Is Parkinson's Disease Inherited?

Is Parkinson's Disease Inherited? That was the question I asked back in 1993 to one of my neurobiology professors, a Parkinson's expert and researcher. On that day he told me definitively, "No." Even back then, 15 years ago, I suspected he was wrong. I really thought that there was probably some sort of genetic connection that was not understood at all.

Today scientists believe that there is a genetic connection, in fact, they have identified several mutations that can give rise to Parkinson's Disease. That being said, scientists estimate that less than 25% of all PD cases are genetically linked and they also believe that not all those with the gene mutations develop PD.

The information about familial (genetic) Parkinson's is actually quite extensive now. (Isn't it amazing what we have learned in 15 years?) Now scientists have numerous genetic suspects. Here is a summary of some of the most prevalent.

1. LRRK2 (leucine-rich repeat kinase)- This gene is a dominant gene, meaning that a person only needs one copy of this gene in order for it to be expressed in an individual. Scientists have identified at least 20 mutations in families that exhibit late onset PD. This genetic "flaw" is the most common form of Parkinson's as far as scientists know at this time. This is the genetic mutation that Sergey Brin identified in his gene make up.

2. GIGYF2- Mutations on this gene are known to cause a single amino acid substitution in the protein this gene encodes for. What does this mean? Essentially one link in the chain of a protein is swapped out for a different kind of link which then leads to the protein being formed incorrectly. The interesting aspect of this genetic mutation is that it is also assoicated wiht Insulin production. Scientists aren't sure, but they think there might be a connection between PD and Insulin and thereby possibly diabetes. There are now ongoing studies to try to piece together how these diseases are inter-related, if at all.

3. A study of a handful of French families with Parkinson's uncovered that duplications in the gene that creates the alpha-synuclein protein may cause PD. It is known that alpha-synuclein protein is a major component of Lewy Bodies, an abnormal "clump" of proteins that form inside nerve cells. The French study showed that a duplication of this gene caused PD similar to other types of PD, but that a triplication of the same gene caused a devastating form of PD with an average onset of 34 and a rapid decline into dementia. I know from reading other articles in the past that there is a big push to look into whether or not limiting or removing "extra" alpha-synuclein could slow the progression of PD.

4. LI66P mutation- This particular mutation is linked to an early onset form of familial PD. It is thought that this mutation disrupts DJ-1 protein folding. By disrupting folding of a protein this mutation would essentially render the DJ-1 protein useless and upset the functions that it performs in the body. LI66P is recessive so someone would have to receive the same gene mutation from both parents in order to have its affects exhibit.

There are several other genetic mutations that are linked to PD, but I think 4 is enough for any one blog posting. Just because someone has one of these mutations does not appear to be enough to develop Parkinson's Disease. It is thought that the genetic mutations, at least for the most part, make someone more susceptible, but that some sort of environmental trigger needs to occur as well for a person to develop the disease. The exact mechanisms are not known.

So I now have a question- if PD ran in your family would you want to know if you had any of these genetic factors if there was nothing to do to prevent the disease? PD does run in my family, my Mom, my Grandpa, but as of now I have no desire to have any genetic tests done. That may change in the future especially if preventative methods are developed. Only time will tell.