POP-1 AND ANTERIOR-POSTERIOR FATE DECISIONS IN C-ELEGANS EMBRYOS

Blastomeres in C. elegans embryos execute lineage programs wherein the fate of a cell is correlated reproducibly with the division sequence by which that cell is born. We provide evidence that the pop-1 gene fu nctions to link anterior-posterior cell divisions with cell fate decis ions. Each anterior cell resulting from an anterior-posterior division appears to have a higher level of nuclear POP-1 protein than does its posterior sister. Genes in the C. elegans Wnt pathway are required fo r this inequality in POP-1 levels. We show that loss of pop-1(+) activ ity leads to several types of anterior cells adopting the fates of the ir posterior sisters. These results suggest a mechanism for the invari ance of blastomere lineages.