Distinct adhesion-independent functions of ß-catenin control stage-specific sensory neurogenesis and proliferation.

ABSTRACT

BACKGROUND: ß-catenin plays a central role in multiple developmental processes. However, it has been difficult to study its pleiotropic effects, because of the dual capacity of ß-catenin to coordinate cadherin-dependent cell adhesion and to act as a component of Wnt signal transduction. To distinguish between the divergent functions of ß-catenin during peripheral nervous system development, we made use of a mutant allele of ß-catenin that can mediate adhesion but not Wnt-induced TCF transcriptional activation. This allele was combined with various conditional inactivation approaches. RESULTS: We show that of all peripheral nervous system structures, only sensory dorsal root ganglia require ß-catenin for proper formation and growth. Surprisingly, however, dorsal root ganglia development is independent of cadherin-mediated cell adhesion. Rather, both progenitor cell proliferation and fate specification are controlled by ß-catenin signaling. These can be divided into temporally sequential processes, each of which depends on a different function of ß-catenin. CONCLUSIONS: While early stage proliferation and specific Neurog2- and Krox20-dependent waves of neuronal subtype specification involve activation of TCF transcription, late stage progenitor proliferation and Neurog1-marked sensory neurogenesis are regulated by a function of ß-catenin independent of TCF activation and adhesion. Thus, switching modes of ß-catenin function are associated with consecutive cell fate specification and stage-specific progenitor proliferation.