Fig. 5. Analysis of the organization of the contractile cytoskeleton in embryonic cardiomyocytes. Cells were transfected with the WT GFP-myosin and the three FHC mutants and fixed 72 hours post-transfection. The fixed cells were counter-stained with antibodies to muscle specific markers (either anti-titin, RT11, or anti-myosin, F18). The GFP-myosin-positive cells were scored in one of the four classifications illustrated in Fig. 4 and described in the text. The counterstaining for other muscle-specific protein was used to confirm the myofilament organization. The non-transfected control cells were scored after staining with anti-titin or anti-myosin. These data summarize the results from four separate experiments and include over 4400 cells. The number of cells in each group varied between 200-400 cells for a total of 1100 cells/experiment. Pairwise comparison of the distribution of cells in classes for the different groups was done using Student's t-test with a confidence level of P<0.05. Error bars correspond to the standard deviation within each class of the four experiments.