Time course of female-to-male sex reversal in 38,XX fetal and postnatal pigs.

In an attempt to understand the etiology of intersexuality in pigs, we thoroughly analyzed the gonads of 38,XX (SRY negative) female to male sex-reversed animals at different developmental stages: during fetal life [50 and 70 days postcoitum (dpc)], just after birth [35 days postpartum (dpp)] and during adulthood. For each animal studied, we performed parallel histological and ultrastructural analyses on one gonad and RT-PCR analysis on the other gonad in order to define the expression profiles of sexually regulated genes: SOX9, 3beta-HSD, P450 aromatase, AMH, FOXL2, and Wnt4. Light and electron microscopic examination showed that testicular cords differentiated in XX sex-reversed gonads but were hypoplastic. Although the testicular cords contained gonia at the fetal stages, the germ cells had all died through apoptosis within a few weeks after birth. Ultrastructurally normal Leydig cells also differentiated, but later, and enclosed whorl-like residual bodies. At the fetal stages, three of the six genes studied in the intersex gonads presented, as early as 50 dpc, a modified expression profile corresponding to an elevated expression of SOX9 and the beginning of AMH and P450 aromatase gene transcription. In addition to genes involved in the testicular pathway, the same gonads expressed FOXL2, an ovarian-specific factor. The ovaries of true hermaphrodites were ineffective in ensuring correct folliculogenesis and presented abnormal expression profiles of ovarian specific genes after birth. These results indicate that the genes involved in this pathology act very early during gonadogenesis and affect the ovary-differentiating pathway with variable expressivity from ovarian germ cell depletion through to trans-differentiation into testicular structures.