Contributes to the epidermal integrity and skin barrier function. Plays a role in the lamellar granule (LG) secretory system and in the stratum corneum (SC) epithelial cell formation. Colocalized with TGOLN2 in the trans-Golgi network. Colocalized with LAMP1 in the lysosome. Expressed in the epidermis of the skin. Expressed in epithelial cells of the outermost layer of the stratum granulosum (SG) and in hair follicles (at protein level). Defects in Tmem79 are the cause of the spontaneous matted (matt) mutant phenotype, a model for human atopic dermatitis. Atopic dermatitis (ma/ma) mice have a matted hair phenotype with progressive dermatitis-like skin inflammation and a scratching behavior. Mice display an altered skin barrier that facilitates allergic sensitization.