Figure 8.

 In the absence of cell division, GMC4-2a differentiation is dependent on Numb. Dorsal view of dissected stage 15 embryos; anterior is up. (A) GA339 stained with rabbit anti-Eve, note that each hemisegment has an Eve-positive cell at the RP2 position; note the decrease in the number of Eve-expressing cells in the position of the CQ neurons, see Discussion. (B) GA339 double stained with rabbit anti-Eve (red) and mouse anti-Zfh-1 (green). Note that the undivided GMC4-2a expresses Zfh-1, a marker gene, which in wild-type embryos is not expressed in GMC4-2a but only the mature RP2 neuron. (C) GA339 double stained with rabbit anti-Eve (red) and mouse mAb 22C10 (green). Note that the undivided GMC4-2a forms an ipsilateral axon projection characteristic for the RP2 neuron. (D) nb⁷⁹⁶ GA339 double mutant, note the loss of Eve-positive cells at the RP2 position and the increase in the number of Eve-expressing cells in the position of the CQ neurons. (Arrows) Position of the RP2 neuron; (arrowhead in C) the RP2 axon; [asterisk (*) in C] aCC neuron.