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| Studying the regulatory genomes of the bat sea star and the purple sea urchin. Image Credit: Courtesy of University of Barcelona |
The study outlines a new scenario for understanding how genome regulation and chromatin organization influence the evolution of animal body plans. “Our study opens up new paths for understanding the biological and evolutionary significance of this extreme conservation, since for the first time we can compare these very ancient regulatory elements across different lineages, a scientific breakthrough that allows us to understand what properties they share,” says Ignacio Maeso, professor at the UB’s Department of Genetics, Microbiology and Statistics.
Gene regulation and evolutionary novelties in vertebrates
Echinoderms are a large group of invertebrates that include sea urchins, starfish, sea cucumbers, ophiuroids, and sea lilies. They are the phylum closest to chordates — the group to which vertebrates belong — and have a unique phylogenetic position that allows for meaningful evolutionary comparisons between vertebrates and invertebrates.
For example, echinoderm larvae exhibit bilateral symmetry, while their adult forms have pentaradial symmetry, meaning that their body parts are arranged in five (or multiples of five) sections around a central axis. Animal morphology depends on the spatiotemporal control of gene expression — where, when, and which genes are activated in the body — which determines body plans in embryos and adults. But how are the genome and genes of each species regulated? How is chromatin folding an essential element in gene regulation, controlled?
In this study, the sea urchin (Strongylocentrotus purpuratus) and the starfish (Patiria miniata) have been used as models to unravel the mysteries surrounding the evolution of echinoderms. To this end, the team has applied cutting-edge techniques to analyze 3D genomic organizations — such as Hi-C and long-read sequencing — which have been little used in echinoderms to date.
The results reveal an extensive conservation of regulatory DNA elements across echinoderms and other animal groups. These highly conserved elements are most active during key stages of early development, suggesting that they control fundamental developmental programs that have remained unchanged throughout animal evolution.
“This type of deep preservation may be a much more common phenomenon than we previously thought and is probably present in many more animal lineages,” notes Ignacio Maeso.
Furthermore, the study reveals that the CTCF protein — an essential factor in chromatin folding in vertebrates — does not play a crucial role in the organization of the 3D structure of chromatin in echinoderms, similar to what has been described in other invertebrates such as the fruit fly (Drosophila melanogaster).
“This discovery suggests that some of these mechanisms related to the function of CTCF in gene regulation could be evolutionary novelties in vertebrates. Furthermore, our study adds to other recent studies showing how the mechanisms responsible for the 3D organization of chromatin are more diverse than previously thought and that each animal lineage has evolved different types of strategies for folding its genome,” concludes the researcher.
Published in journal: Nature Ecology & Evolution
Authors: Marta S. Magri, Danila Voronov, Saoirse Foley, Pedro Manuel Martínez-García, Martin Franke, Gregory A. Cary, José M. Santos-Pereira, Claudia Cuomo, Manuel Fernández-Moreno, Marta Portela, Alejandro Gil-Galvez, Rafael D. Acemel, Periklis Paganos, Carolyn Ku, Jovana Ranđelović, Maria Lorenza Rusciano, Panos N. Firbas, José Luis Gómez-Skarmeta, Veronica F. Hinman, Maria Ina Arnone, Ignacio Maeso
Source/Credit: University of Barcelona
Reference Number: ebio010826_02
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