Scientists discover Alzheimer's risk gene

To find the gene, they used a new imaging method that screens the brain's connections - the wiring, or circuitry, that communicates information. Switching off such Alzheimer's risk genes (nine of them have been implicated over the last 20 years) could stop the disorder in its tracks or delay its onset by many years.

"We found a change in our genetic code that boosts our risk for Alzheimer's disease," said the study's senior author, Paul Thompson. "If you have this variant in your DNA, your brain connections are weaker. As you get older, faulty brain connections increase your risk of dementia," he said in a statement.

The researchers including Neda Jahanshad, Priya Rajagopalan, Xue Hua, Derrek P Hibar, Talia M Nir and Arthur W Toga screened more than a thousand people's DNA to find the common "spelling errors" in the genetic code that might heighten their risk for the disease later in life.

The study was the first of its kind to also give each person a "connectome scan", a special type of scan that measures water diffusion in the brain, allowing scientists to map the strength of the brain's connections. The new scan reveals the brain's circuitry and how information is routed around the brain, in order to discover risk factors for disease.

The researchers then combined these connectivity scans with the extensive genomic screening to pinpoint what causes faulty wiring in the brain. In people whose genetic code differed in one specific gene called SPON1, weaker connections were found between brain centers controlling reasoning and emotion. The rogue gene also affects how senile plaques build up in the brain - one of the hallmarks of Alzheimer's disease.

It has also been found that the SPON1 gene can be manipulated to develop new treatments for the devastating disease, Thompson noted. When the rogue gene was altered in mice, it led to cognitive improvements and fewer plaques building up in the brain. The study was published in the journal Proceedings of the National Academy of Sciences.