Heads or tails: Wnts and anterior-posterior patterning.

Cell-cell communication is critical during embryogenesis for organizing the vertebrate body plan. Members of the Wnt family of secreted signaling molecules possess axis-inducing and posteriorizing activity when overexpressed. Wnt signals are modulated extracellularly by a diverse group of secreted Wnt antagonists and cofactors. Recent work has revealed that inhibition of posteriorly localized Wnt signaling by anteriorly localized Wnt antagonists is critical for inducing the anterior structures, forebrain and heart, from neural ectoderm and mesoderm, respectively. This review centers on the role that Wnts and Wnt antagonists play in the patterning of the vertebrate anterior-posterior axis.