Transformation of a neural activation and patterning model

Abstract

The activation and transformation model of vertebrate nervous system formation posits that neural tissue is initially induced, or acti- vated, with anterior forebrain character. Once established, a subset is then trans- formed into the more posterior midbrain, hindbrain, and spinal cord by signals emanating from the posterior of the embryo. This has been a predominant model in the field for decades. In the June issue of EMBO Reports, Polevoy and colleagues eval- uate the role of signals thought to act as the neural transforming factors during Xenopus development, and find that while these signals are consistent with the activation transformation model during brain pattern- ing, they do not fit the model with respect to spinal cord formation [1]. This work, alongwith other recent studies on the origin of the spinal cord, necessitates an updated model of vertebrate nervous system forma- tion, where spinal cord induction and patterning is distinct fromthat ofthe brain.