Figure 1.

Generation and characterization of the skin-specific K14-CreERTM/GFPmmIL33 mouse overexpressing mature IL-33. (A) Schematic illustration of the generation of skin-specific mouse mature (mm) IL-33 expression constructs. Mouse-containing transgene DNA with loxP-flanked GFP and STOP codon which prevents transcription of the mature form of mouse IL-33 cDNA was crossed with tamoxifen (TM) inducible K14-CreERTM mouse. (B) The genotyping was performed using flow cytometric analysis of blood for GFP expression. MFI, mean fluorescence intensity. (C) Topical administration every day with 20 mg tamoxifen in a total volume of 200 µl (“induced”) results in Cre-mediated recombination with the deletion of the loxP-flanked GFP and STOP codon and strong induction of IL-33 expression under the K14 promoter in keratinocytes. (D) Cutaneous manifestations of induced K14-CreERTM/GFPmmIL33 (iIL-33) mice compared to control induced K14-CreERTM/WT (iWT). (E) Reduction of weight of iIL-33 mice compared to iWT after the administration of tamoxifen. (F) Expression of the mmIL-33 gene in iIL-33 mice relative to iWT mice and fold skin expression of the mmIL-33 gene in iIL-33 mice (Tg/WT; transgene compared to wild-type). Total RNA from skin of mice was used as template for quantitative real-time PCR. On day 15, after the tamoxifen administration, (G) the skin was analyzed for epidermal, dermal thickness (μm), and collected for H&E (4× magnification) and (H) toluidine blue staining (10× magnification). Toluidine blue-positive mast cells were increased in the lesional skin of iTg compared to iWT after the administration of tamoxifen and results shown of n = 9 (WT) and n = 12 (Tg). *p < 0.05, **p < 0.01, ***p < 0.0001 (Mann-Whitney).