Sleep Helps To Repair Damaged DNA In Neurons, Scientists Find

An anonymous reader quotes a report from The Guardian: Scientists have discovered that broken DNA builds up in brain cells in the daytime and repair work reverses the damage only during sleep. For an act so universal, sleep has enormous benefits. Found in organisms from flies to worms and jellyfish, it restores the body and helps learning and memory. But despite extensive research, the purpose of sleep is still mysterious. Lior Appelbaum from Bar-Ilan University and his student, David Zada, reasoned that if sleep had evolved in all organisms with a nervous system, then it might be working at the level of individual neurons.

To find out, they genetically engineered small, transparent zebrafish so the chromosomes in their neurons carried colorful chemical tags. The researchers then used a powerful, specialized microscope to watch how the chromosomes moved in the neurons, and how often DNA was broken, when the fish were awake and asleep. When the fish were awake, the chromosomes did not move much and broken strands of DNA built up in the neurons, as part of the normal wear and tear of life. If the fish were sleep-deprived, by tapping on their tank for example, some of the neurons accumulated so much genetic damage they were in danger of dying off. But, when the fish fell asleep, the picture changed. The scientists noticed that the chromosomes changed shape far more often in sleeping fish, and that DNA damage in their neurons plummeted. The same happened when the researchers added a sleep-inducing drug to the tank, causing the fish to fall asleep in the daytime. 'Appelbaum said that chromosomes are constantly changing shape to allow the cells' natural repair mechanisms to mend DNA damage at different points,' the report adds. 'When awake, the repair work cannot keep up with the rate at which damage builds up, but in the calm hours of sleep, the repair mechanisms have a chance to get on top of the job.' The study has been published in Nature Communications.

Read more of this story at Slashdot.