Identification of a Mutation Near a Functional Site of the β cardiac myosin Heavy Chain Gene in a Family with Hypertrophic Cardiomyopathy

Several mutations within the gene coding for the cardiac β myosin heavy chain (designed MYH7) have been shown to be responsible for Familial Hypertrophic Cardiomyopathy (FHC) in several families, and evidence of genetic heterogeneity has been reported. To investigate the MYH7 gene as the cause of the disease in a small family with FHC, inheritance of the disease and chromosome 14 q11-q12 markers haplotype were studied, exons coding for the head domain of the cardiac β myosin heavy chain (β MHC) were analysed for mutations by MDE gel electrophoresis, and sequenced. We report a mutation within exon eight of the MYH7 gene at a very conserved amino acid at position 232, which results in the conversion of an asparagine to serine. This residue Asn-232 is located in a MHC area that has been recently identified as a critical site for ATPase activity. According to recent results on the three-dimensional structure of the myosin head or subfragment-1 (S1), Asn-232 is located in an α-helix which forms part of the nucleotide binding pocket. Although this mutation affects an active site, it seems to be associated with a favourable prognosis and a weak penetrance in this family.