HBB and Alzheimer disease: 1. 9 cell subsets (including smooth muscle cells, fibroblasts, endothelial cells) and 2000 highly variable genes (e.g., IGKC, JCHAIN, HBB, IGHG1) were identified from the dataset; smooth muscle cells are the core pathological cells in AD.2. Pseudo-time trajectory analysis revealed the differentiation direction of cell subsets during AD progression.