siRNA targeting human Dll1 No. 1, 5′-ACG GAU CUC GAG AAC AGC UAC UCC U-3′, Dll1 No. 2, 5′-CGG ACU CGG GCU GUU CAA CUU CAA A-3′, Dll1 No. 3, 5′-CGG GAU GGC GUG AAC GAC UUC UCC U-3′, and negative control Dll1, 5′-CCA CAA GGA UGG GAA CGU CUU AGG A-3′ were purchased from Life Technologies (Stealth RNAi). We checked knockdown efficiencies of the siRNA and selected siRNA targeting human Dll1 No. 2 (Figure S2). Stealth RNAi for Dll1 No. 2 (20 nM) or control (20 nM) were transfected into astrocytes and neurons before 2 days of co-culture with ECs and pericytes using Lipofectamine RNAiMAX (Life Technologies) according to the manufacturer's instructions. After co-culture day 5, differentiated cells were examined by qPCR and immunohistochemistry.
