Inducible deletion of JunB and Jun and in the epidermis of adult mice. Mice carrying floxed alleles for the Jun and/or JunB locus were used to delete one or both genes in the epidermis by inducible Cre-recombinase activity. (a) Schematic representation of the floxed Jun and JunB loci before and after tamoxifen-induced activation of the Cre-ER-fusion protein, which is under the control of the keratin 5 promoter. (b) Eight-week-old mice were injected for five consecutive days with tamoxifen to activate Cre-mediated deletion of Jun and JunB. Two weeks after the last injection ((c), (e) and (g), control mice), the double-mutant mice ((d), (f) and (h)) showed a strong skin and arthritis phenotype reminiscent of psoriasis mainly affecting the (d) ears, (f) tail and (h) paws. H&E staining of (e) control mice and (f) mutant skin mice reflects the histological hallmarks of psoriasis with abnormally thickened epidermis, parakeratosis, hyperkeratosis and fingerlike epidermal projections into the dermis.