Fig. 1. Two differentiated motoneurons undergo segment-specific rpr-dependent cell death. An NB7-3 lineage (A-C) and an NB2-4t lineage (D-F) of wild-type (A-D,F) and eg-Gal4,UAS-mCD8::GFP (E) Drosophila embryos at late stage 16. Dashed lines mark the midline. Dashed circles indicate NB7-3 (B) and NB2-4t (E). B',B'' and E',E'' show magnified single scans of one lineage as boxed in B and E, respectively. Anterior is up in all images. (A) A DiI-labeled NB7-3 clone. The GW motoneuron (arrow) lies at the posterior end of the cluster and exhibits an ipsilateral outward projection. (B) GWs (arrows) undergo apoptosis in segments T3 and A1, but not in T2 (arrowheads). Asterisk indicates that the GW has already been removed. (B') A magnified single scan of the A1 NB7-3 lineage. The apoptotic GW is outlined. (B'') Same image as in B', showing only the activated Caspase 3 (act Casp3) staining. (C) A magnified single scan of an A1 NB7-3 lineage. (C') rpr is transcriptionally activated in apoptotic GWs (outlined). (D) A DiI-labeled NB2-4t clone. The motoneurons (arrows) are the most medial and most dorsal cells of the cluster and show contralateral outward projections. (E) The anterior NB2-4t motoneuron in segment T3 undergoes apoptosis (arrows). In A1, only one motoneuron lies in the same position (curved arrows). (E') A magnified single scan of the T3 NB2-4t. The apoptotic MNa is outlined. (E'') Same image as in E', showing only the activated Caspase 3 staining. (F) A magnified single scan of a T3 NB2-4t lineage. (F') rpr is transcriptionally activated also in apoptotic MNas (outlined).