While analysis of early onset AD firmly implicated amyloid precursor protein metabolism and Aß production in the etiology of the disease, GWASs and exome and genome sequencing have implicated with varying degrees of confidence a number of potentially biologically relevant pathways in late onset AD pathogenesis.21, 22 Of course, pathway construction is an imperfect art both because of the knowledge base used in the generation of the pathways and because proteins may have more than one function in more than one cell type. The gene discussed is APP; the disease is Alzheimer disease.