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 be ta-cardiac myosin heavy chain (MHC) gene mutations that cause familial hypertrophic cardiomyopathy (FHC). Since more than 10 different mutat ions within this gene have been demonstrated to cause FHC in unrelated individuals, the genetic diagnosis of this condition will involve scr eening the beta-MHC gene. The accuracy with which RNase protection ide ntifies such mutations is critical to defining the utility of this met hodology in detecting mutations that cause FHC. Methods and Results Tw elve unrelated individuals with FHC were selected for further study be cause their beta-MHC genes had been screened for mutations by use of R Nase protection, and no mutation was found. We performed linkage analy sis of the families of these 12 probands using polymorphic short tande m repeats within the beta-MHC gene to determine whether FHC was geneti cally linked to the MHC locus on chromosome 14. FHC was not geneticall y linked to the MHC locus in 11 families whose beta-cardiac MHC gene d id not contain mutations detectable by RNase protection. Conclusions W e conclude that RNase protection is a sensitive method for screening f or mutations within the beta-cardiac MHC gene. Further, mutations in t he noncoding regions of the beta-MHC gene and mutations in the alpha-c ardiac MHC gene are not a common cause of FHC. Negative RNase protecti on assays of affected individuals suggest that their FHC is due to mut ations at other loci.