Fig. 1: Robust compartmentalization is observed in vitro and in vivo, but theory and simulations predict a physical instability.
From: Robust cytoplasmic partitioning by solving a cytoskeletal instability
a, Schematic of an early zebrafish embryo, with microtubule asters in green and actin cortex in cyan (left), and a schematic of cytoplasmic compartmentalization (right). An aster–aster interaction can be described by a network of two self-amplifying loops interacting via local inhibition. b, Light-sheet fluorescence microscopy image of a live zebrafish embryo after the first division. Asters partition the cytoplasm before furrow ingression. Microtubules are shown in green with eGFP–Doublecortin and the actin cortex in cyan with utrophin–mCherry. c, Cell membrane (top) and microtubules (bottom) of a zebrafish embryo with PH-Halo and eGFP–Doublecortin. d, Mitochondria of a zebrafish embryo with mito–GFP. e,f, Live imaging of a syncytial zebrafish embryo. Asters coexist and form boundaries of low microtubule (e) and actin density (f). Cyto B, cytochalasin B. g, Cell membrane (top) and microtubules (bottom) of a syncytial zebrafish embryo. h, Mitochondria of a syncytial zebrafish embryo. i, Live imaging of cycling frog egg extract showing cytoplasmic partitioning. Microtubules are shown in green. j, Cytoplasmic compartments are visualized in magenta by labelling lipid organelles. k, Two asters interacting. l, Microtubule density profile of two interacting asters. \({x}\) indicates the linear coordinates from the centre of one aster (0 µm) to the centre of the adjacent aster (approximately 200 µm). Experimental data are shown in black and green with s.e.m. (n = 8 independent samples), agent-based simulations are in grey with 95% confidence interval (n = 6 independent simulations) and one-dimensional theory is in orange. m, Numerical time evolution of microtubule densities. The inset shows the interface position over time. n, Top view of a 3D agent-based simulation of interacting asters in a slab showing boundary formation. Grey and green indicate microtubules of the two asters. The inset shows the interface details. o, Side view of temporal evolution of a 3D agent-based simulation showing invasion.
