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Differences in the concentration of sonic hedgehog (a single protein) can determine the fate of multiple neuronal classes in the ( ventral, dorsal, caudal, rostral ) part of the neural tube.
In a first step a ventral-to-dorsal Shh gradient ( activates and represses, activates, represses ) different transcription factors.
These ( repress, enhance ) each other's expression to confer cell identity to progenitor cells unambiguously.
Five cardinal progenitor domains are established:
Four types of ( interneurons, sensory neurons ) (V0 - V3) and ( motor neurons, sensory neurons ).