CD33 and Alzheimer disease: Many of these genes have been previously implicated in AD-relevant processes such as amyloid deposition and synaptic loss including C1qa, Csf1r, Tyrobp, Cx3cr1, Cd68 and Ctsz. Importantly, DNA variations in two genes in the light yellow module, Trem2 and Cd33, have previously been associated with human AD suggesting these genes may be early drivers of AD pathogenesis.