Anti arid1a

Brains were cut into 10‐µm‐thick cryosections. For immunofluorescence analyses, brain slices were washed three times in PBS (10 min each time). To detect BrdU incorporation, fixed brain slices were pre‐treated with 1 M HCl for 30 min at 37°C. The slices were then washed with 0.1 M borate buffer (pH 8.5) for 30 min (15 min each time) and with PBS for 30 min (10 min each time). Slices were fixed in 4% paraformaldehyde for 15 min at room temperature and washed three times in PBS (10 min each time). Next, the slices were blocked in a blocking solution (2% bovine serum albumin, 0.3% Triton X‐100 and 0.1% sodium azide) at room temperature for 2 h. The slices were then incubated with the primary antibodies (anti‐ARID1A, Sigma, HPA005456; anti‐Nestin, Aves Labs, NES; anti‐Tuj1, Biolegend, 801202; anti‐PAX6, Biolegend, 901301; anti‐BrdU, abcam, ab6326‐125; anti‐PHH3, Millipore, 09‐797; anti‐Ki67, Labvision, RM‐9106‐S1) diluted in the blocking solution at 4°C overnight and labelled using the appropriate secondary antibodies (Goat anti‐mouse 488, A11001; Goat anti‐rabbit 488, A11034; Goat anti‐rabbit 568, A11011; Goat anti‐rat 568, A11077; Goat anti‐chicken 488, A11039; Donkey anti‐goat 568, A11057) at room temperature for 2 h.

Total RNA from FACS sorted or primary microglia was reverse transcribed into cDNA using Transcript One‐Step gDNA Removal and cDNA synthesis Kit (TransGen Biotech, Beijing, China). Then, cDNA was quantified by using Hieff® qPCR SYBR® Green Master Mix (Yeasen Biotech, 11201ES08). The analysis of relative gene expression was executed by the 2^−ΔΔCT method, and actin was used as endogenous control. RT‐PCR primers are listed in Table S1 (Supplementary Information).
The total protein of primary microglia was extracted using RIPA buffer containing 10 mM PMSF (Beyotime Biotechnology, ST505), and the concentration of it was defined using BCA protein assay kit (Beyotime Biotechnology, P0012). The membranes were blocked in 5% milk in TBS‐T (0.1% Tween 20) and incubated with the primary antibodies, including Anti‐beta Tubulin (1:5000, Abcam) and anti‐Arid1a (1:2000, Sigma) at 4°C overnight. The membranes were then washed in TBS‐T for 10 min × 3 times, and then incubated with the secondary antibodies at room temperature for 2 h. ECL system (Pierce) and Tanon‐5200 Chemiluminescent Imaging System (Tanon, China, Shanghai) was used for signal detection conducting.

The brain isolated from perfused mice was post‐fixed with 4% paraformaldehyde (PFA) overnight, and dehydrated with 30% sucrose later. The tissue was used for cryo embedding, and cut into 35‐μm‐thick cryosections. For primary cells, cultured cells were seeded on coverslips and fixed with PFA. To get immunofluorescence analysis results, sagittal brain slices or coverslips were permeabilized (0.5% Triton X‐100, 3% BSA in PBS) for 15 min and blocked (0.3% Triton X‐100, 3% BSA in PBS) for 1 h at room temperature, first. Next, slices were incubated with the relevant primary antibodies (0.3% Triton X‐100, 3% BSA in PBS) overnight at 4°C, including anti‐Arid1a (1:500, Sigma), anti‐Iba1 (1:500, Wako), anti‐Tuj1 (1:1000, Biolegend), anti‐GFAP (1:500, Abcam), anti‐BrdU (1:500, Abcam), anti‐NeuN (1: 1000, Millipore) and Anti‐Doublecortin (1:500, Abcam). Alexa Fluor 488, 568, 594 or 647 secondary antibodies (1:500, Life Technologies) were used for corresponding staining, and Nuclei were counterstained with DAPI (1:1000, Sigma).