Fig. 4: A role for microtubules in the high Brillouin shift within central mesodermal cells.
From: Highly dynamic mechanical transitions in embryonic cell populations during Drosophila gastrulation
a Visualisation of microtubules (α-Tubulin, top: green; bottom: inverted grayscale) and centrosomes (Asterless-YFP, top: magenta; middle: inverted grayscale) in physical cross-sections of fixed embryos at the onset, and during VFF. White squares indicate inset’s areas (right column); yellow dashed line: approximate centrosomal position based on Asterless larger puncta. Scale bars are 25 μm; for insets: 10 μm. b Super-resolution visualisation of sub-apical microtubules (top: inverted grayscale; middle: green; bottom: inverted grayscale) during VFF. Top: central mesoderm; middle and bottom: peripheral mesoderm. Scale bars are 5 μm. VF ventral furrow. c Spinning disk images of the ventral side of living embryos expressing EB1-GFP (grayscale). Top: onset (t = 0’); bottom: VFF (t − 10’). Dashed-yellow rectangle: sub-apical area used for the analyses of microtubule alignment (MTSD; panel d, e). Green arrows: centrosomes before (top) and during VFF (bottom). Blue arrow: ventral midline. Blue arrowhead: basal-lateral microtubules. Scale bars are 25 μm. d Quantification of MTSD within the sub-apical compartment (yellow dashed rectangle). MTSD was calculated between the onset (t = 0’) until fold formation (t = 13’−14’). Each line is the MTSD mean per embryo, with standard error of the mean (SEM, light blue area). e Scatter-plot of selected timepoints (panel d) of mean MTSD for each embryo (dots) and median across all embryos (blue line). Statistical test: non-parametric one-way ANOVA (Friedman) test, followed by multiple comparisons (FDR corrected). Friedman statistic = 10.67, p = 0.0040. p Values of multiple comparisons in Results. f BS maps at apical constriction (left), mesoderm folding (centre) and invagination (right) in control (top) and Colcemid-treated embryos (bottom) with labelled membranes (Gap43-mCherry, inverted grayscale). Yellow area (in Gap43-mCherry channel) and white dashed line (in BS channel) indicate quantified areas shown in panel d. Scale bar is 50 μm. g Box-whiskers plot showing the maximum BS in control (black) and Colcemid-treated (red) embryos. Each dot represents the mean of the 6-cell area in a single slice of an embryo. N = 5 independent experiments. Statistical test: two-tailed Mann–Whitney test (non-parametric). Box-whiskers plots: line is median, top/bottom edges are 1st and 3rd quartiles and whiskers indicate maximum and minimum values. Source data are provided as a Source Data file. For statistical comparisons: * is p < 0.05, ** is p < 0.01.
