NGF binds to cell surface MOG on myelin and MOG-expressing CHO cells. Purified oligodendrocyte-DRG co-cultures were established using cells from MOG^+/+ and MOG^−/− mice to examine binding of NGF to oligodendrocyte myelin internodes, and requirement of MOG for NGF binding to myelin. Internodes were stained for MBP, MOG, and NGF binding. (A) Binding of NGF to MOG^+/+ myelin internodes. (B). Absence of NGF-binding to MOG^−/− myelin internodes. Magnified images of internodes from the corresponding merged image are shown on the right. Neurotrophin binding to MOG-expressing CHO cells was also examined. CHO or MOG-CHO cells were incubated with increasing concentrations (1–100 ng/ml) of neurotrophins (NGF, NT-3, and BDNF) and analyzed for binding by immunostaining for the respective neurotrophins. (C) Strong of NGF to MOG-CHO cells at 10 ng/ml NGF. (D) Absence of NGF binding to untransfected CHO cells. (E) Intense binding of NGF at 100 ng/ml can be observed against MOG-CHO cells. (F and G) Absent or only weak binding of BDNF or NT-3 to MOG-CHO cells at 100 ng/ml. Bars, 50 µm.