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08:46
Studying Age-dependent Genomic Instability using the S. cerevisiae Chronological Lifespan Model
Published on: September 29, 2011
A phylogenetically based transcriptome age index mirrors ontogenetic divergence patterns.
Tomislav Domazet-Lošo1, Diethard Tautz
1Max-Planck-Institut für Evolutionsbiologie, August-Thienemannstrasse 2, 24306 Plön, Germany. tdomazet@irb.hr
Nature
|December 15, 2010
Summary
The phylotypic stage, a conserved phase in embryonic development, is marked by the expression of ancient genes across diverse species. This study reveals a molecular signature for this stage, showing conserved patterns in gene evolution from flies to nematodes.
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Genomics
Background:
- The phylotypic stage, a period of high similarity among species within a phylum during development, has been historically linked to recapitulating evolutionary history.
- While previously thought to reflect ancestral traits, the phylotypic stage is now understood as a phase of constrained developmental regulation and gene interactions.
- Previous research indicated slower gene evolution during the phylotypic stage, but a definitive molecular signature remained elusive.
Purpose of the Study:
- To identify a molecular signature for the phylotypic stage by analyzing the evolutionary age of gene expression across ontogeny.
- To investigate the relationship between gene expression patterns, evolutionary age, and developmental stages in model organisms.
- To determine if the observed patterns are conserved across different animal phyla.
Main Methods:
- Phylostratigraphy combined with stage-specific gene expression data analysis.
- Development of a cumulative index to quantify the evolutionary age of the transcriptome at different ontogenetic stages.
- Comparative analysis of gene expression data from zebrafish, flies, and nematodes.
Main Results:
- The phylotypic stage in zebrafish exhibits the oldest set of expressed genes, consistent with the hourglass model of evolution.
- Early and late developmental stages express younger gene sets, while reproductively active animals show the youngest transcriptome with sex-specific differences.
- Ageing animals display an increase in the expression of older genes.
- Cross-phyla comparisons confirm that an ancient transcriptome characterizes the phylotypic phase, with younger genes correlating with phylogenetic divergence at other stages.
Conclusions:
- The phylotypic stage is molecularly defined by the expression of evolutionarily conserved, older genes.
- The hourglass model of development is supported by gene expression patterns, with conserved gene sets at the phylotypic stage and novel gene expression during early/late development and reproduction.
- These findings provide a conserved molecular framework for understanding developmental constraints and evolutionary divergence across diverse animal lineages.
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