library_construction_protocol: Mice were transcardially perfused with a buffered saline solution containing heparin and actinomycin D. Meningeal dural whole mounts were immediately dissected from the skulls of 12-month-old male and female mice expressing APOE3 or APOE4 and digested into a single-cell suspension. Cells were enriched for CD45+, LYVE-1+, and/or CD31+ cells via positive selection using MACS. 5000 cells per sample were used with the 10x Genomics Chromium Next GEM Single Cell 3ʹ Kit