XBP1 and diabetes mellitus: To further confirm the role of endogenous XBP1 on RPE tight junctions, we examined the tight junctions by immunofluorescent labeling of ZO-1 (Fig. 6A) or using fluor-conjugated phalloidin (Fig. 6B) on RPE whole mounts from XBP1RPE−/− and control mice with or without diabetes.