An environmental risk factor-gene interactome in Alzheimer’s disease. Risk factors diminished in Alzheimer’s disease (vitamin A deficiency, NGF levels, immune competence, and glutathione depletion) are shown in blue and those increased in red. Solid lines indicate a positive, and dashed or dotted lines a negative effect of risk factor X on risk factor Y. All risk factors feed into increased beta-amyloid deposition. A selection of susceptibility genes relevant to each process is shown (see Table 2 and http://www.polygenicpathways.co.uk/alzpolys.html.