Fig. 4. Sox9 expression in embryonic testes of single and double Sf1 and Dax1 mutants. In situ hybridization for Sox9 was performed at 11.5 dpc (A-D) and at 12.5 dpc (E-H). Sox9 expression is detected in the wild-type male gonad during the bipotential stage at E11.5 (A). Sox9 expression in Sertoli cells is diminished in the Sf1 heterozygous mutant, the Dax1 null mutant and the double mutant (B-D), when compared with wild type. At 12.5 dpc, normal testis cord organization and the presence of Sertoli cells is indicated by Sox9 expression in both wild-type and Sf1^+/– gonads (E,F). Although Sertoli cells are present, testis cords are not easily identifiable in either the Dax1^-/Y gonad or the Sf1/Dax1 double mutant gonad (G,H).