Ex vivo cultures combined with vivo-morpholino induced gene knockdown provide a system to assess the role of WT1 and GATA4 during gonad differentiation
During testis development, WT1 is required for activating various testis promoting genes, i.e. Amh, Amhr2, Nr5a1(Sf1), Star, Sox9, Gli1, Gli2, Smo, Dhh and Ptch1. GATA4 represses ovarian promoting transcripts such as Ctnnb1, Bmp2, and Fst, in the testis, and thereby may be essential for the maintenance of the testis phenotype. GATA4 is also involved in repressing Dhh and Ptch1 transcript levels in embryonic testis, which may contribute to the fine-tuning of their threshold levels. Given such a pivotal role of GATA4, it is likely that sufficient GATA4 levels are ensured by a back-up mechanism provided by the GATA4 E1b isoform in the testis. During ovary development, i.e. in the absence of SRY, WNT4 and RSPO-1 levels are stabilized and promote canonical Wnt signaling. In the ovary, WT1 is required for Dax1 expression. GATA4 acts as a repressor of Ctnnb1 and serves as an activator for the transcripts Gli2, Gli3, and Smo, the latter of which may be regulated synergistically by both WT1 and GATA4. WT1 and GATA4 may also synergize on Foxl2 transcription, which contributes to an ovarian specific signature. Suggested stimulatory (→) and inhibitory (⊥) pathways identified herein are marked in red color.