Fig. 1.

Continuous NG2 gene activation in a subset of microglia after tMCAO. a Overview of transgene structures of mouse lines used in tMCAO model. CX₃CR₁-EGFP, NG2-CreERT2, and Rosa26-tdTomato mice were crossbred to generate a triple transgenic mouse termed NG2^tdTxCXCR^EGFP. b NG2^tdTxCXCR^EGFP mice were used for tMCAO. Subsequently injured mice were injected with tamoxifen (TAM) for three consecutive days from 0 to 2 days post injury (0–2 dpi), 2–4 dpi, or 4–6 dpi, and were analyzed at 7, 9, and 11 dpi respectively (7 days after the first day of TAM injection). c Overview of a coronal brain section of a NG2^tdTxCXCR^EGFP mouse treated with TAM at 2–4 dpi after tMCAO. EGFP⁺ microglia were drastically activated in the infarct-related area of the brain. d and e Magnified views from white boxes in c showing that in general the expression of EGFP (triangles) and tdT (open arrowheads) were found in distinct cell populations. However, tdT⁺ EGFP⁺ cells (arrowheads) could also be observed. White boxes in d and e highlighted the morphology of tdT⁺ EGFP⁺ cells representing activated microglia. f and g Quantification of tdT⁺ EGFP⁺ cells in the infarcted striatum (depicted by the dashed line in c) when tamoxifen was injected at different time points, represented as either the numbers of tdT⁺ EGFP⁺ cells per coronal brain slice (f) or the density of tdT⁺ EGFP⁺ cells (g). The color coding shows the data points per animal (n = 3–5 mice indicated as big circles with 2–6 data points (small ones) per mouse). Scale bars = 1000 μm in c, and 50 μm in d and e