Extended Data Figure 7.

Both Gas6 and Pros1 drive microglial phagocytosis of ACs in vitro. a, Cultured microglia express Mer but little or no Axl under basal conditions. Microglia were cultured from WT Cx3cr1^GFP/+ mice, visualized for GFP (1st column), and immunostained for Iba1 (3rd column), Mer (2nd column, top), and Axl (2nd column, bottom). Scale bar 10 μm. b-d, In vitro pHrodo-based assay of AC phagocytosis by microglia (see Methods). b, In serum-containing medium (10% FBS), WT microglia are vigorous phagocytes; mean phagocytic activity is substantially reduced in Axl^−/−Mertk^−/− (A^−/−M^−/−) microglia. c, d, Both purified Gas6 (c) and purified Pros1 (d) stimulate AC phagocytosis by cultured microglia in serum-free medium, and this stimulation is entirely TAM-dependent. e, The phagocytic activity of cultured astroglia prepared from Cx3cr1^GFP/+ mice that were either WT or Axl^−/−Mertk^−/− was measured in the same pHrodo-based assay in serum-free medium ± Gas6. For this FACS-based assay, astrocytes were gated using an astrocyte-specific surface antigen-2 (ACSA-2) antibody (see Methods). Bar graphs represent mean phagocytic activity (± SEM); n = 2 replicates from 2 mice per genotype for b-d, and 2 replicates from 4 mice per genotype for e.