September 21st, 2011
12:01 PM ET
Researchers have identified a genetic abnormality which they believe to be the most common cause of two devastating neurological diseases and could provide future clues to treatment. Two new studies, published online in the journal Neuron, found that amyotrophic lateral sclerosis (ALS) also known as Lou Gehrig's disease and frontotemporal dementia or FTD that run in families are caused in many cases by a mutation on a single gene on chromosome number 9. This mutation causes a short DNA sequence to repeat over and over, much more frequently than in healthy people. The ALS Association, which funded both studies, calls the identification of this genetic mutation "a major milestone in ALS research."
According to the data, in healthy individuals the DNA sequence repeats 2 to 23 times. In 23% of familial ALS patients and 12% of familial FTD patients the sequence repeated 700-1,600 times.
ALS and FTD are both fatal neurological diseases of the brain. In ALS, nerve cells in the brain and spinal cord begin to degenerate and patients lose the ability to move their bodies and breathe. Almost 6,000 American are diagnosed with the crippling disease each year. FTD causes the degeneration of parts of the brain that control language, emotion, behavioral control and the ability to make decisions (the temporal and frontal lobes). About 20-40% of people with FTD have a family history of the disease.
One study looked at patients in Finland which has a high population of ALS patients, according to lead study author Dr. Bryan Traynor from the National Institute on Aging (NIA).
"With this finding we've gone from understanding a quarter of familial ALS to two-thirds of familial ALS," Traynor said. "In terms of thinking of the future, what this provides us with is a target to go after. What this allows us to do is to design cell models and animal models of disease we can use to start to screen drugs, and therapeutic agents to see if they are effective in turning off this particular genetic mutation."
Traynor says there are 4 genes known to account for 25% of all familial ALS cases. The chromosome 9 gene accounts for an additional 40%.
In the second study, researchers at the Mayo Clinic in Jacksonville, Florida also found the same repeat DNA sequence. "This finding has the potential to lead to significant insights into how both of these neurodegenerative diseases develop," Senior Investigator Dr. Rosa Rademakers, neuroscientist at the Mayo Clinic said. "And may give us much needed leads into new ways to treat our patients."
The ALS Association's Chief Scientist Lucie Bruijn calls the new data tremendously exciting. "These findings will significantly impact the field as we begin to understand more about the consequences of these changes to the disease process, aid or understanding of FTD and ALS, potentially provide a diagnostic tool, and enable the development of new therapeutic approaches."
Still, Traynor says he wants to keep expectations within bounds and be careful not to raise false hopes. That's because typically it's 10 years from gene discovery to clinical trial. He says that's a long time when ALS patients usually live 2-3 years after the onset of symptoms.
"It's a step forward, Traynor said. "Now we know which room in which house on which street in which city and that knowledge facilitates ultimately working up a treatment that will slow down this fatal disease.".
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