Fig. 8. Abd-B prevents apoptosis by repressing rpr and grim. (A) In H99, Abd-Bm double-mutant embryos (dMP2-GAL4, Df(3L)H99, Abd-BM5/dMP2-GAL4, Df(3L)H99, Abd-BM5; UAS-nls-myc-EGFP) posterior dMP2 and MP1 neurons are generated normally; at stage 16, two dMP2 neurons express Odd and dMP2-GAL4, whereas two MP1 neurons express Odd only. Abd-B expression is absent from both neuronal types, and only the posterior tip of the VNC expresses Abd-Br. (B) In late embryos, neither anterior nor posterior dMP2 and MP1 neurons undergo apoptosis (100% survival, n=6 VNCs), indicating that rpr and grim are epistatic to Abd-B. Insets show two dMP2 and two MP1 neurons in A6, both at stage 16 (left) and at air-filled trachea stages (right). (C) Proposed mechanism of apoptosis regulation in dMP2 and MP1 neurons. See text for details.