WNT4 and Sex Development

Although factors involved in male sexual differentiation have been well studied, the pathways regulating female sexual differentiation remain incompletely defined. To date, no genes have been identified to play a similar role in ovarian development as was shown for the <i>SRY </i>or <i>SOX9 </i>genes in testicular development. In mice, Wnt4 regulates the development of the female reproductive tract, antagonizes the production of testosterone, and is important for oocyte development. The recent demonstration of heterozygous <i>WNT4</i> defects in patients with Müllerian agenesis and signs of ovarian hyperandrogenism added <i>WNT4</i> to the growing list of genes such as <i>SRY, SOX9, WT1, DAX1,</i> and <i>SF-1</i> contributing to human sexual development. In particular, <i>WNT4</i> was the first human gene to be identified to direct development of the bipotential gonad towards ovaries. From a more clinical point of view, it seems that the absence of a uterus (and not other Müllerian abnormalities) and the androgen excess are the pathognomonic signs of WNT4 defects, suggesting that WNT4 deficiency might be a clinical entity distinct from the typical Mayer-Rokitansky-Kuster-Hauser syndrome.