Breaks and fixes the genes are what make memories

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Neurons do not divide: Evidence of a DNA-driven inflammation cycle in the hippocampal neuron is due to the centrosome TLR9

The subset of hippocampal neurons in which the breaks in the DNA are resistant to repair was most active in TLR9. Damage to the DNA in the centrosome is associated with cell division and differentiation in these cells. However, mature neurons don’t divide, Radulovic says, so it is surprising to see centrosomes participating in DNA repair. She wonders whether memories form through a mechanism that is similar to how immune cells become attuned to foreign substances that they encounter. During the cycle of damage and repair, brain cells might be able to remember the event that triggered the DNA breaks.

It also suggests a tantalizing possibility: this cycle might be faulty in people with neurodegenerative diseases such as Alzheimer’s, causing a build-up of errors in a neuron’s DNA, says study co-author Jelena Radulovic, a neuroscientist at the Albert Einstein College of Medicine in New York City.

The team was able to identify a key factor in the inflammation: a gene called TLR9 which causes an immune response. This inflammatory response is also similar to one that immune cells use in defense of their genetic material. However, in this case, the nerve cells were responding not to invaders, but to their own DNA, the researchers found.

Clara Ortega de San Luis, a neuroscientist who works with Ryan at Trinity College Dublin, says that these results bring much-needed attention to mechanisms of memory formation and persistence inside cells. She says that although we know a lot about how neurons are connected, we don’t think much about what happens inside them.