The epidermis is a stratified epithelium that protects the organism against environmental insults. The maintenance of the epidermis is provided by sustained proliferation and differentiation of the keratinocyte stem cells localized to the basal layer of the epidermis (Fuchs and Nowak, 2008; Blanpain and Fuchs, 2009). As keratinocyte stem cells commit to differentiate, they cease to proliferate and start to move upward to form suprabasal layers, including spinous, granular, and stratum corneum with different biochemical contents and morphologies (Fuchs and Nowak, 2008). In this differentiation process, transcription factor p63, which is the well-known master regulator of keratinocyte differentiation, regulates the expression of a plethora of proteins involved in keratinocyte differentiation and maintenance, including receptor-interacting protein kinase 4 (RIPK4), interferon regulatory factor 6 (IRF6), inhibitory kappa B kinase α (IKKα), and keratin 14 (KRT14)