Half a century of neural prepatterning:: The story of a few bristles and many genes

In 1954, Curt Stern proposed the concept of the neural prepattern, meaning the underlying positional information in an undifferentiated epithelium that determined where neural differentiation could take place. Subsequent work gave a molecular basis to this concept, which was equated to a combination of transcription factors deployed in partially overlapping spatial domains that regulated proneural genes and, thereby, neural differentiation. Here, we review the work that, in the past few years, has identified many prepattern genes and has disclosed that their function is not limited to the regulation of proneural genes.