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. This transformation is the opposite of the numb phenotype, which consists of two glial cells instead of two dbd neurons. Staining with an md-specific marker reveals another feature of spdo mutants. Es neurons are programmed to become md neurons in spdo mutants. This observation is particularly interesting because the same phenotype occurs in Notch mutants, suggesting that Notch signaling is impaired in spdo mutants.