COL4A1 and COL4A1/A2-related disorder: We introduced a heterozygous COL4A1 G755R mutation, which causes Gould syndrome,48 into a human microvascular brain endothelial cell line (HBEC) via CRISPR (Supplemental Fig. S7a–c) to measure basal Ca2+ levels and in response to acetylcholine.