Figure 2

Mutations identified in the pupal lethal screen. (A-C') The PL26 mutation causes misorientation of the mitotic spindle in dividing neuroblasts. DNA staining (blue); Miranda (red); Inscuteable (green). The orientation of the mitotic spindle as judged by the orientation of the metaphase plate or anaphase chromosomes is indicated by a dotted white line; Bar: 10 μm. In wild type neuroblasts (A) the mitotic spindle is oriented perpendicular with respect to the Miranda crescent. In PL26 mutant larvae (B) the spindle is misoriented with respect to the Miranda crescent in 16% of neuroblasts (n = 75). (C, C') Cortical crescents of Inscuteable and Miranda are correctly localized to opposite poles of the cell in PL26. Note the misorientation of the spindle during anaphase in the cell to the left (arrows). (D, D') Miranda is mislocalized in PL17 neuroblasts. DNA staining (blue); Miranda (red); Inscuteable (green, D'). Bar: 10 μm. In mitotic PL17 neuroblasts, Miranda is localized to discrete cytoplasmic regions; in some neuroblasts Miranda crescents are also seen. Localization of the apical marker Inscuteable is not affected (D'). (E-G) The PL13 and PL17 mutations affect cell proliferation. DNA staining (blue); Miranda (red); Phospho-Histone H3 (green); Bar: 50 μm. In wild type optic lobes (E) 45% (n = 60) of neuroblasts stain with anti-PH3. In PL13 larvae (F) fewer neuroblasts are present and of these only 22% (n = 37) stain with anti-PH3. PL17 optic lobes (G) are reduced in size but 76% (n = 45) of neuroblasts stain with anti-PH3. (H) IV61 is allelic to sticky, and homozygous larval neuroblasts are large and have an increased DNA content. DNA staining (blue); Miranda (red); Bar: 20 μm.