Tag Archive: Parkinson’s disease


Ok, let’s start off with the basics:

Parkinson’s disease is a neurological disorder where nerve cells that make dopamine are destroyed. Dopamine is an important neurotransmitter and without it, nerve cells are unable to properly send messages to other parts of the body. Eventually, the destruction of dopamine-producing cells leads to a loss of muscle function that gets worse over time. The typical symptoms of Parkinson’s are shaking and difficulty with walking, movement, and muscle coordination.  Unfortunately, not a lot is known about why these nerve cells waste away in the first place.

In gene therapy, a gene variant is used to alter the function of a cell or an organ. The way that genes are transferred into cells is pretty interesting: the gene is put into an inert virus, which is then injected into the target cell to deliver the gene.

Now, a new large-scale study suggests that a type of gene therapy (called NLX-P101) may be able to improve Parkinson’s symptoms. The gene that was targeted is called GAD (stands for glutamic acid decarboxylase). This gene produces a chemical called GABA (stands for Gamma-aminobutyric acid), which is a neurotransmitter than inhibits the excessive firing of neurons seen among Parkinson’s patients. From an interview in ScienceDaily with one of the researchers, Dr. Matthew During:

“In Parkinson’s disease, not only do patients lose many dopamine-producing brain cells, but they also develop substantial reductions in the activity and amount of GABA in their brains. This causes a dysfunction in brain circuitry responsible for coordinating movement,” explains Dr. During.

So, what they’ve done is inject a fully-functioning GAD gene into the brains of Parkinson’s patients. Those that were injected showed substantial improvement compared to individuals that did not receive the treatment.  

References

LeWitt, P.A. et al. (2011). AAV2-GAD gene therapy for advanced Parkinson’s disease: a double-blind, sham-surgery controlled, randomised trial. Lancet Neurology in press.

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Last month, Diane Rehm of NPR had an interesting dicussion on DNA sequencing and personal genomics (you can listen to the 51-minute show in its entirety here). The completion of the human genome project in 2003 held the promise of using an individual’s genetic information to optimize their treatment. One example that the show uses is that of Google co-founder Sergey Brin, who has discovered that he possesses a mutation in his LRRK2 gene that may increase the likelihood of him developing Parkinson’s disease later in life. Nevertheless, the program’s guests demonstrate that there are still significant hurdles to truly effective genetic-based “personalized medicine.” A couple of interesting points from the show:

1. The cost of genome sequencing has declined greatly over the past decade or so. Some companies, like 23andMe (which was founded by Brin’s wife Anne Wojcicki) will sequence parts of your genome for about $500. For those of you interested in getting your entire genome (all 3 billion base pairs) sequenced, you can, with the consent of your doctor, send samples to companies like Illumina for the bargain price of about $20,000 (if you think that’s a bit pricey, consider that a decade ago it would have cost you about $1,000,000).

2. One of the guests, Dr. Arthur Caplan, provides examples of how people can react to genetic information. The most striking is the case where a father wanted to have his 13-year-old daughter tested for mutations associated with breast cancer risk (the family had a history of the disease). The father stated that if his daughter tested positive for one or more of the mutations, he would have her breast buds surgically removed to make sure that she did not suffer the same fate as other family members (Dr. Caplan does not tell us what ultimately happened with this case). One of the points that Dr. Caplan makes with this and other examples is that, although genetic screening can provide useful information, external environmental factors interact with genes in very complex ways, which currently makes it very difficult to assess an individual’s chances of developing conditions like cancer based simply on the presence or absence of particular genetic mutations (but see Personalized medicine in 10 years?).

3. All three of the guests discuss the issues surrounding genetic privacy. Once you submit samples for genetic sequencing, how can you be sure that your information will be kept private? If it is not kept private, what can it be used for? The importance of this issue is revealed by the signing of the Genetic Information Non-discrimination Act (GINA) by president Bush in 2008, which prevents discrimination based on genetic information when it comes to insurance and/or employment.  

Check out the show and hit us up with your comments: Would you want your genome to be publicly available? Would you even want to know what your genome looked like? If you had the information, what would you do with it?

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