Fig. 1. Differential expression of p120ctn isoforms in epidermal keratinocytes and melanocytes. Horizontal bars along the schematic structure of p120ctn (A) show the domains recognized by MAb 6H11 and MAb pp120. Cryosections of adult human epidermis (B,C) showed prominent immunofluorescence with MAb pp120 at the cell-cell adhesion junctions (C). Melanocytes residing within the basal cell layer, and their dendrites extending up to the upper spinous layer, were positive for MAb 6H11 (B, arrow). The prominent staining of the cornified layer with MAb 6H11 was considered non-specific and was not characterized further. Keratinocytes in primary cultures, when grown in KGM containing 60 µM Ca²⁺ were negative for MAb 6H11 signal (D), whereas MAb pp120 stained intracellular structures and gave a weak signal at the cell-cell adhesion junctions (E). Keratinocyte cultures grown in the presence of 1 mM Ca²⁺ (F-I) were also negative for MAb 6H11 (F), whereas pp120 brightly stained keratinocyte cell-cell adhesion junctions (G). Melanocytes (arrows in E and G) were difficult to distinguish with MAb pp120 owing to the intense staining of keratinocytes. Bright staining of melanocytes with MAb 6H11 (D,F) revealed that 1A is the major p120ctn isoform in melanocytes. Phase contrast images (H,I) of panels (F) and (G) demonstrate the pigmented melanocytes against the keratinocyte background.