For the first time, scientists have pinpointed the location of a gene they believe is responsible for some cases of Parkinson’s disease. Their discovery provides strong evidence that a genetic alteration is capable of causing the disease.
The impact of the current finding is to show that a single gene alteration can cause the disease. The next step will be to find and identify the specific gene involved, which is located somewhere within a region of DNA on the long arm of chromosome 4. Learning the gene’s exact location and isolating it may eventually lead to genetic testing that will help early diagnosis and treatment. Learning what the gene is and how it works may help researchers design treatments for all forms of Parkinson’s disease–not only inherited cases, but also those with no familial link
“We don’t know that this gene affects all people with Parkinson’s disease, since we’ve only found it in one family,” says Dr. Duvoisin. “But this is a very important step. We now know what we have to do to understand what causes the disease.”
Until recently, most scientists believed the disease was due almost exclusively to environmental factors such as drugs or toxic chemicals, although in most cases, no environmental cause has been identified. But many people appear to have an inherited susceptibility to the disease.
The researchers identified the gene region by studying the DNA of 28 members of a large Italian family containing almost 600 people. People in this family, some of whom migrated to the United States between 1890 and 1920, can trace their ancestry to a single couple who lived in Italy in the 18th century. More than 60 family members on both sides of the Atlantic have been diagnosed with Parkinson’s disease.
The gene mutation in this family is inherited in a dominant fashion, meaning that people who possess the mutation have a 50 percent chance of passing it on to their children. Only one parent must carry the mutation for the disease to appear in a couple’s offspring. The symptoms of familial Parkinson’s are identical to those in families with no history of the disease, except that the inherited form sometimes develops earlier in life.