Fig. 7. The effects of ephrin-A5 on muscle precursor cells are direct and specific. Surgically isolated muscle precursor cells from somites at forelimb levels were applied to tissue culture dishes upon which alternating lanes of proteins had been applied. Twenty-four hours later, muscle precursor cells and the striped substrates were visualized and photographed. (A) EphA4 protein (arrow) is distributed in a fine manner on the surfaces of migrating dermomyotomal cells; phase contrast (top) and fluorescence (bottom) microscopy. (B) EphA4 protein is absent on a presumed non-migratory subset of muscle precursors; phase contrast (top) and fluorescence (bottom) microscopy. (C) Dermomyotomal cells on ephrin-A5/fibronectin (fn) versus fn lanes express Pax7, indicating they are muscle precursors. (D) Muscle precursors avoid substrate-bound ephrin-A5/fn (light lanes) and migrate instead on fn alone (dark lanes). (E) Addition of soluble ephrin-A5 blocks the repulsive effects of substrate-bound ephrin-A5 on muscle precursor cells. (F) Muscle precursors grow uniformly on substrates coated with Fc/fn versus fn.
