Limb-girdle muscular dystrophy (LGMD) is a clinically and genetically heterogeneous group of myopathies, including autosomal dominant and recessive forms. To date, two autosomal dominant forms have been recognized: LGMD1A, linked to chromosome 5q, and LGMD1B, associated with cardiac defects and linked to chromosome 1q11-21. Here we describe eight patients from two different families with a new form of autosomal dominant LGMD, which we propose to call LGMD1C, associated with a severe deficiency of caveolin-3 in muscle fibres. Caveolin-3 (or M-caveolin) is the muscle-specific form of the caveolin protein family, which also includes caveolin-1 and -2 (refs 4-9). Caveolins are the principal protein components of caveolae (50-100 nm invaginations found inmost cell types) which represent appendages or sub- compartments of plasma membranes. We localized the human caveolin-3 gene (CAV3) to chromosome 3p25 and identified two mutations in the gene: a missense mutation in the membrane-spenning region and a micro-deletion in the scaffolding domain. These mutations may interfere with caveolin-3 oligomerization and disrupt caveolae formation at the muscle cell plasma membrane.
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