A century-old question--whether Parkinson's disease can be passed down from generation to generation--appears to be solved. In a report in the 15 November issue of Science, researchers present compelling evidence that the disease, for some families at least, is in the genes.
Geneticist Mihael Polymeropoulos of the U.S. National Institutes of Health's Center for Human Genome Research and his colleagues analyzed blood samples from 28 members of a large Parkinson's-prone family whose ancestors originated in a small town in southern Italy. They found a region in chromosome 4 that is strongly linked to the disease. Polymeropoulos and his colleagues are now trying to identify the specific gene or genes in the 16 million base-pair region they've implicated.
The discovery traces its roots to 1983, when co-authors Roger Duvoisin and Lawrence Golbe of the Robert Wood Johnson Medical School in Piscataway, New Jersey, published the results of a study on twins showing no evidence of a genetic cause for Parkinson's, which is marked by slow movements, rigid muscles, and involuntary tremors. Those findings propelled researchers on a hunt for environmental clues ranging from herbicides to head trauma. But two patients with extensive family histories of the disease inspired the researchers to rethink the earlier study. Tracing the patients' genealogies, they found that both were linked to a single person living in southern Italy more than 2 centuries ago. It took 8 or 9 years to collect the samples from family members living everywhere from New York City to Argentina. But the researchers' persistence has now paid off handsomely.
The mapping is "a very major discovery" which will spark intensive new research into other families with multiple cases of Parkinson's, says Demetrius Maraganore, a neurologist at the Mayo Clinic in Rochester, Minnesota. He says it's likely that further research on other families will implicate other genes, as well as environmental triggers.
Duvoisin agrees. "Now we know what steps we have to take," he says. "We're not just casting about looking for an unknown environmental factor. There's a light at the end of the tunnel."