Fig. 4.

GT1-7 cells recognize SynCAM1 as an adhesive partner. A, Many SynCAM1-Fc-coated polystyrene beads (green circles) adhere to GT1-7 cells, stained with phalloidin (red). B, Few, if any, ΔECD-Fc-coated beads (green circle) adhered to GT1-7 cells. C, Quantification of the data illustrated in A and B. Numbers above bars are number of coverslips per group (20–35 fields per coverslip). ***, P < 0.01 vs. ΔECD-Fc group. Numbers in parentheses on top of bars represent the number of coverslips analyzed for each group, and vertical lines are sem. D, Low-magnification SEM image of SynCAM1-Fc-coated beads adhering to GT1-7 neurons. The arrow depicts the two beads shown at higher magnification in G. E, Secondary electron image of an individual neuron contacting a SynCAM1-Fc bead via fine processes, including a process bearing a growth cone. F, Higher magnification of the contact shown in E demonstrating that the neuronal processes generate a biofilm (arrows) that spreads over the region of the microsphere surrounding the adhesion point. Wavy distortion on the upper right is due to charging (electrostatic field). G, Higher-magnification image of the two SynCAM1-Fc beads from D. H, Secondary electron image of a ΔECD-Fc bead adhered to the poly-l-lysine coating, near GT1-7 neurons, but not adhering to them. I and J, Overlaid projection of confocal images showing that the neuronal processes trapping SynCAM1-Fc-coated beads (red) are rich in SynCAM1 (green). Arrows point to sites of close contact between neuronal processes and the microspheres. Cell nuclei stained with Hoechst are seen in blue. Bars (A and B), 20 μm; (D), 60 μm; (E), 4 μm; (F), 1 μm; (G), 2 μm; (H), 15 μm; (I and J), 10 μm.