Our DNA holds the instructions that all our cells need in order to function, including the brain cells and the blood cells. It is by switching on and off different genes or segments of DNA that cells can take on specialized functions. It is the same for every type of organism, as cells differentiate when genes are turned on or off. These “switches”, which are used to activate or deactivate genes, can be found in simple organisms only a few centimeters away. In complex organisms these switches can be separated from their genes by thousands of lines of DNA. Research has shown that the long-distance gene regulation found in complex organisms is much older than previously thought. The research, published today in Nature, reveals these remote on-off switch likely first appeared in animals’ evolution, between 700 million and 650 millions years ago. This is about 150,000,000 years earlier than was previously thought.
Turning distant genes on and off
To achieve long-distance regulation of gene expression, also known as distal regulation or remote regulation, the DNA must be folded into complex loops. The loops bring separated DNA segments closer in space and allow on/off switches to be controlled by genes located tens or thousands of letters apart. It was long believed that animals who appeared 500 million years before humans developed this capability, which helped them to specialize their cells. The new Nature study has shown that distal regulatory mechanisms originated much earlier, possibly in the common ancestor to all animals alive today.
This creature can repurpose their genetic toolkit like a Swiss-army knife in order to explore and refine innovative survival strategies. According to a release, Iana Kim is the study’s lead author. She’s a researcher with the Spanish Centre for Genomic Regulation and Centro Nacional de’Analisis Genomica.
The authors of this new study examined the gene regulatory mechanisms of 11 different species to trace the origins of distant gene switches. These species include ctenophores and other early animals like poriferans. Some of Earth’s most primitive animals are found in these lineages. They include the sea sponges and jellyfish as well as other creatures like corals and anemones. Some species are descended from single-celled organisms, which share an ancestor that is common to all living things. You can learn a great deal about biology from strange sea creatures. According to the press release, the CRG’s Arnau Sbe-Pedros is another author of the study and group leader. He said that we have been comparing genomes but now we know [analyze] what gene regulatory mechanisms are controlling genome function in different species. The study authors were able to create 3D maps that followed folds in DNA sequences using a method called Micro-C.
The loops that regulate long distance gene regulation did not appear on the DNA maps for the single-celled animals, but they appeared in those of the ctenophores (ctenophore-like organisms), placozoans and cnidarians. This suggests the origins of distal regulation around 700 to 650 millions of years ago. The authors of the study also discovered that the structure of DNA loops in different animals is influenced by different proteins. The looping in later animal species (like birds, mammals, fish, amphibians and reptiles) is organized using CTCF. This protein helps to order genes into DNA segments. However, earlier animals, like ctenophores, are organized with a different protein of the same family. It is amazing that the same issue has been resolved using two different methods. According to the press release, thanks to this study, we know you can use different proteins to bring distal [pieces] DNA together in space forming a circle. Marc A. Marti Renom is another author of the study and a leader group at CRG and CNAG. Study authors emphasize that their work helps to track the evolution in genomic regulation, and gives practical insight into regulatory mechanisms which control the functions of cells both for humans and animals. Read more: Before plants evolved, this predatory jellyfish lived
