Recently, genome-wide association studies have identified variants of the myeloid cell genes triggering receptor expressed on myeloid cell 2 (TREM2) (Jonsson et al., 2013), complement receptor 1 (Lambert et al., 2009), and CD33 (Hollingworth et al., 2011) as novel AD risk genes, sparking renewed interest in microglia from the aspect of genetics (Hashioka et al., 2020). This evidence concerns the gene TREM2 and Alzheimer disease.