Tang, J.C.Y. et al. Nat. Neurosci. 18, 1334–1341 (2015).

Mouse lines expressing GFP are a valuable resource that is mainly used for imaging or labeling purposes. Tang et al. have now developed a tool called CRE-DOG to expand the utility of these GFP lines. CRE-DOG consists of a split Cre recombinase, the two parts of which are fused to GFP-binding nanobodies. Cre can be brought together in the presence of GFP, resulting in an active recombinase. The researchers generated recombinant adeno-associated virus vectors encoding this tool and showed that CRE-DOG can be used to recombine Lox sites in both transgenic and viral constructs. They used the system to control reporter gene or channelrhodopsin expression in GFP-positive cells in various regions in the mouse brain.