Practice question

EMS polarity relies heavily on Wnt signaling from P2. P2 expresses MOM-2 Wnt ligand and MOM-5 Frizzled, activating both canonical Wnt/beta-catenin asymmetry pathway and Src/MES-1 pathway in EMS. MOM-2 binding causes WRM-1 beta-catenin nuclear accumulation in E but not MS, along with reduction of POP-1 TCF, converting POP-1 to transcriptional activator with SYS-1 beta-catenin to induce end-1, end-3 endoderm genes. Mutations in mom-2, mom-5, wrm-1 cause both EMS daughters to become MS-like. Therefore EMS fate specification uses Wnt signal to establish E versus MS asymmetry downstream of initial SKN-1 competence input.