An mRNA has been identified which encodes a protein (SpEGF2) containing four domains related to epidermal growth factor and which accumulates at the onset of morphogenesis in developing sea urchin embryos (Strongylocentrotus purpuratus). Dr. Angerer's hypothesis is that this protein, or peptides derived from it, function as a signaling factor secreted into the blastocoel. SpEGF2 protein contains a hydrophobic leader, lacks a transmembrane domain and is very similar to short, blastocoelic peptides found in another sea urchin species (Anthocidaris crassispina) that cause a specific developmental abnormality, exogastrulation, when added to cultures of embryos of either genus. The developmental function in sea urchin embryogenesis of the SpEGF2 peptide receptor signaling system will be investigated using techniques of molecular genetics, immunology, biochemistry and experimental embryology. Targets of SpEGF2 function will be identified by 1) using anti-SpEGF2 antibodies, 2) binding labeled synthetic or endogenous SpEGF2 peptide(s) to cells of the embryo and 3) determining which cells express the SpEGF2 receptor mRNA and peptide. Finally, the effects of blocking the activity of the SpEGF2/SpEGF2-receptor signaling system on morphogenesis, cell division, and tissue specific gene expression in intact embryos will be analyzed.
