Loss of Delta, Notch, Supressor of Hairless or Kuzbanian leads to an increase in the number of neurons, the neurogenic phenotype. Another component, Numb , has been integrated into the Notch signaling pathway. Numb is a cytoplasmic protein that has been shown to bind to the intracellular domain of Notch and to repress Notch function. Interestingly, in the SOPI of es organs the Numb protein is localized to a crescent at the cell surface.
All mutants are embryonic lethal.
This phenotype is the basis for the name Sanpodo, the Korean word for mountain grapes. It has been shown that in spdo mutants there are no extra SOPs recruited, and that the total number of cells within the dorsal and lateral clusters of the PNS is not increased significantly. The dbd neuron is often duplicated in spdo embryos. Glial markers show no glia associated with the duplicated dbd neurons. Hence the sibling cell is transformed into an md neuron.