Inter-embryo gene expression variability recapitulates the hourglass pattern of evo-devo

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genomics

Background:

• Embryological development exhibits deep conservation, particularly during the phylotypic stage in mid-embryogenesis.
• Existing hypotheses for the embryonic hourglass pattern focus on purifying selection of gene regulation.
• An alternative hypothesis suggests stage-specific gene regulation and varying capacities to respond to expression perturbations.

Purpose of the Study:

• To investigate the robustness of gene expression regulation during different stages of embryogenesis.
• To test the hypothesis that intrinsic differences in gene regulatory mechanisms explain the conserved phylotypic stage.

Main Methods:

• Quantified expression variability of isogenetic single embryo transcriptomes in Drosophila melanogaster.
• Analyzed robustness to both stochastic and genetic variations in gene expression.

Main Results:

• Expression variability was significantly lower at the phylotypic stage.
• The phylotypic stage exhibits greater robustness to stochastic variations in gene expression.
• Evidence suggests robustness to genetic variations and highlights the role of chromatin regulation.

Conclusions:

• The phylum-level pattern of embryonic conservation is explained by intrinsic differences in gene regulatory mechanisms across developmental stages.
• The phylotypic stage's robustness is a key factor in evolutionary conservation.