Abstract
Asymmetric cell divisions produce new cell types during animal development. Studies in Caenorhabditis elegans have identified major signal-transduction pathways that determine the polarity of cell divisions. How these relatively few conserved pathways interact and what modulates them to ensure the diversity of multiple tissue types is an open question. The Wnt/beta-catenin asymmetry pathway governs polarity of the epidermal T seam cell in the C. elegans tail. Here, we show that the asymmetry of T-seam-cell division and morphogenesis of the male sensory rays require NHR-25, an evolutionarily conserved nuclear receptor. NHR-25 ensures the neural fate of the T-seam-cell descendants in cooperation with the Wnt/beta-catenin asymmetry pathway. Loss of NHR-25 enhances the impact of mutated nuclear effectors of this pathway, POP-1 (TCF) and SYS-1 (beta-catenin), on T-seam-cell polarity, whereas it suppresses the effect of the same mutations on asymmetric division of the somatic gonad precursor cells. Therefore, NHR-25 can either synergize with or antagonize the Wnt/beta-catenin asymmetry pathway depending on the tissue context. Our findings define NHR-25 as a versatile modulator of Wnt/beta-catenin-dependent cell-fate decisions.