An evaluation of ribonuclease protection assays for the detection of beta-cardiac myosin heavy chain gene mutations.

BACKGROUND: Ribonuclease (RNase) protection has been used to identify beta-cardiac myosin heavy chain (MHC) gene mutations that cause familial hypertrophic cardiomyopathy (FHC). Since more than 10 different mutations within this gene have been demonstrated to cause FHC in unrelated individuals, the genetic diagnosis of this condition will involve screening the beta-MHC gene. The accuracy with which RNase protection identifies such mutations is critical to defining the utility of this methodology in detecting mutations that cause FHC. METHODS AND RESULTS: Twelve unrelated individuals with FHC were selected for further study because their beta-MHC genes had been screened for mutations by use of RNase protection, and no mutation was found. We performed linkage analysis of the families of these 12 probands using polymorphic short tandem repeats within the beta-MHC gene to determine whether FHC was genetically linked to the MHC locus on chromosome 14. FHC was not genetically linked to the MHC locus in 11 families whose beta-cardiac MHC gene did not contain mutations detectable by RNase protection. CONCLUSIONS: We conclude that RNase protection is a sensitive method for screening for mutations within the beta-cardiac MHC gene. Further, mutations in the noncoding regions of the beta-MHC gene and mutations in the alpha-cardiac MHC gene are not a common cause of FHC. Negative RNase protection assays of affected individuals suggest that their FHC is due to mutations at other loci.