Fig. 1.

A small population of microglia are mobile in the normal adult brain. (A) Time lapse two-photon maximum intensity projection images of Cx3cr1-eGFP-labeled microglia/macrophages and vasculature over 12-h intervals (Left). The % cells that were “stable” or “unstable” (i.e., those that moved, appeared, or disappeared) is shown on the right. (Scale bars, 20 µm.) (B) Schematic showing timeline of experimental procedures and imaging. (C) In vivo maximum intensity projection images showing sparse tdTomato-labeled microglia and FITC-labeled blood vessels in the somatosensory cortex. (Scale bars, 100 and 20 µm.) (D) Time-lapse in vivo images of stationary (top row) or mobile (bottom row) microglia over a 24-h period. (Scale bars, 20 µm.) (E) Fraction of mobile or stationary microglia (out of 272 cells, n = 9 mice, 5 male and 4 female) imaged over 0 to 12 h, 12 to 24 h, or the sum of each window. Any microglia that moved >7.46 µm in a 12-h period was considered “mobile”. (F) Distance moved for each mobile microglia (Left) or the average distance per mouse (Right). Two-tailed paired t test indicated no difference between 0 to 12-h and 12 to 24-h periods in distance traveled per cell (t₍₁₄₎ = 0.59, P = 0.57), or per mouse (t₍₅₎ = 1.48, P = 0.20). Data are mean ± SEM.