TORONTO - Canadian scientists have discovered that a particular gene appears to be essential for protecting the brain as people age and that missing one copy may boost the likelihood of developing Alzheimer's disease or other neurodegenerative disorders.
In a study of genetically altered mice, researchers at Toronto's Hospital for Sick Children determined that mice with only one copy of the brain-protective p73 gene -- instead of the normal two copies -- exhibited the physical and behavioural traits of Alzheimer's disease.
The rodents' brains contained tangles, which are believed to clog up the pathways between brain cells, impairing their ability to learn and remember. The animals' co-ordination was also affected.
"Those mice when they were young seemed to be just the same as mice that had both copies of the gene," said co-principal author Dr. David Kaplan, a senior scientist in the cell biology program at Sick Kids.
"But when we aged the mice to ages equivalent to older people, say over 65 years of age, then the mice with one copy of the p73 gene started to show all the hallmarks of a very aging, very old human brain," Kaplan said Wednesday from Israel, where he was attending a research meeting.
"So what this gene does, we think, is it helps protect the nerve cells from dying."
The study is published in the September issue of the journal Neuron.
Kaplan said an earlier study from the University of British Columbia determined that an estimated 10 per cent of the population has only one copy of the p73 gene, while research from Columbia University has suggested there may be a link between people with just one copy of the gene and an elevated risk of Alzheimer's disease.
"It's not proven that those people will be the ones that are more susceptible to Alzheimer's or Parkinson's or ALS," he said. "What we now have to do is look precisely at Alzheimer's patients and at people without Alzheimer's and see if there really is an association or not."
The Sick Kids research team, which is jointly led by Kaplan's wife Dr. Freda Miller, has begun collecting DNA samples from people with Alzheimer's and those without the disease so they can compare the number of p73 copies in the two groups.
If a strong link does exist, the work could lead to a test to detect the genetic anomaly in children and therapies to try to prevent the development of the disease.
"We think (p73) might be a cell death monitor for your nerve cells," said Kaplan, noting that the protein expressed by the gene is also known as p73.
"So p73 might be something that we need to keep our nerve cells alive and if we don't have enough of it, it might make your brain more susceptible to things like Alzheimer's disease or Parkinson's and aging."
"The goal then would be to find ways to increase the levels, hopefully (using) just a drug or a pill you can take, that will increase the level of this protein, that will then keep our brain from aging and keep it from getting Alzheimer's."
The Alzheimer's Society of Canada estimates that 450,000 Canadians over age 65 have Alzheimer's or another degenerative brain disease.
