1. Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
2. Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, MO 63110, USA.
3. Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
4. MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
5. Departments of Neuroscience and Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
6. Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.