CD177 and Alzheimer disease: These two AD risk genes encode similar proteins that associate with lipoproteins in the brain (Koch et al., 2001; Elliott et al., 2010) to interact with a shared family of cell surface receptors (Kounnas et al., 1995; Leeb et al., 2014) that promote neurite outgrowth (Nathan et al., 1994; Kang et al., 2005), cholesterol metabolism (for review, see Holtzman et al., 2012), and clearance of the AD pathological hallmark, amyloid-β (Demattos et al., 2004).