Expression profiles of whole skin samples from keratinocyte-specific TRAF6 deficient mice treated with and without IMQ treatment

Tumor necrosis factor receptor associated factor 6 (TRAF6) is an adaptor protein that regulates NF-κB and MAPK signaling pathway and is reported to affect immune response and cell death in immune cells. However, the roles of TRAF6 in epithelium have not been well investigated. Using a mouse model of imiquimod-induced psoriasis dermatitis, we show that TRAF6 in epithelial cells totally regulates IL-17-mediated inflammation in the skin. Mice lacking TRAF6 in keratinocytes were unable to activate dendritic cells and failed to produce IL-23 or initiate IL-17 production from γδ T cells at the imiquimod-treated sites. Subcutaneous administrations of IL-23 restored IL-17 production in the mutant animals, suggesting that the induction of IL-23 production is the major TRAF6-dependent contribution of keratinocytes to this process. Therefore, the epithelial TRAF6 signaling is supposed to play an essential role in instructing and propagating the cutaneous immune response. To broadly characterize the impact of the lack of TRAF6 in keratinocytes on the skin inflammation, we analyzed gene expression in IMQ-treated whole ears of Traf6EKO mice and Traf6f/f mice using a cDNA microarray. Total RNAs prepared from the ears of Traf6 epithelial knockout (Traf6EKO ) mice and Traf6f/f mice treated with imiquimod (IMQ) for 2 consecutive days (n = 2) were subjected to the microarray analysis. Total RNA from skin samples was immediately isolated with Trizol according to the manufacturer's protocol. An amplified sense-strand DNA product was synthesized with the Ambion WT Expression Kit (Life Technologies, Carlsbad, CA, USA), was fragmented and labelled by the WT Terminal Labelling and Controls Kit (Affymetrix, Santa Clara, CA, USA) and was hybridized to a Mouse Gene 1.0 ST Array (Affymetrix, Santa Clara, CA, USA).