title: How geometry and internal bias affect the accuracy of eukaryotic gradient sensing.
abstract: Many motile eukaryotic cells determine their direction by measuring external chemical gradients through the binding of ligands to membrane bound receptors. This process is limited by fluctuations arising from the binding process and from the diffusion of the ligand molecules. Here, we apply estimation-theoretic methods to determine the physical limits of gradient sensing for cells that are noncircular and for cells that have an internal bias. Specifically, we derive theoretical expressions for the accuracy of gradient sensing in elliptical cells. This accuracy for highly elliptical cells can significantly deviate from the gradient sensing limits derived for circular cells. Furthermore, we find that a cell cannot improve its sensing of the gradient steepness and direction simultaneously by elongating its cell body. Finally, we derive a lower bound on the accuracy of gradient sensing for cells that possess an internal bias and compare our analytical results with recent experimental findings.
authors.affiliation: Department of Physics and Center for Theoretical Biological Physics, University of California, San Diego, La Jolla, California 92093-0374, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Hu
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.forename: Wouter-Jan
authors.initials: WJ
authors.lastname: Rappel
authors.forename: Herbert
authors.initials: H
authors.lastname: Levine
mesh_terms: D048429:Cell Size; D002633:Chemotaxis / Q000502:physiology*; D003198:Computer Simulation; D005057:Eukaryotic Cells / Q000502:physiology*; D008954:Models, Biological