Research scientists at Stanford's School of Medicine and Lucile Packard Children's Hospital claim that they might have found a possible cause for mental retardationin Down syndrome, in a gene that causes neurons in the brain to stop functioning normally, affecting attention, and memory.
The researchers in US have explained in journal Neuron, that they have identified a gene that, if over-produced, could cause certain brain cells to stop working properly. They further stated that they would now concentrate on trying to figure out the mechanism that triggers this response. They also added that they hope that this would ultimately lead for finding a way to reduce the activity of the gene so as to stop the mental decline or at least to try and reverse the effects.
It was explained that people with Down's syndrome have three copies of chromosome 21, instead of the normal two, which is known as trisomy 21. Many of the patients with Down's syndrome were also found to develop dementia by the age of 40, similar to early-onset Alzheimer's disease. It was also stated that in both Down's syndrome Alzheimer's of early onset, brain cells, or neurons, which are responsible for learning, memory, and attention, waste away and die.
Professor William Mobley, director of the Neuroscience Institute at Stanford University, and the lead researcher of the study said, "We've been interested in those neurons and why they get sick for some time." He explained that his team studied mouse models, and found that mice with three copies of a gene called the 'amyloid precursor protein gene', or App, which was present on the 21st chromosome, had larger neurons than the mice with two copies of the gene.
This discovery has led the researchers to believe that App could be causing the cell death by disrupting the signals between cells that is essentially needed to keep them healthy. He further mentioned that though it is known that a mutation in the App gene is responsible for early onset Alzheimer's disease, having three copies of the gene could somehow have a harmful effect on the brain.
Professor Mobley said, "There are all of these genes on chromosome 21, and undoubtedly all of them contribute in some way to these changes that you see in people with Down's syndrome. The challenge is to say can you find specific abnormalities linked to specific genes." Stating that as the next step, the mechanism for this process should be found, and then it should be seen if there is any way by which these manifestations by the gene can be 'turned down', He said, "If we can decrease the expression of this gene, we may be able to provide something more than supportive care to people with Down's syndrome."
Professor Elizabeth Fisher, of the Institute Neurology, UCL, said, "This is a very interesting paper. This may be some way towards an explanation of why people with Down's syndrome develop the hallmark brain signs of Alzheimer's disease."