Expression of α‐tropomyosin during cardiac development in the chick embryo

A new monoclonal antibody (mAb) that recognizes alpha-tropomyosin in cardiac muscle cells was used in a qualitative (polyacrylamide gel electrophoresis and indirect immunofluorescence) and quantitative (fluorescence-activated cell sorting) study of the expression of this protein during heart development. alpha-Tropomyosin expression was weak in early stages of chick embryo development (Hamburger and Hamilton stage 18), and increased steadily until Hamburger Hamilton stage 40. In early stages, the protein was found mainly in cytoplasm, whereas by the final stages, it was more abundant in the cytoskeletal compartment. The mAb cross-reacted with alpha-tropomyosin in smooth and striated muscle cells from chickens, mice, and humans, but did not cross-react with nonmuscle tropomyosin.