Figure 1.

Development of the C lineage and experimental design. The C blastomere is born at the eight-cell embryonic stage and follows an invariant cell lineage to produce 32 muscle cells, 13 epidermal cells, 2 neurons (N), and 1 cell death (X). The two arrows indicate the asymmetric cell divisions where muscle and epidermal cell fates are segregated in the lineage, as depicted by gray and yellow lines. Temporal and spatial expression patterns for 13 TFs expressed in the C lineage under the control of pal-1 are summarized to the right of the lineage. The background color indicates the temporal and spatial expression pattern of each TF. ‘X' indicates time of initial detection of zygotic gene product and ‘O' indicates a time point collected for mRNA expression analysis following RNAi of each TF. ELT-1 is initially detected in Cap and Cpp, but diminishes quickly while persisting in the epidermal precursors and their descendants as shown (Page et al, 1997). hnd-1 expression is first detected at the 4C stage (Baugh et al, 2005a), but expression in the C lineage is first detected at the 8C stage (Mathies et al, 2003).