ABSTRACT
We found some intrinsic factors, which induced exogastrulation when added outside the embryos, in homogenate of sea urchin embryos. These factors were found to be 4 different polypeptides and named exogastrula-inducing peptides (EGIPs) A,B,C and D. It is conceivable that EGIPs may have an important role in inducing normal gastrulation when they function inside the embryo. Four EGIPs were isolated from the homogenate of embryos of the sea urchin, Anthocidaris crassispina, with successive chromatographic fractionations and their complete amino acid sequences were determined by analysis of the peptides generated by their digestion with endopeptidases. They were composed of 52,52,58 and 53 amino acid residues with molecular weights of around 6000 and contained 6 cysteine residues per molecule in common. The cytological studies using fluorescent antibody suggested that EGIPs induce exogastrulation by affecting the polymerization of cytoskeletal proteins of blastomeres.
