Figure 4

Changes in Cldn1 expression in skin tumorigenesis. In the normal (not shown) and vehicle-treated (a, after 12 weeks) epidermis, Cldn1 is localized in the basal and suprabasal layers; however in response to the two-stage chemical carcinogenesis protocol, the number of Cldn1-positive epithelial cells was progressively reduced starting from the basal layer and moving upwards at 2 (b), 4 (c), 8 (d) and 12 (e) weeks. Although a distinctly membranous Cldn1 association was maintained in the upper layers of the treated epidermis, as the number of Cldn1-negative epidermal cells in the lower epidermal layers increased, only sporadic Cldn1 localization was evident (c-e). The epidermal basal layer is indicated by a dotted line, and the suprabasal compartment is marked with a bracket (a-c); note that the basal layer is out of view in panels d and e; the entire view is therefore the suprabasal compartment and is marked with a double-ended arrow.