Practice question

Cerberus and related Dan family protein expressed in chick hypoblast and anterior endoderm is multifunctional antagonist binding Nodal, BMP and Wnt extracellularly. In left-right patterning, at Hensen's node asymmetric Shh and FGF8 induce Nodal left side, Cerberus on right inhibits Nodal preventing activation of Pitx2 left program that controls heart looping and gut laterality. Knockdown causes bilateral Nodal and heterotaxia. While also regulating head formation anteriorly, in gastrula stage chick its key regulatory role is left-right asymmetry via restriction of Nodal pathway rather than dorso-ventral or neural crest formation.