Figure 5.

PS is involved in the microglial membrane extension along targeted spines to proceed phagocytosis in adult-born neurons in the OB. (A) Experimental scheme. In vivo two-photon imaging of dendritic spines of tdTomato⁺ granule cells and EGFP⁺ microglia in the adult Dcx-CreER^T2; R26-EPT; R26-tdTomato; Iba1-EGFP (EPT; Iba1-EGFP) and Dcx-CreER^T2; R26-D89E; R26-tdTomato; Iba1-EGFP (D89E; Iba1-EGFP) mice was performed at 28–42 dpi. (B) Classification of microglia–spine interaction in two-photon imaging. (C–F) Representative two-photon images of dendrites of tdTomato⁺ granule cells (red) and EGFP⁺ microglial processes (green) in the adult OB of EPT (C–E, also see Fig. S5, A and B; and Video 4; n = 3 mice) or D89E (F, also see Video 5; n = 5 mice); Iba1-EGFP mice. Dotted line boxes in C and D are magnified and shown in orthogonal view (C¹ and D¹), respectively. Dotted line boxes (F, 15 and 21 min) are magnified and shown in orthogonal view (F¹ and F²), respectively. (G) Frequency of microglial touching to, wrapping of, and phagocytosis of tdTomato⁺ spines in EPT or D89E; Iba1-EGFP mice (n = 3 or 5 mice pooled from three or five independent experiments, respectively; wrapping, t₍₆₎ = 2.5, P = 0.047, unpaired t test; Phagocytosis, P = 0.032, Welch’s t test). EPL, external plexiform layer. Dashed and solid arrows indicate microglial touching to and wrapping of spines, respectively (B–F). Arrowheads indicate phagocytosed spines observed in the microglial processes (B and E). Numbers (C–F) indicate minutes after the first imaging frame. Scale bars, 2 µm. *, P < 0.05. Data shown are mean ± SEM.