Tropmodulin but not tropomyosin found in cardiac “c” mutant axolotl ventricle. CH1 anti-sarcomeric TM antibody labels the conus but not the ventricle in stage 38/39 cardiac mutant axolotl hearts. Stage 38/39 normal (a–c) and mutant (d–f) axolotl hearts were double stained for immunofluorescent microscopy with CH1 anti-sarcomeric TM antibody (FITC channel) and polyclonal anti-tropomodulin antibody, R1749 (Rhodamine channel). Only the FITC channel is shown for whole heart images (a, d) demonstrating the lack of staining in the ventricle of mutant hearts while all higher magnification images utilize a dual rhodamine-FITC filter. Letter labeled boxes in A and D correspond with the area shown in their respective higher magnification image. TM labeled with CH1 antibody is found in a cross-striated pattern in the ventricle of normal hearts (c) and in the conus of both normal (b) and mutant (e) hearts. Tropomyosin staining is markedly absent in mutant ventricle (f) resulting in a failure of normal sarcomere formation with tropmodulin found in linear arrays near the surface of the membranes (Arrows, F). Scale Bar = 100 μm.