The I4895T mutation in the type 1 ryanodine receptor induces fiber-type specific alterations in skeletal muscle that mimic premature aging.

Abstract

The I4898T (IT) mutation in type 1 ryanodine receptor (RyR1), the Ca(2+) release channel of the sarcoplasmic reticulum (SR) is linked to a form of central core disease (CCD) in humans and results in a nonleaky channel and excitation-contraction uncoupling. We characterized age-dependent and fiber-type-dependent alterations in muscle ultrastructure, as well as the magnitude and spatiotemporal properties of evoked Ca(2+) release in heterozygous Ryr1(I4895T/WT) (IT/+) knock-in mice on a mixed genetic background. The results indicate a classical but mild CCD phenotype that includes muscle weakness and the presence of mitochondrial-deficient areas in type I fibers. Electrically evoked Ca(2+) release is significantly reduced in single flexor digitorum brevis (FDB) fibers from young and old IT/+ mice. Structural changes are strongly fiber-type specific, affecting type I and IIB/IIX fibers in very distinct ways, and sparing type IIA fibers. Ultrastructural alterations in our IT/+ mice are also present in wild type, but at a lower frequency and older ages, suggesting that the disease mutation on the mixed background promotes an acceleration of normal age-dependent changes. The observed functional and structural alterations and their similarity to age-associated changes are entirely consistent with the known properties of the mutated channel, which result in reduced calcium release as is also observed in normal aging muscle. In strong contrast to these observations, a subset of patients with the analogous human heterozygous mutation and IT/+ mice on an inbred 129S2/SvPasCrl background exhibit a more severe disease phenotype, which is not directly consistent with the mutated channel properties.

• Authors: Simona Boncompagni, Ryan E Loy, Robert T Dirksen, Clara Franzini-Armstrong
• Journal: Aging cell (Aging Cell) Vol. 9 Issue 6 Pg. 958-70 (Dec 2010) ISSN: 1474-9726 [Electronic] England
• PMID: 20961389 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
• Copyright: © 2010 The Authors. Aging Cell © 2010 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.

Chemical References

• Ryanodine Receptor Calcium Release Channel
• Calcium

Topics

• Aging, Premature (genetics)
• Animals
• Calcium (metabolism)
• Electrophysiological Phenomena
• Mice
• Mice, Knockout
• Muscle Fibers, Skeletal (physiology)
• Mutation
• Ryanodine Receptor Calcium Release Channel (genetics, metabolism)