Fig. 5. Location of FGF receptors. The FGF receptors 1, 3 and 4 (green) were found in many somatic cells, and, at a higher level, in germ cells (red) in both XX and XY gonads at 11.5 dpc. FGFR1 (A,B) and FGFR4 (E,F) were concentrated at the cell surface, while FGFR3 (C,D) was found within the cell. FGFR2 (G,H) was detected in somatic cells at and near the coelomic epithelium in both XY and XX gonads (arrows). FGFR2 was also detected in the nuclei of scattered cells within the XY gonad (G, arrowheads). Nuclear FGFR2 was not observed in XX gonads (H). The number of cells with nuclear FGFR2 increased in the interior of the XY gonad between 11.0 and 11.6 dpc (arrows in I-K). Scale bar: 50 µm.