Stabilization of β-catenin promotes melanocyte specification at the expense of the Schwann cell lineage

The canonical Wnt/beta-catenin pathway governs a multitude of developmental processes in various cell lineages, including the melanocyte lineage. Indeed, beta-catenin regulates transcription of Mitf-M, the master regulator of this lineage. The first wave of melanocytes to colonize the skin is directly derived from neural crest cells, whereas the second wave of melanocytes is derived from Schwann cell precursors (SCPs). We investigated the influence of beta-catenin in the development of melanocytes of the first and second waves by generating mice expressing a constitutively active form of beta-catenin in cells expressing tyrosinase. Constitutive activation of beta-catenin did not affect the development of truncal melanoblasts but led to marked hyperpigmentation of the paws. By activating beta-catenin at various stages of development (E8.5-E11.5), we showed that the activation of beta-catenin in bipotent SCPs favored melanoblast specification at the expense of Schwann cells in the limbs within a specific temporal window. Furthermore, in vitro hyperactivation of the Wnt/beta-catenin pathway, which is required for melanocyte development, induces activation of Mitf-M, in turn repressing FoxD3 expression. In conclusion, beta-catenin overexpression promotes SCP cell fate decisions towards the melanocyte lineage.

Automated summary

This study found that overexpression of β-catenin promotes differentiation of Schwann cell precursors (SCPs) towards the melanocyte lineage within a specific temporal window. Additionally, excessive activation of β-catenin also leads to marked hyperpigmentation in the paws.