Figure 1.

Battle of Recombinases

BATTLE-1: split-tunable allocation of transgenes by recombinase “fights.”

(A) In the BATTLE-1 technology, Cre and FLPO are expressed under the control of CamKIIa promoter. The Cre transgene flanked by two FRT5 is designed to be a target of the FLPO recombinase. The FLPO transgene flanked by two loxN is designed to be a target of the Cre recombinase. Cre- and FLPO-dependent AAVs expressing mCherry and YFP, respectively, were used.

(B) Representative maximum intensity projection image of injected hippocampus. When the Cre to FLPO ratio was 1:1, the splitting allocation of YFP and mCherry was observed in hippocampal neurons.

(C) Magnified confocal image of the boxed area in (B).

(D) Quantification of percentage of cells expressing fluorescent proteins in the dentate gyrus.

(E) Representative maximum intensity projection image of injected hippocampus. When the ratio of Cre to FLPO was 1:0.01, most of the cells expressed mCherry, whereas few cells expressed YFP in the hippocampus.

(F) Magnified confocal image of the boxed area in (E).

(G) Quantification of percentage of cells expressing fluorescent proteins in the dentate gyrus.

(H) Illustration shows the battle of recombinases and BATTLE-1 system at a Cre to FLPO ratio of 1:1. After the first injection of mixed viruses, Cre and FLPO started recombinase battles in each infected neuron. Then, only the winning recombinase survived to induce its specific mutually exclusive allocation of transgenes (mCherry or YFP).

(I) Illustration shows the battle of recombinases and BATTLE-1 system at Cre to FLPO ratio of 1:0.01. In this situation, Cre wins over FLPO in many cells. Then mCherry is allocated in many cells, whereas YFP is allocated in a few cells.