Fig. 2

A polarised and active actomyosin network is required for Par complex polarisation. a 8-cell stage (blebbistatin, LatB group and its control) or 4–8 cell stage embryos (ML-7 and its control) were treated with DMSO, blebbistatin, ML-7 or LatB, and fixed at the late 8-cell stage. Early 8-cell stage embryos treated with DMSO were also fixed as a control. Embryos were immunostained for F-actin and Pard6. b, c Cell-contact-free enrichment of F-actin (b) or Pard6 (c) as a function of the IEA in embryos from (a). Each dot represents an individual measurement. d Percentage of polarised embryos in the groups of (a). The number of embryos per category is indicated. Embryos that did not show any blastomere with the enrichment of F-actin and Pard6 at the cell-contact-free surface were considered non-polarised. Otherwise embryos were classified as polarised. Data are shown as a contingency table. ****p < 0.0001, NS = not significantly different, Fisher’s exact test (six independent experiments). e DMSO and ML-7-treated embryos immunostained for ppMRLC. f Quantification of ppMRLC cell-contact-free cortical enrichment in ML-7-treated and control embryos. Each dot represents an individual measurement. Data are shown as individual data points with Box and Whiskers graph (bottom: 25%; top: 75%; line: median; whiskers: min to max). ****p < 0.0001, Mann–Whitney test. N = 10 embryos for DMSO and N = 12 embryos for ML-7, four independent experiments. g ppMRLC and F-actin staining from the late 4-cell stage to the late 8-cell stage. The ppMRLC signal intensity of the indicated blastomeres is plotted in 3D. White stars indicate the cell-contact-free surface. Arrowheads indicate cortical localisation of ppMRLC. h Quantification of ppMRLC enrichment at the cell-contact and cell-contact-free domains from the late 4-cell stage to the late 8-cell stage. Data are shown as mean ± s.e.m. For all panels, squares indicate the magnified regions. N = 32 measurements from 7 late 4-cell stage embryos; N = 69 measurements from 11 early 8-cell stage embryos; N = 86 measurements from 11 mid 8-cell stage embryos; N = 50 measurements from 13 late 8-cell stage. All scale bars, 15 μm