Sarcomeric tropomyosin expression in normal, mutant, and TPM1α -transfected mutant hearts. a. Confocal micrograph of stage-39 normal hearts stained with CH1 anti-tropomyosin antibdody (and rabbit anti-mouse lissamine rhodamine secondary antibody), well-organized sarcomeric myofibrils can be seen throughout the ventricle of the heart (arrow). b. Heart from stage-39 mutant embryo stained with CH1 does not show any organized myofibril, Only small areas of amorphous staining can be visualized within the ventricle (arrow). c. Stage-36 mutant heart lipofected with an expression construct containing a murine TPM1α cDNA under the control of α-Myosin Heavy Chain promoter, which subsequently induced TM and promoted myofibrillogenesis. Mutant heart stained with α-actinin primary antibody. Well-organized sarcomeric myofibrils can be seen throughout the heart (arrows). Staining of the Z-lines confirmed the sarcomeric organization seen in TPM1α transfected hearts that were stained with tropomyosin primary antibody (results not shown here) [ref]. Interestingly, statge-36 mutant heart tansfected with a murine TPM2α cDNA under the same promoter did express some TM protein but sarcomeric myofibrils did not form throughout the heart in contrast to TPM1α transfected hearts .