Developmental trajectory of Caenorhabditis elegans nervous system governs its structural organization
Fig 3
Lineage distance reveals developmental patterns of ganglia.
(A-B) Statistically significant features of the distribution of intra and inter-ganglionic lineage distances, quantified by deviations of the mean 〈l〉 (A) and coefficient of variation CV (B), from a surrogate ensemble of randomized lineage trees of neurons in the C. elegans somatic nervous system. These deviations (measured by z-score) show that the mean intra-ganglionic lineage distances (represented by diagonal blocks of the matrix) are significantly lower than that of the inter-ganglionic lineage distances (off-diagonal blocks), with the exception of G6 and G9. By contrast, CV for the intra-ganglionic lineage distances are significantly higher than that of the inter-ganglionic lineage distances. (C-E) Developmental chrono-dendrograms for three representative ganglia (viz., G1, G4 and G5) show that each comprises multiple localized clusters of neurons occurring at different locations on the developmental lineage tree, explaining the statistically significant deviations of the mean and CV for intra-ganglionic lineage distances. Colored nodes represent neurons belonging to the specified ganglion while gray nodes show the other neurons. Branching lines trace all cell divisions starting from the single cell zygote (located at the origin) and terminating at each differentiated neuron. The time and rung of each cell division are indicated by its position along the vertical and radial axis respectively. The entire time period is divided into four stages, viz., Embryo (indicated as E), L1, L2 and L3. A planar projection at the base of each cylinder shows the rung (concentric circles) of each progenitor cell and differentiated neuron. (F-H) The probability distribution functions for the intra-ganglionic lineage distances show bimodality (unlike that of the inter-ganglionic distances), which is consistent with the segregation of a ganglion into multiple clusters along the chrono-dendrogram. The different ganglia are indicated by symbols G1-G9 (1: Anterior, 2: Dorsal, 3: Lateral, 4: Ventral, 5: Retrovesicular, 6: Posterolateral, 7: Preanal, 8: Dorsorectal and 9: Lumbar) and the Ventral cord as G10.