A newly discovered genetic disease could help scientists discover ways of finding brain disorders such as Alzheimer's and Parkinson's.
The rare condition, ataxia oculomotor type XRCC1A, causes a DNA repair system to go into overdrive and destroy brain cells.
It is linked to single-strand breaks in DNA, one of the most common types of genetic damage.
The findings could aid research into other diseases related to DNA repair, say scientists.
They could also be important for work on more common neurodegenerative and brain-ageing conditions including Alzheimer's, Parkinson's and Huntington's disease, it is claimed.
A defective gene triggers the new disorder by boosting activity of a DNA-repair enzyme called PARP1.
Lead researcher Professor Keith Caldecott, from the University of Sussex, said: "Discovering this new disease and its cause is a huge step towards developing drug-based therapies for other rare neurodegenerative conditions.
"Drugs which target this key DNA repairing enzyme in the right way, could prove vital for treating people suffering from diseases caused by the over-activation of this protein - it is now crucial we determine what diseases these are."
The study is published in the latest issue of Nature journal.