AN ORTHODENTICLE-RELATED PROTEIN FROM STRONGYLOCENTROTUS-PURPURATUS

Orthodenticle-related proteins function as regulators of head formatio n and other developmental events in flies and mice. Here, we character ize a cDNA clone encoding an orthodenticle-related protein from the se a urchin Strongylocentrotus purpuratus. The cDNA, termed SpOtx, has a highly conserved orthodenticle homeobox but otherwise diverges in sequ ence from its fly and mouse counterparts. Orthodenticle-related protei ns bind with high affinity to DNA containing the sequence motif TAATCC /T. The S. purpuratus aboral ectoderm-specific Spec2a gene has several TAATCC/T sites in its control region, and we provide evidence, using bandshift analysis, that Spec2a may be target gene for SpOtx. Two SpOt x transcripts accumulate during embryogenesis, an early transcript who se level peaks at blastula stage and a late transcript accumulating to highest concentrations at gastrula stage. SpOtx transcripts were foun d initially in all cells of the cleaving embryo, but they gradually be came restricted to oral ectoderm and endoderm cells. In contrast, SpOt x protein was found in nuclei of all cells at both blastula and pluteu s stages. Our results suggest that SpOtx plays a role in the activatio n of the Spec2a gene and most likely has additional functions in the d eveloping sea urchin embryo. (C) 1995 Academic Press, Inc.