Figure 5. Spontaneous recombination of Rosa26^mTmG in microglial CreER lines.

(A) Diagram of experimental protocol used to assess spontaneous Cre/loxP recombination of Rosa26^mTmG/+ in microglia by flow cytometry and immunofluorescence.

(B) Representative flow cytometry results show the percentage of recombined mGFP⁺ (mG) and mTomato⁺ (mT) microglia from individual animals from each group from Figure 1 and uninjected (no oil) Cx3cr1^{YFP–CreER/+ (Litt)} mice.

(C) Quantification of the percentage of recombined mGFP⁺ microglia shows increased spontaneous recombination of the Rosa26^mTmG allele in the Cx3cr1^{YFP–CreER (Litt)} line compared with the Cx3cr1^{CreER (Jung)}, Tmem119^CreER, Hexb^CreER, and P2ry12^CreER lines (one-way ANOVA with Tukey’s post hoc test; n = 5 Cx3cr1^{YFP–CreER/+ (Litt)}, 5 Cx3cr1^{CreER/+ (Jung)}, 8 Tmem119^CreER/+, 9 Hexb^CreER/+, and 4 P2ry12^CreER/+ mice; *p < 0.05, ****p < 0.0001).

(D) Representative immunofluorescent images of brain sections from right hemispheres of oil-injected mice used for flow cytometry analysis in (B) and (C). Sections were immunolabeled for anti-P2RY12 (AF647 pseudo-colored red) to identify microglia and anti-GFP (green) to identify recombined cells. The number of recombined mGFP⁺ microglia (white arrows) matches the results observed by flow cytometry. In the Cx3cr1^{YFP–CreER/+ (Litt)} line, the soma of non-recombined microglia are also immunolabeled by anti-GFP because of the constitutive expression of YFP (asterisks), but it can be distinguished from recombined mGFP⁺ microglia by fluorescence intensity and membrane labeling. Scale bars, 50 μm.

All data are presented as mean ± SEM. Individual data points indicate males (squares) and females (circles). See also Figure S5.