Fig. 3. Co-culture experiments suggest that meiotic germ cells inhibit the testis pathway via short-range effects. An 11.5 or 14.5 dpc XX GFP gonad (green) was cultured on top of an 11.5 dpc XY gonad for 48 hours. In situ hybridization for Sox9 (dark purple) or immunocytochemical staining for laminin (blue) and germ cells and vasculature (red), reveal no interference with the testis pathway. Red and blue broken lines outline the XX and XY components, respectively. Broken white lines outline the mesonephros. Arrows indicate testis cord boundaries.