Figure 7.

Inductive activities of signaling molecules produced in BA1 ectoderm. Schematic diagram illustrating effects of FGF8 signaling in BA1. According to this model, FGF8 signaling is not required to induce gene expression in the distal region. However, in the proximal region, expression of Barx1, Pax9, Lhx6, and Gsc in the mesenchyme is directly or indirectly dependent on FGF8, which is also required for Et1 expression in the ectoderm. Signaling molecules produced in the ectoderm are shown in red; transcription factors expressed in the mesenchyme are shown in black.