Dorsoanterior axis formation in Xenopus is initiated by the dorsal accumulation of β-catenin. It is known that factors that increaseβ-catenin stability are translocated to the prospective dorsal side of the embryo in a microtubule-dependent manner soon after fertilisation, but the identity of these factors, and how they are moved around the embryo, is unclear. Now, Weaver and colleagues report that GBP, a protein inhibitor of glycogen synthase kinase 3 (GSK3), binds to kinesin light chain (KLC), and that green fluorescent protein fusions of GBP and KLC form particles that translocate during the cortical rotation that occurs soon after egg fertilisation (see ). The researchers propose a model in which a GBP-containing complex is transported to the future dorsal side of the embryo by a conventional kinesin motor. Here, they suggest, GBP regulates the accumulation of β-catenin by dissociating from KLC and subsequently inhibiting GSK3,which would otherwise phosphorylate β-catenin and mark it for degradation.
