title: The zebrafish dag1 mutant: a novel genetic model for dystroglycanopathies.
abstract: In a forward genetic approach to identify novel genes for congenital muscle diseases, a zebrafish mutant, designated patchytail, was identified that exhibits degenerating muscle fibers with impaired motility behavior. Genetic mapping identified a genomic locus containing the zebrafish ortholog of the dystroglycan gene (DAG1). Patchytail fish contain a point mutation (c.1700T>A) in dag1, resulting in a missense change p.V567D. This change is associated with reduced transcripts and a complete absence of protein. The absence of α-dystroglycan and β-dystroglycan caused destabilization of dystroglycan complex, resulting in membrane damages. Membrane damage was localized on the extracellular matrix at myosepta as well as basement membrane between adjacent myofibers. These studies also identified structural abnormalities in triads at 3 days post fertilization (dpf) of dystroglycan-deficient muscles, significantly preceding sarcolemmal damage that becomes evident at 7 dpf. Immunofluorescence studies identified a subpopulation of dystroglycan that is expressed at t-tubules in normal skeletal muscles. In dag1-mutated fish, smaller and irregular-shaped t-tubule vesicles, as well as highly disorganized terminal cisternae of sarcoplasmic reticulum, were common. In addition to skeletal muscle defects, dag1-mutated fish have brain abnormalities and ocular defects in posterior as well as anterior chambers. These phenotypes of dystroglycan-deficient fish are highly reminiscent of the phenotypes observed in the human conditions muscle-eye-brain disease and Walker-Warburg syndrome. This animal model will provide unique opportunities in the understanding of biological functions of dystroglycan in a wide range of dystroglycanopathies, as disruption of this gene in higher vertebrates results in early embryonic lethality.
authors.affiliation: Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Children's Hospital Boston, Boston, MA 02115, USA.
authors.forename: Vandana
authors.initials: V
authors.lastname: Gupta
authors.forename: Genri
authors.initials: G
authors.lastname: Kawahara
authors.forename: Stacey R
authors.initials: SR
authors.lastname: Gundry
authors.forename: Aye T
authors.initials: AT
authors.lastname: Chen
authors.forename: Wayne I
authors.initials: WI
authors.lastname: Lencer
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhou
authors.forename: Leonard I
authors.initials: LI
authors.lastname: Zon
authors.forename: Louis M
authors.initials: LM
authors.lastname: Kunkel
authors.forename: Alan H
authors.initials: AH
authors.lastname: Beggs
mesh_terms: D000818:Animals; D001483:Base Sequence; D004195:Disease Models, Animal; D049030:Dystroglycans / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009043:Motor Activity; D018482:Muscle, Skeletal / Q000378:metabolism; D009136:Muscular Dystrophies / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D020125:Mutation, Missense; D017354:Point Mutation; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C560199:DAG1 protein, zebrafish; D029961:Zebrafish Proteins; D049030:Dystroglycans