When kept in hypotonic medium, psoriasis mutants carrying the krt4:atp1b1a-gfp transgene displayed a partial restoration of epidermal cell polarity both in the periderm and in the basal layer (cytokeratin and Lgl2 localization; Figure 8—figure supplement 1e,I,m and f,j,n) and a partial, but significant amelioration of basal cell malignancy (Figure 8—figure supplement 1a–c), including reduction in the expression of the malignancy markers pAKT and mmp9 (Figure 8f–h; Figure 8—figure supplement 1g,k,o). Here, MMP9 is linked to psoriasis.