Cell polarization is a prerequisite for essential processes such as cell migration, proliferation or differentiation. The yeast Saccharomyces cerevisiae under control of the GTPase Cdc42 is able to polarize without help of cytoskeletal structures and spatial cues through a pathway depending on its guanine nucleotide dissociation inhibitor (GDI) Rdi1. We show that GDI-mediated polarization provides precise spatial and temporal control of Cdc42 signaling and give experimental evidence for our findings. Cell cycle induced changes of Cdc42 regulation enhance positive feedback loops of active Cdc42 production, and thereby allow simultaneous switch-like regulation of polarity and Cdc42 activation. This regulation drives the direct formation of a unique polarity cluster with characteristic narrowing dynamics and optimized spatial focus. more

In recent years, kinetic theory has gained considerable popularity to asses the large scale properties of self-propelled particle (SPP) systems. Specifically, the Boltzmann equation provides a compelling link between a microscopic, particle-level description of active systems, and the corresponding set of macroscopic equations. Yet, the applicability of Boltzmann's equation in the context of active media, as well its limitations due to the molecular chaos assumption remain largely elusive. more