ΔNp63 Is Essential for Epidermal Commitment of Embryonic Stem Cells

Abstract

In vivo studies have demonstrated that p63 plays complex and pivotal roles in pluristratified squamous epithelial development, but its precise function and the nature of the isoform involved remain controversial. Here, we investigate the role of p63 in epithelial differentiation, using an in vitro ES cell model that mimics the early embryonic steps of epidermal development. We show that the ΔNp63 isoform is activated soon after treatment with BMP-4, a morphogen required to commit differentiating ES cells from a neuroectodermal to an ectodermal cell fate. ΔNp63 gene expression remains high during epithelial development. P63 loss of function drastically prevents ectodermal cells to commit to the K5/K14-positive stratified epithelial pathway while gain of function experiments show that ΔNp63 allows this commitment. Interestingly, other epithelial cell fates are not affected, allowing the production of K5/K18-positive epithelial cells. Therefore, our results demonstrate that ΔNp63 may be dispensable for some epithelial differentiation, but is necessary for the commitment of ES cells into K5/K14-positive squamous stratified epithelial cells.

Notch signaling represses p63 expression in the developing surface ectoderm

“…Our data suggest that epidermal keratinocyte specification requires active BMP4 signaling and inhibition of Notch signaling. This observation is consistent with previous studies showing that p63 induction of epidermal keratinocyte fate in mouse ESCs requires BMP4 signaling (Medawar et al, 2008). Additionally, BMP signaling can induce ectodermal fate in hESCs Harvey et al, 2010) and in surface ectoderm progenitors of Xenopus embryos (Wilson and Hemmati-Brivanlou, 1995).…”

“…S11C). These data suggest that P63 expression is induced by inhibition of Notch signaling and active BMP4 signaling, which is consistent with the upregulation of P63 mRNA after BMP4 addition (Medawar et al, 2008) and the inability of p63 overexpression to induce keratinocyte formation in the absence of BMP4 addition in mouse ESCs (Medawar et al, 2008).…”

“…Taken together these results suggest that this differentiation protocol generates primarily ectodermal cells, including epidermal keratinocyte progenitor cells. p63 is expressed before K14 during ectoderm development To further characterize keratinocyte formation during hESC differentiation, we analyzed the expression of P63, which is expressed in stratified epithelial cells of the thymus and skin (Koster and Roop, 2007;Senoo et al, 2007) and during ectoderm specification in mouse ESCs (Medawar et al, 2008). A small percentage of P63 + cells were present at the end of the differentiation protocol ( Fig.…”

p63 is a suppressor of tumorigenesis and metastasis interacting with mutant p53

“…This has also been shown using an embryonic stem cell model in vitro. 109 A contribution by TAp63 remains possible, as the message is indeed expressed during various stages of development as well as in adulthood, and TAp63 À/À mice have a detectable epithelial phenotype with blisters and epidermal ulcers. 37 Moreover, in a different animal model, TAp63 contributes to the maintenance of dermal and epidermal precursors, genomic stability, and organismal longevity; 28,37 mice age prematurely and develop blisters, skin ulcerations, senescence of hair follicle-associated dermal and epidermal cells, and decreased hair morphogenesis.…”

Diverse p63 and p73 isoforms regulate Δ133p53 expression through modulation of the internal TP53 promoter activity

“…29,30 Therefore, to gain further insight into the regulation of D133p53 expression during keratinocyte differentiation, we used induced pluripotent stem cell (iPSC) lines derived from EEC patients and control individuals. Skin fibroblasts from two patients carrying R304W or R204W single mutation in the p63 DNA-binding domain were reprogrammed into iPSCs (Petit et al, manuscript in preparation).…”