We have confirmed this by showing that dominant negative retinoid receptor mutants ablate expression of the homeodomain gene HoxD1. We are currently identifying these using a novel cloning technique. Regulatory genes induced as an early response to induction. Most of these genes encode novel proteins. This gene, Xopa, is the earliest expressed neurectoderm-specific marker yet isolated in Xenopus and may be a primary regulator of neurogensis.
Functional studies are in progress.
Induction of the cement gland. The cement gland is a simple, mucus-secreting organ that lies at the front of the embryo. It is induced by the same signals as neural tissue, however, cement gland differentiates many hours before neurons appear. It is therefore an excellent anterior marker. Surprisingly, cement gland induction is very complex.