Fig. 5. Ed and Nrg protein are heterophilic binding partners, when expressed on separate populations of transfected S2 cells. Shown are representative areas of four combinations of S2 cell mixtures, which have been co-aggregated. The left sides of all panels show areas of S2 cells using Nomarski optics, with the same areas shown on the right side using epifluorescence, thereby visualizing the DiI-labeled cells. For all experiments, DiI-labeled cells and unlabeled cells were mixed at a ration of 1: 1 and subsequently aggregated on a shaking platform. (A) A mixture of DiI-labeled, Ed-expressing cells with unlabeled, Nrg-expressing S2 cells; (B) DiI-labeled, native S2 cells with unlabeled, Nrg-expressing cells; (C) DiI-labeled, Ed-expressing cells with unlabeled, Fasciclin 1-expressing cells; (D) DiI-labeled, native S2 cells with unlabeled, Fasciclin 1-expressing S2 cells. The inserts in C depict a small aggregate of S2 cells, which consists entirely of DiI-labeled and therefore Ed-expressing cells. Scale bar: 70 µm.