ARRB1 and Alzheimer disease: Gene co-expression modules in FB functionally related to vascular homoeostasis were significantly enriched in the DEG downregulated with AD, e.g., Module 2, which is significantly enriched in NOTCH signalling genes (e.g., NOTCH1 and NOTCH2 and regulators of NOTCH expression34, ARRB1 and DTX2; Fig. 3G, Supplementary Files 4 and 5).