Regulation of neural determination by evolutionarily conserved signals: anti-BMP factors and what next?

The evolutionary conservation of Chordin/bone morphogenetic protein (BMP) s ignaling supports the hypothesis of dorsal-ventral axis inversion of verteb rates and invertebrates, and implies that the invention of a central nervou s system occurred only once during animal evolution. This hypothesis is fur ther strengthened by recent findings of the conservation of downstream gene s and modifier genes of neural induction. On the other hand, in contrast wi th such gross conservation, recent data suggest that the requirement for so me signals in neural determination may differ even within the vertebrate su bphylum.