Figure 2.
Apical constriction of epi-NSCs correlates with pulses of medial-apical MyoII.(A) Surface view of wild-type NE stained for E-cad (red) and Neur-GFP (green) showing that epi-NSCs have smaller apical areas. Scale bars = 10 μm. (B) Quantification of apical area (normalized; A.U., arbitrary units) plotted against distance from epi-NSCs (in μm; x = 0 corresponds to a line joining the center of each epi-NSCs), showing that apical area decreases toward the medial edge of the TZ (n = 13 brains; means ± SEM of all pooled cells, 373–890 cells per binned distance). (C) Density along the D-V axis of epi-NSCs and other TZ cells relative to those of lateral NE cells (n = 8 brains; boxplots display the mean ratios, with the density of distal NE cells normalized to 1 for each brain). (D) Snapshots from a video of a brain expressing MyoII-GFP (green) and Par3-mCherry (red) showing an apically constricting TZ cell (dotted outline) undergoing phases of constriction and expansion. Constriction is associated with increased levels of medial-apical MyoII (arrow). Scale bars = 10 μm. (E–H) plots of apical area and MyoII intensity values over time for a representative epi-NSC and NE (G) cells, along with the rates of changes in apical area and MyoII levels (F and H). Increased MyoII levels were associated with reduced apical area in both epi-NSC and NE cells. (I and J) Cross-correlation values between area and myosin rates of change (mean ± SEM calculated for the different peaks) plotted as a function of the time shift in representative epi-NSC (10 contraction phases from one epi-NSC; n = 9; I) and NE cells (14 contraction phases from a single NE cell; n = 10; J). Anticorrelation was maximal with a 10–20-s time shift, i.e., offset, with maximal increase of MyoII preceding maximal rate of apical constriction. (K) Mean offset time between maximal rates of MyoII accumulation and area changes in epi-NSCs (n = 9) and NE cells (n = 10). MyoII accumulation similarly precedes constriction in both cell types (ns, no significant difference, two-tailed t test). (L) Offset times between maximal accumulation of MyoII and maximal constriction rates in epi-NSCs (n = 191 peaks, from 9 epi-NSCs).

Apical constriction of epi-NSCs correlates with pulses of medial-apical MyoII. (A) Surface view of wild-type NE stained for E-cad (red) and Neur-GFP (green) showing that epi-NSCs have smaller apical areas. Scale bars = 10 μm. (B) Quantification of apical area (normalized; A.U., arbitrary units) plotted against distance from epi-NSCs (in μm; x = 0 corresponds to a line joining the center of each epi-NSCs), showing that apical area decreases toward the medial edge of the TZ (n = 13 brains; means ± SEM of all pooled cells, 373–890 cells per binned distance). (C) Density along the D-V axis of epi-NSCs and other TZ cells relative to those of lateral NE cells (n = 8 brains; boxplots display the mean ratios, with the density of distal NE cells normalized to 1 for each brain). (D) Snapshots from a video of a brain expressing MyoII-GFP (green) and Par3-mCherry (red) showing an apically constricting TZ cell (dotted outline) undergoing phases of constriction and expansion. Constriction is associated with increased levels of medial-apical MyoII (arrow). Scale bars = 10 μm. (E–H) plots of apical area and MyoII intensity values over time for a representative epi-NSC and NE (G) cells, along with the rates of changes in apical area and MyoII levels (F and H). Increased MyoII levels were associated with reduced apical area in both epi-NSC and NE cells. (I and J) Cross-correlation values between area and myosin rates of change (mean ± SEM calculated for the different peaks) plotted as a function of the time shift in representative epi-NSC (10 contraction phases from one epi-NSC; n = 9; I) and NE cells (14 contraction phases from a single NE cell; n = 10; J). Anticorrelation was maximal with a 10–20-s time shift, i.e., offset, with maximal increase of MyoII preceding maximal rate of apical constriction. (K) Mean offset time between maximal rates of MyoII accumulation and area changes in epi-NSCs (n = 9) and NE cells (n = 10). MyoII accumulation similarly precedes constriction in both cell types (ns, no significant difference, two-tailed t test). (L) Offset times between maximal accumulation of MyoII and maximal constriction rates in epi-NSCs (n = 191 peaks, from 9 epi-NSCs).

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