Evidence for the involvement of muscle tropomyosin in the contractile elements of the coelom-esophagus complex in sea urchin embryos.

The sea urchin morphogenesis, especially formation of the coelom-esophagus complex, was observed correlating the distribution of tropomyosin-specific immunofluorescence. Coelomic cells arranged at both sides of the esophagus extended their pseudopods toward the esophagus to form the contractile bands, which surrounded the esophagus and brought about the contraction of the esophagus. The earliest stage at which the tropomyosin-specific immunofluorescence was recognized coincided with the appearance of the coelomic pseudopods. The tropomyosin-specific immunofluorescence located at the contractile bands and the cell bodies from which they derived, when the ectoderm-disrupted embryos were used to investigate the detailed distribution of tropomyosin. The tropomyosin-specific immunofluorescence remained in the same regions when the embryos were stained with the antiserum absorbed with egg tropomyosin, which detected only muscle tropomyosin. From these observations, the coelomic pseudopod-forming cells were conclusively shown to be muscle cells.