Heart-to-heart. New approaches for gene transfer in the myocardium.

T he advent of molecular cloning has led to the rapid isolation, identification, and characterization of genes critical for the maintenance of normal contractile, conduction, and adaptive responses of the heart. Several studies have employed specific gene probes to precisely identify molecular defects in a variety of hereditary cardiovascular diseases such as familial hypercholesterolemia,' abetalipoproteinemia,2 and hypertrophic cardiomyopathy.3'4 Using a panel of gene probes to analyze qualitative and quantitative alterations in specific cardiac messenger RNAs, several investigators have delineated complex genetic responses during cardiac growth and hypertrophy that include the induction of proto-oncogenes and immediate early genes5-7 as well as the upregulation of constitutively