A mini-organ has recently been discovered in mammalian cells, according to a new study by the ETH Institute of Biochemistry in Zurich, Switzerland. According to researchers, it acts like a trap that closes around small rings of DNA. The study believes that the “exclusive”, as it was called, could be a defense system embedded in the genome and a relic from a time before complex cells.
All animals in nature, plants and fungi are eukaryotic, which means that their cells house their DNA in a special compartment called the nucleus. However, part of the cell’s DNA exists outside this structure, in a fluid-filled body called the cytoplasm. Scientists still don’t know for sure how these floating pieces of genetic material are kept outside the nucleus, but the unique discovery could bring more answers on the subject.
Impressive genetic discovery
In the recent study, researchers identified a unique structure that could help explain how cells can keep part of their DNA away from the nucleus. The never-before-seen structure, dubbed “exclusive” by researchers, would be responsible for enclosing this genetic material.
And what does it mean? According to the scientists involved in the study, it is possible that this new organelle, or specialized cellular compartment, may use a mechanism similar to the way the nucleus developed in the first eukaryotic cells to isolate part of the DNA. This research could shed light on how cells respond to invaders and on the development of cancer and autoimmune diseases.
Study senior author Ruth Kroschewski and her colleagues introduced small loops of DNA called plasmids into different types of human cells to take a closer look at the reaction. Then, they discovered that, in all cases, a double membrane formed around the plasmid, forming the unique structure. Within this structure, they also found genetic material that codes for telomeres — the “caps” at the ends of chromosomes that protect DNA from being destroyed.
Understanding the exclusive
Just like the nucleus of cells, the exclusive has a double membrane and some of the same proteins. However, its form lacks some elements, such as structures that only allow selected molecules to enter the nucleus. The plasmid capture process carried out by this mini-organ may be an evolutionary relic that helped form the first nuclear membranes around chromosomal DNA, Kroschewski said.
However, the exclusive does not appear to be unique, because they only capture genetic material that the cell considers potentially dangerous or unnecessary. This organelle may also play a key role in autoimmune diseases, researchers believe. If a pathogen’s DNA remains in the cell long after it has been injected by an invader, this could indicate to the body that there is still an infection to fight.
Therefore, understanding how cells respond to DNA outside chromosomes could be crucial to understanding the relationship between plasmids and some diseases, such as cancer. New studies will be necessary to better understand how the exclusive works in the human body, but its discovery is already an intriguing starting point.
