Fig. 5. β-catenin phosphorylation at Y654 regulates axon growth and branching induced by NTs. (A) Hippocampal neurons transfected with EYFP alone (control) or with EYFP and WT or mutant (Y654F or Y142F) β-catenin. BDNF and NT-3 (50 ng/ml) induce axon growth and branching in control neurons and in neurons overexpressing WT or Y142F β-catenin, but NT-induced axon growth is inhibited in neurons expressing the mutation Y654F. Treatment with BDNF plus K252a results in axons with lengths and branching values similar to those of untreated neurons and of Y654F-expressing cells. Scale bar: 70 µm. (B) Quantification of axon length normalized to the respective control. BDNF and NT-3 increase axon length in control EYFP neurons and in neurons expressing WT or Y142F β-catenin, but not in neurons expressing the Y654F mutant. Treatment with BDNF together with NT-3 (B+NT3) does not result in a significant further increase. Treatment with K252a (100 nM) and BDNF (B+K252a) abolishes the increase in axon length induced by BDNF. (C) Quantification of axon branching (TABTN) shows that BDNF and NT-3 increase branching of axons expressing WT and Y142F β-catenin, but expression of Y654F β-catenin abolishes the branching induced by NTs. K252a (100 nM) together with BDNF abolishes BDNF-promoted branching (^*P0.05, ^**P0.01, ^***P0.001; n=3-8 experiments).