A, Yap1 expression (brown) indicated by immunohistochemical staining on E18.5 murine wild-type epidermis. B, Immunofluorescence staining for Yap1 shows a dynamic localization pattern in human keratinocytes that is cell density-dependent. C, H&E staining shows an abnormally thick epidermis and hyperkeratinization in adult Tg mouse skin after 8 days of doxycyclin (Dox) induction. D-E, Immunofluorescence analysis on frozen sections of adult epidermis shows an expansion of the proliferative Ki-67 positive compartment as well as the stem cell compartment (p63-positive, K5-positive) in Tg skin after 8 days of dox induction. Dashed line marks epidermal-dermal junction. F, Rhodamine B staining of primary mouse keratinocytes isolated from 8-day Dox-treated Tg mice, and cultured for 9 days on feeders, shows a significant expansion of the epidermal stem cell compartment demonstrated by a higher colony-forming efficiency in Tg skin. G, Rhodamine B staining and colony counts show a significant increase in the self-renewal capacity of colony-forming progenitors after Dox administration measured by serial replating assays (shown is passage 2, P2). * p< 0.05, **p value < 0.01. Scale bars represent 20 µm. See also Supplementary Figure S1A–C.