A genome-wide association study points out the causal implication of SOX9 in the sex-reversal phenotype in XX pigs.

Among farm animals, pigs are known to show XX sex-reversal. In such cases the individuals are genetically female but exhibit a hermaphroditism, or a male phenotype. While the frequency of this congenital disease is quite low (less than 1%), the economic losses are significant for pig breeders.