Fig. 7.

Coordination of Shh and dUE signaling in patterning the cloaca and in formation of the mouse GT. Shh signals (dark-blue arrows) to adjacent cloacal mesenchyme to activate Hox gene expression and to coordinate patterning and growth of the whole cloacal field. The addition of dUE signaling (red), activated by Wnt signaling, functions as an AER-like outgrowth genetic cassette, triggering the distal growth of the mesenchymal cells and resulting in the formation of the genital primordia (red arrows). Shh might also signal to genital mesenchyme to activate noggin expression, which in turn inhibits Bmp activity and thus maintains dUE signaling (purple arrows).