Fig. 2. A model of cell-cell adhesion during aggregation. (A) During early aggregation, cells express DdCAD-1 (red), which is enriched on F-actin-containing filopodia. (F-actin is shown in green.) Cells initially contact make through these filopodia. (B) As cells form and enter the streams, csA (blue) is expressed at the points of contact. DdCAD-1 is relocated to cell surfaces facing away from the streams.