Evolution of DNA Methylation Across Ecdysozoa

Area of Science:

• Evolutionary biology
• Genetics
• Molecular biology

Background:

• DNA methylation is a vital epigenetic mechanism for gene regulation in vertebrates.
• Its prevalence varies significantly across metazoan organisms, being absent in model species like Drosophila melanogaster and Caenorhabditis elegans.
• Understanding its distribution in other phyla provides insights into evolutionary history.

Purpose of the Study:

• To comprehensively investigate the presence and absence of DNA methyltransferases (DNMTs) across 138 Ecdysozoan species.
• To identify instances of independent gene loss and predict the presence or absence of DNA methylation.
• To elucidate the diverse evolutionary trajectory of DNA methylation in Ecdysozoa over a 700-million-year phylogenetic range.

Main Methods:

• Phylogenetic analysis of DNA methyltransferases (DNMTs) across 138 Ecdysozoan species from Arthropoda, Nematoda, Priapulida, Onychophora, and Tardigrada.
• Computational prediction of DNA methylation presence using CpG rates in coding sequences via Gaussian Mixture Modeling (MethMod).
• Integration of DNMT presence/absence data with methylation predictions to infer evolutionary patterns.

Main Results:

• Independent loss of individual DNMTs occurred multiple times across ecdysozoan phyla.
• Two novel predicted losses of DNA methylation were identified: within Chelicerata (Mesostigmata) and Tardigrada.
• The early-branching Ecdysozoan Priapulus caudatus is predicted to possess a full set of DNMTs and DNA methylation.

Conclusions:

• DNA methylation exhibits a highly diverse and independent evolutionary history within Ecdysozoa.
• The study reveals previously unrecognized patterns of DNA methylation loss and presence across a broad phylogenetic spectrum.
• Findings contribute to understanding the dynamic evolution of epigenetic mechanisms in invertebrates.