Fig. 2. Proliferation is reduced in early Fgf9^-/- XY gonads. (A-C) Proliferating cells (red) were concentrated at and near the surface of the XY gonads, examples indicated by arrows. At 11.2 dpc, most somatic cell proliferation was observed in cells expressing SF1 (green). By 11.5 dpc, the wild-type XY gonad underwent an increase in the amount of proliferation observed at and beneath the surface of the gonad. (D-F) Fewer proliferating cells were observed in Fgf9^-/-XY gonads at all stages examined. (G-I) In wild-type XX gonads, most proliferation was observed in SF1-expressing cells at and near the surface of the gonad. No increase in proliferation is observed at these stages. (J-L) Proliferation in Fgf9^-/- XX gonads was not noticeably different from XX gonads. Scale bar: 25 µm.