Development of Neural Tissues in Xenopus laevis

The Xenopus nervous system has contributed greatly to our understanding of the various signals that induce, specify and differentiate cells away from ectoderm and towards neural fates. Following the discovery of the Spemann organizer in 1924, much work has been undertaken to identify the fundamental signals that pattern the embryo, and in time, better tools to identify the molecules became available and began to provide answers. By applying such tools in Xenopus, researchers have revised dogmas to advance the field of neural development, for example, the arrival and experimental support in the 1990's for the "default model" of neural specification. This chapter presents an overview of the early processes and signals that form the central and peripheral nervous systems of Xenopus laevis, with attention made to select discoveries that promoted our understanding of these tremendously complex systems.