Fig. 5. rpr is required to eliminate neuroblasts. (A-D) Anti-Grainyhead staining labels persistent neuroblasts throughout the abdominal neuromeres of rpr mutant larvae. (A) Very few neuroblasts are found in the abdominal neuromeres in the VNC of wild-type larvae. The white arrow indicates the boundary between the thoracic and abdominal neuromeres. (B) Many neuroblasts are present in the abdominal neuromeres of rpr mutant larvae (XR38/H99). (C) No ectopically surviving neuroblasts are seen in hid mutant larvae, even when one copy of grim and rpr are also deleted (hid⁰⁵⁰¹⁴/H99). (D) Mutation of dark, an Apaf1 homolog, also results in a few ectopically surviving neuroblasts in the abdominal neuromeres. (E-H) BrdU labeling reveals ectopic cell division in the abdominal neuromeres of the ventral nerve cord of rpr mutant larvae. (E) CNS from a wild-type third instar larva fed continuously on BrdU-containing food. Very little division is seen in the abdominal neuromeres. H99/+ animals also appear wild type (data not shown). (F) In the rpr mutant (XR38/H99), the abdominal region is filled with dividing cells. (G) A few cells labeled with BrdU during larval life are present in the small condensed abdominal neuromeres of wild-type adults. (H) Many cells labeled with BrdU during larval life are found in the enlarged abdominal neuromeres of the XR38/H99 adult.