Structuring Role of Tau-Tubulin Co-Condensates in Early Microtubule Organization

Tau protein, a key microtubule-associated protein in neurons, is traditionally known for stabilizing microtubules. However, its recently discovered ability to undergo liquid-liquid phase separation (LLPS) reveals a broader, dynamic role in nucleating and organizing microtubule networks. Here, using a combination of real-time imaging and a geometric approach based on Voronoi tessellation, we examined how tau condensation leads to clustering and local tubulin enrichment, supporting microtubule organization. Our observations show that tau-tubulin co-condensates not only initiate nucleation and branching of microtubules but also drive the networks gradual evolution through a "dynamic weaving" process. By generating Voronoi diagrams from super-resolution and confocal microscopy images of the stabilized network, we quantitatively mapped tubulin enrichment as a function of tau density, revealing that high-density tau clusters, approximately 0.2 m in size, correlate with tubulin-rich spots at equilibrium. Overall, these findings provide new insights into tau-tubulin co-condensates as dynamic structuring elements, whose liquid-like properties continuously reshape the microtubule network, creating a flexible and adaptive architecture essential for cellular function.