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Am J Hum Genet. 2013 Feb 7;92(2):271-8. doi: 10.1016/j.ajhg.2012.12.007. Epub 2013 Jan 17.

Constitutive activation of the calcium sensor STIM1 causes tubular-aggregate myopathy.

Author information

1
Département de Médecine Translationelle et Neurogénétique, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.

Abstract

Tubular aggregates are regular arrays of membrane tubules accumulating in muscle with age. They are found as secondary features in several muscle disorders, including alcohol- and drug-induced myopathies, exercise-induced cramps, and inherited myasthenia, but also exist as a pure genetic form characterized by slowly progressive muscle weakness. We identified dominant STIM1 mutations as a genetic cause of tubular-aggregate myopathy (TAM). Stromal interaction molecule 1 (STIM1) is the main Ca(2+) sensor in the endoplasmic reticulum, and all mutations were found in the highly conserved intraluminal Ca(2+)-binding EF hands. Ca(2+) stores are refilled through a process called store-operated Ca(2+) entry (SOCE). Upon Ca(2+)-store depletion, wild-type STIM1 oligomerizes and thereby triggers extracellular Ca(2+) entry. In contrast, the missense mutations found in our four TAM-affected families induced constitutive STIM1 clustering, indicating that Ca(2+) sensing was impaired. By monitoring the calcium response of TAM myoblasts to SOCE, we found a significantly higher basal Ca(2+) level in TAM cells and a dysregulation of intracellular Ca(2+) homeostasis. Because recessive STIM1 loss-of-function mutations were associated with immunodeficiency, we conclude that the tissue-specific impact of STIM1 loss or constitutive activation is different and that a tight regulation of STIM1-dependent SOCE is fundamental for normal skeletal-muscle structure and function.

PMID:
23332920
PMCID:
PMC3567276
DOI:
10.1016/j.ajhg.2012.12.007
[Indexed for MEDLINE]
Free PMC Article

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