Distribution of cardiac myosin isozymes in cardiomyopathy: immunohistochemical and gene analysis.

We characterized cardiac myosin isoforms by immunohistochemical approaches using monoclonal antibodies and demonstrated the existence of a distinctive type of cardiac myosin heavy chain which predominates in the fetal stage but is depressed during postnatal development. Furthermore, we showed that this type of cardiac myosin heavy chain was markedly expressed in patients with dilated cardiomyopathy. The results suggested that the pathologic process involved in dilated cardiomyopathy affects myocardial differentiation by the inhibition of the myosin gene switching that normally occurs during muscle maturation. However, we could not find any polymorphism in myosin gene in our population sample of dilated cardiomyopathy. The pathophysiological role of fetal type cardiac myosin expression in dilated cardiomyopathy will be clarified by the characterization of the myosin near future.