Fig. 5. Loss of Drosophila citron leads to failure of cytokinesis and hyperploidy in the larval brain. Wild-type (A) and cit²/Df(3)iro-2 mutant (B-H'') brain lobe tissues from third instar larvae. (A,B) Immunochemical staining of whole mount brain lobes with anti-phospho Histone H3 (PH3), to detect cells in mitosis, showing large nuclei (arrow) in cit²/Df(3)iro-2 cells (B) compared to wild-type (A). (C) Binucleate cells dissociated from cit²/Df(3)iro-2 mutant brain lobes stained with Hoechst 33258 to detect DNA (white) overlaid on the phase-contrast image of the cells. (D-F) Mitotic figures from cit²/Df(3)iro-2 mutant cells, which were squashed and stained with Giemsa dye to detect chromosomes. (D) Tetraploid cell at metaphase. (E) Hyperploid cell showing effective chromosome separation at anaphase. (F) Very highly hyperploid cell. (G-G'', H-H'') High magnification view of individual polyploid cells from mutant brain lobes stained with anti--Tubulin (G,H) and anti-PH3 (G',H'). (G'',H'') Merged images. (G-G'') Abnormal metaphase. Three spindle poles are detected by anti--Tubulin staining (cf pebble mutants in Fig. 3E). (H-H'') The cell exhibits a highly polyploid content of condensed DNA and there are eight spindle poles (four in the field of view) associated with defective microtubule spindles that fail to assemble chromosomes at the cell equator (H').