
Abstract
The Arabidopsis CONSTITUTIVE PHOTOMORPHOGENIC/DE-ETIOLATED 1/FUSCA (COP/DET1/FUS) proteins repress photomorphogenesis by degrading positive regulators of photomorphogenesis, such as the transcription factor LONG HYPOCOTYL5 (HY5). The gain-of-function mutant ted3, which partially suppresses the det1 mutant, contains a missense mutation of a Val-to-Met substitution before the C-terminal RING finger domain of the peroxisomal membrane protein PEROXIN2 (PEX2). We hypothesized that a truncated PEX2 protein, which only contains the C-terminal RING domain, is initiated by the ted3 mutation and by-passes the function of DET1 in the nucleus. Although we have not been able to detect this hypothetic peptide in vivo, we show in this study that, when fused with a fluorescent protein and overexpressed, the PEX2 RING domain can localize to the nucleus, where it is able to interact with HY5, and PEX2 RING domain overexpression in det1 also partially suppresses the det1 phenotype. Compared with det1, ted3 det1 plants have significantly decreased levels of the HY5 protein and the expression of most of the analyzed HY5 target genes is altered to levels comparable to those in hy5. We conclude that compromised activity of HY5 may have been mainly responsible for the partial reversal of the det1 phenotype in ted3 det1. Our data support the notion that, when appropriately localized, some RING finger domains may be able to achieve neomorphic effects in the cell.
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Affiliation(s)
- Mintu Desai
- Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan, United States of America
| | - Navneet Kaur
- Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan, United States of America
| | - Jianping Hu
- Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan, United States of America
- Plant Biology Department, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
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Senderek J, Hermanns B, Bergmann C, Boroojerdi B, Bajbouj M, Hungs M, Ramaekers VT, Quasthoff S, Karch D, Schröder JM. X-linked dominant Charcot-Marie-Tooth neuropathy: clinical, electrophysiological, and morphological phenotype in four families with different connexin32 mutations(1). J Neurol Sci 1999; 167:90-101. [PMID: 10521546 DOI: 10.1016/s0022-510x(99)00146-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The sensorimotor neuropathy of the Charcot-Marie-Tooth type (CMT) is the most common hereditary disorder of the peripheral nervous system. The X-linked dominant form of CMT (CMTX) is associated with mutations in the gene for the gap junction protein connexin32. We examined four CMTX pedigrees two of which had potentially novel mutations in the only coding exon of connexin32. One previously unreported missense mutation, Ala39Val, was found in a family displaying a CMT phenotype with additional upper limb postural tremor reminiscent of a Roussy-Lévy syndrome. A novel single base insertion, 679insT, is among the first mutations found in the fourth transmembrane domain of connexin32. Frameshift and premature stop of translation are supposed to result in a non-functional carboxy-terminus. Two further families had the known missense mutations Arg15Trp and Arg22Gln. Several female carriers were found normal on clinical presentation, however, the genotype was paralleled by decreased nerve conduction velocities (NCV) and slowed central conduction of brain stem auditory evoked responses (BAER). Median motor NCVs showed mild (in women) to intermediate (in males) reduction, indicating a peripheral neuropathy with a predominating axonal component. Nerve biopsy findings were consistent with the electrophysiological data showing a marked loss of large myelinated fibres and clusters of regenerating axons. Electron microscopy revealed various alterations of the axoglial attachment zone. This suggests defective axon-Schwann cell interactions which may induce the axonopathy in CMTX.
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Affiliation(s)
- J Senderek
- Institut für Neuropathologie, Universitätsklinikum der Rheinisch-Westfälischen Technischen Hochschule, Pauwelsstrasse 30, D-52074, Aachen, Germany
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3
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Valentijn LJ, Baas F. Genetic basis of peripheral neuropathies. PROGRESS IN BRAIN RESEARCH 1999; 117:249-64. [PMID: 9932413 DOI: 10.1016/s0079-6123(08)64020-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Affiliation(s)
- L J Valentijn
- Department of Neurology, K2-214 Academic Medical Center, Amsterdam, The Netherlands
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4
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Nelis E, Haites N, Van Broeckhoven C. Mutations in the peripheral myelin genes and associated genes in inherited peripheral neuropathies. Hum Mutat 1999; 13:11-28. [PMID: 9888385 DOI: 10.1002/(sici)1098-1004(1999)13:1<11::aid-humu2>3.0.co;2-a] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The peripheral myelin protein 22 gene (PMP22), the myelin protein zero gene (MPZ, P0), and the connexin 32 gene (Cx32, GJB1) code for membrane proteins expressed in Schwann cells of the peripheral nervous system (PNS). The early growth response 2 gene (EGR2) encodes a transcription factor that may control myelination in the PNS. Mutations in the respective genes, located on human chromosomes 17p11.2, 1q22-q23, Xq13.1, and 10q21.1-q22.1, are associated with several inherited peripheral neuropathies. To date, a genetic defect in one of these genes has been identified in over 1,000 unrelated patients manifesting a wide range of phenotypes, i.e., Charcot-Marie-Tooth disease type 1 (CMT1) and type 2 (CMT2), Dejerine-Sottas syndrome (DSS), hereditary neuropathy with liability to pressure palsies (HNPP), and congenital hypomyelination (CH). This large number of genetically defined patients provides an exceptional opportunity to examine the correlation between phenotype and genotype.
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Affiliation(s)
- E Nelis
- Flanders Interuniversity Institute for Biotechnology (VIB), Born-Bunge Foundation, University of Antwerp, Department of Biochemistry, Belgium
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5
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Haites NE, Nelis E, Van Broeckhoven C. 3rd workshop of the European CMT consortium: 54th ENMC International Workshop on genotype/phenotype correlations in Charcot-Marie-Tooth type 1 and hereditary neuropathy with liability to pressure palsies 28-30 November 1997, Naarden, The Netherlands. Neuromuscul Disord 1998; 8:591-603. [PMID: 10093067 DOI: 10.1016/s0960-8966(98)00067-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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6
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Bell C, Haites N. The peripheral neuropathies and their molecular genetics. ADVANCES IN GENETICS 1998; 36:1-44. [PMID: 9348652 DOI: 10.1016/s0065-2660(08)60306-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- C Bell
- Department of Medicine and Therapeutics, University of Aberdeen Medical School, Scotland
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7
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Abstract
The X-linked form of Charcot-Marie-Tooth neuropathy is associated with mutations in the connexin32 (Cx32) gene. The functional role of Cx32 in Schwann cells and the relationship of these mutations to the progressive axonal loss and distal limb weakness seen in this disease have not been elucidated. To investigate the local influence of Schwann cells bearing the Cx32 gene defect on axonal cytoskeleton and the myelination process, the nerve xenograft model was used to transfer a Cx32 missense mutation (Glu102Gly) from human to an in vivo myelination system in nude mice. Twelve nerve grafts from two family members with Cx32 mutations and 17 grafts from three healthy individuals were generated by end-to-end anastomosis of approximately 6-mm sural nerve fascicles into the cut ends of the sciatic nerve in nude mice. Specimens were examined at 2, 4, 8, 12, and 16 weeks. Ultrastructural morphometric analysis showed Schwann cells with Cx32 mutation have a profound effect on the nude mice axons, resulting in an increase in neurofilament density, a depletion of microtubules associated with fragmentation of smooth axonal reticulum, and increased vesicles and mitochondria. At 16 weeks, axonal enlargement was evident within the proximal part of the graft; axonal atrophy, degeneration, and fiber loss were seen in distal-graft and host segments. The myelination process was not affected. We conclude that Cx32 mutation impairs a modulatory function of Schwann cells on axons, resulting in profound cytoskeletal alterations leading to distal axonal degeneration. These observations emphasize the role of impaired Schwann cell-axon interactions in the pathogenesis of hereditary neuropathies.
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Affiliation(s)
- Z Sahenk
- Department of Neurology, Neuromuscular Disease Center, The Ohio State University, Columbus 43210, USA.
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Affiliation(s)
- E Sorour
- Institute of Medical Genetics, University Hospital of Wales Heath Park, Cardiff
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9
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Sillén A, Annerén G, Dahl N. A novel mutation (C201R) in the transmembrane domain of connexin 32 in severe X-linked Charcot-Marie-Tooth disease. Hum Mutat 1998; Suppl 1:S8-9. [PMID: 9452025 DOI: 10.1002/humu.1380110104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- A Sillén
- Department of Clinical Genetics, Uppsala University Childrens Hospital, Sweden
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10
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Oh S, Ri Y, Bennett MV, Trexler EB, Verselis VK, Bargiello TA. Changes in permeability caused by connexin 32 mutations underlie X-linked Charcot-Marie-Tooth disease. Neuron 1997; 19:927-38. [PMID: 9354338 DOI: 10.1016/s0896-6273(00)80973-3] [Citation(s) in RCA: 188] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The relationship between the loss of connexin 32 function and clinical manifestations of X-linked Charcot-Marie-Tooth (CMTX) disease is unknown. Here, we report that eight of nine CMTX mutations investigated form channels with measurable electrical conductance. Single-channel studies of two mutations demonstrate reduced junctional permeability caused by a decrease in either pore size (S26L) or open channel probability (M34T) that favors residency in a low-conductance substate. Permeation of second messengers such as cAMP through reflexive gap junctions between adjacent cytoplasmic loops of myelinating Schwann cells is likely to be reduced or absent in these channels. We propose that CMTX mutations impair the transduction of signals arising from normal glial-neuronal interactions and thereby cause demyelination and axonal degeneration.
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Affiliation(s)
- S Oh
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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11
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Abstract
The distribution and cellular localization of connexin32 (Cx32) in the brain and spinal cord of the mouse and rat was investigated by light microscope (LM) and electron microscope (EM) immunohistochemistry by using several different antibodies against Cx32. By double immunofluorescence staining for Cx32 and either the oligodendrocyte markers cyclic nucleotide phosphodiesterase (CNPase) or Rip, Cx32 was consistently found in oligodendrocyte cell bodies and proximal processes. Cx32 immunoreactivity was also clearly visualized along CNPase- and Rip-positive myelinated fibers. Both immunopositive cells and fibers were heterogeneously distributed and were often more intensely labeled when dispersed in or associated with regions of gray matter than when concentrated in major white matter tracts. Labeling of myelin sheaths along fibers was restricted to subpopulations of myelinated axons. In the cerebellar cortex, for example, it was selectively localized to sheaths around Purkinje cell axons. Punctate staining, distinct from that corresponding to cells or fibers, was evident in the olfactory bulb and hippocampus. By EM, oligodendrocytes exhibited cytoplasmic labeling associated with rough endoplasmic reticulum and Golgi apparatus. Their processes were intermittently stained, most intensely when surrounding myelinated fibers and occasionally in paranodal loops. Cx32-immunoreactive gap junctions with symmetric labeling (staining on both junctional membranes) were observed between oligodendrocytic somata and processes as well as between presumptive oligodendrocytic processes. Unidentifiable elements forming asymmetrically labeled gap junctions (staining only one side of junctional membranes) were less frequently encountered. Western blot analysis confirmed anti-Cx32 antibody detection of Cx32 in whole brain homogenates and an enrichment of the protein in isolated myelin fractions. These results are consistent with earlier ultrastructural studies showing the occurrence of inter-oligodendrocytic gap junctions, but indicate that these may be more prevalent than previously thought. Furthermore, the results suggest a specialized role of gap junctions composed of Cx32 along myelinated fibers belonging to subpopulations of neurons.
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Affiliation(s)
- J Li
- Department of Physiology, University of Manitoba, Winnipeg, Canada
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12
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Nelis E, Simokovic S, Timmerman V, Löfgren A, Backhovens H, De Jonghe P, Martin JJ, Van Broeckhoven C. Mutation analysis of the connexin 32 (Cx32) gene in Charcot-Marie-Tooth neuropathy type 1: identification of five new mutations. Hum Mutat 1997; 9:47-52. [PMID: 8990008 DOI: 10.1002/(sici)1098-1004(1997)9:1<47::aid-humu8>3.0.co;2-m] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- E Nelis
- Born Bunge Foundation, University of Antwerp, Department of Biochemistry, Belgium
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13
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Bone LJ, Deschênes SM, Balice-Gordon RJ, Fischbeck KH, Scherer SS. Connexin32 and X-linked Charcot-Marie-Tooth disease. Neurobiol Dis 1997; 4:221-30. [PMID: 9361298 DOI: 10.1006/nbdi.1997.0152] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Mutations in the gap junction gene connexin32 (Cx32) cause the X-linked form of Charcot-Marie-Tooth disease, an inherited demyelinating neuropathy. More than 130 different mutations have been described, affecting all portions of the Cx32 protein. In transfected cells, the mutant Cx32 proteins encoded by some Cx32 mutations fall to reach the cell surface; other mutant proteins reach the cell surface, but only one of these forms functional gap junctions. In peripheral nerve, Cx32 is localized to incisures and paranodes, regions of noncompact myelin within the myelin sheath. This localization suggests that Cx32 forms "reflexive" gap junctions that allow ions and small molecules to diffuse directly across the myelin sheath, which is a thousandfold shorter distance than the circumferential pathway through the Schwann cell cytoplasm. Cx32 mutations may interrupt this shorter pathway or have other toxic effects, thereby injuring myelinating Schwann cells and their axons.
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Affiliation(s)
- L J Bone
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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14
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Rouger H, LeGuern E, Birouk N, Gouider R, Tardieu S, Plassart E, Gugenheim M, Vallat JM, Louboutin JP, Bouche P, Agid Y, Brice A. Charcot-Marie-Tooth disease with intermediate motor nerve conduction velocities: characterization of 14 Cx32 mutations in 35 families. Hum Mutat 1997; 10:443-52. [PMID: 9401007 DOI: 10.1002/(sici)1098-1004(1997)10:6<443::aid-humu5>3.0.co;2-e] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Charcot-Marie-Tooth disease can be inherited either autosomal dominantly or recessively or linked to the X chromosome. X-linked dominant Charcot-Marie-Tooth disease (CMTX) is a sensorimotor peripheral neuropathy in which males have usually more severe clinical symptoms and decreased nerve conduction velocities than do females. CMTX is usually associated with mutations in exon 2 of the connexin 32 (Cx32) gene. DNA from 35 unrelated CMT patients, without the 17p11.2 duplication, but with median nerve conduction between 30 and 40 m/s, were tested for the presence of Cx32 mutations. The entire coding sequence of the Cx32 gene was explored using a rapid nonradioactive technique to detect single-strand conformation polymorphisms (SSCP) on large PCR fragments. Thirteen abnormal SSCP profiles were detected and characterized by sequencing. In addition, systematic sequencing of the entire Cx32 coding region in the remaining index cases revealed another mutation that was not detected by SSCP. A total of 14 mutations were found, five of which were not previously reported. These results demonstrate the high frequency (40%) of mutations in the coding region of the Cx32 gene in CMT patients with intermediate MNCV, without 17p11.2 duplications. Most of these mutations (93%) can be detected by SSCP.
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15
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Murakami T, Garcia CA, Reiter LT, Lupski JR. Charcot-Marie-Tooth disease and related inherited neuropathies. Medicine (Baltimore) 1996; 75:233-50. [PMID: 8862346 DOI: 10.1097/00005792-199609000-00001] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Charcot-Marie-Tooth disease (CMT) was initially described more than 100 years ago by Charcot, Marie, and Tooth. It was only recently, however, that molecular genetic studies of CMT have uncovered the underlying causes of most forms of the diseases. Most cases of CMT1 are associated with a 1.5-Mb tandem duplication in 17p11.2-p12 that encompasses the PMP22 gene. Although many genes may exist in this large duplicated region, PMP22 appears to be the major dosage-sensitive gene. CMT1A is the first autosomal dominant disease associated with a gene dosage effect due to an inherited DNA rearrangement. There is no mutant gene, but instead the disease phenotype results from having 3 copies of a normal gene. Furthermore, these findings suggest that therapeutic intervention in CMT1A duplication patients may be possible by normalizing the amount of PMP22 mRNA levels. Alternatively, CMT1A can be caused by mutations in the PMP22 gene. Other forms of CMT are associated with mutations in the MPZ (CMT1B) and Cx32 (CMTX) genes. Thus, mutations in different genes can cause similar CMT phenotypes. The related but more severe neuropathy, Dejerine-Sottas syndrome (DSS), can also be caused by mutations in the PMP22 and MPZ genes. All 3 genes thus far identified by CMT researchers appear to play an important role in the myelin formation or maintenance of peripheral nerves. CMT1A, CMT1B, CMTX, hereditary neuropathy with liability to pressure palsies (HNPP), and DSS have been called myelin disorders or "myelino-pathies." Other demyelinating forms, CMT1C and CMT-AR, may be caused by mutations of not yet identified myelin genes expressed in Schwann cells. The clinically distinct disease HNPP is caused by a 1.5-Mb deletion in 17p11.2-p12, which spans the same region duplicated in most CMT1A patients. Underexpression of the PMP22 gene causes HNPP just as overexpression of PMP22 causes CMT1A. Thus, 2 different phenotypes can be caused by dosage variations of the same gene. It is apparent that the CMT1A duplication and HNPP deletion are the reciprocal products of a recombination event during meiosis mediated through the CMT1A-REPs. CMT1A and HNPP could be thought of as a "genomic disease" more than single gene disorders. Other genetic disorders may also prove to arise from recombination events mediated by specific chromosomal structural features of the human genome (102). Further studies on the recombination mechanism of CMT and HNPP might reveal the causes of site specific homologous recombination in the human genome. The discovery of the PMP22 gene in the 1.5-Mb CMT1A duplication/HNPP deletion critical region also suggests that the clinical phenotype of chromosome aneuploid syndromes may result from the effect of a small subset of dosage-sensitive genes mapping within the region of aneuploidy. The understanding of the molecular basis of CMT1 and related disorders has allowed accurate DNA diagnosis and genetic counseling of inherited peripheral neuropathies and will make it possible to develop rational strategies for therapy. As several loci for CMT2 have been identified, the genes responsible for CMT2 will most likely be disclosed using positional cloning and candidate gene approaches in the near future.
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Affiliation(s)
- T Murakami
- Departments of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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16
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Neuhaus IM, Bone L, Wang S, Ionasescu V, Werner R. The human connexin32 gene is transcribed from two tissue-specific promoters. Biosci Rep 1996; 16:239-48. [PMID: 8842374 DOI: 10.1007/bf01207338] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The connexin32 (cx32) gene codes for the gap junction protein found in liver, pancreas and nervous tissue. Recently mutations in the coding region of this gene have been associated with the dominant X-linked form of Charcot-Marie-Tooth (CMTX1) neuropathy. Since some CMTX1 patients show no mutations in their cx32 gene coding region, it was speculated that these patients carry mutations in the promoter region of the gene. This paper describes the organization of the human cx32 gene and its tissue-specific transcription. The gene consists of three exons that are alternatively spliced to produce mRNAs with different 5'-untranslated regions (UTRs). Transcription is initiated from two tissue-specific promoters. In liver and pancreas, promoter P1, located more than 8 kb upstream of the translation start codon, is used, and the transcript is processed to remove a large intron. In contrast, in nerve cells, transcription is initiated from promoter P2, located 497 bp upstream from the translation start codon, and the transcript is processed to remove a small 355-pb intron. The downstream exon, which includes the entire coding sequence, is shared by both mRNAs. CMTX1 patients with a normal cx32 coding region are expected to have mutations in this newly described promoter P2 rather than the known promoter P1.
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Affiliation(s)
- I M Neuhaus
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Florida 33101, USA
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17
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Omori Y, Mesnil M, Yamasaki H. Connexin 32 mutations from X-linked Charcot-Marie-Tooth disease patients: functional defects and dominant negative effects. Mol Biol Cell 1996; 7:907-16. [PMID: 8816997 PMCID: PMC275942 DOI: 10.1091/mbc.7.6.907] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have characterized the function of connexin (Cx) 32 gene mutations found in X-linked dominant Charcot-Marie-Tooth disease with respect to their ability to form functional gap junctions among themselves and to inactivate wild-type Cx32 by a dominant negative mechanism. We prepared four types of Cx32 mutant cDNAs and transfected them into HeLa cells, which do not show detectable levels of gap junctional intercellular communication (GJIC), nor expression of any connexins examined. Cells transfected with the wild-type Cx32 gene, but not those transfected with three different base substitution mutations (i.e. Cys 60 to Phe, Val 139 to Met, and Arg 215 to Trp), restored GJIC. Unexpectedly, in cells transfected with a nonsense mutant at codon 220, there was also restored GJIC. When we double-transfected these mutant constructs into the HeLa cells that had already been transfected with the wild-type Cx32 gene and thus were GJIC proficient, three base substitution mutants inhibited GJIC, suggesting that these three mutants can eliminate the function of wild-type Cx32 in a dominant negative manner. The nonsense mutation at codon 220 did not show such a dominant negative effect. Since both mutant and wild-type Cx32 mRNAs were detected, but only poor Cx32 protein expression at cell-cell contact areas was observed in the double transfectants, it is suggested that certain mutants form nonfunctional chimeric connexons with wild-type connexins, which are not properly inserted into the cytoplasmic membrane.
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Affiliation(s)
- Y Omori
- Unit of Multistage Carcinogenesis, International Agency for Research on Cancer, Lyon, France
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Oterino A, Montón FI, Cabrera VM, Pinto F, Gonzalez A, Lavilla NR. Arginine-164-tryptophan substitution in connexin32 associated with X linked dominant Charcot-Marie-Tooth disease. J Med Genet 1996; 33:413-5. [PMID: 8733054 PMCID: PMC1050613 DOI: 10.1136/jmg.33.5.413] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A Spanish family with X linked dominant Charcot-Marie-Tooth (CMTX1) neuropathy was screened for point mutations in the connexin32 gene (GJ beta 1). The patients showed a C-T transition at position 552 which predicts arginine to tryptophan substitution at amino acid 164 (R164K). This mutation destroys an AciI restriction site at position 552 and creates a PflMI restriction site.
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Affiliation(s)
- A Oterino
- Hospital Nuestra Señora La Candelaria, Santa Cruz de Tenerife, Spain
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19
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Yoshimura T, Ohnishi A, Yamamoto T, Fukushima Y, Kitani M, Kobayashi T. Two novel mutations (C53S, S26L) in the connexin32 of Charcot-Marie-Tooth disease type X families. Hum Mutat 1996; 8:270-2. [PMID: 8889588 DOI: 10.1002/(sici)1098-1004(1996)8:3<270::aid-humu12>3.0.co;2-#] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- T Yoshimura
- Department of Neurology, Neurological Institute, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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20
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21
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Tan CC, Ainsworth PJ, Hahn AF, MacLeod PM. Novel mutations in the connexin 32 gene associated with X-linked Charcot-Marie tooth disease. Hum Mutat 1996; 7:167-71. [PMID: 8829637 DOI: 10.1002/(sici)1098-1004(1996)7:2<167::aid-humu14>3.0.co;2-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- C C Tan
- Department of Medical Biochemistry, University of Western Ontario, Victoria Hospital, London, Canada
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22
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Schiavon F, Fracasso C, Mostacciuolo ML. Novel missense mutation of the connexin32 (GJB1) gene in X-linked dominant Charcot-Marie-Tooth neuropathy. Hum Mutat 1996; 8:83-4. [PMID: 8807343 DOI: 10.1002/(sici)1098-1004(1996)8:1<83::aid-humu14>3.0.co;2-n] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- F Schiavon
- Department of Biology, University of Padua, Italy
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23
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Gupta S, Benstead T, Neumann P, Guernsey D. A point mutation in codon 3 of connexin-32 is associated with X-linked Charcot-Marie-Tooth neuropathy. Hum Mutat 1996; 8:375-6. [PMID: 8956046 DOI: 10.1002/(sici)1098-1004(1996)8:4<375::aid-humu14>3.0.co;2-#] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- S Gupta
- Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
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Snipes GJ, Suter U. Molecular basis of common hereditary motor and sensory neuropathies in humans and in mouse models. Brain Pathol 1995; 5:233-47. [PMID: 8520723 DOI: 10.1111/j.1750-3639.1995.tb00600.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The Hereditary Motor and Sensory Neuropathies (HMSNs) are well known to be clinically, morphologically, and genetically heterogeneous. Yet, recent advances in the cellular and molecular biology of the peripheral nervous system coupled with remarkable progress in human and mouse genetics have provided a framework that has profoundly changed our understanding of the pathogenesis of these diseases. It now appears that most of the HMSNs are related to mutations affecting genes encoding Schwann cell proteins, specifically the Peripheral Myelin Protein PMP22, Myelin Protein Zero, and one of the gap junction proteins, connexin-32. Accordingly, these findings are discussed in the context of the clinical and pathologic features of the human HMSNs, but are interpreted in the context of basic research findings on the cellular and molecular biology of the peripheral nervous system derived from in vivo and in vitro studies in spontaneously-occurring and genetically engineered animal models for the HMSNs.
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Affiliation(s)
- G J Snipes
- Department of Neurobiology, Stanford University School of Medicine, California 94305, USA
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25
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Spray DC, Dermietzel R. X-linked dominant Charcot—Marie—Tooth disease and other potential gap-junction diseases of the nervous system. Trends Neurosci 1995. [DOI: 10.1016/0166-2236(95)80004-l] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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