Duke University Medical Center researchers have identified a group of chromosomes that could be responsible for controlling the onset of Alzheimer’s or Parkinson’s diseases.
The finding is significant because until now, geneticists have focused on finding individual genes that control the risk of developing a disease. However the age at which genetically-predisposed individuals develop symptoms of the disease is equally important. This is according to a study published in the April 2002 issue of American Journal of Human Genetics.
“Risk is only one mode of genetic expression. Age at onset of disease can also be genetically influenced. Understanding the regulation of onset will open new avenues of research that could one day make it possible to delay onset beyond an individual’s normal lifespan,” said Margaret Pericak-Vance, Ph.D., director of the Center for Human Genetics at Duke and principal investigator of the study.
The Duke research team conducted a genetic screening of 449 families that have multiple members diagnosed with Alzheimer’s disease, and 174 families with multiple family members that are diagnosed with Parkinson’s disease.
The age of onset of Alzheimer’s disease is generally considered the time at which an individual begins to suffer short-term memory loss or disorientation in a manner serious enough to interfere with daily activities. The average age at onset for individuals in the study with Alzheimer’s disease was 72.8 years old and 60.1 years old for Parkinson’s disease.
Clinically, a significant number of Alzheimer’s disease patients develop signs of Parkinson’s disease, such as rigidity and gait abnormalities.
Past research by Duke and other researchers show that chromosome 10 could contain a risk gene for Alzheimer’s disease. The new Duke research shows that chromosome 10 could contain an age at onset gene that affects both Alzheimer’s and Parkinson’s diseases. They also identified strong evidence for an age at onset gene for Parkinson’s disease on chromosome 1.
“We tested the hypothesis that in some cases the same gene controls onset in two distinct neurodegenerative disorders that share some common features: Alzheimer’s disease and Parkinson’s disease. We found evidence supporting this hypothesis on chromosome 10,” Pericak-Vance said.
Researchers also found evidence for age at onset linkage to chromosomes 4 and 8, however, the linkage was not as statistically significant.