Ritsuko Takada et al. show that Wnt3a assembles into high molecular weight complexes that restrict the diffusion of Wnt within Xenopus embryos. These results suggest that Wnt diffusion in cells is controlled by a balance between higher order complex assembly and dissociation by Wnt-binding proteins.

Tracheal development arises due to tube morphogenesis but how this is regulated is unclear. Here, the authors identify polarization of smooth muscle progenitors as controlling murine tracheal development, activating noncanonical Wnt signaling followed by subepithelial morphogenesis and ring cartilage development.

Stimulation of Wnt and Nodal pathways in micropatterned human embryonic stem cell colonies induce these colonies to exhibit characteristic spatial expression patterns of the organizer and reproduce organizer function when grafted into a host embryo.

Independently of the LGR4/5/6 receptors, RSPO2 acts as a direct antagonistic ligand to RNF43 and ZNRF3 during embryogenesis, and specifies the position and number of limbs that an embryo should form.