Deletion of Wt1 during early gonadogenesis leads to differences of sex development in male and female adult mice

Author summaryThe WT1 transcription factor (WT1) is a protein expressed during gonad development. WT1 mutations have been reported in several human conditions in which patients present a variable range of genital malformations varying from ambiguous external genitalia to gonadal dysgenesis. Mouse models in which Wt1 has been deleted indicate that WT1 has a critical role in early gonadogenesis. However, assessing the role of this protein in early gonad formation and its impact on adult sex development has been difficult due to the complete gonadal agenesis or embryonic lethality observed in these mouse models. Here, we describe a new genetically engineered mouse model in which Wt1 expression is deleted from an early stage in gonad formation. The analyses of these mice revealed the importance of Wt1 for early gonad differentiation and the impact of its early deletion on the formation of the adult reproductive system. Adult mutant mice lacked mature gonads, with both XX and XY mutants displaying genital tracts containing both male and female structures as well as ambiguous external genitalia. Notably, mutant gonads remained in an undifferentiated stage, indicating that WT1 is important for the differentiation of different populations of progenitor cells. Assessing the role of the WT1 transcription factor (WT1) during early gonad differentiation and its impact on adult sex development has been difficult due to the complete gonadal agenesis and embryonic lethality exhibited by Wt1KO mouse models. Here, we generated Wt1(LoxP/GFP);Wt1(Cre) mice, the first Wt1KO mouse model that reaches adulthood with a dramatically reduced Wt1 expression during early gonadogenesis. Wt1(LoxP/GFP);Wt1(Cre) mice lacked mature gonads and displayed genital tracts containing both male and female genital structures and ambiguous genitalia. We found that WT1 is necessary for the activation of both male and female sex-determining pathways, as embryonic mutant gonads failed to upregulate the expression of the genes specific for each genetic programme. The gonads of Wt1(LoxP/GFP);Wt1(Cre) mice showed a lack of production of Sertoli and pre-granulosa cells and a reduced number of germ cells. NR5A1 and the steroidogenic genes expression was modulated differently in XY and XX Wt1(LoxP/GFP);Wt1(Cre) gonads, explaining the mutant phenotypes. Further studies of the XX Wt1(LoxP/GFP);Wt1(Cre) gonads revealed that deletion of WT1 at an early stage impaired the differentiation of several cell types including somatic cells and the ovarian epithelium. Through the characterisation of this Wt1KO mouse model, we show that the deletion of Wt1 during early gonadogenesis produces dramatic defects in adult sex development.

Automated summary

The study describes a new genetically engineered mouse model in which Wt1 expression is deleted from an early stage in gonad formation. The findings show the importance of Wt1 for early gonad differentiation and its impact on the formation of the adult reproductive system.