Volume 9, Issue 6 pp. 958-970

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

Simona Boncompagni

Simona Boncompagni

IIM - Interuniversitary Institute of Myology, DNI – Department of Neuroscience and Imaging, Ce.S.I.- Centro Scienze dell’Invecchiamento, University of Studi G. d’Annunzio , 66013 Chieti, Italy

Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA, USA

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Ryan E. Loy

Ryan E. Loy

Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA

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Robert T. Dirksen

Robert T. Dirksen

Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA

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Clara Franzini-Armstrong

Clara Franzini-Armstrong

Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA, USA

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First published: 06 September 2010
Citations: 34
Simona Boncompagni, PhD, CeSI, Center of Research on Ageing, Università G. d’Annunzio of Chieti, Chieti, CH I-66013, Italy. Tel.: +39 0871 541218; fax: +39 0871 541422; e-mail: [email protected]

Summary

The I4898T (IT) mutation in type 1 ryanodine receptor (RyR1), the Ca2+ 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 Ca2+ release in heterozygous Ryr1I4895T/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 Ca2+ 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.

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