Long-Lived RNA that is Never Replaced in Neurons

The question of whether there are long-lived molecules in long-lived neurons in the brain is an interesting one. Are there specific molecules in the brain that never get replaced across a lifetime, and thus might be vulnerable to damage in the form of modifications that disrupt function? This remains a somewhat hypothetical concern, in the sense that there is no direct demonstration that this is a significant source of dysfunction in late life. Researchers have found evidence for long-lived nuclear pore proteins, however, and here another group presents evidence for long-lived RNA molecules.

Most cells in the human body are regularly renewed, thereby retaining their vitality. However, there are exceptions: the heart, the pancreas, and the brain consist of cells that do not renew throughout the whole lifespan, and yet still have to remain in full working order. Now researchers were able to demonstrate for the first time that certain types of ribonucleic acid (RNA) that protect genetic material exist just as long as the neurons themselves.

"This is surprising, as unlike DNA, which as a rule never changes, most RNA molecules are extremely short-lived and are constantly being exchanged. We succeeded in marking the RNAs with fluorescent molecules and tracking their lifespan in mice brain cells. We were even able to identify the marked long-lived RNAs in two year old animals, and not just in their neurons, but also in somatic adult neural stem cells in the brain."

In addition, the researchers discovered that the long-lived RNAs, that they referred to as LL-RNA for short, tend to be located in the cells' nuclei, closely connected to chromatin, a complex of DNA and proteins that forms chromosomes. This indicates that LL-RNA play a key role in regulating chromatin. In order to confirm this hypothesis, the team reduced the concentration of LL-RNA in an in-vitro experiment with adult neural stem cell models, with the result that the integrity of the chromatin was strongly impaired.

Link: https://www.eurekalert.org/news-releases/1040098

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