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Prukop T, Wernick S, Boussicault L, Ewers D, Jäger K, Adam J, Winter L, Quintes S, Linhoff L, Barrantes-Freer A, Bartl M, Czesnik D, Zschüntzsch J, Schmidt J, Primas G, Laffaire J, Rinaudo P, Brureau A, Nabirotchkin S, Schwab MH, Nave KA, Hajj R, Cohen D, Sereda MW. Synergistic PXT3003 therapy uncouples neuromuscular function from dysmyelination in male Charcot-Marie-Tooth disease type 1A (CMT1A) rats. J Neurosci Res 2020; 98:1933-1952. [PMID: 32588471 DOI: 10.1002/jnr.24679] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 05/13/2020] [Accepted: 05/31/2020] [Indexed: 12/11/2022]
Abstract
Charcot-Marie-Tooth disease 1 A (CMT1A) is caused by an intrachromosomal duplication of the gene encoding for PMP22 leading to peripheral nerve dysmyelination, axonal loss, and progressive muscle weakness. No therapy is available. PXT3003 is a low-dose combination of baclofen, naltrexone, and sorbitol which has been shown to improve disease symptoms in Pmp22 transgenic rats, a bona fide model of CMT1A disease. However, the superiority of PXT3003 over its single components or dual combinations have not been tested. Here, we show that in a dorsal root ganglion (DRG) co-culture system derived from transgenic rats, PXT3003 induced myelination when compared to its single and dual components. Applying a clinically relevant ("translational") study design in adult male CMT1A rats for 3 months, PXT3003, but not its dual components, resulted in improved performance in behavioral motor and sensory endpoints when compared to placebo. Unexpectedly, we observed only a marginally increased number of myelinated axons in nerves from PXT3003-treated CMT1A rats. However, in electrophysiology, motor latencies correlated with increased grip strength indicating a possible effect of PXT3003 on neuromuscular junctions (NMJs) and muscle fiber pathology. Indeed, PXT3003-treated CMT1A rats displayed an increased perimeter of individual NMJs and a larger number of functional NMJs. Moreover, muscles of PXT3003 CMT1A rats displayed less neurogenic atrophy and a shift toward fast contracting muscle fibers. We suggest that ameliorated motor function in PXT3003-treated CMT1A rats result from restored NMJ function and muscle innervation, independent from myelination.
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Affiliation(s)
- Thomas Prukop
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Institute of Clinical Pharmacology, University Medical Center Göttingen, Göttingen, Germany
| | - Stephanie Wernick
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
| | | | - David Ewers
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
| | - Karoline Jäger
- Department of Neurology, University Medical Center Göttingen, Göttingen, Germany
| | - Julia Adam
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Lorenz Winter
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Susanne Quintes
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
| | - Lisa Linhoff
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
| | | | - Michael Bartl
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
| | - Dirk Czesnik
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
| | - Jana Zschüntzsch
- Department of Neurology, University Medical Center Göttingen, Göttingen, Germany
| | - Jens Schmidt
- Department of Neurology, University Medical Center Göttingen, Göttingen, Germany
| | | | | | | | | | | | - Markus H Schwab
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | | | | | - Michael W Sereda
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Department of Clinical Neurophysiology, University Medical Center Göttingen, Göttingen, Germany
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Chittoor-Vinod VG, Bazick H, Todd AG, Falk D, Morelli KH, Burgess RW, Foster TC, Notterpek L. HSP90 Inhibitor, NVP-AUY922, Improves Myelination in Vitro and Supports the Maintenance of Myelinated Axons in Neuropathic Mice. ACS Chem Neurosci 2019; 10:2890-2902. [PMID: 31017387 PMCID: PMC6588339 DOI: 10.1021/acschemneuro.9b00105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
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Hereditary
demyelinating neuropathies linked to peripheral myelin
protein 22 (PMP22) involve the disruption of normal protein trafficking
and are therefore relevant targets for chaperone therapy. Using a
small molecule HSP90 inhibitor, EC137, in cell culture models, we
previously validated the chaperone pathway as a viable target for
therapy development. Here, we tested five commercially available inhibitors
of HSP90 and identified BIIB021 and AUY922 to support Schwann cell
viability and enhance chaperone expression. AUY922 showed higher efficacy,
compared to BIIB021, in enhancing myelin synthesis in dorsal root
ganglion explant cultures from neuropathic mice. For in vivo testing,
we randomly assigned 2–3 month old C22 and 6 week old Trembler
J (TrJ) mice to receive two weekly injections of either vehicle or
AUY922 (2 mg/kg). By the intraperitoneal (i.p.) route, the drug was
well-tolerated by all mice over the 5 month long study, without influence
on body weight or general grooming behavior. AUY922 improved the maintenance
of myelinated nerves of both neuropathic models and attenuated the
decline in rotarod performance and peak muscle force production in
C22 mice. These studies highlight the significance of proteostasis
in neuromuscular function and further validate the HSP90 pathway as
a therapeutic target for hereditary neuropathies.
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Affiliation(s)
- Vinita G. Chittoor-Vinod
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
| | - Hannah Bazick
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
| | - Adrian G. Todd
- Department of Pediatrics, Powell Gene Therapy Center, University of Florida, Gainesville, Florida 32611, United States
| | - Darin Falk
- Department of Pediatrics, Powell Gene Therapy Center, University of Florida, Gainesville, Florida 32611, United States
| | - Kathryn H. Morelli
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, Maine 04469, United States
- The Jackson Laboratory, Bar Harbor, Maine 04609, United States
| | - Robert W. Burgess
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, Maine 04469, United States
- The Jackson Laboratory, Bar Harbor, Maine 04609, United States
| | - Thomas C. Foster
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
| | - Lucia Notterpek
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
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Prukop T, Stenzel J, Wernick S, Kungl T, Mroczek M, Adam J, Ewers D, Nabirotchkin S, Nave KA, Hajj R, Cohen D, Sereda MW. Early short-term PXT3003 combinational therapy delays disease onset in a transgenic rat model of Charcot-Marie-Tooth disease 1A (CMT1A). PLoS One 2019; 14:e0209752. [PMID: 30650121 PMCID: PMC6334894 DOI: 10.1371/journal.pone.0209752] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 12/11/2018] [Indexed: 12/13/2022] Open
Abstract
The most common type of Charcot-Marie-Tooth disease is caused by a duplication of PMP22 leading to dysmyelination, axonal loss and progressive muscle weakness (CMT1A). Currently, no approved therapy is available for CMT1A patients. A novel polytherapeutic proof-of-principle approach using PXT3003, a low-dose combination of baclofen, naltrexone and sorbitol, slowed disease progression after long-term dosing in adult Pmp22 transgenic rats, a known animal model of CMT1A. Here, we report an early postnatal, short-term treatment with PXT3003 in CMT1A rats that delays disease onset into adulthood. CMT1A rats were treated from postnatal day 6 to 18 with PXT3003. Behavioural, electrophysiological, histological and molecular analyses were performed until 12 weeks of age. Daily oral treatment for approximately 2 weeks ameliorated motor deficits of CMT1A rats reaching wildtype levels. Histologically, PXT3003 corrected the disturbed axon calibre distribution with a shift towards large motor axons. Despite dramatic clinical amelioration, only distal motor latencies were improved and correlated with phenotype performance. On the molecular level, PXT3003 reduced Pmp22 mRNA overexpression and improved the misbalanced downstream PI3K-AKT / MEK-ERK signalling pathway. The improved differentiation status of Schwann cells may have enabled better long-term axonal support function. We conclude that short-term treatment with PXT3003 during early development may partially prevent the clinical and molecular manifestations of CMT1A. Since PXT3003 has a strong safety profile and is currently undergoing a phase III trial in CMT1A patients, our results suggest that PXT3003 therapy may be a bona fide translatable therapy option for children and young adolescent patients suffering from CMT1A.
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Affiliation(s)
- Thomas Prukop
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
- University Medical Center Göttingen, Institute of Clinical Pharmacology, Göttingen, Germany
| | - Jan Stenzel
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | - Stephanie Wernick
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | - Theresa Kungl
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | - Magdalena Mroczek
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | - Julia Adam
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | - David Ewers
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | | | - Klaus-Armin Nave
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | | | | | - Michael W. Sereda
- Max-Planck-Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
- University Medical Center Göttingen, Department of Clinical Neurophysiology, Göttingen, Germany
- * E-mail:
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Abstract
For a subset of genes in our genome a change in gene dosage, by duplication or deletion, causes a phenotypic effect. These dosage-sensitive genes may confer an advantage upon copy number change, but more typically they are associated with disease, including heart disease, cancers and neuropsychiatric disorders. This gene copy number sensitivity creates characteristic evolutionary constraints that can serve as a diagnostic to identify dosage-sensitive genes. Though the link between copy number change and disease is well-established, the mechanism of pathogenicity is usually opaque. We propose that gene expression level may provide a common basis for the pathogenic effects of many copy number variants.
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Affiliation(s)
- Alan M Rice
- Smurfit Institute of Genetics, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - Aoife McLysaght
- Smurfit Institute of Genetics, Trinity College Dublin, University of Dublin, Dublin 2, Ireland.
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5
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Wood J, Sames L, Moore A, Ekins S. Multifaceted roles of ultra-rare and rare disease patients/parents in drug discovery. Drug Discov Today 2013; 18:1043-51. [PMID: 23968993 DOI: 10.1016/j.drudis.2013.08.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 07/29/2013] [Accepted: 08/07/2013] [Indexed: 01/10/2023]
Abstract
Individual parents and patients are increasingly doing more to fund, discover and develop treatments for rare and ultra-rare diseases that afflict their children, themselves or their friends. They are performing roles in business development that would be classed as entrepreneurial; and their organizational roles in driving the science in some cases are equivalent to those of principal investigators. These roles are in addition to their usual positioning as advocates. Through their efforts and those of the collaborative networks that they have developed, they could be positioned to disrupt the usual course of drug discovery. This can be illustrated using three different ultra-rare disease parent/patient advocate groups and the diseases for which they are developing treatments. This represents an alternative model for pharmaceutical research.
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Affiliation(s)
- Jill Wood
- Jonah's Just Begun, P.O. Box 150057, Brooklyn, NY 11215, USA; Phoenix Nest, P.O. Box 150057, Brooklyn, NY 11215, USA
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Tavakoli M, Marshall A, Banka S, Petropoulos IN, Fadavi H, Kingston H, Malik RA. Corneal confocal microscopy detects small-fiber neuropathy in Charcot-Marie-Tooth disease type 1A patients. Muscle Nerve 2012; 46:698-704. [PMID: 22996176 PMCID: PMC3469745 DOI: 10.1002/mus.23377] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2012] [Indexed: 11/08/2022]
Abstract
INTRODUCTION Although unmyelinated nerve fibers are affected in Charcot-Marie-Tooth type 1A (CMT1A) disease, they have not been studied in detail due to the invasive nature of the techniques needed to study them. We established alterations in C-fiber bundles of the cornea in patients with CMT1A using non-invasive corneal confocal microscopy (CCM). METHODS Twelve patients with CMT1A and 12 healthy control subjects underwent assessment of neuropathic symptoms and deficits, electrophysiology, quantitative sensory testing, corneal sensitivity, and corneal confocal microscopy. RESULTS Corneal sensitivity, corneal nerve fiber density, corneal nerve branch density, corneal nerve fiber length, and corneal nerve fiber tortuosity were significantly reduced in CMT1A patients compared with controls. There was a significant correlation between corneal sensation and CCM parameters with the severity of painful neuropathic symptoms, cold and warm thresholds, and median nerve CMAP amplitude. CONCLUSIONS CCM demonstrates significant damage to C-fiber bundles, which relates to some measures of neuropathy in CMT1A patients.
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Affiliation(s)
- Mitra Tavakoli
- Division of Cardiovascular Medicine, University of Manchester and Wellcome Trust Clinical Research Facility, Manchester, UK
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7
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Verrier JD, Semple-Rowland S, Madorsky I, Papin JE, Notterpek L. Reduction of Dicer impairs Schwann cell differentiation and myelination. J Neurosci Res 2011; 88:2558-68. [PMID: 20648646 DOI: 10.1002/jnr.22418] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The process of Schwann cell myelination requires precisely coordinated gene expression. At the onset of myelination, there is an increase in the expression of differentiation-promoting transcription factors that regulate key Schwann cell genes. Further control of myelin gene expression occurs at the posttranscriptional level and, in part, is mediated by RNA binding proteins and micro-RNAs (miRNAs). miRNAs are small, endogenously derived RNA molecules that repress gene expression by specifically binding to their mRNA targets. In the experiments described here, we tested whether miRNAs were essential in controlling myelination by reducing the levels of Dicer, an essential endoribonuclease in miRNA biogenesis. We decreased the expression of Dicer by about 60% within Schwann cells using a lentiviral vector expressing an shRNA against Dicer. The reduced levels of Dicer led to a decrease in the steady-state expression of selected miRNAs and of the transcription factors Oct6 and Egr2/Krox20, both of which are critical for Schwann cells differentiation and myelination. In contrast, the levels of c-jun and Sox2 were up-regulated by the reduction in Dicer and were associated with an increase in Schwann cell proliferation. In dorsal root ganglion cocultures, Schwann cells transduced with Dicer shRNA synthesized less myelin, which was accompanied by significant reductions in the levels of myelin basic protein and protein zero. These findings support a critical role for Dicer and miRNAs in Schwann cell differentiation and myelination.
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Affiliation(s)
- Jonathan D Verrier
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida 32610-0244, USA
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8
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Verrier JD, Lau P, Hudson L, Murashov AK, Renne R, Notterpek L. Peripheral myelin protein 22 is regulated post-transcriptionally by miRNA-29a. Glia 2009; 57:1265-79. [PMID: 19170179 DOI: 10.1002/glia.20846] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Peripheral myelin protein 22 (PMP22) is a dose-sensitive, disease-associated protein primarily expressed in myelinating Schwann cells. Either reduction or overproduction of PMP22 can result in hereditary neuropathy, suggesting a requirement for correct protein expression for peripheral nerve biology. PMP22 is post-transcriptionally regulated and the 3'untranslated region (3'UTR) of the gene exerts a negative effect on translation. MicroRNAs (miRNAs) are small regulatory molecules that function at a post-transcriptional level by targeting the 3'UTR in a reverse complementary manner. We used cultured Schwann cells to demonstrate that alterations in the miRNA biogenesis pathway affect PMP22 levels, and endogenous PMP22 is subjected to miRNA regulation. GW-body formation, the proposed cytoplasmic site for miRNA-mediated repression, and Dicer expression, an RNase III family ribonuclease involved in miRNA biogenesis, are co-regulated with the differentiation state of Schwann cells. Furthermore, the levels of Dicer inversely correlate with PMP22, while the inhibition of Dicer leads to elevated PMP22. Microarray analysis of actively proliferating and differentiated Schwann cells, in conjunction with bioinformatics programs, identified several candidate PMP22-targeting miRNAs. Here we demonstrate that miR-29a binds and inhibits PMP22 reporter expression through a specific miRNA seed binding region. Over-expression of miR-29a enhances the association of PMP22 RNA with Argonaute 2, a protein involved in miRNA function, and reduces the steady-state levels of PMP22. In contrast, inhibition of endogenous miR-29a relieves the miRNA-mediated repression of PMP22. Correlation analyses of miR-29 and PMP22 in sciatic nerves reveal an inverse relationship, both developmentally and in post-crush injury. These results identify PMP22 as a target of miRNAs and suggest that myelin gene expression by Schwann cells is regulated by miRNAs.
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Affiliation(s)
- Jonathan D Verrier
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida 32610-0244, USA
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9
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Katona I, Wu X, Feely SME, Sottile S, Siskind CE, Miller LJ, Shy ME, Li J. PMP22 expression in dermal nerve myelin from patients with CMT1A. Brain 2009; 132:1734-40. [PMID: 19447823 DOI: 10.1093/brain/awp113] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by a 1.4 Mb duplication on chromosome 17p11.2, which contains the peripheral myelin protein-22 (PMP22) gene. Increased levels of PMP22 in compact myelin of peripheral nerves have been demonstrated and presumed to cause the phenotype of CMT1A. The objective of the present study was to determine whether an extra copy of the PMP22 gene in CMT1A disrupts the normally coordinated expression of PMP22 protein in peripheral nerve myelin and to evaluate PMP22 over-expression in patients with CMT1A and determine whether levels of PMP22 are molecular markers of disease severity. PMP22 expression was measured by taking skin biopsies from patients with CMT1A (n = 20) and both healthy controls (n = 7) and patients with Hereditary Neuropathy with liability to Pressure Palsies (HNPP) (n = 6), in which patients have only a single copy of PMP22. Immunological electron microscopy was performed on the skin biopsies to quantify PMP22 expression in compact myelin. Similar biopsies were analysed by real time PCR to measure PMP22 mRNA levels. Results were also correlated with impairment in CMT1A, as measured by the validated CMT Neuropathy Score. Most, but not all patients with CMT1A, had elevated PMP22 levels in myelin compared with the controls. The levels of PMP22 in CMT1A were highly variable, but not in HNPP or the controls. However, there was no correlation between neurological disabilities and the level of over-expression of PMP22 protein or mRNA in patients with CMT1A. The extra copy of PMP22 in CMT1A results in disruption of the tightly regulated expression of PMP22. Thus, variability of PMP22 levels, rather than absolute level of PMP22, may play an important role in the pathogenesis of CMT1A.
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Affiliation(s)
- Istvan Katona
- Department of Neurology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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10
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Abstract
Pelizaeus-Merzbacher disease (PMD) is a recessive X-linked dysmyelinating disorder of the central nervous system (CNS). The most frequent cause of PMD is a genomic duplication of chromosome Xq22 including the region encoding the dosage-sensitive proteolipid protein 1 (PLP1) gene. The PLP1 duplications are heterogeneous in size, unlike duplications causing many other genomic disorders, and arise by a distinct molecular mechanism. Other causes of PMD include PLP1 deletions, triplications and point mutations. Mutations in the PLP1 gene can also give rise to spastic paraplegia type 2 (SPG2), an allelic form of the disease. Thus, there is a spectrum of CNS disorder from mild SPG2 to severe connatal PMD. PLP1 encodes a major protein in CNS myelin and is abundantly expressed in oligodendrocytes, the myelinating cells of the CNS. Significant advances in our understanding of PMD have been achieved by investigating mutant PLP1 in PMD patients, animal models and in vitro studies. How the different PLP1 mutations and dosage effects give rise to PMD is being revealed. Interestingly, the underlying causes of pathogenesis are distinct for each of the different genetic abnormalities. This article reviews the genetics of PMD and summarises the current knowledge of causative molecular and cellular mechanisms.
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Hung CC, Lee CN, Lin CY, Cheng WF, Chen CA, Hsieh ST, Yang CC, Jong YJ, Su YN, Lin WL. Identification of deletion and duplication genotypes of thePMP22 gene using PCR-RFLP, competitive multiplex PCR, and multiplex ligation-dependent probe amplification: A comparison. Electrophoresis 2008; 29:618-25. [DOI: 10.1002/elps.200700340] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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12
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Ou Z, Jarmuz M, Sparagana SP, Michaud J, Décarie JC, Yatsenko SA, Nowakowska B, Furman P, Shaw CA, Shaffer LG, Lupski JR, Chinault AC, Cheung SW, Stankiewicz P. Evidence for involvement of TRE-2 (USP6) oncogene, low-copy repeat and acrocentric heterochromatin in two families with chromosomal translocations. Hum Genet 2006; 120:227-37. [PMID: 16791615 DOI: 10.1007/s00439-006-0200-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 04/28/2006] [Indexed: 10/24/2022]
Abstract
We report clinical findings and molecular cytogenetic analyses for two patients with translocations [t(14;17)(p12;p12) and t(15;17)(p12;p13.2)], in which the chromosome 17 breakpoints map at a large low-copy repeat (LCR) and a breakage-prone TRE-2 (USP6) oncogene, respectively. In family 1, a 6-year-old girl and her 5-year-old brother were diagnosed with mental retardation, short stature, dysmorphic features, and Charcot-Marie-Tooth disease type 1A (CMT1A). G-banding chromosome analysis showed a der(14)t(14;17)(p12;p12) in both siblings, inherited from their father, a carrier of the balanced translocation. Chromosome microarray and FISH analyses revealed that the PMP22 gene was duplicated. The chromosome 17 breakpoint was mapped within an approximately 383 kb LCR17pA that is known to also be the site of several breakpoints of different chromosome aberrations including the evolutionary translocation t(4;19) in Gorilla gorilla. In family two, a patient with developmental delay, subtle dysmorphic features, ventricular enlargement with decreased periventricular white matter, mild findings of bilateral perisylvian polymicrogyria and a very small anterior commissure, a cryptic duplication including the Miller-Dieker syndrome region was identified by chromosome microarray analysis. The chromosome 17 breakpoint was mapped by FISH at the TRE-2 oncogene. Both partner chromosome breakpoints were mapped on the short arm acrocentric heterochromatin within or distal to the rRNA cluster, distal to the region commonly rearranged in Robertsonian translocations. We propose that TRE-2 together with LCR17pA, located approximately 10 Mb apart, also generated the evolutionary gorilla translocation t(4;19). Our results support previous observations that the USP6 oncogene, LCRs, and repetitive DNA sequences play a significant role in the origin of constitutional chromosome aberrations and primate genome evolution.
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Affiliation(s)
- Zhishuo Ou
- Department of Molecular & Human Genetics, Baylor College of Medicine, One Baylor Plaza, Rm T821, Houston, TX 77030, USA
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13
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Schuierer MM, Mann CJ, Bildsoe H, Huxley C, Hughes SM. Analyses of the differentiation potential of satellite cells from myoD-/-, mdx, and PMP22 C22 mice. BMC Musculoskelet Disord 2005; 6:15. [PMID: 15762989 PMCID: PMC1079863 DOI: 10.1186/1471-2474-6-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Accepted: 03/11/2005] [Indexed: 12/19/2022] Open
Abstract
Background Sporadic and sometimes contradictory studies have indicated changes in satellite cell behaviour associated with the progressive nature of human Duchenne muscular dystrophy (DMD). Satellite cell proliferation and number are reportedly altered in DMD and the mdx mouse model. We recently found that satellite cells in MSVski transgenic mice, a muscle hypertrophy model showing progressive muscle degeneration, display a severe ageing-related differentiation defect in vitro. We tested the hypothesis that similar changes contribute to the gradual loss of muscle function with age in mdx and PMP22 mice, a model of human motor and sensory neuropathy type 1A (HMSN1A). Methods Single extensor digitorum longus muscle fibres were cultured from mdx and PMP22 mice and age- and genetic background-matched controls. Mice at several ages were compared with regard to the differentiation of satellite cells, assayed as the proportion of desmin-expressing cells that accumulated sarcomeric myosin heavy chain. Results Satellite cells of 2 month, 6 month, and 12 month old mdx mice were capable of differentiating to a similar extent to age-matched wild type control animals in an in vitro proliferation/differentiation model. Strikingly, differentiation efficiency in individual 6 month and 12 month old mdx animals varies to a much higher extent than in age-matched controls, younger mdx animals, or PMP22 mice. In contrast, differentiation of myoblasts from all myoD null mice assayed was severely impaired in this assay system. The defect in satellite cell differentiation that occurs in some mdx animals arises from a delay in differentiation that is not overcome by IGF-1 treatment at any phase of cultivation. Conclusion Overall, a defect in satellite cell differentiation above that arising through normal ageing does not occur in mdx or PMP22 mouse models of human disease. Nonetheless, the impaired differentiation of satellite cells from some mdx animals suggests that additional factors, environmental or epigenetic, may lead to deteriorating muscle repair through poor differentiation of satellite cells in genetically predisposed individuals.
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Affiliation(s)
- Marion M Schuierer
- Insitute of Pathology, Medical School of the University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Christopher J Mann
- MRC Centre for Developmental Neurobiology and Randall Division for Cell and Molecular Biophysics, Guy's Campus, King's College, London, UK
| | - Heidi Bildsoe
- MRC Centre for Developmental Neurobiology and Randall Division for Cell and Molecular Biophysics, Guy's Campus, King's College, London, UK
| | - Clare Huxley
- Division of Biomedical Sciences, and Clinical Sciences Centre, Imperial College School of Science, Technology and Medicine, London, UK
| | - Simon M Hughes
- MRC Centre for Developmental Neurobiology and Randall Division for Cell and Molecular Biophysics, Guy's Campus, King's College, London, UK
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14
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Carvalho AAS, Vital A, Ferrer X, Latour P, Lagueny A, Brechenmacher C, Vital C. Charcot-Marie-Tooth disease type 1A: clinicopathological correlations in 24 patients. J Peripher Nerv Syst 2005; 10:85-92. [PMID: 15703022 DOI: 10.1111/j.1085-9489.2005.10112.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We examined nerve biopsies from 24 patients with Charcot-Marie-Tooth disease type 1A (CMT1A) and proven 17p11.2-12 duplication. There were seven males and 17 females with a mean age of 27.85 +/- 18.95 years at the time of nerve biopsy. A family history consistent with dominant inheritance was present in 17 patients. Clinical features were classical in 16 patients and were atypical in the other eight: one had calf hypertrophy; two had Roussy-Levy syndrome; one had had a subacute inflammatory demyelinating polyneuropathy 11 years earlier and presented a relapse on the form of a chronic inflammatory demyelinating polyneuropathy; one had carpal tunnel syndrome; one had a recent painful neuropathy in both legs; and two had chronic inflammatory demyelinating polyneuropathy. Onion bulb formations (OMFs) were present in every case and most of them were characteristic, whereas burnt-out or cluster-associated OMFs were less common. Depletion of myelinated fibers was severe in 20 cases (169-2927/mm2) and varied from 5187 to 3725/mm2 in three children (4-9 years old). In addition, features of macrophage-associated demyelination were observed in the last four atypical cases. Known for more than 20 years, inflammatory demyelination superimposed in the course of CMT1A has been reported in a few cases in the past few years, mainly concerning asymptomatic or atypical patients. Such an association deserves to be better known because corticotherapy improves weakness in most of these patients.
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Affiliation(s)
- Alzira A S Carvalho
- Neuropathology Department, Victor Segalen University, Pessac, Bordeaux, France
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15
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Abstract
Charcot-Marie-Tooth (CMT), or heritable peripheral neuropathies, is among the most frequent genetic neuromuscular disorders, with a prevalence of approximately 1:2500. Since 1991, remarkable advances have occurred in determining the precise genetic cause of many forms of CMT and in generating animal models of many of these disorders. However, these advances have not yet resulted in cures for CMT. Recently, potential treatments for the most common form of CMT, CMT-1A, have been shown in rodent models of the disorder. Treatment with onapristone, a progesterone antagonist, has improved the neuropathy of the CMT-1A rat. Treatment with large doses of ascorbic acid (vitamin C) has improved the neuropathy of the CMT-1A mouse. Multicentric trials with ascorbic acid are likely to start in the near future to assess if vitamin C supplementation is effective and what is the dosage required in humans to improve neurologic disability. Because of potential side effects with antiprogesterone therapy, particularly in women of child- bearing age, research is actively proceeding with progesterone antagonists to develop safe medications that also can be used in clinical trials of CMT-1A. Although no cures are available for CMT, there are many important treatments available for patients with CMT that can improve their quality of life and help them maintain their independence. Some of these therapies involve physiatry and orthopedic surgery. Others involve pain management. Lastly, there are potential concerns about medications or lifestyle issues that may exacerbate CMT. All of these issues will be discussed.
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Affiliation(s)
- Marina Grandis
- Department of Neurology, Wayne State University, 4201 Saint Antoine Street, Detroit, MI 48201, USA.
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16
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Kobsar I, Hasenpusch-Theil K, Wessig C, Müller HW, Martini R. Evidence for macrophage-mediated myelin disruption in an animal model for Charcot-Marie-Tooth neuropathy type 1A. J Neurosci Res 2005; 81:857-64. [PMID: 16041800 DOI: 10.1002/jnr.20601] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Charcot-Marie-Tooth neuropathy type 1A (CMT 1 A) is the most common inherited neuropathy in humans and is mostly caused by a 1.5-Mb tandem duplication of chromosome 17 comprising the gene for the peripheral myelin protein 22-kDa (PMP 22). Although there are numerous studies on the functional role of PMP 22, the mechanisms of myelin degeneration under PMP 22-overexpression conditions have not yet been fully understood. We have shown previously that in mouse mutants hetero- or homozygously deficient for two other myelin components, P0 and C x 32, respectively, immune cells contribute to the demyelinating neuropathy. To test this possibility for PMP 22 overexpression, we investigated a putative mouse model for CMT 1 A, i.e., the mouse strain C 6 1 mildly overexpressing human PMP 22 in peripheral nerves. Electron microscopic and electrophysiologic investigations revealed that this mouse strain develops pathologic features similar to those found in CMT 1 A patients. A novel finding, however, was the upregulation of CD8- and F4/80-positive lymphocytes and macrophages, respectively, in peripheral nerves. The observation that macrophages enter endoneurial tubes of the mutants and obviously phagocytose morphologically normal myelin strongly suggests that the myelin degeneration is mediated at least partially by these phagocytic cells. By gene array technology and quantitative RT-PCR of peripheral nerve homogenates from PMP 22 mutants, monocyte chemoattractant protein-1 (MCP-1; cc l2) could be identified as a putative factor to attract or activate macrophages that attack myelin sheaths in this model of CMT 1 A.
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Affiliation(s)
- Igor Kobsar
- Developmental Neurobiology, Department of Neurology, University of Würzburg, Würzburg, Germany
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17
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Chan JR, Cosgaya JM, Wu YJ, Shooter EM. Neurotrophins are key mediators of the myelination program in the peripheral nervous system. Proc Natl Acad Sci U S A 2001; 98:14661-8. [PMID: 11717413 PMCID: PMC64738 DOI: 10.1073/pnas.251543398] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Although knowledge of the functions of neurotrophins has advanced rapidly in recent years, studies concerning the involvement of neurotrophins in glial-neuronal interactions rarely extend further than their roles in supporting the survival and differentiation of neuronal cells. In this study endogenous brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) were identified in Schwann cell/dorsal root ganglia neuronal cocultures and shown to modulate the myelination program of the peripheral nervous system. The differential expression of BDNF and NT3 were examined and compared with the expression profiles of myelin proteins in the cocultures throughout the myelination process. BDNF levels correlated with active myelin formation, whereas NT3 expression was initially high and then down regulated throughout the proliferation and premyelination periods. Addition of exogenous BDNF enhanced myelination, whereas the removal of the endogenous BDNF by using the BDNF receptor TrkB-Fc fusion protein inhibited the formation of mature myelin internodes. Interestingly, exogenous NT3 significantly inhibited myelination, whereas the removal of the endogenous NT3 by using the NT3 receptor TrkC-Fc fusion protein resulted in an enhancement similar to that obtained with the addition of BDNF. In addition, in vivo studies were performed during the development of the mouse sciatic nerve. Subcutaneous injections of BDNF resulted in an enhancement of myelin formation in the sciatic nerve, whereas the removal of the endogenous BDNF dramatically inhibited myelination. Injections of NT3 inhibited myelin formation, and the removal of the endogenous NT3 enhanced myelination. These results demonstrate that BDNF and NT3 possess different modulatory roles in the myelination program of the peripheral nervous system and that their mechanisms of action are specific and highly regulated.
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Affiliation(s)
- J R Chan
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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18
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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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19
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Chimelli L. [Peripheral neuropathies in childhood: a neuropathological approach]. ARQUIVOS DE NEURO-PSIQUIATRIA 1996; 54:510-8. [PMID: 9110001 DOI: 10.1590/s0004-282x1996000300025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Peripheral neuropathies affect children more often than the young and middle age adults, but less frequently than the elderly. They differ from those in the adults because of the high incidence of hereditary neuropathies, including those associated with metabolic and degenerative disorders of the central nervous system; the low incidence of toxic neuropathies and those associated with systemic disorders; and a lower incidence of chronic acquire polineuropathies. Nerve biopsies are indicated if the diagnosis has not been made with clinical and electrophysiologic studies and other methods, and should only be performed in laboratories with appropriated techniques for the study of the nerve. It is important to know the normal development of the nerve, the thickness of the myelin sheath and the distribution of small and large fibers, according to the age. The main morphological aspects of the most frequent neuropathies in children--acquired (inflammatory, demyelinating) and hereditary (sensory-motor, sensory-autonomic, ataxic, and those associated with metabolic and degenerative disorders), are reviewed.
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Affiliation(s)
- L Chimelli
- Departamento de Patologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo (USP), Brasil
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20
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21
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Lütschg J, Müller HJ, Malik NJ. The value of family investigations in newly detected Charcot-Marie-Tooth disease in children. Eur J Pediatr 1995; 154:S40-3. [PMID: 8529708 DOI: 10.1007/bf02191504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Charcot-Marie-Tooth disease (CMT) was diagnosed by nerve conduction velocity and histology of the sural nerve in two boys aged 3 and 6 years with clinical signs of a severe neuromuscular disease. DNA analysis revealed the typical duplication on chromosome 17p11.2 (2.7 kb allele) for CMT 1A. Although none of their family members reported symptoms of neuromuscular disease, the nerve conduction velocity was reduced in three members (father and two aunts). They were homozygous for the 2.7 kb allele and were assumed to carry three copies of this allele. The very differing clinical picture from one generation to the next in patients with identical neurophysiological and genetic results is discussed.
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Affiliation(s)
- J Lütschg
- Department of Medical Genetics, University Children's Hospital, Basel, Switzerland
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22
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Hertz JM, Børglum AD, Brandt CA, Flint T, Bisgaard C. Charcot-Marie-Tooth disease type 1A: the parental origin of a de novo 17p11.2-p12 duplication. Clin Genet 1994; 46:291-4. [PMID: 7834893 DOI: 10.1111/j.1399-0004.1994.tb04162.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Charcot-Marie-Tooth disease type 1A (CMT1A) is an autosomal dominant peripheral neuropathy associated with a DNA duplication on chromosome 17p11.2-p12 in the majority of cases. Most of the sporadic cases are due to a de novo duplication. We have screened for this duplication in 11 Danish patients with CMT type 1, using four different techniques, and identified a de novo duplication in a sporadic case. Analysis of the fully informative pVAW409R3a alleles in this family showed the duplication to be of paternal origin.
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Affiliation(s)
- J M Hertz
- Institute of Human Genetics, University of Aarhus, Denmark
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23
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Lester T, de Alwis M, Clark PA, Jones AM, Katz F, Levinsky RJ, Kinnon C. Trisomy X in a female member of a family with X linked severe combined immunodeficiency: implications for carrier diagnosis. J Med Genet 1994; 31:717-20. [PMID: 7815443 PMCID: PMC1050084 DOI: 10.1136/jmg.31.9.717] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We describe a family affected by X linked severe combined immunodeficiency (SCIDX1) in which genetic prediction of carrier status was made using X chromosome inactivation studies together with limited genetic linkage analysis. Linkage studies in this family showed a confusing pattern of inheritance for the X chromosome. A female with a random pattern of X chromosome inactivation in her T cells appeared to have inherited an X chromosome with four recombinations within 10 cM. The odds of this happening in a single meiotic event make this an unlikely explanation. Data obtained from studying the X chromosomes of her two unaffected sons showed that this could be explained simply on the basis of her having inherited three alleles each of the relevant polymorphic DNA loci. We used fluorescent in situ hybridisation (FISH) to confirm that this person had inherited three complete X chromosomes. Thus, although the results from X chromosome inactivation analysis indicated that this subject was not a carrier of the affected chromosome, FISH and genetic linkage analysis showed clearly that the affected chromosome had been inherited. The implications of this finding for diagnosis of carrier status in this family and for other families with X linked inherited immunodeficiencies is discussed.
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Affiliation(s)
- T Lester
- Molecular Immunology Unit, Institute of Child Health, London, UK
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24
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Müller U, Graeber MB, Haberhausen G, Köhler A. Molecular basis and diagnosis of neurogenetic disorders. J Neurol Sci 1994; 124:119-40. [PMID: 7964863 DOI: 10.1016/0022-510x(94)90318-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Over the past few years, molecular neurogenetics has developed into one of the most promising and active research fields. The new discipline applies modern molecular genetic techniques to the investigation of classical neurological disorders. In the following article, a definition of neurogenetic disease is introduced, the molecular basis of four groups of neurogenetic disorders is described and recent diagnostic developments are presented. The first group of diseases is caused by trinucleotide expansions. "Expanding" trinucleotide repeats were not known to occur in any species until about three years ago. Today, disorders such as Huntington's disease, spinocerebellar ataxia type 1, fragile X mental retardation, spinobulbar muscular atrophy and myotonic dystrophy are all known to be caused by the expansion of trinucleotides. The second group is characterized by chromosomal deletions or uniparental disomies. Lissencephaly and the Miller-Dieker syndrome, Prader-Willi and Angelman syndromes and Duchenne and Becker muscular dystrophies belong to this category. The third group includes those neurogenetic disorders that are mainly caused by point mutations such as the X-linked leukodystrophies, including Pelizaeus-Merzbacher disease and adrenoleukodystrophy, Charcot-Marie-Tooth syndrome type 1, familial forms of amyotrophic lateral sclerosis, several types of craniosynostoses and some CNS tumor syndromes. Finally, Alzheimer's and Parkinson's disease are discussed as representatives of group four, i.e. genetically heterogeneous neurological disorders.
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Affiliation(s)
- U Müller
- Institut für Humangenetik, Justus-Liebig-Universität, Giessen, Germany
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25
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Roa BB, Lupski JR. Charcot-Marie-Tooth Disease and Related Inherited Myelin Disorders: Molecular Genetics and Implications for Gene Therapy. ILAR J 1994. [DOI: 10.1093/ilar.36.3-4.64] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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26
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Roa BB, Lupski JR. Molecular genetics of Charcot-Marie-Tooth neuropathy. ADVANCES IN HUMAN GENETICS 1994; 22:117-52. [PMID: 7762451 DOI: 10.1007/978-1-4757-9062-7_3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- B B Roa
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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27
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Abstract
There has been remarkable progress in the identification of mutations in genes that cause inherited neurological disorders. Abnormalities in the genes for Huntington disease, neurofibromatosis types 1 and 2, one form of familial amyotrophic lateral sclerosis, fragile X syndrome, myotonic dystrophy, Kennedy syndrome, Menkes disease, and several forms of retinitis pigmentosa have been elucidated. Rare disorders of neuronal migration such as Kallmann syndrome, Miller-Dieker syndrome, and Norrie disease have been shown to be due to specific gene defects. Several muscle disorders characterized by abnormal membrane excitability have been defined as mutations of the muscle sodium or chloride channels. These advances provide opportunity for accurate molecular diagnosis of at-risk individuals and are the harbinger of new approaches to therapy of these diseases.
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Affiliation(s)
- J B Martin
- Department of Neurology, University of California, San Francisco, 94143-0402
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28
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Roa BB, Dyck PJ, Marks HG, Chance PF, Lupski JR. Dejerine-Sottas syndrome associated with point mutation in the peripheral myelin protein 22 (PMP22) gene. Nat Genet 1993; 5:269-73. [PMID: 8275092 DOI: 10.1038/ng1193-269] [Citation(s) in RCA: 177] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dejerine-Sottas syndrome is a hypertrophic, demyelinating neuropathy which appears to demonstrate autosomal recessive inheritance in most pedigrees. Clinical symptoms are similar but more severe than Charcot-Marie-Tooth disease type 1 (CMT1), of which the major subtype, CMT1A, results either from duplication of a 1.5-megabase DNA region in chromosome 17p11.2-p12 containing the myelin gene PMP22, or from PMP22 point mutation. Mutational analysis of the PMP22 coding region in two unrelated Dejerine-Sottas patients identified individual missense point mutations present in the heterozygous state. These findings suggest that Dejerine-Sottas syndrome can result from dominant point mutation alleles of PMP22.
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Affiliation(s)
- B B Roa
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030
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29
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Roa BB, Garcia CA, Pentao L, Killian JM, Trask BJ, Suter U, Snipes GJ, Ortiz-Lopez R, Shooter EM, Patel PI, Lupski JR. Evidence for a recessive PMP22 point mutation in Charcot-Marie-Tooth disease type 1A. Nat Genet 1993; 5:189-94. [PMID: 8252046 DOI: 10.1038/ng1093-189] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Charcot-Marie-Tooth disease type 1A (CMT1A) is an autosomal dominant neuropathy that can be caused by dominant point mutations in PMP22 which encodes a peripheral nerve myelin protein. Usually, CMT1A is caused by the duplication of a 1.5-megabase (Mb) region on chromosome 17p11.2-p12 containing PMP22. Deletion of a similar 1.5-Mb region is associated with hereditary neuropathy with liability to pressure palsies (HNPP), a clinically distinct neuropathy. We have identified a severely affected CMT1 patient who is a compound heterozygote for a recessive PMP22 point mutation, and a 1.5 Mb deletion in 17p11.2-p12. A son heterozygous for the PMP22 point mutation had no signs of neuropathy, while two others heterozygous for the deletion had HNPP, suggesting that point mutations in PMP22 can result in dominant and recessive alleles contributing to CMT1A.
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Affiliation(s)
- B B Roa
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030
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30
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Roa BB, Lupski JR. Molecular basis of Charcot-Marie-Tooth disease type 1A: gene dosage as a novel mechanism for a common autosomal dominant condition. Am J Med Sci 1993; 306:177-84. [PMID: 8128981 DOI: 10.1097/00000441-199309000-00010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Charcot-Marie-Tooth disease (CMT) comprises a clinically and genetically heterogeneous group of polyneuropathies. Two major types can be distinguished based on electrophysiologic phenotypes: CMT type 1 (CMT1) displays uniformly decreased nerve conduction velocity associated with a demyelinating hypertrophic neuropathy, and CMT type 2 (CMT2) displays normal or near-normal nerve conduction velocity associated with a neuronal defect. Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common form, exhibiting autosomal dominant inheritance and linkage to chromosome 17p11.2p12. This review will focus on the underlying molecular mechanisms leading to CMT1A. DNA duplication of a 1.5-Mb region is associated with CMT1A in the majority of cases. A defined segmental DNA duplication that cosegregates with a disease in a dominant Mendelian pattern had been unprecedented. A candidate gene for CMT1A, PMP22, which maps within the duplication and encodes a myelin-specific protein, was identified from studies on the trembler and tremblerJ mouse models for CMT. Point mutations in PMP22 have since been identified in cases of familial, non-duplication CMT1A. The genetic data presents two alternative molecular mechanisms involving the PMP22 gene that result in the same clinical and electrophysiologic phenotype of CMT1A. The impact of the underlying molecular mechanisms on the prospects for therapeutic development are discussed.
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Affiliation(s)
- B B Roa
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, TX 77030
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31
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Roa BB, Garcia CA, Suter U, Kulpa DA, Wise CA, Mueller J, Welcher AA, Snipes GJ, Shooter EM, Patel PI, Lupski JR. Charcot-Marie-Tooth disease type 1A. Association with a spontaneous point mutation in the PMP22 gene. N Engl J Med 1993; 329:96-101. [PMID: 8510709 DOI: 10.1056/nejm199307083290205] [Citation(s) in RCA: 223] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Charcot-Marie-Tooth disease (CMT) is the most common inherited peripheral neuropathy. CMT type 1A is associated with a 1.5-megabase DNA duplication in region p11.2-p12 of chromosome 17 in most patients. An increased dosage of a gene within the duplicated segment appears to cause the disease. The PMP22 gene, which encodes a myelin protein, has been mapped within the duplication and proposed as a candidate gene for CMT type 1A. METHODS We analyzed DNA samples from a cohort of 32 unrelated patients with CMT type 1 who did not have the 1.5-Mb tandem duplication in 17p11.2-p12 for mutations within the PMP22 coding region. Molecular techniques included the polymerase chain reaction (PCR), heteroduplex analysis to detect point mutations, and direct nucleotide-sequence determination of amplified PCR products. RESULTS A 10-year-old boy was identified with a point mutation in PMP22, which resulted in the substitution of cysteine for serine in a putative transmembrane domain of PMP22. Analysis of family members revealed that the PMP22 point mutation arose spontaneously and segregated with the CMT type 1 phenotype in an autosomal dominant pattern. The patients with the PMP22 point mutation had clinical and electrophysiologic phenotypes that were similar to those of patients with the 1.5-Mb duplication. CONCLUSIONS The PMP22 gene has a causative role in CMT type 1. Either a point mutation in PMP22 or a duplication of the region including the PMP22 gene can result in the disease phenotype.
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Affiliation(s)
- B B Roa
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, TX 77030-3498
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32
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Abstract
Charcot-Marie-Tooth disease type 1A, the most common inherited peripheral neuropathy, is associated with a submicroscopic DNA duplication of 1.5 Mb that can arise de novo, and which is flanked by a > 17 kb mosaic repeat. The PMP22 gene, encoding a peripheral myelin protein, maps within the duplication. In a subset of Charcot-Marie-Tooth patients, point mutations can occur within the gene. Thus, the alternative mechanisms of overexpression of PMP22 and structural alterations in the protein encoded can cause the disease phenotype.
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Affiliation(s)
- P I Patel
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, TX 77030
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33
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Suter U, Welcher AA, Snipes GJ. Progress in the molecular understanding of hereditary peripheral neuropathies reveals new insights into the biology of the peripheral nervous system. Trends Neurosci 1993; 16:50-6. [PMID: 7680499 DOI: 10.1016/0166-2236(93)90015-e] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Since the first description of the autosomal dominant inherited peripheral neuropathy Charcot-Marie-Tooth (CMT) disease over a century ago, there has been considerable disagreement, based on morphological abnormalities of both the axons of peripheral nerves and their surrounding Schwann cells, as to whether this disorder is due primarily to an autonomous Schwann cell defect or an autonomous neuronal defect. Recently, the Schwann cell protein peripheral myelin protein 22 (PMP-22) has been implicated in the molecular pathogenesis of hereditary peripheral neuropathies in mice and humans. Reinterpretations of morphological studies of the diseased nerves in light of these findings strongly suggest that Schwann cells have a much more pronounced influence on their ensheathed axons than previously anticipated.
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Affiliation(s)
- U Suter
- Dept of Neurobiology, Stanford University School of Medicine, CA 94305
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Pentao L, Wise CA, Chinault AC, Patel PI, Lupski JR. Charcot-Marie-Tooth type 1A duplication appears to arise from recombination at repeat sequences flanking the 1.5 Mb monomer unit. Nat Genet 1992; 2:292-300. [PMID: 1303282 DOI: 10.1038/ng1292-292] [Citation(s) in RCA: 287] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We have constructed a 3.1 megabase (Mb) physical map of chromosome 17p11.2-p12, which contains a submicroscopic duplication in patients with Charcot-Marie-Tooth disease type 1A (CMT1A). We find that the CMT1A duplication is a tandem repeat of 1.5 Mb of DNA. A YAC contig encompassing the CMT1A duplication and spanning the endpoints was also developed. Several low copy repeats in 17p11.2-p12 were identified including the large (> 17 kb) CMT1A-REP unit which may be part of a mosaic repeat. CMT1A-REP flanks the 1.5 Mb CMT1A monomer unit on normal chromosome 17 and is present in an additional copy on the CMT1A duplicated chromosome. We propose that the de novo CMT1A duplication arises from unequal crossing over due to misalignment at these CMT1A-REP repeat sequences during meiosis.
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Affiliation(s)
- L Pentao
- Institute for Molecular Genetics, College of Medicine, Houston, Texas 77030
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