| Modification Notes |
In C. elegans embryogenesis, POP-1 is essential for the specification of the blastomere, where it functions to link anterior-posterior cell divisions with cell fate decisions (1,2). Differences in POP-1 expression between anterior and posterior cells suggest that POP-1 aids in determining the polarity of the blastomere (3). The b-catenin homolog WRM-1 downregulates levels of POP-1 in the posterior daughter of the EMS blastomere (4). POP-1 and BAR form a bipartite transcription factor that activates expression of Wnt target genes associated with controlling cell polarization and cell migration (4). A polarizing signal induces endoderm production by the 4-cell stage blastomere. The genes mom-1 through mom-5 are required for the EMS to produce endoderm (5). The genes mom-1 through mom-3 are required in the signaling cell, P2, while mom-4 is required in EMS (5). MOM-4 is expressed as a MAP kinase kinase kinase-related protein that stimulates the WRM-1/LIT-1-dependent phosphorylation of POP-1 (6) Along with WRM-1, the MOM-4 protein downregulates the HMG-domain-containing repressor POP-1 (7). |
