Published on: August 21, 2012
by Dr. Umesh C. Yadav for The Daily News:
A rare gene mutation may protect from Alzheimer’s disease.
Normally, genetic mutations are considered bad and are associated with the loss of functions. But scientists have found a rare form of mutation that may actually be beneficial in Alzheimer’s patients.
The change in the arrangement of DNA letters in the gene, called mutation, occurs during replication of DNA because of many reasons leading to the altered protein derived from that gene. Many genetic diseases result from mutations in the DNA.
In the brains of Alzheimer’s and dementia patients, deposition of a compound called beta-amyloid in the form of amyloid plaque has been associated with disease severity.
This mutation has been identified in a gene that codes for amyloid precursor protein, or APP, which allows the protein to degrade itself before it matures into active beta-amyloid and prevent it from depositing and causing Alzheimer’s disease.
Previously, scientists found several mutations in this gene that were actually harmful, stabilizing the beta-amyloid proteins and causing increased levels in brain. Those mutations were associated with the inherited form of Alzheimer’s appearing early in life as compared to the usual Alzheimer’s that appear in later phase of life.
Dr. Kari Stefansson and his colleagues at deCODE Genetics in Reykjavik, Iceland, analyzed genome data from 1,795 inhabitants of the Iceland and found that nearly 0.45 percent of the population had this rare mutation in the APP gene. The scientists found that 0.79 percent of the population older than 85 years of age had this mutation, of which 0.13 percent had Alzheimer’s while the other 0.67 percent did not have the disease. The study was published in the journal Nature in July.
The scientists also predict that this mutation may also protect from memory loss and other declines in cognitive functions in people who do not develop Alzheimer’s, because, in the population that had the rare mutation, cognitive functioning was significantly better as compared to those who did not.
A prevailing but controversial theory that beta-amyloid may be the primary cause of Alzheimer’s disease has found strong support in the present discovery of the rare genetic mutation.
A number of clinical trials aimed at delaying the breakdown of myloid precursor protein into mature beta-amyloid or preventing amyloid deposition had unvaryingly failed, raising questions about beta-amyloid theory.
Now, scientists argue that the reason for the failure could have been the selection of wrong patient pool where too much irreversible damage had already been done to the brain.
Dr. Stefansson predicted that this discovery may attract pharmaceutical companies to accelerate research to find a new drug that could work in similar fashion. However, it will be interesting to know whether the failed drugs would work if tried in the early patients before the damage become irreversible or those predisposed to Alzheimer’s.
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