Fig. 8. Summary of Bmp2 function in the AV canal. Bmp2 signals to the cushion endocardium through Bmpr1a to promote expression of genes that support EMT, such as Twist and NFATc1. Bmp2 also induces expression of Smad6, an inhibitory Smad, to limit the extent of EMT in the forming AV cushion. An additional function of Bmp2 is to induce expression of Has2, thereby accentuating cardiac jelly deposition. Finally, within the AV myocardium, Bmp2 signaling is required for Tbx2 expression, which normally represses expression of chamber-specific genes in the AV canal. Arrows denote genetic, not necessarily direct, relationships.