Genomic organization of the gene that encodes the precursor to EGF-related peptides, exogastrula-inducing peptides, of the sea urchin Anthocidaris crassispina.

Exogastrula-inducing peptides (EGIPs) were identified in embryos of the sea urchin Anthocidaris crassispina as polypeptides with structural similarity to epidermal growth factor (EGF) that severely affect gastrulation of sea urchin embryos to induce exogastrulation. Here we have obtained genomic clones for the EGIP precursor gene (EGIP) and determined its genomic organization. The EGIP gene spans the length of 9 kb in the genome and is composed of seven exons and six introns. Each of the four EGF motifs in the precursor protein is encoded by a single exon, and all the exon boundaries are in phase 1, suggesting that EGIP have been generated during evolution by duplication of an exon encoding a single ancient EGIP sequence. The 5'-flanking sequence of EGIP from -4372 to +194 revealed the presence of multiple repeat sequences including direct and inverted repeats as well as two clusters of GGGG/CCCC elements. The function of the upstream flanking region of EGIP was examined by introducing the gene constructs into embryos in which different regions from the flanking DNA were placed upstream to the GFP reporter gene. Systematic deletion of the upstream DNA revealed the presence of potent enhancer activity between -372 and -210.