Opposing function of SOX and RSPO1 signaling in the fate of the gonad.

<p>A- In XX gonads, RSPO1 activates WNT/beta-catenin signaling to promote ovarian differentiation. Ablation of <i>Rspo1</i> results in partial sex reversal with ovotestis development, which coincides with <i>Sox9</i> expression. However additional deletion of <i>Sox9</i> in the XX <i>Rspo1</i>^KO (i.e., <i>Rspo1^KOSox9^cKO</i>) still allows ovotestis formation, implying that <i>Sry</i> and <i>Sox9</i> are not required for testicular differentiation in female-to-male sex reversal. B- In XY gonads, whereas <i>Sox9</i> deletion triggers ovarian development, additional deletion of <i>Rspo1</i> in XY <i>Rspo1^KOSox9^cKO</i> gonads restores testis development. This is associated with the expression of other SOX genes like SOX 8 and SOX10, other masculinising factors.