Fig. 5. Ubx induces apoptosis by preventing Antp from promoting survival of the GW motoneuron. NB7-3 neurons in late stage 16 (A-F,J) or stage 15 (G-I) Drosophila embryos. Dashed lines mark the midline. Insets show magnified single scans of NB7-3 as follows: (B,C) the indicated segments from A; (E,F) the indicated segments from D; (H,I) the indicated segments from G. (B',C',E',F',H',I') Only the Antp staining from respective insets is shown. GWs are indicated by arrowheads. Anterior is up in all images. (A) GWs show high Antp expression levels in segments in which they do not undergo apoptosis (arrowheads). In segment T3, in which they undergo apoptosis, they express Antp at low levels (arrows). (B,B') In T1, all NB7-3 cells show strong Antp expression. (C,C') In T2, Antp expression is strong in GW (arrowhead) and barely detectable in the EW interneurons. (D) In Ubx mutants, Antp expression is strongly upregulated in all thoracic segments. (E,E') In T1, Antp expression is unchanged. (F,F') In T2, Antp expression is equally strong in all NB7-3 cells. (G) Ectopic Ubx expression suppresses Antp in the anterior thoracic segments. (H,H') In T1, ectopic Ubx strongly suppresses Antp expression in all cells of NB7-3. (I,I') In T2, GW (arrowhead) also shows reduced Antp levels upon ectopic Ubx expression. (J) In Antp,Ubx double mutants, GW apoptosis is restored (arrow). Asterisks indicate that the GW has already been removed. (J') A magnified single scan of the A6 NB7-3. The apoptotic GW is outlined. (J'') Same image as in J', showing only the activated Caspase 3 (act Casp3) staining.