Fig. 2.

Sex reversal caused by stage-specific conditional inactivation of Fgfr2 by Hs-Cre. (A and B) Hs-Cre efficiency in gonads was accessed in Z/EG reporter mice. Confocal scanning microscopy shows that EGFP reporter (red) is expressed in most cells throughout the gonad and mesonephros after heat shock, but expression is absent in Z/EG gonads in the absence of Hs-Cre, indicating time-specific global recombination in the genital ridge. PECAM (green) is a marker for germ cells and endothelial cells. (C) Stereomicroscopy image of control (left) and Hs-Cre/+;Fgfr2^flox/flox (right) embryos 48 h after heat-shock treatment. Body shape and size is grossly normal after the treatment. However, inactivation of Fgfr2 results in defective growth in limbs and gonads. Asterisks indicate mutant limbs in heat-shock-treated animals. g, gonad, outlined. (D–F) Immunohistohemistry and confocal scanning microscopy of gonads from the heat-shock-treated embryos. Immunostaining with laminin (red) and PECAM (green) reveals that Hs-Cre/+;Fgfr2^flox/flox XY gonads lack testis cords (tc), which normally form by this stage in littermate controls (arrowheads in E). Brackets highlight relative size of control and mutant XY gonads. mt, mesonephric tubules. (G–J) Control and mutant gonads immunostained for SOX9 at 11.5 dpc (G and H) or 12.5 dpc (I and J). SOX9 (red) is present in the mutant gonads at 11.5 dpc, albeit in fewer cells. By 12.5 dpc, SOX9 expression is almost absent in the mutant XY gonads.