Previous work has shown that the loss of RA signalling in the rat caused by dietary deficiency of vitamin A can cause Aβ deposition (Corcoran et al., 2004) and alterations in enzymes involved in APP processing (Husson et al., 2006), and that there is a loss of RARα expression in AD human pathology samples (Corcoran et al., 2004). The gene discussed is APP; the disease is Alzheimer disease.