Vertebrate neural induction.

During early vertebrate development, the cells of the ectoderm choose between two possible fates: neural and epidermal. The process of neural induction was discovered nearly 70 years ago in vertebrates, and molecular analyses in recent years using Xenopus laevis embryos have identified several secreted factors with direct neural-inducing ability. There is considerable evidence that the mechanism of neuralization by these inducing factors is under inhibitory control and involves derepression. This review focuses on factors involved in the specification of neural fate within the frame of the default model of neural induction.