Fig. 4. Merlin(-) meningioma cells demonstrate defects in cell-cell contact and altered α- and β-catenin expression.

(A) Confocal images of phalloidin-stained matched arachnoidal AC006 and merlin(-) meningioma MN302(-) cells. AC006 p27 cells form contacts with adjacent cells at their cell peripheries, unlike MN302(-) p5 cells, which do not adequately recognize cell-cell boundaries, resulting in the overlap of neighboring cells. Bar, 20 μm. (B) Arachnoidal cells (AC006 p5) exhibited distinct, punctate β-catenin staining at sites of cell-cell contact while matched MN302(-) p6 meningioma cells demonstrated a reduced or disrupted β-catenin expression pattern at adherens junction sites, and diffuse, non-specific staining throughout the cytoplasm. Cells were plated in complete media on laminin/poly-D-lysine-coated coverslips, and fixed and stained for β-catenin immunocytochemically. Bar, 20 μm. Inset panels are 2X. (C) Matched arachnoidal and merlin(-) meningioma cells were harvested for total cell lysates and examined for expression of adherens junctions proteins by immunoblotting with α- and β-catenin antibodies. The data suggested that the α-catenin protein levels were reduced in merlin(-) meningioma cells compared to arachnoidal cells, whereas the beta-catenin expression levels were not significantly diminished. Merlin was detected using the C26 rabbit polyclonal antibody that often detects a higher cross-reactive molecular weight band. GAPDH expression was used as a loading control.