Animal developmental cell lineages are robust to necrosis and program failure.
(A) A hypothetical cell lineage. Internal cells are prefixed with “I” and terminal cells are prefixed with “T”. Terminal cells belonging to the same cell type have the same name. Internal cells are colored according to their cell division programs. (B) The same cell lineage showing division programs for internal cells. Internal cells having the same division programs share the same color and program name (prefixed by “P”). (C) An example showing robustness calculation upon a necrotic cell depth. The internal cell I3 dies, which causes the loss of I3 as well as all of its direct and indirect descendant cells. Robustness is calculated by the product of the fraction of live terminal cells of each cell type. (D) An example showing robustness calculation upon a program failure. The failure of program P3 results in the loss of all descendant cells of internal cells that use P3. Robustness is calculated by the product of the fraction of live terminal cells of each cell type. (E–F) The Caenorhabditis elegans developmental cell lineage is more robust than the corresponding random lineages in the presence of (E) necrosis or (F) program failure. The grey bars show the frequency distribution of the robustness of 10,000 random lineages, whereas the arrow indicates the robustness of the C. elegans cell lineage. The random lineages are generated by randomly coalescing the terminal cells of the C. elegans lineage. P-value indicates the probability that a randomly generated lineage is more robust than the real lineage. Z-score is the number of standard deviations (of the random lineages) by which the observation deviates from the mean of the random lineages. (G–H) The Pellioditis marina cell lineage is more robust than the corresponding random lineages in the presence of (G) necrosis or (H) program failure. (I–J) The Halocynthia roretzi cell lineage is more robust than the corresponding random lineages in the presence of (I) necrosis or (J) program failure.