Stem-cell-based models have been employed to analyze the specific effects of AD-associated genetic mutations and also the genetic risk factors, such as SORL1 (sortilin-related receptor 1), TREM2 (triggering receptor expressed on myeloid cells 2) and APOE4 (apolipoprotein E4) [119,144,148,151,153,159]. The gene discussed is TREM2; the disease is Alzheimer disease.