SONIC HEDGEHOG - A MEDIATOR OF INDUCTIVE SIGNALING IN THE NEURAL VENTRAL TUBE

The differentiation of distinct cell types in the ventral neural tube can be induced by Sonic Hedgehog (SHH) a signaling molecule expressed by the notochord. SHH undergoes autoproteolytic cleavage to generate a mino- and carboxy terminal products. Floor plate and motor neurons can be induced by the amino-terminal cleavage product of SHH (SHH-N). The threshold concentration for induction of floor plate cells in neural plate explants is about 5-fold higher than that required to induce mot or neurons, suggesting that the induction of distinct ventral cell typ es by the notochord in vivo is mediated by exposure of neural plate ce lls to different concentrations of SHH-N.