FLG and Alzheimer disease: The DM maft mice have been routinely used for studies of skin barrier–deficient AD in recent years.13-15,17 In mice and human subjects the FLG gene resides in the epidermal differentiation complex, a cluster of more than 70 genes encoding proteins involved in skin barrier formation and differentiation of stratified epithelia,18 including those within the hair follicle.18-21 We suspected the nearby ma gene might also be involved in epithelial barrier function, and in this study we set out to separate this allele from Flgft and identify the causative defect.