β-Catenin-mediated signalling is involved at several stages of vertebrate neural development. Early on, it is essential for the formation of the dorsal organiser, a neural-inducing and dorsalising signalling centre;later, it promotes posterior and ventral fates. On p. , Bellipanni and colleagues use zebrafish to investigate the multiple roles of β-catenin in neural development. They identify a new β-catenin gene (β-catenin-2), the expression of which is reduced by the maternal-effect mutation ichabod - most embryos bred from females homozygous for this mutation lack notochord, head and trunk neurectoderm. Inhibiting β-catenin-2 function with morpholinos shows that it (but not the previously studied β-catenin-1) is needed for dorsal organizer formation. Later in development, however, the two β-catenins function redundantly to repress neurectoderm formation - in the absence of both functions, an abnormal tuft-like projection of neurectoderm forms with an apparently appropriate anteroposterior pattern. Overall, the researchers conclude that different β-catenins can have different, sometimes opposing, roles at different times during neural development.
