Ca2+ dysregulation in Ryr1(I4895T/wt) mice causes congenital myopathy with progressive formation of minicores, cores, and nemaline rods

Proc Natl Acad Sci U S A. 2009 Dec 22;106(51):21813-8. doi: 10.1073/pnas.0912126106. Epub 2009 Dec 3.


Ryr1(I4895T/wt) (IT/+) mice express a knockin mutation corresponding to the human I4898T EC-uncoupling mutation in the type 1 ryanodine receptor/Ca(2+) release channel (RyR1), which causes a severe form of central core disease (CCD). IT/+ mice exhibit a slowly progressive congenital myopathy, with neonatal respiratory stress, skeletal muscle weakness, impaired mobility, dorsal kyphosis, and hind limb paralysis. Lesions observed in myofibers from diseased mice undergo age-dependent transformation from minicores to cores and nemaline rods. Early ultrastructural abnormalities include sarcomeric misalignment, Z-line streaming, focal loss of cross-striations, and myofibrillar splitting and intermingling that may arise from defective myofibrillogenesis. However, manifestation of the disease phenotype is highly variable on a Sv129 genomic background. Quantitative RT-PCR shows an equimolar ratio of WT and mutant Ryr1 transcripts within IT/+ myofibers and total RyR1 protein expression levels are normal. We propose a unifying theory in which the cause of core formation lies in functional heterogeneity among RyR1 tetramers. Random combinations of normal and either leaky or EC-uncoupled RyR subunits would lead to spatial differences in Ca(2+) transients; the resulting heterogeneity of contraction among myofibrils would lead to focal, irreversible tearing and shearing, which would, over time, enlarge to form minicores, cores, and nemaline rods. The IT/+ mouse line is proposed to be a valid model of RyR1-related congenital myopathy, offering high potential for elucidation of the pathogenesis of skeletal muscle disorders arising from impaired EC coupling.

Publication types

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

MeSH terms

  • Animals
  • Calcium / physiology*
  • Mice
  • Microscopy, Electron, Transmission
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / ultrastructure
  • Myopathies, Nemaline / physiopathology*
  • Phenotype
  • RNA, Messenger / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Ryanodine Receptor Calcium Release Channel / genetics
  • Ryanodine Receptor Calcium Release Channel / physiology*


  • RNA, Messenger
  • Ryanodine Receptor Calcium Release Channel
  • Calcium