Building cytoskeletal circuits with branched microtubule networks

Cytoskeletal elements self-organize into intricate hierarchical structures and fulfil essential cellular functions. A remarkable example is the uniformly polarized axonal microtubule (MT) architecture, crucial for controlled neuronal migration, axon extension, and long-distance molecular transport. It has been discovered that branching MT nucleation is responsible for creating and maintaining the uniformly polarized MT scaffold in axons. Inspired by the axonal MT architecture, we generated MTs and guided them in nanochannels with the goal of developing a cytoskeletal circuit. Specifically, by forming branched MT networks in Xenopus egg extract within microfabricated channels, we built a nanotechnology platform to engineer robust MT architectures on a chip. We can control the adaptive self-organization of branched MT networks within microstructures via different geometries, such as turns, divisions, biased divisions, and even MT diodes. In addition, we present a numerical model based on these characteristics that can successfully predict the self-organization of branched MT networks in more complex elements, enhancing our understanding and design of cytoskeletal circuits. Our work holds potential for the development of novel on-chip nanotechnologies including on-chip molecular transport, biosensors, and mechanical actuators. Moreover, cytoskeletal circuits are useful tools for fundamental studies about MT cytoskeleton in confined spaces.