During AD progression, microglia gradually switched from a homeostatic state to DAM, as evidenced by specific markers (e.g., Csf1, Itgax, Cd63, Ank, Axl, Igf1, Clec7a, Tyrobp, Ctsb, Ctsd, Ctsl, Cd9, Ctsz, Ccl6, Trem2, Spp1, Lpl, Cst7, Apoe). Here, CTSD is linked to Alzheimer disease.