Xotx5b, a new member of the Otx gene family, may be involved in anterior and eye development in Xenopus laevis

We describe the cloning, expression pattern and functional overexpression a nalysis of Xotx5b, a new member of the Otx gene family in Xenopus laevis. E arly expression of Xotx5b resembles that of Xotx2, being detected in the or ganizer region at early gastrula stage, and, shortly after, also in anterio r neuroectoderm. During neurula stages Xotx5b exhibits a changing and dynam ic pattern of expression. After neural tube closure, Xotx5b is expressed in the eye and pineal gland, both involved in photoreception. Overexpression of Xotx5b has a similar effect to that of Xotx2, producing posterior trunca tions and inducing ectopic cement gland and neural tissue in whole embryos. In animal cap assays, Xotx5D and Xotx2 are both able to activate XAG, to s trongly suppress the expression of the epidermal marker XK81, and to recipr ocally activate each other. Finally, in einsteck transplantation assays, Xo tx5b is able to respecify a tail/trunk organizer to a head organizer. (C) 2 000 Elsevier Science ireland Ltd. All rights reserved.