Fig. 4. Preference of RGC axons for NrCAM. RGC axons extending from E6 retinal explant strips on alternating substrate lanes coated with Laminin (dark lanes) and Laminin plus the indicated protein, which is stained by the respective antibody (green lanes).(A) Axons showed a preference for NrCAM in 77% of the NrCAM lanes, i.e. they did not cross the borders to the Laminin lanes (3307 borders evaluated; n=56 independent experiments). (B) By contrast, axons did not cross the substrate borders in only 7% of immunoglobulin-containing lanes; most exhibited random growth (1341 borders; n=20).(C) Substrate pre-incubation with NrCAM F(ab) fragments decreases axonal preference for NrCAM lanes to 15% of the lanes, and axon extension is almost completely random (2143 borders; n=38). (D) By contrast, pre-incubation with non-specific F(ab) fragments results in an only slightly reduced axonal preference for NrCAM; 62% of the lanes show axon preference (1351 borders; n=27). IgG, immunoglobulin; LN, Laminin. Scale bar: 200 µm.