DIFFERENTIAL EXPRESSION OF A DISTAL-LESS HOMEOBOX GENE XDLL-2 IN ECTODERMAL CELL LINEAGES

Neural induction in Xenopus requires the activation of new sets of gen es that are necessary for cellular and regional specification of the n eural tube. It has been reported earlier that members of the Distal-le ss homeobox gene family are specifically activated in distinct regions of the central nervous system (CNS) of Xenopus embryos (Dirksen et al ., 1993; Papalopulu and Kintner, 1993). In this paper we describe in d etail a-Xenopus homeobox containing gene Xdll-2, which belongs to the Distal-less gene Family. In contrast to other previously described Xen opus family members, Xdll-2 Is expressed in the embryonic ectoderm and is specifically repressed in the CNS. This repression can be mimicked in isolated animal caps by treatment with activin. Expression of Xdll -2 persists in the epidermis and some neural crest cells. Because of i ts spatial and temporal expression pattern this gene is a good candida te to have a regulatory function in the initial formation of the epide rmis. Its high level of expression in adult skin indicates that its Fu nction is continuously required in this tissue.