The loss of centrioles severely compromises the fidelity of polarity orientation in larval NBs. (A–D) Still images from time-lapse recordings of MARCM clones labeled by the expression of nuclear GFP (NLS-GFP [nlsGFP]). Genotypes and fluorescent reporters are indicated to the left of each row. Colored asterisks, lines, and circles mark the position of apical crescents, the division axes, and small daughter cells, respectively, in successive cell cycles (yellow, first; green, second; red, third; and white, fourth). Dashed circles indicate the position where GMCs will be delivered. (A) NB in a control wild-type (wt) clone dividing three times. Polarity orientation, as judged by apical centrosome position (arrows) and small daughter cell budding sites, changes very little from one cycle to the next (t₀–t₃). The resulting GMCs are clustered (t₃; Video 7). (B–D) dsas-4 mutant NB clones. (B) The position of apical crescents and the place of daughter cell delivery, which appear to be aligned, vary by nearly 90° between two successive cell cycles (t₀ and t₂; Video 8). (C) Projections made to reflect small daughter cell budding sites in successive rounds of division, which are scattered around the NB cortex in four successive divisions (t₀–t₃). (D) Apical crescent positions scatter similarly over three consecutive cell cycles (t₀–t₃). (E) Plot of apical crescent position variations between two consecutive cell cycles of control dsas-4/+ NBs (yellow) and homozygous dsas-4 mutant NBs (green) from mosaic brains. (F) Plot of daughter cell budding site variations between two consecutive cell cycles of control dsas-4/+ NBs (yellow) and homozygous dsas-4 mutant NBs (green). Time is shown in hours:minutes:seconds. Bar,10 µm.