Fig. 4. Citron function during cytokinesis in the Drosophila embryonic PNS depends on Rho activation. Flat preparations of the PNS from abdominal segments of stage 16 embryos stained for the neuronal specific antibody 22C10 (A,A',B,B',D,D'). (C-C''') Embryonic PNS cells stained with: 22C10 (C, blue in C'''), nuclear envelope marker anti-Lamin (C', red in C''') and plasma membrane marker anti- Spectrin (C'', green in C'''). Anterior is to the left and dorsal up. (A,B,D) Dorsal external sensory (DES) cluster area. (A',B',C-C''',D') Lateral chordotonal organ (CH) cluster area. (A,A') w¹¹¹⁸ (control) embryos showing typical organization of the DES and CH cell clusters. (B,B',C-C''') cit²/Df(3)iro-2 mutant embryos exhibit variable abnormalities, such as absence of cells and multinucleate cells (arrows). The number of nuclei in these cells was estimated by presence of Lamin-positive nuclear envelopes within -Spectrin delineated cellular membrane. A general disorganisation of both clusters and axonal misrouting was also observed. (D,D') cit²/Df(3)iro-2 mutant embryos that are also heterozygous for pbl³, showing an increase in the number of multinucleate cells (arrow). (E) To quantitate the effect of loss of one copy of the pbl gene on the cit phenotype, the number of mono- and multinucleate PNS cells in a defined region was scored for each genotype (cells were scored in 30 identical frames). Bars represent the percentage of multinucleate cells in each genotype. Error bars represent one standard deviation.