 Secreted lefty binds to EGF-CFC proteins like one-eyed pinhead in zebrafish keeping the essential cofactor from associating with NODAL/ Activin-like receptor complex.This will effectually block Nodal Signaling.During induction of the primitive streak, lefty confines Nodal activity to the posterior end of the embryo, establishing a posterior signaling center and inducing the formation of the primitive streak and mesoderm.