Figure 7. GRHL3 is required for the non-adhesive function of periderm.

(A) Immunofluorescence staining of desmoglein-1 (green) and E-cadherin (Red) in E14.5 forelimb cross-sections from WT and Grhl3^−/− embryos. Arrows indicate surface periderm cells and point to the expression of Dsg1 (Green) and E-cad (Red) on the apical side of periderm cells in Grhl3^−/− embryos. Magenta and Blue indicate nuclear staining. (B) Whole-mount staining of adhesion complex proteins desmoglein-1 (green) and E-cadherin (gray) at the dorsal epidermis of E14.5 forelimb in WT and Grhl3^−/− embryos. Arrows point to the surface cells in the Ortho-slice. (C) Whole-mount staining of the tight junction protein, Zonula occludens-1 (ZO-1; magenta) at the dorsal epidermis of E14.5 forelimb in WT and Grhl3^−/− embryos. (D) Schematic representation of the experimental design and RNA isolation preformed for RNA-seq analysis (N=3/genotype). (E) Chart showing the number of significantly upregulated and down-regulated genes in Grhl3^−/− compared to WT embryos. (F) Gene Ontology of the differentially expressed genes in Grhl3^−/− forepaws at E14.5. Red asterisks indicate GO categories associated with abnormal epithelial morphology. (G) Schematic model depicting GRHL3-transcriptional regulation during periderm development. During embryonic development of the epidermis, GRHL3 in periderm cells directly or/and indirectly regulates the expression of genes that are required to restrict the expression of adhesion molecules from the apical surface, promoting the anti-adhesive function of the periderm. In the absence of GRHL3, periderm cells development is impaired, with abnormal expression of adhesion molecules on the apical surface, resulting in abnormal adhesion of periderm cells.