Emerging evidence suggests that the gut microbiome and intestinal barrier integrity are altered in AD.36,45,139 Studies have demonstrated decreased gut tight junction protein integrity measured by decreased levels of occludin, ZO-1, and claudin1 mRNA and protein expression in humans and mouse models of AD.36,140 These observations led us to explore this as a potential mechanism contributing to disease progression. The gene discussed is OCLN; the disease is Alzheimer disease.