The cerebrovasculature and parenchyma from mouse brain tissue was isolated using a modified protocol (Triguero et al. 1990 (link)). As above, fresh mouse brains were collected (minus the cerebellum) and the outer vessels and meninges were removed using a dry cotton swab (Coisne et al. 2005 (link)). The mouse brains were pooled and minced with a blade prior to being ground with 6–8 passes of a Teflon pestle in a glass Dounce homogenizer (Erickson et al. 2012 (link)). Brain material was homogenized in fivefold excess of ice-cold HBSS containing 10 mM HEPES (Coisne et al. 2005 (link)). A sample of the brain homogenate was collected as a representation of the whole brain (Mitchell et al. 2011 (link)). An equal volume of 40% dextran solution was added to the brain homogenate for a final concentration of 20% dextran (Erickson et al. 2012 (link)) and immediately centrifuged at 6000g for 15 min at 4°C (Fryer et al. 2003 (link)). This procedure results in a pellet at the bottom of the container (cerebrovasculature) and a compact mass at the top of the solution (parenchyma) separated by a clear dextran interface (soluble fraction). The cerebrovascular pellet was washed with ice-cold HBSS and resuspended in lysis buffer. The parenchyma was collected in HBSS, centrifuged at 6000g for 10 min at 4°C, and the resulting pellet resuspended in lysis buffer. Finally, the dextran supernatant was added to an equal volume of HBSS, and centrifuged at 6000g for 5 min at 4°C to pellet any remaining cellular material. The supernatant was collected and all samples were stored at −80°C until analysis.