APICAL ECTODERMAL RIDGE INDUCTION BY THE TRANSPLANTATION OF EN-1-OVEREXPRESSING ECTODERM IN CHICK LIMB BUD

In the early chick embryo, the dorsal-ventral (DV) boundary organizes the apical ectodermal ridge (AER) structure in the limb bud field. Her e it is reported that Engrailed-1 (En-l), a homolog of the Drosophila segment polarity gene engrailed expressed in the ventral limb ectoderm , participates in AER formation at the DV boundary of the limb bud. Re stricted ectopic expression of En-1 in the dorsal side of the limb bud by transplantation of En-1-overexpressing ectoderm induces ectopic AE R at the boundary of En-1-positive and -negative cells. The results su ggest that En-1 is involved in AER formation at the DV boundary of the limb bud.