Some Cases of Parkinson’s, Alzheimer’s Linked to Common Gene
April 27, 2004
A gene known to have a hand in Alzheimer’s disease may contribute to some cases of Parkinson’s disease as well, according to findings discussed today at the annual meeting of the American Association of Neurology in San Francisco.
University of Rochester scientists and area patients who have Parkinson’s disease played a role in the discovery, which comes through a national Parkinson’s study known as PROGENI – “Parkinson’s Research: The Organized Genetic Initiative.” The study included 600 sibling pairs from 58 sites around North America, including 21 people from 14 families in the Rochester area.
The results were announced by a team from the Indiana University School of Medicine in Indianapolis led by Tatiana Foroud, Ph.D., associate professor of medical and molecular genetics, who heads the PROGENI study nationally.
In the PROGENI study, scientists collect blood samples from brothers and sisters with Parkinson’s disease in an effort to track down genes that play a role in the disease. Doctors have connected a handful of genes to some cases of Parkinson’s, but the causes of most cases are unknown. The PROGENI team has had several previous successes, including identifying a greater role for a gene on chromosome six that had been thought to only cause some cases of early-onset Parkinson’s disease; this gene now appears to also be important in some cases of more typical Parkinson’s disease in other individuals as well. The PROGENI team has also begun work to identify a gene on chromosome two that appears to be key to the disease’s development in some families.
In the latest finding, the team discovered that an area of chromosome 10 previously linked to late-onset Alzheimer’s disease might also play a role in Parkinson’s disease.
“There are several traits that characterize both diseases,” says Roger Kurlan, M.D., the neurologist who led the Rochester portion of the study. “Since there are a limited number of mechanisms by which nerve cells die, it’s not completely unexpected that some genes involved in the process of neurodegeneration are involved in both conditions.”
Alzheimer’s and Parkinson’s diseases are the two most common of a class of diseases known as neurodegenerative diseases, where brain cells sicken and die. There’s more overlap than people realize, doctors say. Foroud says that about one of every four patients with Parkinson’s disease has some dementia, while about one of every five patients with Alzheimer’s disease has some classic symptoms of Parkinson’s. Only a small percentage of Alzheimer’s and Parkinson’s cases have been linked to specific genes thus far.
“The idea that there may be some common pathways for these two diseases is compatible with what we see clinically, and what we actually see happening in the brain,” says Foroud. “If you look at people who have one of these diseases, you will sometimes find evidence of both diseases.”
The scientists are studying brothers and sisters who have been diagnosed with Parkinson’s disease. Since siblings oftentimes do not live near each other, the study is being done at nearly five dozen study sites across North America. The study, funded by the National Institutes of Health, is being coordinated by the Parkinson Study Group, which is based at the University of Rochester. Recently the NIH decided to extend the study for another five years.
In addition to a genetic analysis of people with Parkinson’s disease, scientists are also taking a detailed look at the places where participants live and work, to look at environmental factors that may be related to the disease. For instance, some studies have shown that farmers and others who live in agricultural areas are more prone to developing the disease than others, while basic research has shown how pesticides can cause the equivalent of Parkinson’s disease in animals.