Fig. 3

Rac Is Required for Neuronal Activity-Induced Oriented Movement and Bulbous Ending Formation of Resting Microglial Processes(A) Time-lapse images showing Rac activity subcellular distribution in a resting microglial cell expressing a Rac-FRET sensor before and after beginning of glutamate uncaging. Rac-FRET signal intensity is color-coded. Uncaging performed repetitively at 0, 4.5, 9, 13.5, and 18 min; FRET signals were imaged from 7 min before uncaging with interval of 1.5 min. Position of uncaging, blue dot. Area 20 μm around the uncaging point, truncated dashed circle. Scale bar represents 10 μm.(B) Summary of subcellular distribution of Rac-FRET signal density in resting microglial soma and processes with stick-like or bulbous ending. Data from nine microglial cells in nine larvae.(C and D) Glutamate uncaging-induced changes with time of Rac-FRET density ratio (C) or cell area ratio (D) between the uncaging (unc) and opposite sides (opp). Each data point obtained after uncaging was statistically compared with the mean control value averaged from the data before the uncaging (shadowed area). Number of microglial cells examined in brackets.(E) Time courses of log₁₀(p value) in (C and D). Magenta and green dashed lines indicate first time points, at which these two ratios are significantly changed, respectively. Dashed horizontal line indicates 0.05 of p value.(F) Effects of hCRIB-RasCT expression on the overall microglial morphology. Data normalized to control.(G and H) Tip_unc/tip_all (G) and Bulbous_unc/tip_unc (H) 6 min before (open), 24 min (gray), and 59 min (black) after beginning of glutamate uncaging in microglia expressing hCRIB-RasCT. p < 0.05, p < 0.01, p < 0.001. Error bars represent ± SEM.