Fig. 6

Resident microglia respond to secondary, focal damage following widespread retinal degeneration. A Representative in vivo time course of an Arr1^−/− Cx3cr1^+/GFP retina after focal laser damage. Retinal macrophages (green, GFP⁺) transiently respond to a focal laser damage administered more than 20 days after onset of light exposure. Days indicate days post-laser injury. Top row: focal damage indicated by increased scattering in OCT. Bottom row: GFP⁺ macrophages initially migrate towards and then away from the focal damage locus. Inset locations indicated by dashed squares. INL = inner nuclear layer; IPL = inner plexiform layer. B Representative maximum intensity histological images at 1, 2, 4, 8 and 14 days following focal laser injury administered more than 20 days after onset of light exposure in Arr1^−/− Ai9^KI/KI Cx3cr1^{+/YFP−CreER} post-tamoxifen mice in the inner retina (IPL) and corresponding subretinal layers. Images are thresholded, pseudocolored-overlay projections, as in Fig. 4A, where resident cells (predominantly microglia) are displayed in peach and peripherally derived macrophages are indicated in blue. Dashed circle indicates approximate location of the focal damage locus (diameter = 150 μm) and scale bar = 50 μm. See also Additional file 3: Fig. S3, Additional file 4: Fig. S4, Additional file 5: Fig. S5, Additional file 6: Fig. S6, Additional file 7: Fig. S7, Additional file 8: Fig. S8. C Significantly more resident cells respond to secondary, focal damage than monocytic cells. Quantification indicates the percent of colored pixels inside the injury area from pseudocolored-overlay images in KO animals after laser damage compared to undamaged KO (0 day) and WT (Arr1^+/+) controls. Mean ± SE; **p < 0.01, ***p < 0.001; n = 4–8 laser damage locations in 3–4 retinas (2 mice) per timepoint