Cardiac phenotypic markers expressed in early stages of both cardiac and skeletal muscle development.

We have examined changes in the expression of chicken myosin heavy chain (MHC) mRNAs in the heart and skeletal muscles during normal development and in regenerating adult muscles. cDNA clones isolated from adult heart and regenerating skeletal muscle libraries revealed more than 98% sequence homology in the 3' untranslated regions. Using specific cDNA probes we have detected ventricular MHC transcripts in the heart and in early developmental stages of fast as well as slow skeletal muscles. The expression of ventricular MHC mRNA in skeletal muscles is especially significant since, in contrast to mammals, the avian ventricular and slow MHC mRNAs are encoded by different genes.