Fig. 5 | Nature Communications

Fig. 5

From: The last-born daughter cell contributes to division orientation of Drosophila larval neuroblasts

Fig. 5

Components of the NB/GMC interface contribute to NB division axis maintenance. a Deviation of the division axis from one cell cycle to the next in NBs expressing worniu-Gal4-driven RNAi against the indicated components of the NB/GMC interface, as well as the Cindr interactors Rst and Dock. Asterisks: candidates for which protein depletion was confirmed. See Methods for precise genotypes. Data from, respectively, 2, 2, 1, 2, 2, 1 and 3 independent experiments. b Two successive division of a NB expressing worniu-Gal4-driven Cindr RNAi. The second division axis (green arrow) deviates from the first one (blue arrow) by 53° (quantified in a), due to the mispositioning of the apical Baz crescent (delimited by arrowheads), whereas the apical centrosome (arrow) aligns properly with this crescent. Proper spindle alignment was always observed (n = 5/5, 4/4, 17/17, 12/12, 4/4 and 6/6 cases with deviation >45°, respectively, in Sep1, Sep2, Cindr, dock, Rst and Flare RNAi). Scale bar: 5 µm. c Deviation of the division axis following GMC ablation in control NBs (36 ± 20°, n = 35, also shown in Figs. 2c and 3c, data from ten independent experiment), in NBs expressing worniu-Gal4-driven Sep1 RNAi (32 ± 27°, n = 29) and following GMC ablation in NBs expressing worniu-Gal4-driven Sep1 RNAi (37 ± 19°, n = 21). Data from three independent experiments. d Graphical summary of the findings. Top row: the NB/last-born GMC interface, distinguishable from other interfaces by the presence of the midbody and actin-rich plasma membrane extensions (magenta), biases through an unknown mechanism (magenta arrows) the apical polarization (green crescent) of NBs as they round up in mitosis. The mitotic spindle aligns with this crescent, resulting in division axis maintenance. Bottom row: disruption of this mechanism leads to misplaced apical polarization (with which the mitotic spindle still properly aligns) resulting in defective division axis maintenance

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