114 Involucrin deficiency results in decreased vitamin D receptor-mediated inflammation and Csnk1e isoform bias

Abstract

We previously identified increased involucrin (IVL) expression for human skin barrier evolution that arose out-of-Africa. This led us to re-examine the function of involucrin in both adult and newborn Ivl-/- mice. We investigated the inflammatory responses in adult mice using the MC903 (vitamin D agonist) inducible model for atopic dermatitis. Unexpectedly, Ivl-/- mice exhibited reduced ear thickness compared to WT mice (p<0.001). Underlying this decreased ear skin inflammation was a comparative decrease in thymic stromal lymphopoietin (Tslp) expression in Ivl-/- treated ears. Flow cytometry analysis to determine innate and adaptive immune cell phenotypes identified a notable decrease in CD4+ T cell infiltrate in Ivl-/- treated ears (p<0.05). We investigated a potential mechanism for the reduced MC903-induced inflammation and identified reduced vitamin D receptor (Vdr) expression in Ivl-/- versus WT skin. Thus far, we have identified a new phenotype for Ivl-/- mice with reduced Vdr-mediated inflammation and decreased adaptive CD4+ T cell response as a result of decreased Vdr. We further examined the impact of involucrin deficiency in the skin using a comprehensive multi-omics approach (ATAC-seq, RNA-seq, and LC/MS proteomics) to determine chromatin accessibility, transcriptomic, and proteomic changes in Ivl-/- and WT newborn epidermis (q<0.05). Involucrin was identified at the intersection of all three datasets thus demonstrating the validity and rigor of the approach. Five potential targets at the intersect of ATAC-seq differentially accessible regions and LC/MS differentially expressed proteins were determined. Of most interest, Csnk1e, known to regulate circadian clock, was found to have less accessible chromatin and reduced protein expression. DEXseq analysis identified a bias for Csnk1e alternative transcripts in Ivl-/- mice. Together our findings reveal a functional role for the evolutionarily selected involucrin to regulate VDR-mediated inflammation and potentially for the circadian response in the skin.