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

View Article: PubMed Central - PubMed

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 Cionaintestinalis 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.

No MeSH data available.


Maximum, mean, and minimum values (black dots from top to bottom) for smaller cell volume to larger cell volume ratios for C. elegans summarized by lineage depth (values per division event).
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biology-05-00033-f010: Maximum, mean, and minimum values (black dots from top to bottom) for smaller cell volume to larger cell volume ratios for C. elegans summarized by lineage depth (values per division event).

Mentions: To examine the variation in volume across pairs of daughter cells, we can look at the volumetric ratio between the smaller and larger daughter cell (see Methods, Section 2.5). This ratio can be stratified in terms of depth in a single lineage, while also being comparable more generally across species. Such a measure gives us a global heuristic in terms of detecting the relative contribution of asymmetrical divisions at different depths of a given lineage tree. Figure 9 (Ciona) and Figure 10 (C. elegans) show the range (minimum, mean, and maximum values) of cell volume ratios. For both species, there is a tendency for greater asymmetry as the number of division events increase (e.g., an increase in lineage depth). For the first few depths of the lineage tree (up to the eight-cell stage in Ciona and 16-cell stage in C. elegans), there are virtually no variations in cell asymmetry, and the ratio between smaller cell to larger cell is very close to one. It is of note that the scale of variation is much larger in the Ciona embryo, perhaps reflecting a combination of aforementioned technical variation and the nature of differentiation as captured by the lineage tree. Variation is observed only later in the lineage tree, which may represent selective differentiation events in different parts of the tree. While the mean value decreases in Ciona after this point (and does not decrease in C. elegans), the value fluctuates rather than decreasing monotonically. This may point to a non-uniform but consistent number of cell divisions that exhibit above-threshold volumetric asymmetry.


Quantifying Mosaic Development: Towards an Evo-Devo Postmodern Synthesis of the Evolution of Development via Differentiation Trees of Embryos
Maximum, mean, and minimum values (black dots from top to bottom) for smaller cell volume to larger cell volume ratios for C. elegans summarized by lineage depth (values per division event).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037352&req=5

biology-05-00033-f010: Maximum, mean, and minimum values (black dots from top to bottom) for smaller cell volume to larger cell volume ratios for C. elegans summarized by lineage depth (values per division event).
Mentions: To examine the variation in volume across pairs of daughter cells, we can look at the volumetric ratio between the smaller and larger daughter cell (see Methods, Section 2.5). This ratio can be stratified in terms of depth in a single lineage, while also being comparable more generally across species. Such a measure gives us a global heuristic in terms of detecting the relative contribution of asymmetrical divisions at different depths of a given lineage tree. Figure 9 (Ciona) and Figure 10 (C. elegans) show the range (minimum, mean, and maximum values) of cell volume ratios. For both species, there is a tendency for greater asymmetry as the number of division events increase (e.g., an increase in lineage depth). For the first few depths of the lineage tree (up to the eight-cell stage in Ciona and 16-cell stage in C. elegans), there are virtually no variations in cell asymmetry, and the ratio between smaller cell to larger cell is very close to one. It is of note that the scale of variation is much larger in the Ciona embryo, perhaps reflecting a combination of aforementioned technical variation and the nature of differentiation as captured by the lineage tree. Variation is observed only later in the lineage tree, which may represent selective differentiation events in different parts of the tree. While the mean value decreases in Ciona after this point (and does not decrease in C. elegans), the value fluctuates rather than decreasing monotonically. This may point to a non-uniform but consistent number of cell divisions that exhibit above-threshold volumetric asymmetry.

View Article: PubMed Central - PubMed

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 Cionaintestinalis 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.

No MeSH data available.