Given the recent FDA shutdown of the 23andMe company, many Parkinson's disease patients have been asking if getting a genetic test will impact their care.
Currently there is no reliable biomarker for Parkinson’s disease, with the exception of the small number of families who carry known genetic mutations. If scientists can manage to develop treatments to retard the progression of symptoms, then early identification through biomarkers will be a critical part of early treatment.
We have come a long way since James Watson and Francis Crick discovered the double helix structure of DNA in 1953. Genetics and genetic testing have become widely available, and there has been a race to identify all of the possible Parkinson’s disease genes. We have confirmed that in five to 10 percent of those diagnosed with Parkinson’s disease there will be an identifiable abnormality within their DNA. These alterations in the genetic code, in most cases, can be confirmed by a simple blood test. The current DNA abnormalities are what we have uncovered today. However, there may be many more genetic mutations discovered in the near future. Genetics have provided important clues to the potential underlying causes of Parkinson’s disease.
For example, a mutation in the gene that codes for the protein alpha synuclein (SNCA) will lead to a specific form of Parkinson’s disease. This observation proved vital to the field and has implications beyond the genetic forms of Parkinson’s disease. Accumulation of this protein in the brain has been consistently observed across all cases of Parkinson’s disease, therefore the ability to trace it back to a single gene defect has been a critical discovery. There have been other genes such as PARKIN, LRRK2, and PINK1 that all have been linked to the development of Parkinson’s disease, and all of these genes have pointed scientists toward possible mechanisms underpinning the disease and also to potential drug targets.
Sergey Brin, one of the co-founders of the internet giant Google, changed the world of Parkinson’s disease genetics in a profound way. Now, you might say how in the world did a young computer programmer change the entire field of neurogenetics and genetic testing for a generation of patients? The story as it turns out, is very personal. After a visit to the University of Maryland, Brin discovered that his mother Eugenia had Parkinson’s disease. Following this revelation, Brin himself underwent genetic testing. His blood revealed a small mutation in the genetic code known as the LRRK2 mutation. LRRK2 is currently the most commonly known genetic form of Parkinson’s disease. Following his own genetic testing, Brin has been famously quoted as saying that he regards his own genetic code to be no different than a computer code. If it is flawed, we just need to fix it. Brin and his wife started a company called 23andme, and this company has offered large-scale genetic testing for Parkinson’s disease but without genetic counseling. Genetic counseling is typically provided by trained professionals who explain to patients and families the implications on one’s life of unmasking an underlying genetic mutation. Would you live your life differently if you knew you were destined to suffer from a devastating disease?
The lack of genetic counseling from the 23andme company set off a global controversy. The need for it can be illustrated by an important anecdote from another neurological disease, Huntington’s, and a pair of sisters named the Wexlers. The Wexler story began when their father was diagnosed with Huntington’s disease. Along with Woody Guthrie’s family, they started a movement in the late 1960s to raise money for research. This movement yielded the founding of the Hereditary Disease Foundation. Through Wexler funding and the services of multiple scientists from around the globe, the gene for Huntington’s disease was identified in 1984 by James Gusella, a researcher based at Massachusetts General Hospital.
*The bottom line in genetic testing for Parkinson's disease is that (at the current time in 2013-2014) your gene status will not impact your treatment. In the future, early identification of Parkinson's disease cases by gene testing may be key to delivering very early treatments, before the disease has had time to progress. Remember, many people may choose "not" to know their gene status fearing that their gene status will change how they will live their life (even if you have a Parkinson's gene there is no guarantee it will manifest).
Much of the above blog post is drawn from Parkinson's Treatment: 10 Secrets to a Happier Life and picture from newsatjama.jama.com.