Fig. 7: Model.
From: Phase separation of TPX2 enhances and spatially coordinates microtubule nucleation
Left-side cartoon: at low concentrations (<endogenous), TPX2 localizes to MTs but does not recruit soluble tubulin, likely due to electrostatic repulsion (denoted by “+” and “−”). Right-side cartoon: at high concentrations of TPX2 (≥endogenous), TPX2 colocalizes with soluble tubulin on microtubules. Center: graphical abstraction of data demonstrating that TPX2 promotes branching MT nucleation (in the cytosol) and forms a co-condensate with tubulin (in vitro) in a switch-like manner at or above its endogenous concentration. Top gradient: relative importin-α/β levels existing as a gradient around chromosomes also affect TPX2-tubulin co-condensation and TPX2-mediated branching MT nucleation.
