The avian embryo’s left-right axis is regulated by:
Left-right asymmetry in chick originates at Hensen's node where Sonic hedgehog expressed left side, FGF8 right, and Caronte/Cerberus left paraxial mesoderm. Caronte inhibits BMP signaling left lateral plate mesoderm, permitting Nodal transcription via FoxH1. Nodal autoamplifies and activates Lefty2 and Pitx2 transcription factors left side, directing heart dextral looping and gut rotation. Right side maintains BMP and FGF8 blocking Nodal. Ciliary flow at node not required in chick, but molecular cascade with Cerberus repressing BMP to unleash Nodal is conserved, integrating Shh, BMP, Nodal reg
Ref: Levin et al., Cell 1995; Gilbert, Developmental Biology, Chapter 12: Left-right regulation - Cerberus, BMP, Nodal pathway.
