Fig. 2. SDF1 alters PGC behavior in an organ culture assay. (A) A slice taken from an E9.5 +/Oct4PE:GFP⁺ embryo after 20 hours in culture. PGCs (green) have formed clusters at the genital ridges. A few cells (arrowhead) remain in the hindgut. (B) An E9.5 slice incubated for 20 hours in the presence of 1.6 µg/ml SDF1. Some PGCs have colonized the genital ridges, but many cells remain scattered across the midline. (C) Summary of migration data from four culture experiments. Slices were incubated in the presence of a range of SDF1 concentrations (5 ng/ml to 1 µg/ml). PGC migration was affected at all concentrations (data not shown). Beads coated with 50 µg/ml SDF1 caused a similar effect to treatment with soluble SDF1. (D) An example of a control slice that was scored as dead. The majority of cells remain trapped in the hindgut. (E) Example of a control slice scored as confused. The circled cells have failed to clear the midline. (F) Example of a control slice scored as normal. The midline of the body wall is clear and only a few PGCs (arrowheads) remain in the hindgut. Scale bars: in A, 46 µm for A,B; in D, 68 µm for D-F.