Bipolar undifferentiated CG-4 oligodendroglial line cells adhere, extend processes and disperse on midkine, a heparin-binding growth factor: Orthovanadate and chondroitin sulphate E inhibit cell attachment

Midkine, a secreted basic 13kDa, heparin-binding growth factor, is expresse d in the central nervous system during middle embryogenesis. We show that u ndifferentiated CG-4 oligodendroglial line cells, a model for migratory oli godendrocyte-Type 2-astrocyte (0-2A) progenitor cells, adhere and disperse fully on midkine substrata formed-from coating solutions of 5 and 10 mug/ml as occurs with poly-L-lysine. By 24 hours CG-4 line cells on midkine subst rata of 1 mug/ml and below had mostly aggregated into loosely adherent cell clumps. Highest concentrations of midkine promoted process extension. Chon droitin sulphate E, but not chondroitin sulphates A, B, C or D at 10 mug/ml , blocked CG-4 line cell adherance to midkine as did sodium orthovanadate. Such results implicate a chondroitin sulphate proteoglycan, perhaps a prote in tyrosine phosphatase, in CG-4 line cell adherance to midkine. We confirm that CG-4 oligodendroglial line cells express protein tyrosine phosphatase -zeta, identified by others as a receptor for midkine.