The number of apoptotic cells was not increased in Wt1-inactivated gonads. TUNEL assay was conducted in gonads of Wt1 mutant (A, C: Wt1+/R394W; B, D: Wt1R394W/R394W) and Wt1 knockout (E, G: Wt1flox/flox or Wt1-/flox; F, H: Wt1-/flox; Cre-ERTM) mice. Arrows and arrowheads point to apoptotic cells (green) in gonads and mesonephros, respectively. The nuclei were stained in blue using DAPI. The dotted line denotes the border between the gonads and mesonephros. The gender of the embryos was confirmed with PCR using Sry primers.