Fig. 2.

SDF-1 is neither an attractant nor a repellent on its own but reduces repellent activities in a collagen gel assay. E7 DRG explants were embedded in a collagen–matrigel matrix near cell clumps subjected to a mock transfection procedure (A), transfected with SDF-1 (B), transfected with sema3A (C), transfected with sema3A, and bathed in medium containing 100 ng/ml SDF-1 (D). SDF-1 had no repellent or attractant effects of its own but reduced the repellent effect of sema3A. DRGs were placed next to clumps composed of a mixture of sema3A and mock-transfected cells (E), or sema3A and SDF-1 transfected cells (F). Mixing SDF-1-transfected cells with sema3A-transfected cells blocked the repellent effects of sema3A.