TREM2 and Alzheimer disease: These changes in gene expression have been well studied by single cell RNA sequencing and find heterogenous subsets of microglia in AD, demarcated by the expression of genes such as Trem2 and Tyrobp that conventionally differentiate between disease- vs. non-disease-associated microglia, which in AD roughly correspond to plaque- and non-plaque-associated microglia (PAM and NPAM) respectively [30].