Congenital myopathy results from misregulation of a muscle Ca2+ channel by mutant Stac3

Proc Natl Acad Sci U S A. 2017 Jan 10;114(2):E228-E236. doi: 10.1073/pnas.1619238114. Epub 2016 Dec 21.


Skeletal muscle contractions are initiated by an increase in Ca2+ released during excitation-contraction (EC) coupling, and defects in EC coupling are associated with human myopathies. EC coupling requires communication between voltage-sensing dihydropyridine receptors (DHPRs) in transverse tubule membrane and Ca2+ release channel ryanodine receptor 1 (RyR1) in the sarcoplasmic reticulum (SR). Stac3 protein (SH3 and cysteine-rich domain 3) is an essential component of the EC coupling apparatus and a mutation in human STAC3 causes the debilitating Native American myopathy (NAM), but the nature of how Stac3 acts on the DHPR and/or RyR1 is unknown. Using electron microscopy, electrophysiology, and dynamic imaging of zebrafish muscle fibers, we find significantly reduced DHPR levels, functionality, and stability in stac3 mutants. Furthermore, stac3NAM myofibers exhibited increased caffeine-induced Ca2+ release across a wide range of concentrations in the absence of altered caffeine sensitivity as well as increased Ca2+ in internal stores, which is consistent with increased SR luminal Ca2+ These findings define critical roles for Stac3 in EC coupling and human disease.

Keywords: Native American myopathy; dihydropyridine receptor; excitation–contraction coupling; skeletal muscle; zebrafish.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / physiology*
  • Animals
  • Animals, Genetically Modified
  • Caffeine / pharmacology
  • Calcium
  • Calcium Channels, L-Type / physiology*
  • Embryo, Nonmammalian
  • Microscopy, Electron
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / physiology*
  • Muscle Fibers, Skeletal / ultrastructure
  • Mutation
  • Myotonia Congenita
  • Ryanodine Receptor Calcium Release Channel / physiology*
  • Zebrafish
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / physiology*


  • Adaptor Proteins, Signal Transducing
  • Calcium Channels, L-Type
  • Ryanodine Receptor Calcium Release Channel
  • Stac3 protein, zebrafish
  • Zebrafish Proteins
  • Caffeine
  • Calcium