Indeed, single cell transcriptome from postmortem AD brains suggests that a group of genes, including PICALM, APOE, TREM2, MEF2C and the MHC class II genes HLA-DRB1 and HLA-DRB5 are upregulated in microglial cells in correlation with AD pathology [126]. The gene discussed is TREM2; the disease is Alzheimer disease.