Fig. 8. XGrhl1, with XAP-2, modulates BMP4-dependent epidermal structural gene expression. BMP4-dependent phosphorylation of XMad1 induces IER gene expression directly (unbroken arrow). After an unknown number of intermediary steps (broken arrow), these factors activate Dlx3, Dlx5, AP-2 and XGrhl1 gene expression. Blue arrows indicate newly identified tissue-specific components of the BMP4-signaling cascade. XGRHL1 and AP-2, cooperatively, activate structural gene expression directly (blue and green unbroken arrows). The molecular mechanism(s) by which Dlx3/Dlx5 facilitates gene activation in this context are currently unclear (broken arrow). XGrhl1 also stimulates AP-2 and Dlx3/Dlx5 gene expression (broken red arrows). For simplicity, all BMP4-mediated events are not shown.