Fuelled by the obesity epidemic, there is considerable interest in the developmental origins of white adipose tissue (WAT) and the stem/progenitor cells from which it arises. While increased visceral fat mass is associated with metabolic dysfunction, increased subcutaneous WAT is protective. There are 6 visceral fat depots: perirenal, gonadal, epicardial, retroperitoneal, omental and mesenteric and it is a subject of much debate whether these have common developmental origins and whether this differs from subcutaneous WAT. Here we show that all 6 visceral WAT depots receive a significant contribution from cells expressing Wt1 late in gestation. Conversely, no subcutaneous WAT or brown adipose tissue (BAT) arises from Wt1 expressing cells. Postnatally, a subset of visceral WAT continues to arise from Wt1 expressing cells, consistent with the finding that Wt1 marks a proportion of cell populations enriched in WAT progenitors. We show all visceral fat depots have a mesothelial layer like the visceral organs with which they are associated and provide several lines of evidence that Wt1 expressing mesothelium can produce adipocytes. These results: reveal a major ontogenetic difference between visceral and subcutaneous WAT; pinpoint the lateral plate mesoderm as a major source of visceral WAT; support the notion that visceral WAT progenitors are heterogeneous; and suggest that mesothelium is a source of adipocytes.

Wt1 regulates the epithelial-mesenchymal transition (EMT) in the epicardium and the reverse process (MET) in kidney mesenchyme. The mechanisms underlying these reciprocal functions are unknown. Here, we show in both embryos and cultured cells that Wt1 regulates Wnt4 expression dichotomously. In kidney cells, Wt1 recruits Cbp and p300 as coactivators; in epicardial cells it enlists Basp1 as a corepressor. Surprisingly, in both tissues, Wt1 loss reciprocally switches the chromatin architecture of the entire Ctcf-bounded Wnt4 locus, but not the flanking regions; we term this mode of action "chromatin flip-flop." Ctcf and cohesin are dispensable for Wt1-mediated chromatin flip-flop but essential for maintaining the insulating boundaries. This work demonstrates that a developmental regulator coordinates chromatin boundaries with the transcriptional competence of the flanked region. These findings also have implications for hierarchical transcriptional regulation in development and disease.