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Abstract
Glial glutamate receptors are likely to be involved in neuronal differentiation, migration, and plasticity. Dystrophin, the protein defective in Duchenne muscular dystrophy (DMD) is widely expressed in the Central Nervous System. Activation of internal promoters of the DMD gene leads to the production of several proteins, the Dystrophin-71 (Dp-71) being the most abundant in the encephalon. This protein is known to stabilize neurotransmitter receptors in clusters and its absence has been correlated with cognitive deficits in a mouse model. Using cultured chick Bergmann glia cells and mouse cerebellar fusiform astrocytes, we demonstrate here that glutamate receptor activation results in a time and dose dependent decrease of Dp-71 levels. This effect is mediated through alphaamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. The present results suggest an involvement of Dp-71 in glutamate receptor signaling and possibly clustering and further support the notion of an active role of glia in the physiology of glutamatergic transmission.
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Affiliation(s)
- Roque Galaz-Vega
- Departamento de Genética y Biología Molecular, Cinvestav-IPN Apartado, México
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2
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Abstract
Previously, we reported that PC12 cells with decreased Dp71 expression (antisense-Dp71 cells) display deficient nerve-growth-factor-induced neurite outgrowth. In this study, we show that disturbed neurite outgrowth of antisense-Dp71 cells is accompanied by decreased adhesion activity on laminin, collagen and fibronectin. In wild-type cells, the immunostaining of Dp71 and beta1-integrin overlaps in the basal area contacting the substrate, but staining of both proteins decrease in the antisense-Dp71 cells. Morphology of antisense-Dp71 cells at the electron microscopic level is characterized by the lack of filopodia, cellular projections involved in adhesion. Our findings suggest that Dp71 is required for the efficient PC12 cell attachment to beta1-integrin-dependent substrata and that decreased adhesion activity of the antisense-Dp71 cells could determine their deficiency to extend neurites.
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Affiliation(s)
| | - Joel Cerna-Cortés
- Department of Genetics and Molecular Biology
Centro de Investigation y de Estudios Avanzados del IPNMX
| | - Mario Bermúdez de León
- Department of Genetics and Molecular Biology
Centro de Investigation y de Estudios Avanzados del IPNMX
| | | | - Everardo González
- Department of Genetics and Molecular Biology
Centro de Investigation y de Estudios Avanzados del IPNMX
| | - Dominique Mornet
- Muscle et pathologies
INSERM : ERI25IFR3Université Montpellier I : EA4202hopital arnaud de villeneuve
371, avenue du doyen gaston giraud 34295 Montpellier Cedex 05,FR
- * Correspondence should be adressed to: Dominique Mornet
| | - Bulmaro Cisneros
- Department of Genetics and Molecular Biology
Centro de Investigation y de Estudios Avanzados del IPNMX
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3
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de León MB, Montañez C, Gómez P, Morales-Lázaro SL, Tapia-Ramírez V, Valadez-Graham V, Recillas-Targa F, Yaffe D, Nudel U, Cisneros B. Dystrophin Dp71 Expression Is Down-regulated during Myogenesis. J Biol Chem 2005; 280:5290-9. [PMID: 15550398 DOI: 10.1074/jbc.m411571200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dp71 expression is present in myoblasts but declines during myogenesis to avoid interfering with the function of dystrophin, the predominant Duchenne muscular dystrophy gene product in differentiated muscle fibers. To elucidate the transcriptional regulatory mechanisms operating on the developmentally regulated expression of Dp71, we analyzed the Dp71 expression and promoter activity during myogenesis of the C2C12 cells. We demonstrated that the cellular content of Dp71 transcript and protein decrease in myotubes as a consequence of the negative regulation that the differentiation stimulus exerts on the Dp71 promoter. Promoter deletion analysis showed that the 224-bp 5'-flanking region, which contains several Sp-binding sites (Sp-A to Sp-D), is responsible for the Dp71 promoter basal activity in myoblasts as well as for down-regulation of the promoter in differentiated cells. Electrophoretic mobility shift and chromatin immunoprecipitation assays indicated that Sp1 and Sp3 transcription factors specifically bind to the Sp-binding sites in the minimal Dp71 promoter region. Site-directed mutagenesis assay revealed that Sp-A is the most important binding site for the proximal Dp71 promoter activity. Additionally, cotransfection of the promoter construct with Sp1- and Sp3-expressing vectors into Drosophila SL2 cells, which lack endogenous Sp family, confirmed that these proteins activate specifically the minimal Dp71 promoter. Endogenous Sp1 and Sp3 proteins were detected only in myoblasts and not in myotubes, which indicates that the lack of these factors causes down-regulation of the Dp71 promoter activity in differentiated cells. In corroboration, efficient promoter activity was restored in differentiated muscle cells by exogenous expression of Sp1 and Sp3.
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Affiliation(s)
- Mario Bermúdez de León
- Department of Genetics and Molecular Biology, Centro de Investigación y de Estudios Avanzados del I.P.N., 07360 México
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4
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Hernández-González EO, Mornet D, Rendon A, Martínez-Rojas D. Absence of Dp71 in mdx3cv mouse spermatozoa alters flagellar morphology and the distribution of ion channels and nNOS. J Cell Sci 2004; 118:137-45. [PMID: 15601658 PMCID: PMC2792583 DOI: 10.1242/jcs.01584] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In muscle, the absence of dystrophin alters the dystrophin-associated protein complex (DAPC), which is involved in the clustering and anchoring of signaling proteins and ion and water channels. Here we show that mice spermatozoa express only dystrophin Dp71 and utrophin Up71. The purpose of this study was to explore the effect of the absence of Dp71 on the morphology and membrane distribution of members of the DAPC, ion channels and signaling proteins of spermatozoa obtained from dystrophic mutant mdx3cv mice. Our work indicates that although the absence of Dp71 results in a dramatic decrease in beta-dystroglycan, it induces membrane redistribution and an increase in the total level of alpha-syntrophin, voltage-dependent Na+ (micro1) and K+ (Kv1.1) channels and neural nitric oxide synthase (nNOS). The short utrophin (Up71) was upregulated and redistributed in the spermatozoa of mdx3cv mice. A significant increase in abnormal flagella morphology was observed in the absence of Dp71, which was partially corrected when the plasma membrane was eliminated by detergent treatment. Our observations point to a new phenotype associated with the absence of Dp71. Abnormal flagellar structure and altered distribution of ion channels and signaling proteins may be responsible for the fertility problems of mdx3cv mice.
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5
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Haenggi T, Schaub MC, Fritschy JM. Molecular heterogeneity of the dystrophin-associated protein complex in the mouse kidney nephron: differential alterations in the absence of utrophin and dystrophin. Cell Tissue Res 2004; 319:299-313. [PMID: 15565469 DOI: 10.1007/s00441-004-0999-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Accepted: 09/08/2004] [Indexed: 11/24/2022]
Abstract
The dystrophin-associated protein complex (DPC) consisting of syntrophin, dystrobrevin, and dystroglycan isoforms is associated either with dystrophin or its homolog utrophin. It is present not only in muscle cells, but also in numerous tissues, including kidney, liver, and brain. Using high-resolution immunofluorescence imaging and Western blotting, we have investigated the effects of utrophin and dystrophin gene deletion on the formation and membrane anchoring of the DPC in kidney epithelial cells, which co-express utrophin and low levels of the C-terminal dystrophin isoform Dp71. We show that multiple, molecularly distinct DPCs co-exist in the nephron; these DPCs have a segment-specific distribution and are only partially associated with utrophin in the basal membrane of tubular epithelial cells. In utrophin-deficient mice, a selective reduction of beta2-syntrophin has been observed in medullary tubular segments, whereas alpha1-syntrophin and beta1-syntrophin are retained, concomintant with an upregulation of beta-dystroglycan, beta-dystrobrevin, and Dp71. These findings suggest that beta2-syntrophin is dependent on utrophin for association with the DPC, and that loss of utrophin is partially compensated by Dp71, allowing the preservation of the DPC in kidney epithelial cells. This hypothesis is confirmed by the almost complete loss of all DPC proteins examined in mice lacking full-length utrophin and all C-terminal dystrophin isoforms (utrophin(0/0)/mdx(3Cv)). The DPC thus critically depends on these proteins for assembly and/or membrane localization in kidney epithelial cells.
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Affiliation(s)
- Tatjana Haenggi
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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6
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Szabó A, Jancsik V, Mornet D, Kálmán M. Immunofluorescence mapping of dystrophin in the rat brain: astrocytes contain the splice variant Dp71f, but this is confined to subpopulations. ACTA ACUST UNITED AC 2004; 208:463-77. [PMID: 15340845 DOI: 10.1007/s00429-004-0411-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/22/2004] [Indexed: 11/28/2022]
Abstract
Dystrophins are membrane-associated actin-binding proteins, recognized at first in muscular dystrophies. In the brain the full-length Dp427 has been detected, as well as Dp140 and Dp71 of the shorter variants. Dp71 seems to be their major representative in the brain, and it occurs as splice variants, Dp71f and Dp71d. Dystrophins have been demonstrated mainly in neurons. In tissue cultures, the glial data, mainly in situ, are still insufficient. The present mapping study reveals the astroglial localization of the splice variant Dp71f, using a monoclonal antibody (5F3, developed by D. Mornet) specific for its additional 31 last amino acids. In parallel, another monoclonal antibody was used (Dys2, Novocastra) that detects the Dp71d, Dp427, as well as Dp140 and other short variants. Rats were overdosed with ether and perfused transcardially with 4% phosphate-buffered paraformaldehyde solution. Floating Vibratome sections were processed for immunohistochemical labeling with fluorescent secondary antibodies. In some animals the reactive glia were investigated following stab wounds in ketamine-xylazine anesthesia. Only the 5F3 antibody labeled astrocytes, however, not in general but in special localizations, mainly along the glia limitans of the pial surface, below the ependyma and in the reactive glia. Perivascular astrocytes were consistently labeled only where the vessels entered the brain, and in some circumventricular organs. The 5F3 antibody also labeled the ependyma and the residual subventricular zone. In contrast to the astrocytes, neurons were labeled throughout the brain. Dys2 antibody (to Dp71d and longer isoforms) labeled neurons in a distribution similar to that of 5F3, but rarely labeled astroglia and only in perivascular rings. Dp71f positivity seems to occur in those astrocyte populations that proved to be immunopositive to glial fibrillary acidic protein (GFAP) and produced laminin in former studies.
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Affiliation(s)
- Adrienn Szabó
- Department of Anatomy, Histology and Embryology, Semmelweis University, Tüzoltó 58, 1094 Budapest, Hungary
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7
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Acosta R, Montañez C, Fuentes-Mera L, Gonzalez E, Gómez P, Quintero-Mora L, Mornet D, Alvarez-Salas LM, Cisneros B. Dystrophin Dp71 is required for neurite outgrowth in PC12 cells. Exp Cell Res 2004; 296:265-75. [PMID: 15149856 DOI: 10.1016/j.yexcr.2004.01.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Revised: 01/16/2004] [Indexed: 11/22/2022]
Abstract
To determine the role of Dp71 in neuronal cells, we generated PC12 cell lines in which Dp71 protein levels were controlled by stable transfection with either antisense or sense constructs. Cells expressing the antisense Dp71 RNA (antisense-Dp71 cells) contained reduced amounts of the two endogenous Dp71 isoforms. Antisense-Dp71 cells exhibited a marked suppression of neurite outgrowth upon the induction with NGF or dibutyryl cyclic AMP. Early responses to NGF-induced neuronal differentiation, such as the cessation of cell division and the activation of ERK1/2 proteins, were normal in the antisense-Dp71 cells. On contrary, the induction of MAP2, a late differentiation marker, was disturbed in these cells. Additionally, the deficiency of Dp71 correlated with an altered expression of the dystrophin-associated protein complex (DAPC) members alpha and beta dystrobrevins. Our results indicate that normal expression of Dp71 is essential for neurite outgrowth in PC12 cells and constitute the first direct evidence implicating Dp71 in a neuronal function.
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Affiliation(s)
- Rosalinda Acosta
- Department of Genetics and Molecular Biology, Centro de Investigación y de Estudios Avanzados del IPN, Avenida Instituto Politécnico Nacional 2508, Apartado Postal 14-740, C.P. 07000, Mexico D.F., Mexico
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8
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Akdemir R, Ozhan H, Gunduz H, Yazici M, Erbilen E, Uyan C, Imirzalioglu N. Complete atrioventricular block in Becker muscular dystrophy. N Z Med J 2004; 117:U895. [PMID: 15156213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Ramazan Akdemir
- Department of Cardiology, Düzce Medical School, Abant Izzet Baysal University, Konuralp-Düzce, Turkey.
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9
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Abstract
The dystrophin glycoprotein complex (DGC) is a membrane-associated protein complex binding extracellular matrix (ECM) molecules, such as laminin and forming a bridge towards the cytoskeleton. The molecular composition of the DGC is cell type dependent and it is involved in cell adhesion and motility. Here we present immunocytochemical localization of beta-dystroglycan, the central member of the DGC, utrophin and Dp71f, the spliced 71 kDa dystrophin protein product of the DMD gene, in cultured retinal Muller glial cells. It is shown that beta-dystroglycan and utrophin are colocalized in clusters in all parts of Muller cells including the lamellipodium and leading edge of migrating cells. As a contrast, Dp71f labels are distinct from beta-dystroglycan and confined to the perinuclear cytoplasm of Muller cells indicating that Dp71f is not a member of the DGC in cultured Muller cells.
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Affiliation(s)
- E Méhes
- Department of Anatomy and Histology, Faculty of Veterinary Science, Szent István University, Budapest, Hungary
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10
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Haenggi T, Soontornmalai A, Schaub MC, Fritschy JM. The role of utrophin and Dp71 for assembly of different dystrophin-associated protein complexes (DPCS) in the choroid plexus and microvasculature of the brain. Neuroscience 2004; 129:403-13. [PMID: 15501597 DOI: 10.1016/j.neuroscience.2004.06.079] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2004] [Indexed: 10/26/2022]
Abstract
In the brain, utrophin is present in the choroid plexus epithelium and vascular endothelial cells, whereas the short C-terminal isoform of dystrophin (Dp71) is localized in the glial end-feet surrounding blood vessels. Both proteins serve as anchors for the so-called dystrophin-associated protein complex (DPC), composed of isoforms of syntrophin, dystroglycan and dystrobrevin. Numerous transporter proteins and channels have a polarized distribution in vascular endothelial cells and in glial end-feet, suggesting an association with the DPC. We investigated the composition and localization of the DPC in dependence on the anchoring proteins in mice lacking either utrophin (utrophin0/0) or dystrophin isoforms (mdx3Cv). Three distinct complexes were identified: (i) associated with utrophin in the basolateral membrane of the choroid plexus epithelium, (ii) associated with utrophin in vascular endothelial cells, and (iii) associated with Dp71 in the glial end-feet. Upon ablation of utrophin or Dp71, the corresponding DPCs were disrupted and no compensation of the missing protein by its homologue was observed. Association of the water channel aquaporin 4 with the glial DPC likewise was disrupted in mdx3Cv mice. These results demonstrate the essential role of utrophin and Dp71 for assembly of the DPC and suggest that these proteins contribute to the proper functioning of the cerebrospinal fluid and blood-brain barriers.
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Affiliation(s)
- T Haenggi
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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11
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Wieneke S, Heimann P, Leibovitz S, Nudel U, Jockusch H. Acute pathophysiological effects of muscle-expressed Dp71 transgene on normal and dystrophic mouse muscle. J Appl Physiol (1985) 2003; 95:1861-6. [PMID: 14555666 DOI: 10.1152/japplphysiol.00326.2003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
products of the dystrophin gene range from the 427-kDa full-length dystrophin to the 70.8-kDa Dp71. Dp427 is expressed in skeletal muscle, where it links the actin cytoskeleton with the extracellular matrix via a complex of dystrophin-associated proteins (DAPs). Dystrophin deficiency disrupts the DAP complex and causes muscular dystrophy in humans and the mdx mouse. Dp71, the major nonmuscle product, consists of the COOH-terminal part of dystrophin, including the binding site for the DAP complex but lacks binding sites for microfilaments. Dp71 transgene (Dp71tg) expressed in mdx muscle restores the DAP complex but does not prevent muscle degeneration. In wild-type (WT) mouse muscle, Dp71tg causes a mild muscular dystrophy. In this study, we tested, using isolated extensor digitorum longus muscles, whether Dp71tg exerts acute influences on force generation and sarcolemmal stress resistance. In WT muscles, there was no effect on isometric twitch and tetanic force generation, but with a cytomegalovirus promotor-driven transgene, contraction with stretch led to sarcolemmal ruptures and irreversible loss of tension. In MDX muscle, Dp71tg reduced twitch and tetanic tension but did not aggravate sarcolemmal fragility. The adverse effects of Dp71 in muscle are probably due to its competition with dystrophin and utrophin (in MDX muscle) for binding to the DAP complex.
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Affiliation(s)
- Sascha Wieneke
- Developmental Biology and Molecular Pathology, Bielefeld University, D-33501 Bielefeld, Germany
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12
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Marquez FG, Cisneros B, Garcia F, Ceja V, Velázquez F, Depardón F, Cervantes L, Rendón A, Mornet D, Rosas-vargas H, Mustre M, Montañez C. Differential expression and subcellular distribution of dystrophin Dp71 isoforms during differentiation process. Neuroscience 2003; 118:957-66. [PMID: 12732241 DOI: 10.1016/s0306-4522(03)00063-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dp71 is the major product of the Duchenne muscular dystrophy gene in the brain. In order to study the function of Dp71 in the nervous system we examined the expression of Dp71 isoforms in PC12 rat pheochromocytoma cell line, a well-established system to study neuronal differentiation. We show by reverse transcriptase-polymerase chain reaction and Western blot assays that PC12 cells express two Dp71 isoforms. One isoform lacks exon 71 and the other isoform lacks exons 71 and 78 (Dp71d and Dp71f isoforms respectively). Nerve growth factor-induced neuronal differentiation of PC12 cells results in differential regulation of the expression and subcellular localization of Dp71 isoforms: a) the amount of Dp71f protein increases nine-fold in total extracts while Dp71d increases up to seven-fold in nuclear extracts; b) Dp71f relocates from the cytoplasm to neuritic processes, being prominent at varicosities and the growth cone; c) Dp71d relocates almost entirely to the nucleus and is detected to a lower extent in the cytoplasm and neuritic processes. Dp71f co-localizes with beta-dystroglycan and synaptophysin while Dp71d co-localizes with beta-dystroglycan in the nucleus. Dp71d accumulates at cell-cell contacts where Dp71f is absent. These results suggest that Dp71d and Dp71f associate with different subcellular complexes and therefore may have distinct functions in PC12 cells.
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Affiliation(s)
- F G Marquez
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Avenida Instituto Politécnico Nacional 2508, Apartado Postal 14-740, C.P. 07000, Mexico
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13
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Dalloz C, Sarig R, Fort P, Yaffe D, Bordais A, Pannicke T, Grosche J, Mornet D, Reichenbach A, Sahel J, Nudel U, Rendon A. Targeted inactivation of dystrophin gene product Dp71: phenotypic impact in mouse retina. Hum Mol Genet 2003; 12:1543-54. [PMID: 12812982 DOI: 10.1093/hmg/ddg170] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The abnormal retinal neurotransmission observed in Duchenne muscular dystrophy (DMD) patients and in some genotypes of mice lacking dystrophin has been attributed to altered expression of short products of the dystrophin gene. We have investigated the potential role of Dp71, the most abundant C-terminal dystrophin gene product, in retinal electrophysiology. Comparison of the scotopic electroretinograms (ERG) between Dp71-null mice and wild-type (wt) littermates revealed a normal ERG in Dp71-null mice with no significant changes of the b-wave amplitude and kinetics. Analysis of DMD gene products, utrophin and dystrophin-associated proteins (DAPs), showed that Dp71 and utrophin were localized around the blood vessels, in the ganglion cell layer (GCL), and the inner limiting membrane (ILM). Dp71 deficiency was accompanied by an increased level of utrophin and decreased level of beta-dystroglycan localized in the ILM, without any apparent effect on the other DAPs. Dp71 deficiency was also associated with an impaired clustering of two Müller glial cell proteins-the inwardly rectifying potassium channel Kir4.1 and the water pore aquaporin 4 (AQP4). Immunostaining of both proteins decreased around blood vessels and in the ILM of Dp71-null mice, suggesting that Dp71 plays a role in the clustering and/or stabilization of the two proteins. AQP4 and Kir4.1 may also be involved in the regulation of the ischemic process. We found that a transient ischemia resulted in a greater damage in the GCL of mice lacking Dp71 than in wt mice. This finding points at a crucial role played by Dp71 in retinal function.
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Affiliation(s)
- Cécile Dalloz
- INSERM U-592, Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, Hôpital Saint-Antoine, Bâtiment Kourilsky, 6ème étage, 184 rue du Faubourg Saint-Antoine, 75571 Paris Cedex 12, France
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14
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Dowling P, Lohan J, Ohlendieck K. Comparative analysis of Dp427-deficient mdx tissues shows that the milder dystrophic phenotype of extraocular and toe muscle fibres is associated with a persistent expression of beta-dystroglycan. Eur J Cell Biol 2003; 82:222-30. [PMID: 12800977 DOI: 10.1078/0171-9335-00315] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cell biological hypothesis of Duchenne muscular dystrophy assumes that deficiency in the membrane cytoskeletal element dystrophin triggers a loss in surface glycoproteins, such as beta-dystroglycan, thereby rendering the sarcolemmal membrane more susceptible to micro-rupturing. Secondary changes in ion homeostasis, such as increased cytosolic Ca2+ levels and impaired luminal Ca2+ buffering, eventually lead to Ca2+-induced myonecrosis. However, individual muscle groups exhibit a graded pathological response during the natural time course of x-linked muscular dystrophy. The absence of the dystrophin isofom Dp427 does not necessarily result in a severe dystrophic phenotype in all muscle groups. In the dystrophic mdx animal model, extraocular and toe muscles are not as severely affected as limb muscles. Here, we show that the relative expression and sarcolemmal localization of the central trans-sarcolemmal linker of the dystrophin-glycoprotein complex, beta-dystroglycan, is preserved in mdx extraocular and toe fibres by means of two-dimensional immunoblotting and immunofluorescence microscopy. Thus, with respect to improving myology diagnostics, the relative expression levels of beta-dystroglycan appear to represent reliable markers for the severity of secondary changes in dystrophin-deficient fibres. Immunoblotting and enzyme assays revealed that mdx toe muscle fibres exhibit an increased expression and activity of the sarcoplasmic reticulum Ca2+-ATPase. Chemical crosslinking studies demonstrated impaired calsequestrin oligomerization in mdx gastrocnemius muscle indicating that abnormal calsequestrin clustering is involved in reduced Ca2+ buffering of the dystrophic sarcoplasmic reticulum. Previous studies have mostly attributed the sparing of certain mdx fibres to the special protective properties of small-diameter fibres. Our study suggests that the rescue of dystrophin-associated glycoproteins, and possibly the increased removal of cytosolic Ca2+ ions, might also play an important role in protecting muscle cells from necrotic changes.
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Affiliation(s)
- Paul Dowling
- Department of Biology, National University of Ireland, Maynooth, County Kildare, Ireland
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15
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García-Tovar CG, Luna J, Mena R, Soto-Zárate CI, Cortés R, Pérez A, León-Avila G, Mornet D, Rendón A, Hernández JM. Dystrophin isoform Dp7l is present in lamellipodia and focal complexes in human astrocytoma cells U-373 MG. Acta Histochem 2003; 104:245-54. [PMID: 12389738 DOI: 10.1078/0065-1281-00654] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Dp71 is the most abundant product of the dmd gene in the brain. There are at least 2 isoforms derived from alternative splicing of exon 78 (Dp71d, which contains exon 78 and Dp71f, the spliced isoform) but the precise localization and function of each isoform is still unknown. In the present study, we demonstrate by RT-PCR that the Dp71f isoform is present in an astrocytoma cell line U-373 MG, and its subcellular localization was determined in the cytoplasm, particularly in perinuclear areas, with lower amounts towards the periphery but increasing in the leader borders of lamellipodia and focal complexes. Double labeling indirect immunofluorescence showed that Dp71f colocalized with actin-like beta-dystroglycan and beta-1 integrin. We also demonstrated by triple labeling that Dp71f was colocalized with actin and two members of integrin complexes, alpha-actinin and vinculin, in focal complexes. Ventral plasma membranes were enriched and in those containing focal complex proteins, we found colocalization of Dp71f, actin and vinculin. It is concluded that U-373 MG cells express Dp71f as part of lamellipodia and focal complex proteins, and possibly connected via distroglycan complexes to integrin complexes.
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16
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Austin RC, Fox JEB, Werstuck GH, Stafford AR, Bulman DE, Dally GY, Ackerley CA, Weitz JI, Ray PN. Identification of Dp71 isoforms in the platelet membrane cytoskeleton. Potential role in thrombin-mediated platelet adhesion. J Biol Chem 2002; 277:47106-13. [PMID: 12370193 DOI: 10.1074/jbc.m203289200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Utrophin is a component of the platelet membrane cytoskeleton and participates in cytoskeletal reorganization (Earnest, J. P., Santos, G. F., Zuerbig, S., and Fox, J. E. B. (1995) J. Biol. Chem. 270, 27259-27265). Although platelets do not contain dystrophin, the identification of smaller C-terminal isoforms of dystrophin, including Dp71, which are expressed in a wide range of nonmuscle tissues and cell lines, has not been investigated. In this report, we have identified Dp71 protein variants of 55-60 kDa (designated Dp71Delta(110)) in the membrane cytoskeleton of human platelets. Both Dp71Delta(110) and utrophin sediment from lysed platelets along with the high speed detergent-insoluble pellet, which contains components of the membrane cytoskeleton. Like the membrane cytoskeletal proteins vinculin and spectrin, Dp71Delta(110) and utrophin redistributed from the high speed detergent-insoluble pellet to the integrin-rich low speed pellet of thrombin-stimulated platelets. Immunoelectron microscopy provided further evidence that Dp71Delta(110) was localized to the submembranous cytoskeleton. In addition to Dp71Delta(110), platelets contained several components of the dystrophin-associated protein complex, including beta-dystroglycan and syntrophin. To better understand the potential function of Dp71Delta(110), collagen adhesion assays were performed on platelets isolated from wild-type or Dp71-deficient (mdx(3cv)) mice. Adhesion to collagen in response to thrombin was significantly decreased in platelets isolated from mdx(3cv) mice, compared with wild-type platelets. Collectively, our results provide evidence that Dp71Delta(110) is a component of the platelet membrane cytoskeleton, is involved in cytoskeletal reorganization and/or signaling, and plays a role in thrombin-mediated platelet adhesion.
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Affiliation(s)
- Richard C Austin
- Department of Pathology, McMaster University and the Henderson Research Centre, Hamilton, Ontario L8V 1C3, Canada.
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17
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Leibovitz S, Meshorer A, Fridman Y, Wieneke S, Jockusch H, Yaffe D, Nudel U. Exogenous Dp71 is a dominant negative competitor of dystrophin in skeletal muscle. Neuromuscul Disord 2002; 12:836-44. [PMID: 12398834 DOI: 10.1016/s0960-8966(02)00141-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dystrophin, the protein which is absent or non-functional in Duchenne muscular dystrophy, consists of four main domains: an N-terminal actin binding domain, a rod shaped domain of spectrin-like repeats, a cysteine-rich domain and a unique C-terminal domain. In muscle, dystrophin forms a linkage between the cytoskeletal actin and a group of membrane proteins (dystrophin associated proteins). The N-terminal domain binds to the cytoskeletal actin and the association with the dystrophin associated proteins is mediated mainly by the cysteine-rich and C-terminal domains of dystrophin. The dystrophin gene also encodes two isoforms of non-muscle dystrophins and a number of smaller products consisting of the two C-terminal domains with different extensions into the spectrin-like repeat domain. Dp71, which consist of the C-terminal and the cysteine-rich domains of dystrophin, is the major product of the gene in all non-muscle tissues tested so far, but it is absent in differentiated skeletal muscle. In an attempt to understand the functions of Dp71, we produced transgenic mice over-expressing this protein in several tissues. The highest levels of exogeneous Dp71 were detected in skeletal muscle, in association with the sarcolemma. This resulted in muscle damage similar to that found in mice which lack dystrophin. The data indicates that Dp71 competes with dystrophin for the binding to the dystrophin associated proteins. Since Dp71 lacks the actin binding domain, it cannot form the essential linkage between the dystrophin associated proteins complex and the cytoskeleton.
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Affiliation(s)
- Sigalit Leibovitz
- Department of Molecular Cell Biology, The Weizmann Institute of Science, 76100, Rehovot, Israel
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18
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Hernández-González EO, Martínez-Rojas D, Mornet D, Rendon A, Mújica A. Comparative distribution of short dystrophin superfamily products in various guinea pig spermatozoa domains. Eur J Cell Biol 2001; 80:792-8. [PMID: 11831393 DOI: 10.1078/0171-9335-00202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this study, the presence and cellular distribution of dystrophin family products (i.e. Dp71d, Dp71f-like protein and dystrobrevin) was examined by indirect immunofluorescence and Western blotting in guinea pig spermatozoa. Two dystrophin-associated proteins, beta-dystroglycan and alpha-syntrophin, and nNOS a protein frequently associated with alpha-syntrophin, were determined. In spermatozoa lacking plasma membrane and acrosome, Dp71f-like protein was found in the postacrosomal perinuclear theca and also in the middle piece of the flagellum. In the flagellum, Dp71f-like protein is localized together with alpha-syntrophin and nNOS. Dp71d was present in the plasma membrane of the middle piece with beta-dystroglycan, alpha-syntrophin and nNOS. Dp71d was also present in plasma membrane of the post acrosomal region, but only with nNOS. Finally, dystrobrevin was located all along skeletal flagellum structures and in the subacrosomal hemisphere of the perinuclear theca. This distinct and complementary distribution in various domains of spermatozoa may reveal a specific function for each short dystrophin family product, in the stabilization of the domains where they are located.
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Neely JD, Amiry-Moghaddam M, Ottersen OP, Froehner SC, Agre P, Adams ME. Syntrophin-dependent expression and localization of Aquaporin-4 water channel protein. Proc Natl Acad Sci U S A 2001; 98:14108-13. [PMID: 11717465 PMCID: PMC61176 DOI: 10.1073/pnas.241508198] [Citation(s) in RCA: 352] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The Aquaporin-4 (AQP4) water channel contributes to brain water homeostasis in perivascular astrocyte endfeet where it is concentrated. We postulated that AQP4 is tethered at this site by binding of the AQP4 C terminus to the PSD95-Discs large-ZO1 (PDZ) domain of syntrophin, a component of the dystrophin protein complex. Chemical cross-linking and coimmunoprecipitations from brain demonstrated AQP4 in association with the complex, including dystrophin, beta-dystroglycan, and syntrophin. AQP4 expression was studied in brain and skeletal muscle of mice lacking alpha-syntrophin (alpha-Syn(-/-)). The total level of AQP4 expression appears normal in brains of alpha-Syn(-/-) mice, but the polarized subcellular localization is reversed. High-resolution immunogold analyses revealed that AQP4 expression is markedly reduced in astrocyte endfeet membranes adjacent to blood vessels in cerebellum and cerebral cortex of alpha-Syn(-/-) mice, but is present at higher than normal levels in membranes facing neuropil. In contrast, AQP4 is virtually absent from skeletal muscle in alpha-Syn(-/-) mice. Deletion of the PDZ-binding consensus (Ser-Ser-Val) at the AQP4 C terminus similarly reduced expression in transfected cell lines, and pulse-chase labeling demonstrated an increased degradation rate. These results demonstrate that perivascular localization of AQP4 in brain requires alpha-Syn, and stability of AQP4 in the membrane is increased by the C-terminal PDZ-binding motif.
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Affiliation(s)
- J D Neely
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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20
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Loh NY, Nebenius-Oosthuizen D, Blake DJ, Smith AJ, Davies KE. Role of beta-dystrobrevin in nonmuscle dystrophin-associated protein complex-like complexes in kidney and liver. Mol Cell Biol 2001; 21:7442-8. [PMID: 11585924 PMCID: PMC99916 DOI: 10.1128/mcb.21.21.7442-7448.2001] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
beta-Dystrobrevin is a dystrophin-related and -associated protein that is highly expressed in brain, kidney, and liver. Recent studies with the kidneys of the mdx3Cv mouse, which lacks all dystrophin isoforms, suggest that beta-dystrobrevin, and not the dystrophin isoforms, may be the key component in the assembly of complexes similar to the muscle dystrophin-associated protein complexes (DPC) in nonmuscle tissues. To understand the role of beta-dystrobrevin in the function of nonmuscle tissues, we generated beta-dystrobrevin-deficient (dtnb(-/-)) mice by gene targeting. dtnb(-/-) mice are healthy, fertile, and normal in appearance. No beta-dystrobrevin was detected in these mice by Western blotting or immunocytochemistry. In addition, the levels of several beta-dystrobrevin-interacting proteins, namely Dp71 isoforms and the syntrophins, were greatly reduced from the basal membranes of kidney tubules and liver sinusoids and on Western blots of crude kidney and liver microsomes of beta-dystrobrevin-deficient mice. However, no abnormality was detected in the ultrastructure of membranes of kidney and liver cells or in the renal function of these mice. beta-Dystrobrevin may therefore be an anchor or scaffold for Dp71 and syntrophin isoforms, as well as other associating proteins at the basal membranes of kidney and liver, but is not necessary for the normal function of these mice.
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Affiliation(s)
- N Y Loh
- Department of Human Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, United Kingdom
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21
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Bolaños-Jiménez F, Bordais A, Behra M, Strähle U, Mornet D, Sahel J, Rendón A. Molecular cloning and characterization of dystrophin and Dp71, two products of the Duchenne Muscular Dystrophy gene, in zebrafish. Gene 2001; 274:217-26. [PMID: 11675014 DOI: 10.1016/s0378-1119(01)00606-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Dystrophin, the protein responsible for Duchenne Muscular Dystrophy (DMD), plays a critical role in the maintenance of the muscle membrane integrity. There are several forms of dystrophin derived from the DMD gene by alternative promoter usage. In addition to full-length dystrophin (Dp427), four shorter transcripts have been identified: Dp260, Dp140, Dp116 and Dp71. The functional role played by the different products of the DMD gene is not yet determined. To get insight into the function of dystrophin and related products, we have investigated the presence of dystrophin in zebrafish. This choice takes advantage of large-scale mutagenesis screens in zebrafish, which have led to the identification of several mutants with motility defects. The identification and characterization of the genes affected by these mutations is likely to provide relevant information for the understanding of the molecular mechanisms of muscle development and function. Two cDNA clones encoding the homologues of dystrophin and Dp71 in zebrafish were identified and characterized. Both transcripts exhibit a high degree of sequence homology with the dystrophin and Dp71 proteins described in higher vertebrates. In addition, three alternative spliced transcripts that occur at the C-terminal end of the zebrafish DMD gene have been identified. These transcripts exhibit different patterns of tissue expression. We have also determined the chromosomal localization of dystrophin on the radiation hybrid map of the zebrafish genome. Our results indicate that the dystrophin gene is localized to linkage group one. Altogether, these results give new insights on the physiological role played by dystrophin and related proteins, and provide new tools for the identification of mutated genes associated with muscle defects in zebrafish.
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Affiliation(s)
- F Bolaños-Jiménez
- Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, EMI 99-18, INSERM-Université Louis Pasteur, Strasbourg, France.
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22
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Garcia-Tovar CG, Perez A, Luna J, Mena R, Osorio B, Aleman V, Mondragon R, Mornet D, Rendón A, Hernandez JM. Biochemical and histochemical analysis of 71 kDa dystrophin isoform (Dp71f) in rat brain. Acta Histochem 2001; 103:209-24. [PMID: 11368101 DOI: 10.1078/0065-1281-00591] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Dp71 is a member of the dystrophin family and the most abundant dmd gene product in the brain. In the present study, we focused on a short dystrophin transcript named Dp71f, which is alternatively spliced when exon 78 is absent The topographic localization of this protein in the encephalon has not been properly described yet, nor its cellular or subcellular localization, and even less its functions. Dp71f was found to be a cytoplasmic 70 kDa protein and localized in all encephalon regions studied. Double labeling using specific markers for various cell types confirmed Dp71f distribution in the cytoplasm of all cell types studied. Labeling was more conspicuous near the nucleus and diminished towards the periphery of cells. In some cases, we observed cells that were positive for actin and Dp71f in regions corresponding to lamellipodia-like structures. Dp71f and Dp71d isoforms were differently distributed. Our study is the first specific and unambiguous description of the topography and cellular localization patterns of Dp71f in brain, suggesting that Dp71f is a ubiquitous protein.
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23
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Bolaños-Jiménez F, Bordais A, Behra M, Strähle U, Sahel J, Rendón A. Dystrophin and Dp71, two products of the DMD gene, show a different pattern of expression during embryonic development in zebrafish. Mech Dev 2001; 102:239-41. [PMID: 11287201 DOI: 10.1016/s0925-4773(01)00310-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Dystrophin, the protein defective in Duchenne muscular dystrophy (DMD), plays a critical role in the formation and maintenance of the neuromuscular junction. In addition to dystrophin, activation of internal promoters of the DMD gene leads to the production of several short products. Among these, Dp71, which consists of the C-terminal domain of dystrophin, is the most abundant product of the gene in non-muscle tissues and brain. In this report, we compare the temporal and regional expression patterns of dystrophin and Dp71 at different stages of embryonic development and during retinal differentiation in zebrafish. The Dp71 transcripts are the earliest to be expressed at 9-10 h post-fertilization (hpf) in the axial mesoderm. As development proceeds, intense Dp71 staining is observed in the notochord, the developing brain, the marginal regions of the somites and the eye primordium. At the completion of retinal differentiation, Dp71 is expressed in the ganglion and inner nuclear layers. Transcripts encoding dystrophin have a slightly later onset of expression, 13-14 hpf, and remain restricted to the transverse myosepta through all the developmental stages examined. The complementary patterns of expression of dystrophin and Dp71 suggest that these two proteins exert different functions during embryonic development in zebrafish.
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Affiliation(s)
- F Bolaños-Jiménez
- Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, EMI 99-18 Université Louis Pasteur, Strasbourg, France.
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Aleman V, Osorio B, Chavez O, Rendon A, Mornet D, Martinez D. Subcellular localization of Dp71 dystrophin isoforms in cultured hippocampal neurons and forebrain astrocytes. Histochem Cell Biol 2001; 115:243-54. [PMID: 11326752 DOI: 10.1007/s004180000221] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
It has been suggested that the absence or altered structure of Dp71, a C-terminal dystrophin gene encoded protein, is responsible for mental alterations observed in about 30% of Duchenne muscular dystrophy patients. Most of these patients have premature translational termination or point mutations at the C-terminal domain of this gene. In brain, Dp71 is the major protein product of the dystrophin gene. To determine the function of Dp71 isoforms in this organ, it is important to document their presence and intracellular localization in brain cells. Extracts from cultured hippocampal neurons and forebrain astrocytes and 5F3 and Dys 2 monoclonal antibodies were thus used for western blots. In these conditions, two Dp71 isoforms spliced or not at exon 78 were detected in both cells (Dp71f and Dp71d, respectively). By immunocytochemistry, we mapped Dp71f and Dp71d in the Golgi complex (GC) and in neuronal nuclei. Only Dp71d was found in cytoplasmic neurofilaments. In astrocytes, these isoforms were detected in the GC. These cell localization data suggest that these Dp71 isoforms may have different functions in the same cell or organelle, as well as in the two different cells analyzed.
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Affiliation(s)
- V Aleman
- Department of Fisiologia, Biofisica y Neurociencias, Cinvestav, IPN. Apdo. Postal 14-740, Mexico, DF, CP 07000, Mexico.
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25
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Culligan K, Glover L, Dowling P, Ohlendieck K. Brain dystrophin-glycoprotein complex: persistent expression of beta-dystroglycan, impaired oligomerization of Dp71 and up-regulation of utrophins in animal models of muscular dystrophy. BMC Cell Biol 2001; 2:2. [PMID: 11178104 PMCID: PMC29067 DOI: 10.1186/1471-2121-2-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2000] [Accepted: 02/02/2001] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Aside from muscle, brain is also a major expression site for dystrophin, the protein whose abnormal expression is responsible for Duchenne muscular dystrophy. Cognitive impairments are frequently associated with this genetic disease, we therefore studied the fate of brain and skeletal muscle dystrophins and dystroglycans in dystrophic animal models. RESULTS All dystrophin-associated glycoproteins investigated were reduced in dystrophic muscle fibres. In Dp427-deficient mdx brain and Dp71-deficient mdx-3cv brain, the expression of alpha-dystroglycan and laminin was reduced, utrophin isoforms were up-regulated and beta-dystroglycan was not affected. Immunofluorescence localization of beta-dystroglycan in comparison with glial, endothelial and neuronal cell markers revealed co-localization of von Willebrand factor with beta-dystroglycan. Its expression at the endothelial-glial interface was preserved in dystrophin isoform-deficient brain from mdx and mdx-3cv mice. In addition, chemical crosslinking revealed that the Dp71 isoform exists in mdx brain predominantly as a monomer. CONCLUSIONS This suggests an association of beta-dystroglycan with membranes at the vascular-glial interface in the forebrain. In contrast to dystrophic skeletal muscle fibres, dystrophin deficiency does not trigger a reduction of all dystroglycans in the brain, and utrophins may partially compensate for the lack of brain dystrophins. Abnormal oligomerization of the dystrophin isoform Dp71 might be involved in the pathophysiological mechanisms underlying abnormal brain functions.
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Affiliation(s)
- Kevin Culligan
- Department of Pharmacology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
| | - Louise Glover
- Department of Pharmacology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
| | - Paul Dowling
- Department of Pharmacology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
| | - Kay Ohlendieck
- Department of Pharmacology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
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26
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Masaki T, Matsumura K, Hirata A, Yamada H, Hase A, Shimizu T, Yorifuji H, Motoyoshi K, Kamakura K. Expression of dystroglycan complex in satellite cells of dorsal root ganglia. Acta Neuropathol 2001; 101:174-8. [PMID: 11271373 DOI: 10.1007/s004010000276] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
In Schwann cells, the transmembrane glycoprotein beta-dystroglycan composes the dystroglycan complex together with the extracellular glycoprotein alpha-dystroglycan, which binds laminin-2 (alpha2/beta1/gamma1), a major component of the Schwann cell basal lamina. In the Schwann cell cytoplasm, beta-dystroglycan is anchored to a dystrophin isoform, Dp116. In this study, we investigated the expression of beta-dystroglycan, Dp116 and the laminin-alpha2 chain in satellite cells of rat dorsal root ganglia (DRGs). Immunohistochemical study showed that immunoreactivities for beta-dystroglycan and Dp116 were both localized to the outer rim of neuron-satellite cell and axon-Schwann cell units, indicating that both satellite and Schwann cells expressed these proteins in DRGs. Immunoreactivity for the laminin-alpha2 chain was detected in a similar location, indicating that the basal lamina surrounding satellite and Schwann cells in DRGs contained laminin-2. Ultrastructurally, immunoreactivity for the cytoplasmic domain of beta-dystroglycan as well as that for Dp116 was most intense in the cytoplasm just underlying the outer membrane of satellite cells. The immunoreactivity for laminin was associated with the outer surface of those cells, suggesting that it was localized in the surrounding basal lamina. These results indicate that the dystroglycan complex is expressed in the satellite cell outer membrane and involved in the adhesion with the basal lamina through the interaction with laminin-2.
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Affiliation(s)
- T Masaki
- Third Department of Internal Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan
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27
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Abstract
The dystrophin-associated membrane-integrated protein complex anchors dystrophin in the sarcolemma of striated muscles and is composed of two glycoprotein subcomplexes, the dystroglycan and the sarcoglycan (SG) complexes, and a small membrane protein termed sarcospan (SPN). The SG complex consists of four transmembrane glycoproteins, alpha-SG, beta-SG, gamma-SG and delta-SG. We found that beta-SG and delta-SG were co-expressed with epsilon-SG, a alpha-SG homolog, in the peripheral nerve, but not with alpha-SG or gamma-SG. SPN, which tightly links to the SG complex in the muscle cell membrane, was absent in the peripheral nerve. These peripheral nerve SGs were colocalized at the outermost layer of the myelin sheath of nerve fibers together with the dystroglycan complex, utrophin, and a short dystrophin isoform (Dp116). Immunocytochemical analysis using SG-deficient animals showed that a defect in beta- or delta-SG led to a great reduction of all residual SGs, but not of the other proteins, i.e., dystroglycans, Dp116 and utrophin, in the peripheral nerve. This observation suggests that the epsilon-, beta- and delta-SG molecules form a complex behaving as a single unit similar to the SG complex in muscle cells. An immunoprecipitation study indicated that the SG complex is associated with the dystroglycan complex and Dp116 or utrophin. These results demonstrated that Dp116 and utrophin are anchored to a novel membrane protein architecture, which consists of the SG and dystroglycan complexes, but not SPN, in the Schwann cell membrane.
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Affiliation(s)
- M Imamura
- Department of Cell Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8502, Japan.
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González E, Montañez C, Ray PN, Howard PL, García-Sierra F, Mornet D, Cisneros B. Alternative splicing regulates the nuclear or cytoplasmic localization of dystrophin Dp71. FEBS Lett 2000; 482:209-14. [PMID: 11024462 DOI: 10.1016/s0014-5793(00)02044-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The subcellular distribution of Dp71 isoforms alternatively spliced for exon 71 and/or 78 was examined. The cDNA sequence of each variant was fused to the C-terminus of the green fluorescent protein and the constructs were transfected transiently in the cell lines HeLa, C2C12 and N1E-115. The subcellular distribution of the fused proteins was determined by confocal microscope analysis. The Dp71 isoform lacking the amino acids encoded by exons 71 and 78 was found exclusively in the cytoplasm whereas the variants containing the amino acids encoded by exon 71 and/or exon 78 show a predominant nuclear localization. The nuclear localization of Dp71 provides a new clue towards the establishment of its cellular function.
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Affiliation(s)
- E González
- Department of Genetics and Molecular Biology, Centro de Investigación y de Estudios Avanzados del IPN, Avenida Politécnico Nacional, México D.F; Mexico
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29
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Claudepierre T, Dalloz C, Mornet D, Matsumura K, Sahel J, Rendon A. Characterization of the intermolecular associations of the dystrophin-associated glycoprotein complex in retinal Muller glial cells. J Cell Sci 2000; 113 Pt 19:3409-17. [PMID: 10984432 DOI: 10.1242/jcs.113.19.3409] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The abnormal retinal neurotransmission observed in Duchenne muscular dystrophy patients has been attributed to altered expression of C-terminal products of the dystrophin gene in this tissue. Muller glial cells from rat retina express dystrophin protein Dp71, utrophin and the members of the dystrophin-associated glycoprotein complex (DGC), namely beta-dystroglycan, delta- and gamma-sarcoglycans and alpha1-syntrophin. The DGC could function in muscle as a link between the cystoskeleton and the extracellular matrix, as well as a signaling complex. However, other than in muscle the composition and intermolecular associations among members of the DGC are still unknown. Here we demonstrate that Dp71 and/or utrophin from rat retinal Muller glial cells form a complex with beta-dystroglycan, delta-sarcoglycan and alpha1-syntrophin. We also show that beta-dystroglycan is associated with alpha-dystrobrevin-1 and PSD-93 and that anti-PSD antibodies coimmunoprecipitated alpha-syntrophin with PSD-93. By overlay experiments we also found that Dp71and/or utrophin and alpha-dystroglycan from Muller cells could bind to actin and laminin, respectively. These results indicate that the DGC could have both structural and signaling functions in retina. On the basis of our accumulated evidence, we propose a hypothetical model for the molecular organization of the dystrophin-associated glycoprotein complex in retinal Muller glial cells, which would be helpful for understanding its function in the central nervous system.
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Affiliation(s)
- T Claudepierre
- Inserm EMI 99-18, Laboratoire de Physiopathologie Moléculaire et Cellulaire de la Rétine, CHRU, France
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30
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Abstract
Enteroviral infection can cause an acquired form of dilated cardiomyopathy. We recently reported that dystrophin is cleaved, functionally impaired, and morphologically disrupted in vitro as well as in vivo during infection with coxsackievirus B3. Genetic dystrophin truncations lead to a marked decrease in dystrophin-associated glycoproteins, whereas expression of only the naturally occurring dystrophin carboxyl terminus, Dp-71, restores the sarcolemmal association of the dystrophin-associated glycoproteins. We sought to determine whether acute cleavage of dystrophin leads to a dissociation of the carboxyl-terminal dystrophin fragment and of the sarcoglycans from the sarcolemma during coxsackievirus B3 infection. We found that in cultured cardiac myocytes and murine hearts infected with coxsackievirus B3, the sarcolemmal localization of the dystrophin carboxyl terminus is lost. The dystrophin-associated glycoproteins alpha-, beta-, gamma-, and delta-sarcoglycan and beta-dystroglycan were markedly decreased in the membrane fraction of infected cells in culture, and the typical sarcolemmal localization for each of these proteins was lost in coxsackievirus-B3-infected cardiomyocytes in vivo. Furthermore, sucrose gradient ultracentrifugation demonstrated that delta-sarcoglycan was physically dissociated from dystrophin within the membrane fraction. In vivo, the sarcolemmal integrity was functionally impaired with Evans blue dye uptake even though there was no generalized disruption of the sarcolemma of infected myocytes evidenced by intact wheat germ agglutinin staining. In analogy to hereditary sarcoglycanopathies, this disintegration of the sarcoglycan complex may, in addition to the dystrophin cleavage, play an important role in the pathogenesis of enterovirus-induced cardiomyopathy. These results imply a potential role for disruption of the sarcoglycans in an acquired form of heart failure.
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Affiliation(s)
- G H Lee
- Department of Medicine, University of California, San Diego (La Jolla), CA 92093-0613, USA
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31
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Chávez O, Harricane MC, Alemán V, Dorbani L, Larroque C, Mornet D, Rendon A, Martínez-Rojas D. Mitochondrial expression of a short dystrophin-like product with molecular weight of 71 kDa. Biochem Biophys Res Commun 2000; 274:275-80. [PMID: 10913331 DOI: 10.1006/bbrc.2000.3118] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the brain, Dp71 is the most abundant protein product of the DMD gene and by alternative splicing of exon 78 two isoforms can be expressed, Dp71d and Dp71f. To explore the subcellular distribution of these Dp71 isoforms, specific monoclonal antibodies were used. Dp71d (with exon 78) was found in microsomes, while Dp71f (without exon 78) was detected in mitochondria. To determine the alterations which the absence of dystrophin proteins induces, we compared the expression of Dp71d in microsomes and Dp71f in mitochondria from mdx and mdx(3CV) mice. Dp71d in microsomes of mdx was similar to that of wild-type mice and, as expected, in mdx(3CV) this protein was undetectable. However, in mitochondria from mdx(3CV), Dp71f was overexpressed in comparison to mitochondria from mdx mice. Because in mdx(3CV) mice all the dystrophin proteins are mutated or diminished, we concluded that the protein detected in mitochondria is not a Dp71f but a novel product named Dp71f-like protein.
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Affiliation(s)
- O Chávez
- Department of Physiology, Biophysics and Neuroscience, CINVESTAV-IPN, Av. 1PN2508, Colonia San Pedro Zacatenco, A.p. 14-740, México, D.F, 07360, México
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32
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Abstract
Dystrophin is the key component in the assembly and maintenance of the dystrophin-associated protein complex (DPC) in skeletal muscle. In kidney, dystroglycan, an integral component of the DPC, is involved in kidney epithelial morphogenesis, suggesting that the DPC is important in linking the extracellular matrix to the internal cytoskeleton of kidney epithelia. Here, we have investigated the molecular architecture of dystrophin-like protein complexes in kidneys from normal and dystrophin-deficient mice. Using isoform-specific antibodies, we show that the different cell types that make up the kidney maintain different dystrophin-like complexes. These complexes can be broadly grouped according to their dystrobrevin content: beta-dystrobrevin containing complexes are present at the basal region of renal epithelial cells, whilst alpha-dystrobrevin-1 containing complexes are found in endothelial and smooth muscle cells. Furthermore, these complexes are maintained even in the absence of all dystrophin isoforms. Thus our data suggest that the functions and assembly of the dystrophin-like complexes in kidney differ from those in skeletal muscle and implicate a protein other than dystrophin as the primary molecule in the assembly and maintenance of kidney complexes. Our findings also provide a possible explanation for the lack of kidney pathology in Duchenne muscular dystrophy patients and mice lacking all dystrophin isoforms.
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Affiliation(s)
- N Y Loh
- Department of Human Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
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33
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Moizard MP, Toutain A, Fournier D, Berret F, Raynaud M, Billard C, Andres C, Moraine C. Severe cognitive impairment in DMD: obvious clinical indication for Dp71 isoform point mutation screening. Eur J Hum Genet 2000; 8:552-6. [PMID: 10909857 DOI: 10.1038/sj.ejhg.5200488] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Duchenne muscular dystrophy is associated with variable degrees of selective cognitive defect with lower scores for verbal intelligence and reading abilities. A number of findings have shown that rearrangements located in the second part of the gene seem to be preferentially associated with cognitive impairment. Several dystrophin transcripts are expressed in the brain. The more distal of them, Dp71, is predominant. We have carried out a mutational analysis of Dp71 transcript in 12 DMD patients severely, mildly or not retarded, all without detectable deletion or duplication. We have detected five point mutations causing Dp71 premature translation termination. All were found among the more severely mentally retarded patients of this group (VIQ < 50 and/or no reading acquisition).
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Affiliation(s)
- M P Moizard
- Unité de Génétique, Hôpital Bretonneau, Tours, France.
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34
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Sarig R, Mezger-Lallemand V, Leibovitz S, Nudel U. Increased efficiency of homologous recombination in ES cells by cleavage at both ends of homology in the targeting vector. Transgenic Res 2000; 9:79-80. [PMID: 10951691 DOI: 10.1023/a:1008999109862] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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35
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Abstract
Transcripts encoding the 70-75 kDa C-terminal protein product of the dystrophin gene (Dp71) are alternatively spliced to generate multiple protein products in a number of adult human tissues. In this report, reverse transcriptase-polymerase chain reaction was used to clone and characterize a subpopulation of truncated Dp71 transcripts in adult human brain tissue which did not contain exons 71-74, resulting in an in-frame deletion of 330 bp encoding the syntrophin-binding domain. These truncated Dp71 transcripts are also alternatively spliced for exon 78. Immunoblot analysis, using dystrophin-specific C-terminal antibodies directed against epitopes in either exon 77 (MANDRA1), or 78 (1461), identified full-length dystrophin, Dp140 and Dp71, in total protein lysates from adult human brain tissue. In addition, a minor immunoreactive protein of approximately 58 kDa was also identified (designated Dp71 big up tri, open(110)). The observation that a monoclonal antibody directed against epitopes within exons 73-74 (MANEX7374A) failed to detect this 58 kDa protein provides definitive evidence that Dp71 big up tri, open(110) is derived from Dp71 transcripts deleted for the syntrophin-binding domain. These results, as well as previous findings, demonstrate that alternative splicing of Dp71 in the human brain generates a variety of mRNA transcripts encoding distinct protein variants of Dp71, and further supports the use of exon-specific antibodies in characterizing these variants. The presence of these Dp71 protein variants in brain tissue points to their interaction with various cellular proteins and their involvement in different cellular functions.
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Affiliation(s)
- R C Austin
- Department of Pathology and Molecular Medicine, McMaster University and the Hamilton Civic Hospitals Research Centre, 711 Concession Street, Hamilton, Ontario, Canada.
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36
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Claudepierre T, Mornet D, Pannicke T, Forster V, Dalloz C, Bolaños F, Sahel J, Reichenbach A, Rendon A. Expression of Dp71 in Müller glial cells: a comparison with utrophin- and dystrophin-associated proteins. Invest Ophthalmol Vis Sci 2000; 41:294-304. [PMID: 10634634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
PURPOSE The abnormal retinal electrophysiology observed in patients with Duchenne muscular dystrophy (DMD) has been attributed to an altered expression of C-terminal products of the dystrophin gene. It has been shown that Dp260 is expressed by photoreceptor cells, whereas Dp71 is present in glial cells. The present study was intended to identify all known members of the dystrophin superfamily and their associated proteins expressed in Müller glial cells (MGC). METHODS The expression of the proteins and of their messengers was studied in MGC cultures from 2-week-old rats, by polymerase chain reaction amplification, Western blot analysis, and immunocytochemistry. An immunocytochemical localization of the proteins was also performed on enzymatically dissociated Müller cells from adult rat retinas. RESULTS MGCs expressed a spliced isoform of Dp71 called Dp71f, as well as utrophin, beta-dystroglycan, delta and gamma-sarcoglycans, and alpha1-syntrophin. In morphologically preserved differentiated Müller cells, Dp71f was localized in clusters, utrophin was diffusely distributed in the cytoplasm, and dystrophin-associated proteins (DAPs) were membrane-bound. Most of these proteins were preferentially expressed in the vitread portion of the cells. Dp71f and utrophin expression was restricted to MGCs, whereas all DAPs were also present in other retinal cell types. CONCLUSIONS The exclusive localization of Dp71f and utrophin in MGCs suggests that these proteins, together with DAPs, play a specific role in these cells. Further knowledge of possible interactions of these proteins within a functional complex may provide new insights into the molecular basis of the electroretinogram phenotype in DMD.
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Affiliation(s)
- T Claudepierre
- Institute Nationale de la Santé et de la Recherche Médicale (INSERM) EMI 99-18, Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, Médicale A, CHRU, Strasbourg, France
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37
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Abstract
Duchenne muscular dystrophy is a fatal muscle disease that is often associated with cognitive impairment. Accordingly, dystrophin is found at the muscle sarcolemma and at postsynaptic sites in neurons. In muscle, dystrophin forms part of a membrane-spanning complex, the dystrophin-associated protein complex (DPC). Whereas the composition of the DPC in muscle is well documented, the existence of a similar complex in brain remains largely unknown. To determine the composition of DPC-like complexes in brain, we have examined the molecular associations and distribution of the dystrobrevins, a widely expressed family of dystrophin-associated proteins, some of which are components of the muscle DPC. beta-Dystrobrevin is found in neurons and is highly enriched in postsynaptic densities (PSDs). Furthermore, beta-dystrobrevin forms a specific complex with dystrophin and syntrophin. By contrast, alpha-dystrobrevin-1 is found in perivascular astrocytes and Bergmann glia, and is not PSD-enriched. alpha-Dystrobrevin-1 is associated with Dp71, utrophin, and syntrophin. In the brains of mice that lack dystrophin and Dp71, the dystrobrevin-syntrophin complexes are still formed, whereas in dystrophin-deficient muscle, the assembly of the DPC is disrupted. Thus, despite the similarity in primary sequence, alpha- and beta-dystrobrevin are differentially distributed in the brain where they form separate DPC-like complexes.
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Affiliation(s)
- D J Blake
- Department of Human Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, United Kingdom.
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38
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Abstract
To investigate the function of the major non-muscle dystrophin isoform, Dp71, we substituted a beta-galactosidase (betagal) reporter gene for Dp71 by homologous recombination in embryonic stem cells. Staining for betagal activity in chimeric mice revealed Dp71 promoter activity in glial cells in the CNS, in neurons of the inner nuclear and inner plexiform layers of the retina, and in the kidney tubules and collecting ducts. Our observations demonstrate that Dp71 is widely expressed in the adult CNS (retina, cerebellum, cerebral cortex, ependyma, and choroid) as well as the adult kidney epithelium and suggest a broad function for Dp71 in differentiated tissues.
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Affiliation(s)
- C N Lumeng
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109-0618, USA
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39
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Rivier F, Robert A, Royuela M, Hugon G, Bonet-Kerrache A, Mornet D. Utrophin and dystrophin-associated glycoproteins in normal and dystrophin deficient cardiac muscle. J Muscle Res Cell Motil 1999; 20:305-14. [PMID: 10471993 DOI: 10.1023/a:1005426920070] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this study, various members of the dystrophin family (dystrophin, the short dystrophin product Dp 71, utrophin and DRP2), and different members of the dystrophin-associated glycoprotein (DAG) complex (beta-dystroglycan, alpha-, beta-, gamma- and delta-sarcoglycans) were localized in bovine cardiac muscle using a battery of specific antibodies. We have established that dystrophin is exclusively associated with beta-dystroglycan and both alpha- and delta-sarcoglycans in cardiac muscle cell membranes. In contrast, utrophin is a specific component of intercalated disks together with beta- and gamma-sarcoglycans, while beta-dystroglycan, alpha- and delta-sarcoglycans are not present. Dp 71 is mainly localized at the T tubule transverse area. In dystrophin deficient cardiac muscle, utrophin and beta-sarcoglycan were observed in intercalated disks and at the sarcolemma of each cardiocyte. Our results revealed that complexes of associated glycoproteins differ in cardiac muscle when associated with dystrophin or utrophin. Despite the described sequence homologies between dystrophin and utrophin, the present results indicate that these proteins have different roles in some specific cardiac cell areas.
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Affiliation(s)
- F Rivier
- INSERM U128, IFR 24, Montpellier, France
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40
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Saito F, Masaki T, Kamakura K, Anderson LV, Fujita S, Fukuta-Ohi H, Sunada Y, Shimizu T, Matsumura K. Characterization of the transmembrane molecular architecture of the dystroglycan complex in schwann cells. J Biol Chem 1999; 274:8240-6. [PMID: 10075729 DOI: 10.1074/jbc.274.12.8240] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have demonstrated previously 1) that the dystroglycan complex, but not the sarcoglycan complex, is expressed in peripheral nerve, and 2) that alpha-dystroglycan is an extracellular laminin-2-binding protein anchored to beta-dystroglycan in the Schwann cell membrane. In the present study, we investigated the transmembrane molecular architecture of the dystroglycan complex in Schwann cells. The cytoplasmic domain of beta-dystroglycan was co-localized with Dp116, the Schwann cell-specific isoform of dystrophin, in the abaxonal Schwann cell cytoplasm adjacent to the outer membrane. beta-dystroglycan bound to Dp116 mainly via the 15 C-terminal amino acids of its cytoplasmic domain, but these amino acids were not solely responsible for the interaction of these two proteins. Interestingly, the beta-dystroglycan-precipitating antibody precipitated only a small fraction of alpha-dystroglycan and did not precipitate laminin and Dp116 from the peripheral nerve extracts. Our results indicate 1) that Dp116 is a component of the submembranous cytoskeletal system that anchors the dystroglycan complex in Schwann cells, and 2) that the dystroglycan complex in Schwann cells is fragile compared with that in striated muscle cells. We propose that this fragility may be attributable to the absence of the sarcoglycan complex in Schwann cells.
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Affiliation(s)
- F Saito
- Department of Neurology and Neuroscience, Teikyo University School of Medicine, Tokyo 173-8605, Japan
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41
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Keep NH, Norwood FL, Moores CA, Winder SJ, Kendrick-Jones J. The 2.0 A structure of the second calponin homology domain from the actin-binding region of the dystrophin homologue utrophin. J Mol Biol 1999; 285:1257-64. [PMID: 9887274 DOI: 10.1006/jmbi.1998.2406] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Utrophin is a close homologue of dystrophin, the protein defective in Duchenne muscular dystrophy. Like dystrophin, it is composed of three regions: an N-terminal region that binds actin filaments, a large central region with triple coiled-coil repeats, and a C-terminal region that interacts with components in the dystroglycan protein complex at the plasma membrane. The N-terminal actin-binding region consists of two calponin homology domains and is related to the actin-binding domains of a superfamily of proteins including alpha-actinin, spectrin and fimbrin. Here, we present the 2.0 A structure of the second calponin homology domain of utrophin solved by X-ray crystallography, and compare it to the other calponin homology domains previously determined from spectrin and fimbrin.
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Affiliation(s)
- N H Keep
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK.
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42
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Arsanto JP, Caubit X, Rivier F, Hugon G, Thouveny Y, Mornet D. Expression patterns of dystrophin products, especially of apodystrophin-1/Dp71, in the neural retina of Amphibian urodele Pleurodeles waltl. Int J Dev Biol 1999; 43:75-83. [PMID: 10213085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The expression patterns of the DMD (Duchenne Muscular Dystrophy) gene products, especially of Dp71 (apodystrophin-1) were investigated by immunofluorescence and immunoblotting in the retina of the Amphibian urodele Pleurodeles waltl. H-5A3 monoclonal antibody (mAb), directed against the C-terminal region of dystrophin/utrophin, and 5F3 mAb, directed against the last 31 amino acids of dystrophin and specific of Dp71, were used. Western blot analyses with H-5A3 mAb revealed distinct dystrophin-family isoforms in adult newt retinal extracts: a doublet 400-420 kDa, Dp260 isoform, a protein at about 120 kDa, and a diffuse zone at 70-80 kDa, which might correspond to Dp71. Reactivity with H-5A3 mAb appeared nearly restricted to the outer plexiform synaptic layer. On the other hand, Dp71-specific 5F3 mAb recognized trhee polypeptide bands at 70-80, 60-65 and 50-55 kDa in adult newt retina corresponding most probably to alternative spliced isoforms of Dp71. In immunohistochemistry by conventional epifluorescence microscopy, 5F3 labeling was mainly observed in the plexiform layers, the outer nuclear layer, and the photoreceptor inner segments, especially at the myoid regions. Analysis by confocal scanning laser microscopy (CSLM) revealed that 5F3 labeling was, in addition, present in the pigmented epithelium and the inner nuclear layer. Furthermore, CSLM showed that 5F3 staining at the myoids was concentrated at discrete domains underneath the plasma membrane. Our findings raised the question concerning the functional significance of Dp71 isoforms, especially at the myoid where Dp71 was detected for the first time, although it occurred here highly expressed. Putative role(s) played in this retinal compartment and other ones by Dp71 and/or other dystrophin isoforms were discussed.
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Affiliation(s)
- J P Arsanto
- Institut de Biologie du Développement de Marseille, CNRS-INSERM-Université de la Méditerranée, Laboratoire de Génétique et Physiologie, UMR 9943, France.
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43
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Sarig R, Mezger-Lallemand V, Gitelman I, Davis C, Fuchs O, Yaffe D, Nudel U. Targeted inactivation of Dp71, the major non-muscle product of the DMD gene: differential activity of the Dp71 promoter during development. Hum Mol Genet 1999; 8:1-10. [PMID: 9887326 DOI: 10.1093/hmg/8.1.1] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The dystrophin gene, which is defective in Duchenne muscular dystrophy (DMD), also encodes a number of smaller products controlled by internal promoters. Dp71, which consists of the two C-terminal domains of dystrophin, is the most abundant product of the gene in non-muscle tissues and is the major product in adult brain. To study the possible function of Dp71 and its expression during development, we specifically inactivated the expression of Dp71 by replacing its first and unique exon and a part of the concomitant intron with a beta-galactosidase reporter gene. X-Gal staining of Dp71-null mouse embryos and tissues revealed a very stage- and cell type-specific activity of the Dp71 promoter during development and during differentiation of various tissues, including the nervous system, eyes, limb buds, lungs, blood vessels, vibrissae and hair follicles. High activity of the Dp71 promoter often seemed to be associated with morphogenic events and terminal differentiation. In some tissues the activity greatly increased towards birth.
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Affiliation(s)
- R Sarig
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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44
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Abstract
Duchenne muscular dystrophy is caused by mutations in the dystrophin gene, a complex gene that generates a family of distinct isoforms. In immature muscle cells, two dystrophin isoforms are expressed, Dp427 and Dp71. To characterize the function of Dp71 in myogenesis, we have examined the expression of Dp71 in myogenic cells. The localization of Dp71 in these cells is distinct from the localization of Dp427. Whereas Dp427 localizes to focal adhesions and surface membrane during myogenesis, Dp71 localizes to stress fiberlike structures in myogenic cells. Biochemical fractionation of myogenic cells demonstrates that Dp71 cosediments with the actin bundles thus confirming this interaction. Furthermore, transfection of C2C12 myoblasts with constructs encoding Dp71 fused to green fluorescent protein targeted the protein to the actin microfilament bundles. These results demonstrate involvement of Dp71 with the actin cytoskeleton during myogenesis and suggest a role for Dp71 that is distinct from Dp427.
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Affiliation(s)
- P L Howard
- Department of Molecular and Medical Genetics, University of Toronto, Canada
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45
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Abstract
The Dp71 dystrophin isoform has recently been shown to localize to actin filament bundles in early myogenesis. We have identified an actin binding motif within Dp71 that is not found in other dystrophin isoforms. Actin overlay assays and transfection of COS-7 cells with fusion proteins of wild type and mutated Flag epitope-tagged Dp71 demonstrate that this motif is necessary and sufficient to direct localization of Dp71 to actin stress fibers. Furthermore, this localization is independent of alternative splicing which alters the C-terminus of the protein. The identification of an actin binding site suggests Dp71 may function to anchor membrane receptors to the cytoskeleton.
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Affiliation(s)
- P L Howard
- Department of Molecular and Medical Genetics, University of Toronto, Ont, Canada
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46
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Dorbani-Mamine L, Stoeckel ME, Jancsik V, Ayad G, Rendon A. Dystrophins in neurohypophysial lobe of normal and dehydrated rats: immunolocalization and biochemical characterization. Neuroreport 1998; 9:3583-7. [PMID: 9858364 DOI: 10.1097/00001756-199811160-00008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Dystrophin, utrophin and dystroglycan are present not only in muscle but also in brain. In muscle, they link the extracellular matrix to the cytoskeleton. Their function in brain is not understood. Here we show their presence in the hypothalamo-neurohypophysial system which secretes the neurohormones oxytocin and vasopressin. Using immunocytochemistry, we showed that dystrophins are present in the neurohypophysis of control rats. After water deprivation, immunoreactivity dramatically decreased and appeared in axonal swellings in the hypothalamic tract. Dystrophin immunostaining can be ascribed to dystrophin and/or utrophin as well as the DMD (Duchenne Muscular Dystrophy) gene short products Dp140 and Dp71 as revealed by Western immunoblots of synaptosomes isolated from neurohypophyses of control rats. In synaptosomes isolated from rats under water deprivation, the immunoreactivity entirely disappeared. Further biochemichal characterization of isolated neurosecretory granules (NSG) showed that Dp140 and Dp71 are enriched in the NSG stored in the swellings of the neurohypophysis whereas the NSG of the nerve endings are devoid of these proteins. In addition we observed that the presence of beta-dystroglycan and actin correlates with the presence of dystrophins. Our data favor a direct implication of the dystrophins and/or utrophin, dystroglycan and actin in the neurosecretory processes of the hypothalamo-neurohypophysial system.
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Affiliation(s)
- L Dorbani-Mamine
- Laboratoire de Neurobiologie, Université des Sciences et de la Technologie H. Boumediene, Alger, Algeria
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47
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Moizard MP, Billard C, Toutain A, Berret F, Marmin N, Moraine C. Are Dp71 and Dp140 brain dystrophin isoforms related to cognitive impairment in Duchenne muscular dystrophy? Am J Med Genet 1998; 80:32-41. [PMID: 9800909 DOI: 10.1002/(sici)1096-8628(19981102)80:1<32::aid-ajmg6>3.0.co;2-y] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Molecular study and neuropsychological analysis were performed concurrently on 49 patients with Duchenne muscular dystrophy (DMD) in order to find a molecular explanation for the cognitive impairment observed in most DMD patients. Complete analysis of the dystrophin gene was performed to define the localization of deletions and duplications in relation to the different DMD promoters. Qualitative analysis of the Dp71 transcript and testing for the specific first exon of Dp140 were also carried out. Neuropsychological analysis assessed verbal and visuospatial intelligence, verbal memory, and reading skills. Comparison of molecular and psychometric findings demonstrated that deletions and duplications that were localized in the distal part of the gene seemed to be preferentially associated with cognitive impairment. Two altered Dp71 transcripts and two deleted Dp140 DNA sequences were found in four patients with severe cerebral dysfunction. These findings suggest that some sequences located in the distal part of the gene and, in particular, some DMD isoforms expressed in the brain may be related to the cognitive impairment associated with DMD.
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Affiliation(s)
- M P Moizard
- Unité de Génétique, Hopital Bretonneau, Tours, France
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48
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Abstract
The gene which is defective in Duchenne muscular dystrophy (DMD) is the largest known gene. The product of the gene in muscle, dystrophin, is a 427 kDa protein. The same gene encodes at least six additional products: two non-muscle dystrophin isoforms transcribed from promoters located in the 5'-end region of the gene and four smaller proteins transcribed from internal promoters located further downstream. Several other genes, encoding evolutionarily related proteins, have been identified. These include a structurally very similar gene in vertebrates encoding utrophin (DRP1), which is closely related to dystrophin, and a number of small and simple genes in vertebrates or invertebrates encoding proteins similar to some of the small products of the DMD gene. We have isolated a sea urchin gene showing very strong sequence and structural homology with the DMD and utrophin genes. Sequence and intron/exon structure similarities suggest that this gene is related to a precursor of both the DMD gene and the gene encoding utrophin. The sea urchin gene has the unique complex structure of the DMD gene. There is at least one, and possibly more, product(s) transcribed from internal promoters, as well as a large product of >300 kDa containing at least three of the four major domains of dystrophin. The small product seems to be evolutionarily related to Dp116, one of the small products of the human DMD gene. Partial characterization of this gene helped us to construct an evolutionary tree connecting the vertebrate dystrophin gene family with related genes in invertebrates. The constructed evolutionary tree also implies that the vertebrate small and simple structured gene encoding a Dp71-like protein, called DRP2 , evolved from the dystrophin/utrophin ancestral large and complex gene by a duplication of only a small part of the gene.
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Affiliation(s)
- J Wang
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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49
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Finn DM, Ohlendieck K. Oligomerization of beta-dystroglycan in rabbit diaphragm and brain as revealed by chemical crosslinking. Biochim Biophys Acta 1998; 1370:325-36. [PMID: 9545593 DOI: 10.1016/s0005-2736(97)00283-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The surface component beta-dystroglycan is a member of the dystrophin-glycoprotein complex providing a trans-sarcolemmal linkage between the actin membrane cytoskeleton and the extracellular matrix component laminin-alpha2. Although abnormalities in this complex are involved in the pathophysiology of various neuromuscular disorders, little is known about the organization of dystrophin-associated glycoproteins in diaphragm and brain. We therefore investigated the oligomerization of beta-dystroglycan and its connection with the most abundant dystrophin homologues in these two tissues. Employing detergent solubilization and alkaline extraction procedures of native membranes, it was confirmed that beta-dystroglycan behaves like an integral surface molecule as predicted by its cDNA sequence. Immunoblot analysis following chemical crosslinking of native membranes showed that beta-dystroglycan has a tendency to form high-molecular-mass complexes. Within these crosslinkable complexes, immuno-reactive overlaps were observed between beta-dystroglycan, alpha-dystroglycan, laminin and 427 kDa dystrophin in diaphragm and skeletal muscle. In synaptosomes, the major brain dystrophin isoform Dp116 also exhibited an immuno-reactive overlap with members of the dystroglycan complex. These findings demonstrate that beta-dystroglycan does not exist as a monomer in native membranes and imply that certain dystrophin isoforms and dystrophin-associated components interact with this surface protein in diaphragm and brain as has been previously shown for skeletal and heart muscle.
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Affiliation(s)
- D M Finn
- Department of Pharmacology, University College Dublin, Belfield, Dublin 4, Ireland
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Vita G, Mazzeo A, Muglia U, Girlanda P, Toscano A, Rodolico C, Migliorato A. Dp116, talin, vinculin and vimentin immunoreactivities following nerve transection. Neuroreport 1998; 9:697-702. [PMID: 9559941 DOI: 10.1097/00001756-199803090-00025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The time course of the expression of Dp116, talin, vinculin and vimentin in rat sciatic nerve was investigated after experimental transection. Dp116 was still found at 5 days after experiment in some degenerating myelinated fibers of both proximal and distal stumps. The findings are consistent with the known preservation of electrical excitability of the distal nerve in the first days after injury. Some regenerating nerve fibers into the neuroma also expressed Dp116 at 25 and 40 days after nerve transection. Talin and vinculin markedly and diffusely immunostained the neuroma. Talin in the distal stump and vimentin in both proximal and distal stumps were found decreased during the time course of the experiment. Vinculin binding increased in the distal stump, due to a real overexpression or simply to a cross-reaction to degeneration products.
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Affiliation(s)
- G Vita
- Institute of Neurological and Neurosurgical Sciences, Policlinico Universitario, Messina, Italy
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