Fig. 1

CX3CR1^CRE−ER expression modulated by TAM is spatially and temporally controlled in microglia. A Experimental design to confirm that Cre penetrance targets CX3CR1-expressing cells in the retina and brain without affecting peripheral CX3CR1-expressing immune cells. CX3^CreER:R26^iTdT mice were injected once daily for 5 days with tamoxifen (TAM). One week and 3 weeks after the last TAM injection, flow cytometric analysis was performed on blood leukocytes to track the percentage of TdT⁺CD11b⁺CD45^Hi leukocytes. At 6 weeks post-TAM administration, tissues were collected for flow cytometric and immunohistochemical analysis. B, C IHC analysis of brain and retinal tissues showing the density of TdT⁺Iba1⁺ cells/mm² (B) and Iba1⁺ cells/mm² (C) in vehicle and TAM-treated CX3CR1^CreER:R26^iTdT mice. D Confocal images of retinal tissues to visualize Iba1⁺ microglia (green) and TdTomato (red) in vehicle and TAM-treated CX3CR1^CreER:R26^iTdT mice. E Experimental design to validate the feasibility of depleting CNS-resident microglia without affecting peripheral CX3CR1-expressing immune cells. Four weeks following Cre recombinase induction with TAM (after the 5^th TAM injection), CX3CR1^Cre−ER:R26^iDTR mice were administered 25 ng/g diphtheria toxin (DTx) once daily for 3 days. Tissue collection occurred 24 h after the last DTx injection. Control mice received PBS instead of DTx. F, G, Quantification of Iba1⁺ cells/mm³ (F) and TUJ1⁺ percent immunoreactive area (G) in the retinas of PBS and DTx treated CX3CR1^CreER:R26^iDTR mice. H Confocal images of the retina for Iba1⁺ (green), and TUJ1⁺ (white). Data represent mean ± SD, n = 4–7 mice per group where each dot represents an individual mouse. **P < 0.01, ****P < 0.0001 using Student’s t-test, with Welch’s correction