Memorial-Sloan Kettering Cancer Center
Visualizing neural activity with genetically encoded optical probes
In neural systems, information is often carried by ensembles of neurons rather than by individual units. Optical indicators provide a powerful means to reveal such distributed activity, particularly when protein-based and encodable in DNA: encodable probes can be introduced into cells, tissues, or transgenic organisms by genetic manipulation, selectively expressed in anatomically or functionally defined groups of cells, and recorded in situ, without a need for exogenous cofactors. pHluorins, pH-sensitive mutants of green fluorescent protein, were generated by combinatorial mutagenesis with the aim of exploiting the acidic pH inside secretory vesicles to monitor vesicle exocytosis and recycling. When linked to a vesicle membrane protein, pHluorins are sorted to secretory and synaptic vesicles and report transmission at individual synaptic boutons, as well as secretion and fusion pore ``flicker" of individual secretory granules.