Drosophila Model of Parkinson's Disease

I glue fruit flies to tiny sticks made of tungsten, attach the free end to a magnet, and run a program that handles a 360-degree flight simulator and controlled sprays of odor to see what they do...

NOTE: This is NOT Dr. Frye's equipment at UCLA. This is, however, an example of how to perform behavioral tests on Drosophila.

May 21, 2009

Parkinson's Disease Poster Day!

Click here to read the text on my poster! PDPoster

May 4, 2009

I've signed up to do a poster presentation with my ideas for the Parkinson's Disease Symposium on Thursday, May 21. This is an incredibly impulsive, yet exciting opportunity! My hope is that I'll get some good feedback on my ideas and put my name and lab's name out there for the Parkinson's community at UCLA to recognize in the future when I start writing and trying to publish.

This means more research and more notes!

Shulman JM et al: From fruit fly to bedside: Translating lessons from Drosophila models of neurodegenerative disease.

Basic Idea:
Drosophila neurodegenerative models show promise because they use the same machinery (although less of it than humans) and also behave in complex ways with this machinery much like humans. Their genes are thoroughly studied, and they grow fast. Also, in PD-induced flies, there's a particular uncanny resemblance to the human PD form. "Although still a relative newcomer to neurodegenerative disease research, Drosophila is rapidly making signiȚcant contributions."

Beal MF: Experimental models of Parkinson's disease.

Basic Idea:
MPTP toxicity (in primates and other animals most like humans) would be the ideal animal model for PD. It's also important to note that Beal wrote a number of points that give Drosophila the advantage over other animal models. They are a more accurate human PD model, for example, because mouse models so far have not proven to have PD pathology specifically in their DA neurons in their substantia nigra. Drosophila, on the other hand, HAS had DA-neuron specificity with the alpha-synuclein models. They're also well-characterized genetically, and only one gene is necessary to induce PD. Rapid aging of Drosophila makes for less wait-time for adult-onset PD symptoms.

Doty et al: Olfactory dysfunction in Parkinsonism: a general deficit unrelated to neurologic signs, disease stage, or disease duration.

Basic Idea:
81 PD patients who show minimal dementia were tested for smell detection and identification. Relative to matched controls, the PD patients exhibited consistent and marked decrements on both types of olfactory tests. There were no specific odors or longitudinal changes throughout the experiment, and scores were INDEPENDENT of disease stage and duration. The data support the hypothesis that the olfactory deficit of PD is a general and stable one which likely occurs early in the disease process.

April 30, 2009

Some notes and ideas that I wrote up today:

Gerlach et al. Early Detection of Parkinson's Disease: Unmet Needs

Basic Idea:
This is a discussion of the importance of finding good biomakers for Parkinson's disease (PD) to help diagnose the disorder. "No absolutely safe diagnostic test is currently available."

Some key points:
Biomarkers are important in the study of diseases because they give insight into what is normal and what goes wrong in a given disease. Biomarkers are indicators for the diagnosis and classification of a disease and the progression of a disease, both when a patient is deteriorating or improving.

For PD, much of the known biomarkers are neither sensitive nor specific enough to easily diagnose patients with PD (especially in the early stages of PD). The only known fool-proof diagnosis for familial PD is with a genetic test, but biomarker for sporadic Parkinson's disease lack adequate information on the sensitivity and/or specificity of the tests.

Note: By testing to see whether Parkinsonian Drosophila will exhibit hyposmia/anosmia, it may prove that this particular symptom is a universal biomarker for PD.

Feany et al. A Drosophila model of Parkinson's disease

Basic idea:
Normal and mutant forms of alpha-synuclein are expressed in Drosophila, and the mutant flies produce adult-onset loss of dopaminergic (DA) neurons, filamentous intraneuronal inclusions (consisting of alpha-synuclein) and locomotor dysfunction.

Some key terms to know for this paper:

What they found: Expression of human alpha-synuclein in flies show three key features of the pathology of Parkinson's disease.
  1. Adult Onset. PD is very rarely diagnosed in young people. The destruction of dopaminergic neurons in the substantia nigra also start happening long before symptoms show. Tremors and other obvious PD biomarkers begin to happen when up to 80% of the healthy DA neurons are gone.
  2. Symptoms are restricted to the nervous system. When A30P and A53T are expressed in the mutant flies, they eventually develop locomotor dysfunction, and don't show side effects outside of the known Parkinsonian symptoms.
  3. Anatomical specificity. Alpha-synuclein inclusions could be found in the brains of aged flies by immunostaining. Just like human diffuse Lewy body disease, the brains of the transgenic flies show these Lewy bodies and Lewy neurites, and the wildtype brains were inclusion-free. Retinal degenerationg also occurs by day 10 when alpha-synuclein is expressed in the eye, and day 30 for transgenic flies.
Note: The adult onset of both motor dysfunction and alpha-synuclein inclusions makes it possible for young transgenic Drosophila to be used as a good model for pre-clinical stages of PD.

The Experiments: I paid particular attention to this part because I'd like to see if my idea of using the Frye lab equipment is within the realm of realistic testing.

Bohnen et al. Selective Hyposmia in Parkinson's disease: Association with hippocampal dopamine activity

Basic idea:
Olfactory deficits do not necessarily worsen with the progression of PD, but it has been established that hyposmia is correlated with PD pathology (including early/pre-manifest PD). This paper shows that there is a stronger correlation between selective hyposmia and hippocampal dopamine activity as opposed to dopamine activity in the amygdala.

Fleming et al. Olfactory deficits in mice overexpressing human wildtype alpha-synuclein

Basic idea:
Mouse models of early stage Parkinson's disease show olfactory impairments.

The Experiments: I want to know how and why they performed the experiments that they did, in hopes to gain insight into what to do when designing an olfactory-testing experiment with animals.

April 17-21, 2009

Iiit's my birthday weekend! It's also the weekend when Darcy comes to visit me from the East Coast, and when I am studying for exams in my Neuroscience, O-Chem and Neurobiology of Aging classes. (I can't wait to NOT be an undergrad anymore...)

More to come soon. Progress on "Mission: PD flies" is a bit stagnant because of legally turning a year older and midterms. Woot!

April 9, 2009

Mark is no longer mulling.

I've discussed my options with Yan Zhu and Partha Krishnan, the two post-docs who are awesome for offering some of their time to oversee this experiment. I don't expect to be bothering them too much because I already have most of the techniques down, but the only hang-up with Mark was the fact that a lowly undergrad like me can't just go AWOL with his resources and equipment.

Smooth sailing so far...

Next update: The flies and other hangups

April 7, 2009

Mark is mulling.

My biggest concern with this project at this point is whether these PD model flies will be capable of flying in the flight arena. What if they can't fly because of the devastating effects of the aggregated protein in their little insect brains? All the literature I could find on these flies were walking tests and molecular studies. Nothing on flight. Is this because the researchers don't have the equipment, or are their flies too weak to fly?

As of today, this is no longer my biggest concern! From Mel B. Feany and Welcome W. Bender's Drosophila model of PD research publication in 2000 from Harvard Medical School: "Locomotive behavior is grossly preserved in young flies."

Although I am aware they worsen with age, I am PSYCHED. This may not indicate a 100% guarantee that they are capable of flight, but I think this is worth looking into further.

Next update: More research and ordering the flies!

April 5, 2009

Today I sent my awesome PI, Mark Frye, a research proposal. This means I went online and researched a whole bunch about fruit flies and neurodegenerative disorders and discovered that my idea has never been investigated before.

So here's my idea, simply put: I want to test whether the Drosophila melanogaster with overexpressed alpha-synuclein-type Parkinson's Disease can smell as well as the wildtype flies.

Parkinson's Disease (PD), as you may already know, is a neurogenerative disorder where the dopaminergic neurons inexplicably die off in the substantia nigra, a key component in the brain that controls body movement.

There are a few ways to induce PD in fruit flies. Although there is some research done on the causes of spontaneous PD (the latest culprit is a heavy-duty toxins used in agriculture), about 5% of the cases are genetically triggered. These genes are what we are inserting into the Drosophila DNA, which are essentially causing the flies to overproduce human alpha-synuclein. Alpha-synuclein is a protein naturally found in the brain, but is also the guilty misfolded protein that causes the aggregates in neurodegenerative disorders such as PD and Alzheimer's.

There is no cure, and we don't know exactly how the synuclein protein aggregates in the disease. We do know, however, that early on in the disease, even before the obvious symptoms wreak havoc on the body, PD patients start losing their sense of smell.

Research at the VU Medical University in Amsterdam showed that scientists could guess who was going to get PD even before they had any tremors, just by testing their sense of smell.

Mark (the PI for this lab,) is the perfect guy to work under for a project like this because his grad and post-doc lab members do behavioral experiments with equipment specially designed for fruit flies and their response to odor.

I feel like I've almost won the lottery.

My next update: What will Mark say?

Dr. Michael Levine
Dr. Mark Frye Lab
UCLA Seminar/Lecture Series for Neuroscience