Neuronal progenitor cells often divide asymmetrically to produce two different daughter cells, such as a neuron and another progenitor cell. Although Wnt signalling is known to direct asymmetric cell division, the precise roles of different Wnt ligands is not well understood. In C. elegans, previous work has shown that the asymmetric terminal division of the SMDD/AIY neuronal progenitor requires active Wnt signalling to specify the AIY cell fate. Now, Vincent Bertrand and colleagues demonstrate that three (CWN-1, CWN-2 and MOM-2) of the five Wnt ligands in C. elegans are expressed during the terminal division. Indeed, these ligands regulate AIY cell fate because triple loss-of-function mutants have reduced chances of AIY cell specification, whereas CWN-2 overexpression increases the chance of forming two AIY daughters. The authors show that the ligands act through the MOM 5 Wnt receptor, which is enriched at the posterior pole of the progenitor cell during mitosis. Finally, the authors reveal that the APC orthologue APR-1 is required for cell division orientation along the anterior-posterior axis and for asymmetric cell fate. Furthermore, APR-1 is enriched at the anterior pole of the progenitor cell where it is asymmetrically inherited. Together, these results reveal the role of Wnt ligands during asymmetric cell division.
