Fig. 4. Model of V2 neuron development from a p2 intermediate progenitor. In this model of one unit of lineage, a single p2 intermediate progenitor produces two sibling cells. These cells then undergo Delta-Notch-mediated cell-cell interactions, resulting in different levels of Notch activity between them. The cell with higher Notch activity develops into a V2b neuron and the sister cell with lower activity (but higher levels of Delta expression) develops into a V2a neuron.