Fig. 2. Cdc42 is required for neuroblast polarity. (A) Wild-type embryonic neuroblasts at stages 11 to 13 stained for aPKC, Baz, Mira, Par-6 and PH3. (B-E) Embryonic neuroblasts at stages 11 to 13 expressing Cdc42-DN (N17) driven by worniu-Gal4. aPKC displays ectopic cortical staining (B; 82%, n=45) together with Par-6 (C; 76%, n=41) and Mira (B'; 45%, n=67), whereas Baz displays no defects (D; 100%, n=26). (F) Divisions are asymmetric (100%, n=23). (F-J) Embryonic neuroblasts stages 11-13 expressing Myc–Cdc42-CA (V12) as in (B-E). aPKC displays cortical, with some cytoplasmic, staining (F; 94%, n=50) along with Par-6 (G; 90%, n=29) and Myc–Cdc42-CA (H; 89%, n=19), whereas Mira is cytoplasmic (F'; 94%, n=50). Baz displays no defects (I; 100%, n=13). (J) Neuroblast division becomes symmetric upon overexpression of Cdc42-CA (88%, n=9). (K) Wild-type central brain neuroblasts 120 hours ALH stained for aPKC, Par-6, Baz, and Mira. (L-N) cdc42-3 central brain neuroblasts 96 hours ALH. These neuroblasts show cytoplamsic staining of aPKC (L; 84%, n=19) and Par-6 (M; 100%, n=11), whereas Mira is uniformly cortical (L'-N'; 100%, n=46). Baz displays no defects (N; 100%, n=16). (O) Cdc42 is mislocalized in zygotic baz-4 mutant neuroblasts. Embryonic neuroblasts at stages 13 to 14 expressing Cdc42-Myc in a baz-4 background exhibit loss of Cdc42 apical enrichment. Cdc42-Myc is weakly cortical with some cytoplasmic staining and no apical enrichment (O'), whereas aPKC is cytoplasmic (O) and Mira is uniformally cortical (O"; 100%, n=21). (P) Quantification of the Cdc42 requirement for neuroblast polarity in embryonic and larval neuroblasts.