Construction and characterization of the alpha form of a cardiac myosin heavy chain cDNA clone and its developmental expression in the Syrian hamster.

Abstract

A cDNA clone, pVHCl, was isolated from a Syrian hamster heart cDNA library and was compared to the rat a (pCMHC21) and ,8 (pCMHC5) ventricular myosin heavy chain cDNA clones. The DNA sequence and amino acid sequence deduced from the DNA show more homology with pCMHC21 than pCMHC5. This indicates that pVHCl is an a ventricular myosin heavy chain cDNA clone. However, even though pVHC1 shows a high degree of nucleotide and amino acid conservation with the rat myosin heavy chain sequences, the carboxyl-terminal peptide and the 3'-untranslated region are highly divergent and specific for this cDNA clone. There appears to be an amino acid deletion in the 3' end of the hamster a myosin heavy chain as compared to the rat a myosin heavy chain. S1 nuclease mapping experiments have shown that the mRNA represented by this cDNA clone is scarcely expressed in neonatal development, but its expression increases with age and reaches maximal levels in adult life. This cDNA clone provides a useful tool to follow the myosin heavy chain mRNA changes during development and during the genesis of a cardiomyopathy, an autosomal recessive defect carried by the Syrian hamster.The Syrian hamster has several features that can be used to study myocardial cells during normal growth and during the development of heart disease. Some strains of this animal exhibit an autosomal recessive defect, a cardiomyopathy, which appears 30-45 days after birth (25-27). It has been reported that development of the cardiomyopathy is associated with an altered distribution of the three myosin isozymes (28,29); there is a shift from the V1 form of the ventricular myosin isozymes (which contains a higher ATPase activity than the V3 form) to the V3 form. It has been speculated that this shift in the myosin isozymes to the V3 form and to a lower ATPase activity is a compensatory process that may lead to a more economical working of the myocardial cell (29).This report deals with the construction of a myocardial cDNA library from Syrian hamster ventricular tissue and the characterization of the a form of a ventricular myosin heavy chain cDNA clone. This specific cDNA clone, through the use of the S1 nuclease mapping technique, provides a feasible means of examining the expression of hamster ventricular myosin isoforms during growth and the course of developing cardiomyopathy.Considerable evidence indicates that several muscle-specific contractile proteins, including the myosin heavy chain, are constituted by multigene families. Differential expression of myosin light and heavy chains have been demonstrated in muscle and nonmuscle cell types as well as in invertebrate and avian muscle tissues by peptide mapping, immunological cross-reactivity, and DNA analysis (1-5). The myosin isozymes in cardiac tissue present a particularly intriguing challenge for the examination of differential expression during development.The isoforms of ventricular myosin, which are expressed as either homodimers of the a myosin heavy chain (V1 form) or the 13 myosin heavy chain (V3 ...

Differential gene expressions in atrial and ventricular myocytes: insights into the road of applying embryonic stem cell-derived cardiomyocytes for future therapies

“…This can also provide a reasonable explanation for the different kinetics of contraction and relaxation between atrial and ventricular working myocardium in large animals (79,154,183). However, young small rodents express the ␣-MHC both in the atria and the ventricles (32,49,112,114,142), and they also exhibit faster rates in the atrial myocardium (20). This suggests a role for the light chain isoforms in determining different kinetics.…”

Visualization of cardiac ventricular myosin heavy chain homodimers and heterodimers by monoclonal antibody epitope mapping.

“…It has been found later that r and 13-myosin heavy chains (MHCs) ~ are encoded by two different genes in the rat (Mahdavi et al, 1982) and rabbit (Sinha et al, 1982). No complete amino acid sequence of cardiac MHC has yet been published, but partial r and I~-MHC primary sequences have either been deduced from nucleotide sequences or determined from peptide fragments in various species (Mahdavi et al, 1982;Sinha et al, 1982;Flink and Morkin, 1984;Kavinsky et al, 1984;Mahdavi et al, 1984;Sinha et al, 1984;Lichter et al, 1986;Liew et al, 1986). These sequences indicate a great homology between 0t-and 13-MHC.…”