Fig. 3. Mesonephric endothelial cells migrate into Wnt4^-/- XX gonads. (A) Mesonephroi from 12.5 dpc embryos ubiquitously expressing lacZ were incubated with gonads from 12.5 dpc embryos that were Wnt4^+/+ XX and XY or Wnt4^-/- XX and stained for ß-galactosidase activity. (B) Mesonephroi from 11.5 dpc embryos ubiquitously expressing green fluorescent protein (GFP) (green) were incubated with gonads from 11.5 dpc embryos that were Wnt4^+/+ XX and XY or Wnt4^-/- XX. After incubation the sample was stained with an antibody against Pecam (red). Pecam marks endothelial cells and germ cells (red arrow indicates Pecam-stained germ cells; yellow arrow indicates Pecam-stained endothelial cells).