Fig. 4: A dense MT network is assembled at the spindle midplane during metaphase in medaka early embryos.

a Kymographs showing the first mitotic spindle assembly process in a medaka embryo. Asterisks indicate a telophase chromosome or deformed nucleus migrating to centrosomes. b Schematic representation of spindle assembly and chromosome segregation processes in (a). Spindle length is almost constant during anaphase. c Graphs of relative fluorescence intensities for line scans of spindles in (a). Single z-section images shown in Supplementary Fig. 4d were used for quantification. d Quantification of centrosome-centrosome (black) and separating chromosome (red) distance during the first mitosis (n = 4 at each time point from 4 embryos). An asterisk shows the timing in (a). e–g Live-cell images showing nuclear accumulation of EGFP-α-tubulin (e, g), EGFP-EB1 (f), and mCherry-γ-tubulin (g) at NEBD (t = 0). h, i Live-cell images of EGFP-α-tubulin and RCC1-mCherry in the presence of 170-nM nocodazole (h) or after MT depolymerization by cold treatment (i), showing self-organization of spindle around chromosomes. Error bars indicate mean ± SD. Scale bars = 100 μm. Source data for (c, d) are provided as a Source Data file.