TEMPORALLY AND SPATIALLY RESTRICTED EXPRESSION OF A GLAND CELL GENE DURING REGENERATION AND IN-VITRO TRANSDIFFERENTIATION IN THE HYDROZOAN PODOCORYNE CARNEA

An antiserum to transdifferentiated striated muscle cells from the med usa of Podocoryne carnea was prepared and used to screen a lambda gt11 -expression library prepared from gonozoids of P. carnea. We isolated a cDNA clone termed Pod-EPPT with at least 63 tandem repeats of the te trapeptide-motive glu-pro-pro-thr, named Pod-EPPT. Using Pod-EPPT as a molecular marker for head quality the morphological relationship betw een the two metagenic life stages of this hydroid, the polyp and the m edusa, was studied. In situ hybridization demonstrated that expression of the gene corresponding is restricted to secretory cells in the end oderm of the oral hypostome region of polyps and medusae and, presumab ly, to progenitor cells of this type. Cells expressing Pod-EPPT could not be observed in the larval stage. During head regeneration in polyp s, Pod-EPPT expression is up-regulated soon after head removal in prev iously non-expressing cells and in newly differentiating secretory cel ls. This activation of a head-specific gene precedes the morphological ly obvious events of head regeneration. Pod-EPPT is one of the genes t hat are activated during manubrium (mouth) regeneration from experimen tally combined subumbrellar plate endoderm and striated muscle of the medusa.