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ZFIN ID: ZDB-PUB-070711-8
Zebrafish relatively relaxed mutants have a ryanodine receptor defect, show slow swimming and provide a model of multi-minicore disease
Hirata, H., Watanabe, T., Hatakeyama, J., Sprague, S.M., Saint-Amant, L., Nagashima, A., Cui, W.W., Zhou, W., and Kuwada, J.Y.
Date: 2007
Source: Development (Cambridge, England)   134(15): 2771-2781 (Journal)
Registered Authors: Cui, Wilson, Hirata, Hiromi, Kuwada, John, Saint-Amant, Louis, Sprague, Shawn, Zhou, Weibin
Keywords: Zebrafish, Ryanodine receptor, Muscle, Calcium, Multi-minicore disease
MeSH Terms:
  • Animals
  • Animals, Genetically Modified
  • Base Sequence
  • Calcium Signaling/physiology
  • Central Nervous System/physiology
  • Disease Models, Animal*
  • Embryo, Nonmammalian
  • Models, Biological
  • Molecular Sequence Data
  • Muscle Contraction/genetics
  • Muscle Fibers, Fast-Twitch/metabolism
  • Muscle Fibers, Fast-Twitch/physiology
  • Muscular Diseases/congenital
  • Muscular Diseases/genetics*
  • Muscular Diseases/pathology*
  • Muscular Diseases/physiopathology
  • Protein Isoforms/genetics
  • RNA Splice Sites/genetics
  • Ryanodine Receptor Calcium Release Channel/genetics*
  • Ryanodine Receptor Calcium Release Channel/metabolism
  • Swimming*
  • Zebrafish/embryology
  • Zebrafish/genetics*
PubMed: 17596281 Full text @ Development
FIGURES
ABSTRACT
Wild-type zebrafish embryos swim away in response to tactile stimulation. By contrast, relatively relaxed mutants swim slowly due to weak contractions of trunk muscles. Electrophysiological recordings from muscle showed that output from the CNS was normal in mutants, suggesting a defect in the muscle. Calcium imaging revealed that Ca(2+) transients were reduced in mutant fast muscle. Immunostaining demonstrated that ryanodine and dihydropyridine receptors, which are responsible for Ca(2+) release following membrane depolarization, were severely reduced at transverse-tubule/sarcoplasmic reticulum junctions in mutant fast muscle. Thus, slow swimming is caused by weak muscle contractions due to impaired excitation-contraction coupling. Indeed, most of the ryanodine receptor 1b (ryr1b) mRNA in mutants carried a nonsense mutation that was generated by aberrant splicing due to a DNA insertion in an intron of the ryr1b gene, leading to a hypomorphic condition in relatively relaxed mutants. RYR1 mutations in humans lead to a congenital myopathy, multi-minicore disease (MmD), which is defined by amorphous cores in muscle. Electron micrographs showed minicore structures in mutant fast muscles. Furthermore, following the introduction of antisense morpholino oligonucleotides that restored the normal splicing of ryr1b, swimming was recovered in mutants. These findings suggest that zebrafish relatively relaxed mutants may be useful for understanding the development and physiology of MmD.
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