THE LEVEL OF EXPRESSION OF A PROTEIN-KINASE-C GENE MAY BE AN IMPORTANT COMPONENT OF THE PATTERNING PROCESS IN HYDRA

Several studies have provided strong, but indirect evidence that signa lling through pathways involving protein kinase C (PKC) plays an impor tant role in morphogenesis and patterning in Hydra. We have cloned a g ene (HvPKC2) from Hydra vulgaris which encodes a member of the nPKC su bfamily. In adult polyps, HvPKC2 is expressed at high levels in two lo cations, the endoderm of the foot and the endoderm of the hypostomal t ip. Increased expression of HvPKC2 is an early event during head and f oot regeneration, with the rise in expression being restricted to the endodermal cells underlying the regenerating ends, No upregulation is observed if regenerates are cut too close to the head to form a foot. Elevated expression of HvPKC2 is also observed in the endoderm underly ing lithium-induced ectopic feet. A dynamic and complex pattern of exp ression is seen in developing buds. Regeneration of either head or foo t is accompanied by an increase in the amount of PKC in both soluble a nd particulate fractions. An increase in the fraction of PKC activity which is membrane-bound is specifically associated with head regenerat ion, Taken together these data suggest that patterning of the head and foot in Hydra is controlled in part by the level of HvPKC2 expression , whilst head formation is accompanied by an in vivo activation of bot h calcium-dependent and independent PKC isoforms.