702 dsRNA induces ectopic KRT9 expression via WNT/β-catenin-mediated signaling

Abstract

Double stranded RNA (dsRNA;Poly (I:C)) activates innate immunity against viral infection through its receptor, toll-like receptor 3 (TLR3). Previously, we reported that dsRNA released by wounds also triggers TLR3- to enhance hair regeneration, coincident with activation of WNT/β-catenin signaling. Other groups have shown that WNT/β-catenin signaling is required for the thick epidermis of the palms and soles. Thus, we hypothesized that dsRNA, through WNT/β-catenin, could enhance volar (palmo-plantar) skin features. Using genome-wide analysis, we show that KERATIN 9 (KRT9) is the most uniquely enriched transcript in volar keratinocytes (P<0.05, N=3). KRT9 is activated by volar compared to non-volar fibroblast in vitro co-cultures (P<0.01, N=4); we also find, however, that induction of KRT9 in non-volar keratinocytes alone occurs in the absence of fibroblasts. In both cases, ectopic expression of KRT9 is either activated (P<0.01, N=3) or inhibited (P<0.02, N=3) through the WNT pathway agonist SB216763 or siRNA of β-catenin respectively demonstrating the overlapping paracrine or autocrine requirement of WNT/β-catenin. To begin testing the connection to dsRNA, we find it stimulates the expression of WNT5a and β-catenin (P<0.05, N=3) and induces nuclear localization of β-catenin(P<0.01, N=3). Coincidentally, Poly (I:C) robustly increases KRT9 expression in keratinocytes alone and in co-cultures with volar fibroblasts (P<0.05, N=5). KRT9 expression induced by Poly (I:C) was attenuated by loss of function β-catenin with either knockdown or DKK-1 treatment (P<0.05, N=3-4). Finally to demonstrate the clinical relevance of keratinocyte cell autonomous KRT9 expression apart from volar fibroblasts, we find ectopic expression of KRT9 in the human skin disease Lichen Simplex Chronicus (LSC) coincident with WNT5a expression. Collectively, ours results suggest a model where damage from friction/weight might release dsRNA and augment KRT9 in palms and soles through β-catenin signaling.