Complete sequence and characterization of chick ventricular myosin heavy chain in the developing atria

We isolated five complementary DNA (cDNA) clones, encoding the chick ventri cular myosin heavy chain (MyHC) by reverse transcription polymerase chain r eaction (RT-PCR). The entire cDNA consists of 5995 nucleotides with the 52 bp 5'-untranslated region and the 129 bp 3'-untranslated region. The comple te cDNA encodes 1937 amino acids. Expression of the chick ventricular MyHC gene was also studied by Northern blot analysis. This gene continued to be strongly expressed in the ventricle during cardiac development. On the othe r hand, its expression was moderate in the early embryonic atria, and was d own-regulated during development. In the adult atria, this gene was express ed at very low levels. To determine the localization of the ventricular MyH C protein, an immunohistochemical study was performed. The ventricular MyHC was present in early embryonic atrial myocytes. During development, the ex pression of this protein in the atrial myocytes was down-regulated, but con tinued to be present in the atrial conduction system. Our results indicate that the ventricular MyHC appears in the primary atrial myocardium and is t hen localized in the conduction cells of the atria. (C) 2000 Elsevier Scien ce B.V. All rights reserved.