Research initiative aims to delve into the genetic roots of Parkinson’s disease

When Mel Mitchell was diagnosed with Parkinson’s disease in 2013, he wasn’t all that interested in learning what caused the condition.

“I have to be honest,” he said. “I just wanted to figure out how to deal with it.”

But after retiring from his human resources job, Mitchell started volunteering with the Minnesota chapter of the Parkinson’s Foundation. The work made him more curious about the causes of the disease. When he learned about how researchers were using genetic testing to develop new treatments and therapies, Mitchell, 72, told himself that if the opportunity ever arose to take part in a study, he’d gladly step forward.  

In 2019, Mitchell learned that the foundation was sponsoring PD GENEration (PD stands for Parkinson’s disease), a national initiative offering genetic testing for clinically relevant Parkinson’s genes.

The tests were free of charge at select Parkinson’s clinics around the nation, including the Struthers Parkinson’s Center in Golden Valley, not far from where Mitchell lives. Researchers plan to one day use the results to help develop improved treatments and personalized medicine to treat Parkinson’s.

“When the opportunity to get involved in PD GENEration came along,” Mitchell said, “it struck a chord for several reasons. It piqued my curiosity. It seemed like an easy way to find out more, to help out, to take action.”

Nance, who is trained in neurology and genetics, is excited about PD GENEration’s promise for the treatment of Parkinson’s.

“Research in this area has been slowed down by the lack of genetic testing,” she said. There are about two dozen genes associated with Parkinson’s. The study will be testing for seven of the most common. 

“By identifying people who have specific genetic forms of PD we may find that certain genetic forms of the disease are more common than we think,” Nance said, adding with a rueful chuckle: “I have been waiting for 20 years for genetics to be relevant to PD.”

Even though testing revealed that, rather than having a rarer genetically linked form of the disease, he had “just run-of-the-mill Parkinson’s,” Mitchell said he’s glad he took part in the study.

“I think I have a responsibility to take part in research,” he said. “Today’s research is tomorrow’s cure.”

Developing targeted treatments with genetics

Using genetic information to design medicine targeted to treat specific forms of disease is not a new concept, said James Beck, the Parkinson’s Foundation senior vice president and chief scientific officer. 

Advances in genetic research have made it possible to discover specific genes linked to individual diseases, Nance said. “We have the tools available right now to look at the genetic aspects of just about anything. The gene genie is out of the bottle, and Parkinson’s researchers are starting to take advantage of that.”

Of the two dozen genes linked to Parkinson’s disease, two specific mutations stand out, Beck said.

“One is called LRRK2. The other genetic mutation is in a gene called the GBA gene. These are the two most common in this long list of mutations. Right now pharmaceutical companies are beginning to develop therapies to help treat PD in people who have been found to have those mutations.”

Like Mitchell, the majority of people with Parkinson’s do not appear to have a specific genetic cause to their disease.

“We now think that 10 percent of people with PD have a genetic cause,” Nance said. In other people, the cause for their Parkinson’s may be environmental, she added. In still others, the disease may be idiopathic —or spontaneous, with no known cause. 

“There are people with clear environmental risks for Parkinson’s, like welders,” Nance said. “The VA has also acknowledged that exposure to Agent Orange is also a risk for developing PD.”

Until recent decades, Parkinson’s was thought to be a disease that afflicted only older people. “The average onset is between 60 and 65,” Nance said. “But every so often you see a 30-year-old or a 40-year-old with PD.” In those cases, she continued, “You think, ‘Is this really the same disease?’”

The answer, Nance explained, is that there are “multiple causes of PD. Now we have the tools available to tease out the genetic forms of Parkinson’s. But it is still hard to tease out the environmental forms.” She believes that widespread genetic testing of people with the disease might actually hold treatment options for people like Mitchell, as well.

Beck said that it’s time for a new, large-scale Parkinson’s study.

“For too long we’ve been looking at PD in the wrong way,” he said. “It’s been 50-plus years since levodopa, the main drug for treating Parkinson’s symptoms, was approved. There has not been a huge change in treatment options since that time.”

He hopes that this new genetic research will ultimately unlock information that could forever change treatment options and the long-term outlook for people with Parkinson’s disease.

More results mean more progress

PD GENEration backers like Nance and Beck hope that more people with PD will follow Mitchell’s lead and sign up for genetic testing. Though the percentage of people with genetically linked forms of Parkinson’s is thought to be low, there is a possibility that by gathering information from thousands of participants, researchers may actually be able to learn more about how to best treat individuals with non-genetic forms of the disease.

“Maybe by doing a big study like this one, we can start to recognize characteristics that suggest somebody is more likely to have a genetic cause for their disease,” Nance said. “Maybe in the end we aren’t going to be testing every 90-year-old who walks in the door with a little bit of a tremor.”

And because genetic testing still isn’t common in Parkinson’s treatment, researchers actually don’t have a clear picture of the origins of most cases of the disease, Nance said. By gathering results from thousands of people with the disease, they hope to bring Parkinson’s into sharper focus.

“It may turn out that this treatment we are proposing for LARRK2 PD may help people with other forms of PD.”

The enrollment goal for the PD GENEration initiative is 15,000, Beck said. “So far our study has found that 17 percent of participants have a genetic form of PD. That number might not remain as high as we continue the study. We hope to find 1,500 people with a genetic form of PD.”

“We have had a tremendous interest in this study. In fact, there is a bit of a waiting list at Struthers,” Beck said. Parkinson’s Foundation officials are working to increase capacity, but the waiting list now stretches into January. “Our hope here is that by looking closely at individuals who have genetic mutations for PD we can develop, through the pharmaceutical industry, a cure or a new way to treat PD.” 

Mitchell is pleased to hear hopeful talk like this. Even if new Parkinson’s treatments, or the promise of a cure, are decades away, he’s pleased that he’s been able to do his part.

“PD GENEration is really about applying science to the disease in a way that hasn’t been done before,” he said. “This is an opportunity to get a lot of people involved and discover what our genes say about this disease.”