Cardiac myosin binding protein-C gene splice acceptor site mutation is associated with familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (FHC) is an autosomal dominant disease characterized by a ventricular hypertrophy predominantly affecting the interventricular septum and associated with a large extent of myocardial and myofibrillar disarray. It is the most common cause of sudden death in the young. In the four disease loci found, three genes have been identified which code for beta-myosin heavy chain, cardiac troponin T and alpha-tropomyosin. Recently the human cardiac myosin binding protein-C (MyBP-C) gene was mapped to chromosome 11p11.2 (ref. 8), making this gene a good candidate for the fourth locus, CMH4 (ref. 5). Indeed, MyBP-C is a substantial component of the myofibrils that interacts with several proteins of the thick filament of the sarcomere. In two unrelated French families linked to CMH4, we found a mutation in a splice acceptor site of the MyBP-C gene, which causes the skipping of the associated exon and could produce truncated cardiac MyBP-Cs. Mutations in the cardiac MyBP-C gene likely cause chromosome 11-linked hypertrophic cardiomyopathy, further supporting the hypothesis that hypertrophic cardiomyopathy results from mutations in genes encoding contractile proteins

A disease locus for familial hypertrophic cardiomyopathy maps to chromosome 1q3

Familial hypertrophic cardiomyopathy (FHC) is caused by missense mutations in the beta cardiac myosin heavy chain (MHC) gene in less than half of affected individuals. To identify the location of another gene involved in this disorder, a large family with FHC not linked to the beta MHC gene was studied. Linkage was detected between the disease in this family and a locus on chromosome 1q3 (maximum multipoint lod score = 8.47). Analyses in other families with FHC not linked to the beta MHC gene, revealed linkage to the chromosome 1 locus in two and excluded linkage in six. Thus mutations in at least three genetic loci can cause FHC. Three sarcomeric contractile proteins--troponin I, tropomyosin and actin--are strong candidate FHC genes at the chromosome 1 locus

A mutation in the α tropomyosin gene TPM3 associated with autosomal dominant nemaline myopathy

Nemaline myopathies are diseases characterized by the presence in muscle fibres of pathognomonic rod bodies. These are composed largely of alpha−actinin and actin. We have identified a missense mutation in the alpha−tropomyosin gene, TPM3, which segregates completely with the disease in a family whose autosomal dominant nemaline myopathy we had previously localized to chromosome 1p13−q25. The mutation substitutes an arginine residue for a highly conserved methionine in a putative actin−binding site near the N terminus of the alpha−tropomyosin. The mutation may strengthen tropomyosin − actin binding, leading to rod body formation, by adding a further basic residue to the postulated actin−binding motif