Development of the AVC and AVN Development of the AVC and AVN. Schematic depicting the molecular pathways regulating the development and boundary establishment of the AVC (purple) and chamber myocardium (grey). Development of the AVC and AVN. Schematic depicting the molecular pathways regulating the development and boundary establishment of the AVC (purple) and chamber myocardium (grey). Note that the regulation of tbx2b by foxn4 has only been shown in zebrafish, not in mammals. Jan Hendrik van Weerd, and Vincent M. Christoffels Development 2016;143:197-210 © 2016. Published by The Company of Biologists Ltd