Fig. 3. CNS phenotypes of stage 15 embryos. (A-G) Embryos were immunostained for Eg (red), Zfh-2 (green) and Hb (blue). (A) A wild-type segment showing the four NB7-3 progeny. 1, 2, 3 and GW label the EW1, EW2, EW3 and GW neurons, respectively. M indicates the midline. (B) Segments from numb¹ mutant embryos show an absence of EW2 and EW3 neurons, only Hb-positive neurons remain (EW1 and GW). (C) Twenty-two percent of numb¹ hemisegments have three Eg-positive cells. The third cell expresses Zfh-2 at reduced levels relative to wild type. (D) UAS-Notch^ACT: eggal4 embryos shows a variable pattern, some hemisegments are identical to the wild-type pattern and some hemisegments having a reduced number of Eg-positive cells. (E-G) Hemisegments from spdo^G104, UAS-numb:eg-gal4 and eg-gal4/UAS-p35 embryos show a similar phenotype of five to six Eg-positive cells. The ectopic cells express Zfh-2. (H-K) Embryos were immunostained with Eg (red) and Zfh-1 (green). (H) A wild-type segment showing the four NB7-3 progeny and expression of Zfh-1 in the GW neuron. (I,J) Hemisegments from numb¹ mutant embryos show that the expression of Zfh-1 in GW is unaltered. J shows an example of a numb¹ hemisegment were both remaining cells express Zfh-1, indicating a transformation of EW1 to a GW cell fate. (K) UAS-Notch: eg-gal4 embryos show a variable number of cells similar to D and two Zfh-1 staining cells indicating a transformation of EW1 to a GW cell fate. Scale bar in J: 5 µm.