Abstract
We have determined that a missense mutation in exon 13 of the β-myosin heavy chain (βMHC) gene is expressed in the messenger RNA (mRNA) isolated from a right ventricular endomyocardial biopsy obtained from the proband of a family with hypertrophic cardiomyopathy. The mutation is the result of a substitution of an adenine for a guanine residue in one allele of the βMHC gene and creates a second recognition site for the restriction endonuclease Ddel in exon 13. The mutation is inherited in a Mendelian fashion and co- segregates with hypertrophic cardiomyopathy in this family. Complementary DNAs synthesized from RNA isolated from the endomyocardial biopsy were cloned into a plasmid vector and sequenced to confirm the expression of both the normal and mutant allele in mRNA of myocardial tissue. This is the first report of the transcription of a mutant βMHC gene allele into mRNA of the myocardium.