[extropy-chat] 2nd precursor gene for Alzheimer's

[Damien Broderick]

Gene for Alzheimer's discovered

Monday, 15 January 2007
Agençe France-Presse
Gene for Alzheimer's discovered

A second gene responsible for late-onset 
Alzheimer's diesease, a condition affecting 
millions worldwide, has been discovered by an 
international team of researchers.

CHICAGO: A second gene responsible for the most 
common form of Alzheimer's disease has been 
identified by U.S. and Canadian researchers.

"The importance of the finding is that it opens 
new pathways to explore the cause of the disease, 
as well as potential targets for treatment," said 
Richard Mayeux of Columbia University's Taub 
Institute for Research on Alzheimer's Disease and 
the Ageing Brain, and one of the authors of the study.

In genetic studies involving some 6,000 
volunteers, the researchers discovered that 
variants of the gene SORL1 were more common in 
people with late-onset Alzheimer's than in healthy people of the same age.

Additionally, the Alzheimer's sufferers had less 
than 50 per cent as much of the protein produced 
by SORL1 in their blood compared with the healthy group.

In healthy people, SORL1, which is a 'traffic 
cop' regulating the flow of amyloid precursor 
protein (APP) inside nerve cells in the brain, 
sends APP to a part of the cell where it is recycled.

But in people with the gene variants, the protein 
produced by the SOR1 gene appears to drive APP to 
another region of the cell where it accumulates 
and is degraded into amyloid plaques. Plaques, 
according to the researchers, are the abnormal 
sticky proteins that gum up the brain of 
Alzheimer's victims. "SORL1 is another critical 
piece of the Alzheimer's disease puzzle," said Mayeux.

In 1993, U.S. scientists identified the first 
genetic marker for late-onset Alzheimer's and two 
years later Canadian researchers linked two genes 
to the aggressive early-onset form of the disease.

But a decade on, effective treatments for the 
progressive brain disease are still lacking, and 
the only definitive way to diagnose the illness is by autopsy.

Pharmacuetical companies are scrambling to 
develop drugs, many of them targeting the 
beta-amyloid protein fragments that are 
considered a prime suspect in the nerve cell 
death that is a feature of the disease, according 
to the Alzheimer's Association in Chicago, Illinois.

Some of those drugs are in clinical trials and 
should be on the market in five to 10 years, but 
it's a race against the clock as the number of 
Alzheimer's cases is predicted to surge with the greying of the population.

In the United States alone, some 4.5 million 
people have been afflicted with the 
memory-sapping illness, and the prevalence is 
expected to double in the next 25 years.

The authors of this study, published today in the 
British journal Nature Genetics, said they hoped 
that this discovery would speed the search for 
drug therapies, and once they are in place, help 
identify people at risk for the disease.

"Right now, there are questions about the value 
of screening people for the disease, because we 
can't do much about it. All that changes if there 
are effective therapies that can prevent brain 
damage occurring," said co-author Peter St. 
George-Hyslop, of the Centre for Research in 
Neurodegenerative Diseases at the University of Toronto in Canada.