Fig. 6.

Models of intermediate mesoderm regionalization and nephron patterning. (A) Summary of data from the current study. Wnt signaling from the nephric duct prior to the initiation of PTA formation promotes dorsalization of the mesonephric mesenchyme and specification of tubules, and inhibits specification of podocytes. There may be also podocyte-promoting signals from ventral tissues such as the aorta, although this is currently not clear. (B,C) Alternative models for the contribution of the renal vesicle to the S-shaped body. In b1, the RV is a hybrid structure comprising dorsal tubule precursors and ventral podocyte precursors. In b2, the RV is a precursor structure to the tubule, and the pre-podocytes reside in the mesenchyme ventral to the RV. Regardless of which model from part B is correct, the S-shaped body (C) comprises contributions from both the ventral and the dorsal mesenchyme compartments. ao, aorta; d, nephric duct; po, podocytes; rv, renal vesicle; tu, tubule.