![Figure 1. Microtubule depolymerization severely compromises the fidelity of cortical crescent position in larval NBs. (A–G) Still images from time-lapse recordings of larval NBs before (t0) and after (t1 and t2) treatment with colcemid. NBs are shown oriented with their apical side up in all t0 panels. Fluorescent reporter constructs are indicated to the left of each row. (A–F) Yellow and green asterisks mark pre- and posttreatment crescent position, respectively. Arrows mark apical centrosomes; white arrowheads refer to the basal centrosome in t0 and motile centrosomes in t1 and t2. (A) Before colcemid treatment, the apical centrosome nucleates an aster, and the basal shows migratory behavior (t0). When microtubules are depolymerized, the apical centrosome detaches from the cortex, and both centrosomes localize randomly (t1 and t2; Video 1). (B–D) In the control division, metaphase crescents and position of centrosomes reflect the polarity axes (t0; yellow lines). Behavior of Dlg (B), Pins (C) and Baz (D; Video 2) crescents upon colcemid treatment is shown. Loss of microtubules renders both centrosomes motile (t1). The place of crescent formation becomes unpredictable, suggesting a change in polarity axis orientation that bears no apparent relation with centrosome position at the time of crescent assembly (t2; green lines). (E and F) Yellow and green lines represent pre- and posttreatment cortical polarity orientation, respectively. (E) Basal crescent positioning responds similarly to colcemid treatment (Video 2). (F) Alignment of apical with basal crescents is unperturbed in colcemid-arrested cells despite occurring at an ectopic position (t0 and t2; yellow and green arrowheads, highlighting the limits of the basal crescent, before and after microtubule depolymerization, respectively). Depolymerizing microtubules can prolong interphase, but crescent formation occurred always closely preceding or at the time of NEB, as in controls (not depicted). (G) A crescent assembled before colcemid treatment (t0, yellow asterisk, arrow [apical centrosome], and arrowhead [basal centrosome]) does not change position when microtubules are depolymerized (visible with the loss of centrosome anchoring; t1 and t2, arrowheads). (H and I) Plot of the angle of crescent position in two successive cycles in control cells (yellow) and before and after colcemid treatment (green). Time is shown in hours:minutes:seconds. Bar, 10 µm.](https://cdn.rupress.org/rup/content_public/journal/jcb/188/5/10.1083_jcb.200905024/6/jcb_200905024_rgb_fig1.jpeg?Expires=1767711022&Signature=Qw-WLRdaf~a0NUvYzKMkJyJ~w0-h6WhQ86X-8PN8bXxScrhhf-Emn3UPvKMniKAy6gi5rbu7d1n6BENcPogewErgDJcg27d3wL4575h0GYVAKWT8a4PfkcdFa-W-nzSFtzH1JVgF~QjDJkaYk~6sHmTtgRHxEpPCmnZ51uV5mBu8IKSSd0~XcXspWIaxrXhJoghIW8l1dW6xC9qGGbR~vSYAKn4BP0wALyQSPeRuLL0n~Ybj-pTBi-KjlYxQl7Ivx~qT9Fl7jK7~dUBLiSkGzkmkFIZ53z2oZNleaiY8e23cRGXTGWZsW6nHwBvHkY1nt14qub2lOEqb9w5y8XCdmQ__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Microtubule depolymerization severely compromises the fidelity of cortical crescent position in larval NBs. (A–G) Still images from time-lapse recordings of larval NBs before (t0) and after (t1 and t2) treatment with colcemid. NBs are shown oriented with their apical side up in all t0 panels. Fluorescent reporter constructs are indicated to the left of each row. (A–F) Yellow and green asterisks mark pre- and posttreatment crescent position, respectively. Arrows mark apical centrosomes; white arrowheads refer to the basal centrosome in t0 and motile centrosomes in t1 and t2. (A) Before colcemid treatment, the apical centrosome nucleates an aster, and the basal shows migratory behavior (t0). When microtubules are depolymerized, the apical centrosome detaches from the cortex, and both centrosomes localize randomly (t1 and t2; Video 1). (B–D) In the control division, metaphase crescents and position of centrosomes reflect the polarity axes (t0; yellow lines). Behavior of Dlg (B), Pins (C) and Baz (D; Video 2) crescents upon colcemid treatment is shown. Loss of microtubules renders both centrosomes motile (t1). The place of crescent formation becomes unpredictable, suggesting a change in polarity axis orientation that bears no apparent relation with centrosome position at the time of crescent assembly (t2; green lines). (E and F) Yellow and green lines represent pre- and posttreatment cortical polarity orientation, respectively. (E) Basal crescent positioning responds similarly to colcemid treatment (Video 2). (F) Alignment of apical with basal crescents is unperturbed in colcemid-arrested cells despite occurring at an ectopic position (t0 and t2; yellow and green arrowheads, highlighting the limits of the basal crescent, before and after microtubule depolymerization, respectively). Depolymerizing microtubules can prolong interphase, but crescent formation occurred always closely preceding or at the time of NEB, as in controls (not depicted). (G) A crescent assembled before colcemid treatment (t0, yellow asterisk, arrow [apical centrosome], and arrowhead [basal centrosome]) does not change position when microtubules are depolymerized (visible with the loss of centrosome anchoring; t1 and t2, arrowheads). (H and I) Plot of the angle of crescent position in two successive cycles in control cells (yellow) and before and after colcemid treatment (green). Time is shown in hours:minutes:seconds. Bar, 10 µm.
