Scientists have announced the discovery of another gene responsible for late-onset Alzheimer's disease. This is the most common type of the disease (occurring in around 90 percent of patients) and develops after 65 years.
Scientists from Boston University, the University of Toronto, and Columbia University have discovered the gene named SORL1.The findings were published in Nature Genetics.
The reasearchers spent five years locating the newly discovered gene, using DNA samples. These were collected from more than 6,000 volunteers from four distinct ethnic groups.
Scientists have been intensively searching for genes related to Alzheimer's for decades with little success. The first major gene for late-onset Alzheimer's, ApoE4, was discovered 14 years ago,in 1993.
Scientists are relieved to find out that the new finding affirms their hypotheses on the diagnosis, progress and treatment of the disease , though a permanent cure is still not forseable .
Most of the present efforts are aimed at blocking sticky deposits of plaque in the brain formed from a protein called amyloid. Many scientists believe that the amyloid plaque plays a leading role in destroying brain cells.
Currently more than 60 drugs are in clinical trials for Alzheimer's, and most of these drugs aim to block or remove amyloid in the brain.
The scientists say that when it is working normally, the gene SORL1, plays a key protective role by recycling amyloid through the brain, preventing it from accumulating and turning into toxic plaque. This protection declines in patients with a defective SORL1 gene, resulting in accumulation of amyloid in the brain.
Yet, having a defect in the SORL1 gene does not guarantee that a patient will develop Alzheimer's ,though it does increase the risk.
Researchers continue to search for other genetic variants linked to the disease, and there could be 20 or more.
Says Dr. Richard Mayeux, co-director of Columbia's Taub Institute for Research on Alzheimer's Disease regarding the new discovery "It opens new pathways to explore the cause as well as potential targets for treatment of this devastating disease."
About 4.5 million elderly Americans are currently diagnosed with Alzheimer's, an incurable disease that slowly destroys the patient's brain and always ends in death. The prevalence of the disease ,which is the top cause of dementia,is expected to double over the next 25 years as the population ages.
The discovery of this genetic risk factor is definitely an advance in understanding the disease and expressed well by Rudy Tanzi, of the Mass General Institute of Neurodegenerative Disease in Cambridge, Mass.
'It is still necessary to know of every gene that is involved in AD risk," said "No matter what the effect on risk, each fills in a piece of the puzzle regarding the biological underpinnings of the disease.'