ISOLATION OF A MARKER FOR HEAD-SPECIFIC CELL-DIFFERENTIATION IN HYDRA

A cDNA was isolated from Hydra vulgaris coding for a 360 amino acid lo ng polypeptide with no significant similarity to any known protein. In situ hybridization showed that the corresponding transcript is expres sed exclusively in endodermal cells of the hypostome, hence its name h yp I. Hyp 1 therefore represents a highly specific marker for the head region of hydra. In accordance with this, we found that hyp 1 express ion was strong in tissues regenerating a head. Hyp 1 reappeared early during head regeneration, namely 6-8 h after initiation of regeneratio n by cutting. These findings imply that hyp 1 is an excellent marker f or monitoring early events in head-specific differentiation processes in hydra.