An obligatory caravanserai stop on the silk road to neural induction: inhibition of BMP/GDF signaling

Work in Xenopus laevis produced the first molecular explanation for neural specification, the default model, where inactivation of the BMP pathway in ectodermal cells changes fates from epidermal to neural. This review covers the present status of our understanding of neural specification, with emphasis on Xenopus, but including relevant facts in other model systems. While recent experiments have increased the complexity of the molecular picture, they have also provided additional support for the default model and the central position of the BMP pathway. We conclude that synergy between accumulated knowledge and technical progress will maintain Xenopus at the forefront of research in neural development.