2I1730 Myosin isoform expression in murine embryonal carcinoma cells after cardiac differentiation

Gene expression of cardiac myosin isoforms is regulated in chamber- and/or developmental stage-specific manners. Multipotent CL6 cells, a clonal derivative of P19 murine embryonal carcinoma cells, are known to efficiently differentiate into cardiomyocytes in the presence of 1% DMSO. However, their phenotypic profiles at the terminal differentiation have been unclear. To characterize the cardiac differentiation, myosin isoform expression in DMSO-treated (16 days) CL6 cells, which showed spontaneous contractions, was compared with that in mouse cardiac tissues, using real-time RT-PCRs. The mRNA ratio of myosin light chain 2a relative to 2v isoform was extremely elevated in DMSO-treated CL6 cells, compared to that in adult and neonatal ventricles. Alpha-myosin heavy chain was expressed in DMSO-treated CL6 cells, neonatal and adult ventricles, and adult atria. In contrast, beta-myosin heavy chain isoform was barely detectable in DMSO-treated CL6 cells, as well as in adult atria. These results indicate that, in terms of the myosin isoform composition, CL6 cells acquire phenotypes similar to cardiac atria in 1% DMSO culture.