A Hydrodynamic Instability Drives Protein Droplet Formation on Microtubules to Nucleate Branches

Liquid-liquid phase separation occurs not only in bulk liquid, but also on surfaces. In physiology, the nature and function of condensates cellular structures is just beginning to be explored. Here, we study how condensed protein TPX2 behaves microtubules initiate branching microtubule nucleation, process by which nucleate off sides preexisting microtubules. This autocatalytic nucleation pathway critical for spindle assembly eukaryotic cells. Using fluorescence, electron, atomic force microscopies hydrodynamic theory, show that a reorganizes according Rayleigh-Plateau instability. same phenomenon causes film dew form droplets along spider web. After uniformly coating microtubules, forms regularly spaced from branches nucleate. Droplet size spacing increase with greater concentration. A stochastic model shows make more efficient confining space where multiple necessary factors colocalize branch. Our work first demonstration instability nanoscale molecular biology. Although it context generic requires coat filament. Thus, anticipate similar effects may play important roles other areas wherever proteins biological filaments meet.