Cell membranes are like two-dimensional fluids whose molecules are distributed evenly through lateral diffusion but many important cellular processes depend on cortical polarity, the locally elevated concentration of specific membrane proteins.
Roland Wedlich-Soldner at the Max Planck Institute of Biochemistry in Martinsried, Germany, and his colleagues at Harvard Medical School, Boston, The Stowers Institute for Medical Research, Kansas City, and the University of Texas Southwestern Medical Center, Dallas, have analysed and quantified how cortical polarity develops and how an asymmetric distribution of molecules can be dynamically maintained.