Fluorescent proteins as sensors for cellular functions.

The exploitation of green fluorescent protein-based biosensors promises to revolutionize functional imaging of the nervous system. Various approaches have created a multitude of reporters of neuronal activity and of activation of biochemical signaling pathways. Although the number of different probes has increased significantly, the critical step remains to bring these probes from the cuvette through the imaging of single cells to the imaging of whole organisms in vivo. The recent development of new genetically encoded sensors and their functional expression in model organisms are encouraging signs that the field is moving ahead in this direction.