Fig. 5: Active myosin-II accumulates in extra-soft oocytes and decreasing its activity rescues chromosome misalignment.

a Cropped images of representative control, cVCA, and ML-7-treated oocytes stained for active phosphorylated myosin-II (pMLC2, gray) at BD + 6 h 30 min. Insets are magnification of the chromosomes (gray) and of regions marked by yellow dashed line boxes. Same oocytes as in Fig. 4a. Scale bar: 10 µm. Three independent experiments. b Dot plot representing pMLC2 spindle intensity at BD + 6 h 30 min in control and cVCA oocytes. n is the number of oocytes analyzed. Data are from three independent experiments. Statistical significance of differences is assessed with a two-sided Mann–Whitney test: **P-value = 0.0042. c Dot plot representing pMLC2 cytoplasm intensity at BD + 6 h 30 min in controls and cVCA oocytes. n is the number of oocytes analyzed. Data are from three independent experiments. Statistical significance of differences is assessed with a two-sided Mann–Whitney test: **P-value =  0.0004. d Representative time-lapse movies of cVCA oocytes treated or not with ML-7, expressing Histone(H2B)-GFP (blue or black) and cVCA (red). Acquisitions were taken every 30 min starting 2 h before anaphase I. Scale bar: 10 µm. Six independent experiments. e Dot plot representing the metaphase I plate width 30 min before anaphase I in control and cVCA oocytes treated or not with ML-7. n is the number of oocytes analyzed. Data are from six independent experiments. Statistical significance of differences is assessed with a two-sided Mann–Whitney test: n.s. P-value = 0.1708 and ***P-value < 0.0001. f Same as e for control oocytes treated or not with ML-7. n is the number of oocytes analyzed. Data are from four independent experiments. Statistical significance of differences is assessed with a two-sided t-test: n.s. P-value = 0.0547. g Same as e for control oocytes treated or not with U0126. n is the number of oocytes analyzed. Data are from three independent experiments. Statistical significance of differences is assessed with a two-sided t-test: n.s. P-value = 0.5756. For b, c, e–g, black bars and whiskers represent mean and SD.