Quantifying Mosaic Development: Towards an Evo-Devo Postmodern Synthesis of the Evolution of Development via Differentiation Trees of Embryos

Abstract

Embryonic development proceeds through a series of differentiation events. The mosaic version of this process (binary cell divisions) can be analyzed by comparing early development of Ciona intestinalis and Caenorhabditis elegans. To do this, we reorganize lineage trees into differentiation trees using the graph theory ordering of relative cell volume. Lineage and differentiation trees provide us with means to classify each cell using binary codes. Extracting data characterizing lineage tree position, cell volume, and nucleus position for each cell during early embryogenesis, we conduct several statistical analyses, both within and between taxa. We compare both cell volume distributions and cell volume across developmental time within and between single species and assess differences between lineage tree and differentiation tree orderings. This enhances our understanding of the differentiation events in a model of pure mosaic embryogenesis and its relationship to evolutionary conservation. We also contribute several new techniques for assessing both differences between lineage trees and differentiation trees, and differences between differentiation trees of different species. The results suggest that at the level of differentiation trees, there are broad similarities between distantly related mosaic embryos that might be essential to understanding evolutionary change and phylogeny reconstruction. Differentiation trees may therefore provide a basis for an Evo-Devo Postmodern Synthesis.

Periodicity in the embryo: Emergence of order in space, diffusion of order in time

“…One quantitative analysis we could not conduct is to assess the correlation between cell/embryo volume and the onset of bursty cell division events. This is true for both C. elegans and Zebrafish, and we have done a similar analysis using the C. elegans data comparing cell volume against developmental stage in [27]. Nevertheless, we can assume that sudden changes in the number of cells might reflect changes in embryo volume.…”

Embodied Cognitive Morphogenesis as a Route to Intelligent Systems

“…To account for the local symmetries and asymmetries that emerge from a spherical embryo, we can use a differentiation tree [66]. A differentiation tree (Figure 2) represents the emergence of new cell and tissue types as a binary tree, and can account for both two-fold and four-fold embryogenetic symmetry [67]. This allows us to not only draw from the differentiation history, but also modify this process at different points to examine cognitive emergence in action.…”

Periodicity in the embryo: emergence of order in space, diffusion of order in time

“…Other types of fishes (Astyanax, see [23]) exhibit morphological changes in neural crest cell proliferation based on evolutionary changes due to ecological constraints. In C. elegans, asymmetrical cells (or daughter cells with significantly different volumes) result from physical constraints and compose 40% of C. elegans developmental cell divisions [24,25]. Asymmetric cell divisions set up key cell-cell interactions [24] that are highlighted by the edges of embryo networks.…”