What Causes Parkinson’s Disease?
The symptoms of Parkinson’s are thought to stem from a loss of dopamine-producing brain cells that normally control movement, but what causes these cells to die off in the first place is difficult to answer. Toxins and other environmental factors can play a role, but so does genetics. In some cases Parkinson’s is primarily due to genetics, in other cases it is largely environmental, and most of the time it’s a mix of the two.
About 1.5 million Americans have Parkinson’s and about 50,000 new patients are diagnosed each year. Many of us have seen loved ones suffer through years of trembling and muscle weakness knowing that things will eventually get worse because there isn’t a cure.
But that’s where science comes in. The primary goal of the more than 800 Parkinson’s genetic association studies published to date is to identify the genetics underlying this condition so that we can understand what goes wrong and develop therapies.
Dozens of genetic factors have been linked to Parkinson’s disease and some of these findings meet 23andMe’s internal scientific standards and are reported to customers. We’ve been providing genetic results for Parkinson’s to customers since 2008 and last week we added five more factors to our report.
(See below for a timeline of 23andMe’s contributions to Parkinson’s research and history of providing customers with genetic results for Parkinson’s.)
Our first report on Parkinson’s disease included the G2019S mutation in the LRRK2 gene. Only about 1-2% of the general population develops Parkinson’s, but studies have shown that about 50% of people with the G2019S mutation will develop the disease in their life time. We later added the G2385R mutation in the LRRK2 gene, which is applicable to people with Asian ancestry and is associated with about three times higher odds of developing Parkinson’s.
In April of 2011 (and timed for Parkinson’s disease awareness month) we added variants in the GBA, SNCA and MAPT genes to our genetic report on Parkinson’s. The N370S mutation in the GBA gene is associated with about four times higher risk of Parkinson’s and may exert its influence by making cells more sensitive to toxins. The rest of the factors reported by 23andMe, including the SNCA and MAPT variants and versions of PARK16, DGKQ, BST1, STK39 added last week, have much smaller effects on risk for the disease but are much more common in the population than LRRK2 or GBA mutations.
Alongside reporting genetic results to customers we’ve also been carrying out research on Parkinson’s. Over 7,000 individuals have enrolled in our Parkinson’s Disease community and with their help and the participation of other customers we’ve discovered new genetic factors for Parkinson’s that we report back to our customers. We’ve also identified a genetic factor in a gene called SGK1 that may protect individuals with risky versions of LRRK2 from developing Parkinson’s. We’re currently partnering with other researchers to see if this initial finding can lead to new treatments.
People with Parkinson’s disease still suffer too much, but it’s clear that research efforts over the last decade are getting us closer to understanding what causes this disorder. It’s also becoming clear that early detection can help delay the progression of Parkinson’s and that’s good news all around. There are many more outstanding questions, for instance understanding how genetic and environmental factors interact, and hopefully in time we’ll find some answers. The 23andMe community has progressed Parkinson’s research tremendously and we hope that you’ll continue to give us your hand in the years ahead.
The author’s paternal grandfather passed away from Parkinson’s disease in 2005. He was deeply loved and in her thoughts as she wrote this piece.