Chen, Y. et al. Neuron 81, 280–293 (2014).

Several methods for labeling synaptic proteins and their interactions exist, but most of these strategies rely on overexpression of the tagged proteins. To avoid this overexpression, Chen et al. label synaptic proteins by modifying the endogenous genomic loci encoding synaptic proteins with bacterial artificial chromosomes. In addition, they make the expression of the labeled proteins dependent on recombination so that the labeling can happen in a cell type–specific manner. They name the method STaR, synaptic tagging with recombination, and apply it to characterize the number and distribution of synapses in the visual system of flies. Using two different recombination systems, one can also colabel presynaptic and postsynaptic partners. In principle, the system can be adapted to other model organisms such as zebrafish or mice.