Figure 4. Ablating cadherin expression inhibits p14-mediated syncytiogenesis.

(A) Transfected QM5 cells were surface immunostained for p14 (green), then permeabilized and immunostained for N-cadherin (red) at 4 h post-transfection. Arrows in the merged image point to regions of N-cadherin and p14 co-localization at cell–cell contacts as indicated by the yellow pixels. The differential interference microscopy (DIC) image of the same field is shown. Scale bar = 10 µm. (B) HT-1080 cells were transfected with control siRNA or siRNA directed against human N-cadherin, then co-transfected with p14 and cultured under normal (black bars) or low (white bars) calcium conditions. Cells were fixed at 9 h post p14-transfection and syncytiogenesis was quantified by syncytial indexing. Data is presented as the extent of fusion relative to control siRNA-transfected cells cultured under normal calcium conditions. Values represent the mean±S.E. (n = 4). The average number of syncytial nuclei per field under normal calcium levels (i.e. the 100% level) was 53.8. The inset shows Western blot analysis of N-cadherin (N-Cad) and actin expression in the cells transfected with control (Cont) or N-cadherin (N-Cad) siRNA. Numbers indicate the mobilities of M_r standards.