Research of our laboratory focuses on developing quantitative imaging tools that are capable of revealing dynamics of cellular signaling at high spatial and temporal resolution (biosensors), or that enable optical control of signaling proteins at precise times and subcellular locations (optogenetics). These tools are being applied in live cell microscopy to understand the signaling networks that govern polarity and motility of epithelial cells, axon guidance and development of dendritic spines in neurons.Biosensors Our current studies employ structural design strategies and technologies of fluorescent proteins to design FRET-based, activity reporters for signaling proteins with high specificity, fast kinetics, minimal perturbation, and superior dynamic range. Multiple live cell imaging modalities are being used in the lab including TIRF, confocal, intensity-based ratiometric imaging, and fluorescence lifetime microscopy (FLIM). We are also interested in developing methods of analysis and modeling to quantitatively extract and process biosensor data for a better understanding of signalingOptogenetics Optogenetics has become one of the most exciting areas of research for its promise of enabling biologists to exert precise control of signaling in living systems. The core of optogenetics relies on both development of new optical manipulation technologies and molecular engineering at the genetic level using natural photosensory proteins. We are interested in exploring the use of the flavin-binding LOV (light-oxygen-voltage) domain from the plant photoreceptor phototropin. Upon light illumination, the LOV domain undergoes conformational changes including dissociation and unwinding of a C-terminal helical extension. Tethering the LOV domain to the N-terminus of a constitutively-active mutant of Rac, a member of the Rho family of small G proteins, can sterically block the interactions of Rac with its downstream effectors in the dark and restore its binding upon blue light illumination. This produced a genetically-encoded photoactivatable analog of Rac (PA-Rac) that enables precise modulation of Rac activity at regions that are submicrons in size and capable of controlling activation with microseconds precision in living cells. Current projects in the lab focus on extending such technology to other signaling proteins.