Transcriptional regulation of the gene for epidermal growth factor-like peptides in sea urchin embryos

Exogastrula-inducing peptides (EGIPs), which are epidermal growth factor-re lated peptides of the sea urchin Anthocidaris crassispina, are substances t hat elicit abnormal gastrulation (exogastrulation) during embryogenesis of the sea urchin. In the present study we have examined the regulation of the expression of the EGIP precursor gene (EGIP) in sea urchin embryos. Whole mount in situ hybridization showed that EGIP is zygotically expressed after the onset of gastrulation in subdomains of the embryonic and larval ectode rm. The expression is confined in early gastrulae to small ectodermal regio ns adjoining the vegetal plate, which progressively expand to almost the en tire ectoderm except the oral hood and postoral tips of the arms in later s tages. In adults the expression is restricted to the ovary. Zygotic EGIP ex pression is sensitive to dissociation of embryonic cells, as well as to dis ruption of the extracellular matrix (ECM) with 5-cis-hydroxyproline. sugges ting requirements for interaction with neighboring cells and/or with the EC M. The expression of reporter genes (chloramphenicol acetyl transferase and green fluorescent protein) under the regulation of the 4.6 kb upstream reg ion of EGIP is temporally and spatially similar to that of the endogenous g ene, showing that EGIP expression is regulated at the transcription level d uring embryogenesis by the cis-elements within the 4.6 kb upstream region.