ZFIN ID: ZDB-PUB-070427-21
The zebrafish candyfloss mutant implicates extracellular matrix adhesion failure in laminin {alpha}2-deficient congenital muscular dystrophy
Hall, T.E., Bryson-Richardson, R.J., Berger, S., Jacoby, A.S., Cole, N.J., Hollway, G.E., Berger, J., and Currie, P.D.
Date: 2007
Source: Proceedings of the National Academy of Sciences of the United States of America   104(17): 7092-7097 (Journal)
Registered Authors: Berger, Joachim, Berger, Silke, Bryson-Richardson, Robert, Cole, Nicholas, Currie, Peter D., Hall, Thomas, Jacoby, Arie
Keywords: muscle, degeneration, fiber, time-lapse
MeSH Terms:
  • Adhesiveness/drug effects
  • Alleles
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cell Death/drug effects
  • Codon, Nonsense/genetics
  • Embryo, Nonmammalian/cytology
  • Embryo, Nonmammalian/drug effects
  • Embryo, Nonmammalian/innervation
  • Embryo, Nonmammalian/ultrastructure
  • Extracellular Matrix/drug effects
  • Extracellular Matrix/metabolism*
  • Gene Expression Regulation/drug effects
  • Intercellular Junctions/drug effects
  • Intercellular Junctions/ultrastructure
  • Laminin/chemistry
  • Laminin/deficiency*
  • Laminin/genetics
  • Laminin/metabolism
  • Molecular Sequence Data
  • Motor Activity/drug effects
  • Muscle Fibers, Skeletal/drug effects
  • Muscle Fibers, Skeletal/pathology
  • Muscular Dystrophy, Animal/congenital*
  • Mutant Proteins/metabolism*
  • Oligonucleotides, Antisense/pharmacology
  • Open Reading Frames/genetics
  • Sarcolemma/drug effects
  • Sarcolemma/pathology
  • Sequence Homology, Amino Acid
  • Zebrafish/abnormalities*
  • Zebrafish/embryology
  • Zebrafish Proteins/metabolism*
PubMed: 17438294 Full text @ Proc. Natl. Acad. Sci. USA
FIGURES
ABSTRACT
Mutations in the human laminin alpha2 (LAMA2) gene result in the most common form of congenital muscular dystrophy (MDC1A). There are currently three models for the molecular basis of cellular pathology in MDC1A: (i) lack of LAMA2 leads to sarcolemmal weakness and failure, followed by cellular necrosis, as is the case in Duchenne muscular dystrophy (DMD); (ii) loss of LAMA2-mediated signaling during the development and maintenance of muscle tissue results in myoblast proliferation and fusion defects; (iii) loss of LAMA2 from the basement membrane of the Schwann cells surrounding the peripheral nerves results in a lack of motor stimulation, leading to effective denervation atrophy. Here we show that the degenerative muscle phenotype in the zebrafish dystrophic mutant, candyfloss (caf) results from mutations in the laminin alpha2 (lama2) gene. In vivo time-lapse analysis of mechanically loaded fibers and membrane permeability assays suggest that, unlike DMD, fiber detachment is not initially associated with sarcolemmal rupture. Early muscle formation and myoblast fusion are normal, indicating that any deficiency in early Lama2 signaling does not lead to muscle pathology. In addition, innervation by the primary motor neurons is unaffected, and fiber detachment stems from muscle contraction, demonstrating that muscle atrophy through lack of motor neuron activity does not contribute to pathology in this system. Using these and other analyses, we present a model of lama2 function where fiber detachment external to the sarcolemma is mechanically induced, and retracted fibers with uncompromised membranes undergo subsequent apoptosis.
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