Characterization of the allelic differences in the mouse cardiac α-myosin heavy chain coding sequence

We have obtained and sequenced the coding sequence of the mouse cardiac α-myosin heavy chain (Myhcα) from the A J, BALB cByJ, C57BL 6J, and DBA 2J inbred mouse strains. Overlapping cDNA sequences were obtained using RNA-PCR and anchor-PCR techniques for these studies. In the A J mouse strain, the full-length message is 5989 bp long and encodes for a protein consisting of 1938 amino acids (M_r 223,689). The protein deduced sequence of the A J Myhcα was compared with corresponding sequences of human and rat Myhcα and β. These results demonstrated that the mouse Myhcα is highly conserved and has maintained the α-isoform-specific divergent cluster observed in other Myhcα proteins. One difference was the loss of a glutamine at residue 1932, which is due to a change in an RNA splicing site sequence. Allelic variability was observed in both nucleotide and amino acid sequences among the four different inbred mouse strains and generally appears to be random in nature. Three of the nucleotide changes resulted in a different amino acid, while the remaining 46 were silent substitutions.