Isolation of a neural-specific gene of Xenopus laevis by representational difference analysis.

Neural induction of the competent ectoderm can be considered as the third major phase of vertebrate embryonic development. In Xenopus laevis, the south african clawed frog, the first phase is the establishment of the primary asymmetries like dorsal-ventral, anterior-posterior and inside-<Jutside. This process is followed by the induction of the mesoderm between the ectoderm in the animal hemisphere and the endoderm in the vegetal ha~. The dorsal mesoderm then induces the neighbouring competent ectoderm to form neural structures. Akhough there are many substances described, which have a neural inductive effect on isolated ectoderm, there is still little known about the complex interactions that leads to the determination of the central nervous system in vivo. Our main interest is focussed on the isolation of ganes, which may play an important rote in induction and in the response to those inductive signals wohin the target cells.