DNA ability to regulate separated genes gave birth to animals
One of the evolution unsolved enigmas was the emergence of animals coming from their unicellular ancestors, and what mechanisms were involved in the development of their complex bodies. Everything leads to the idea that the responsible genetic mechanisms for this successful evolution would be found in all the animal kingdom, including humans, but not in our unicellular ancestors, according to an article published in magazine Cell, where professor Iñaki Ruiz Trillo -from the Department of Genetics, Microbiology and Statistics and the Biodiversity Research Institute (IRBio) of the University of Barcelona- participates.
One of the evolution unsolved enigmas was the emergence of animals coming from their unicellular ancestors, and what mechanisms were involved in the development of their complex bodies. Everything leads to the idea that the responsible genetic mechanisms for this successful evolution would be found in all the animal kingdom, including humans, but not in our unicellular ancestors, according to an article published in magazine Cell, where professor Iñaki Ruiz Trillo -from the Department of Genetics, Microbiology and Statistics and the Biodiversity Research Institute (IRBio) of the University of Barcelona- participates.
According to this new project, led by a team in the Institute of Evolutionary Biology (mixed centre of CSIC and UPF), the great innovation differentiating animals from their unicellular relatives is the distal gene regulation: the capacity of the DNA to regulate genes which are separated from each other and determine the exact moment when that happens. DNA sequences which are placed in other chromosome or very distanced from a specific gene are able to activate or inhibit it. “This ability helped to increase our body building, to the point of creating millions of cells, as it happened with mammals”, says Iñaki Ruiz-Trillo, also ICREA Research professor in the Institute of Evolutionary Research and awarded with a Consolidator Grant from the European Research Council (ERC) in 2014.
Researchers compared the genetic and epigenetic regulatory mechanisms of the amoeba Capsaspora owczarzaki, isolated from the hemolymph of a Puerto Rico snail. According to the researchers, the quantity of mechanisms that both groups share is higher than their differences. For instance, they share key elements that contribute to the development of animals such as the gen Brachyury -important for the embryogenesis- and the oncogene Myc, involved in cellular proliferation.
The life cycle of C. owczarzaki is complex and has clear transitions between stages, which range from a single cell to several dozens of them. In this case, the amoeba uses epigenetic mechanisms such as non-coding RNA and histone marks to regulate the transitions between the different cellular stages. “While C. owczarzaki uses the gene regulatory mechanisms to control the transition between life stages, the animals use them to specialize the cells to get neurones or muscle cells”, explains Ruiz-Trillo.
Multicellular beings
A big advantage of multicellularity -which appeared for its first time 1,000 million years ago- is that it allowed to increase body sizes, inhabit new cavities and divide its work among other cell types. According to the results of this study, the origin of animals was not a compendium of evolutionary innovations. It was rather a recycling process (or a genetic one) which added genomic complexity and enabled to regulate in a more accurate way the different cells that create complex organisms. The next step is to isolate the C. owczarzaki individual cells and analyse them in detail so as to determine whether they are all equal or some specialization between them already exists.
Reference article:
Sebé Pedrós, A.; Ballare, C.; Parra Acero, H.; Chiva, C.; Tena, J.; Sabidó, E.; Gómez Skarmeta, J.-L.; Di Croce, L.; Ruiz Trillo, I. "The dynamic regulatory genome of Capsaspora owczarzaki and the origin of animal multicellularity". Cell. DOI: 10.1016/j.cell.2016.03.034