Each year the Bailey College of the Environment provides faculty-student research grants to provide faculty and their students an opportunity to conduct research that would not have been otherwise possible. Research in the O’Neil lab is focused on understanding the structure-function relationship of proteins involved in neurodegenerative diseases, specifically ALS (amyotrophic lateral sclerosis; commonly called Lou Gehrig’s disease) and Alzheimer’s Disease. Thanks to a COE faculty-student research grant and a COE summer fellowship, Alison O’Neil, assistant professor of chemistry, Gloster Aaron, professor of biology, and Aaron Berson ‘24, an NS&B (neuroscience and behavior) and IDEAS (Integrated Design, Engineering, Arts & Society) major with a minor in chemistry, were able to collaborate on Professor O’Neil’s investigation of cis-chlordane as an environmental trigger of ALS.
Can you tell me about your research and your project?
In my lab, we study neurodegenerative diseases, focusing on ALS and Alzheimer’s. The ALS project is the research that was funded by a Bailey COE faculty-student research grant. This is actually the second time getting this grant, so we love the COE! They’ve supported some great students who have been working on this project over the last few years.
ALS has a genetic component, but then there’s a large component of unknowns, while there’s definitely genetic risk factors, they’re not necessarily causal. Then there’s a huge piece that’s some kind of “environmental exposure.” If you live in a state where there’s a lot of industry and farming, you’re more likely to get ALS. In the military, you’re almost twice as likely to get ALS, and you don’t have to go into active combat. If you are an Italian soccer player, you’re more likely to get ALS. Italian soccer players play on grass, so maybe the reason is because of pesticide use on the grass. But these are all hypotheses. Ninety percent of ALS cases are caused by non-inherited factors such as environmental exposures and the other10 percent are caused by causitive genetic mutations. So researchers study the 10 percent that are known genetic causes because it is easy to model in the lab, including us. In our other work, we study SOD1 mutations which cause only 10 percent of the 10 percent.
We wanted to figure out a way to look at the other 90 percent of ALS cases. The genetic risk genes aren’t all known but with the environmental factors, a couple studies have pointed to pesticides. There are millions of pesticides. The first student I worked with on this project, Daniel Kulick ‘21, was actually the first recipient of a COE student-faculty grant that we received. He did this big literature survey and found an awesome paper where they took blood from actual ALS patients and did a risk survey and then took blood from healthy people who live in the same area and compared what they found in the blood. And they found a few pesticides that if they found this chemical in your blood, you were much more likely to be in the ALS group than in the healthy group. So we bought those pesticides. We bought three to start with, and we did what’s called a dose-response curve, where you start with the high concentration of the pesticide and just go down. We tested the doses on human stem cell derived motor neurons, because motor neurons are what are susceptible in ALS.
We found one chemical, cis-chlordane, that really had beautiful dose-response curves. In high concentration, it kills. And as you dilute it, it kills less. We worked with Professor Stephen Devoto in the Biology Department to test cis-chlordane on zebrafish. We added it to their water, and when they’re larva the pesticide just soaks in, so we were able to test it on the motor neurons–which, in zebrafish, are very similar to ours. The ALS phenotype is that you slowly lose control of your muscles, and the zebrafish had a really strong motor defect as well. So we saw that not only is cis-chlordane toxic to humans, it’s also toxic to zebrafish. We worked with a collaborator at UMass Amherst who has really fast imaging capabilities and we could see that when we poked the zebrafish larva, our fish didn’t have the natural reaction, which would be to swim away. It’s called touch-evoked escape response. At that stage, as larvae, if they touch something, they have a natural reaction to swim away from it; like to get away from a predator. Healthy fish swim away. Our fish didn’t swim-–they were completely uncoordinated. Our collaborators at UMass,who are experts in fish locomotion, took all these videos,analyzed them, and determined the treated fish had decreased swim efficiency. Which is how much the fish moved its body versus how far it traveled.
We also work with Professor Gloster Aaron’s group in the Biology Department. The other property of neurons is that they fire action potentials: They send electric currents, and that’s how they talk to each other. Professor Aaron’s lab is set up to measure those pulses, those electrical charges that are neurons talking. The main function of a motor neuron is to take thoughts from your brain and translate it to muscles. If they can’t send signals properly, they can’t transmit that signal. If you add the pesticides to the neurons, and then you measure how well they can talk, as changes in electrical pulses, the pesticide causes a big change. One of the students that’s working on it, Aaron Berson ‘24, is continuing these studies, funded by the Bailey COE.
We published these findings last December. What we showed is just this incredible phenotype. The most incredible thing is that we already know how cis-chlordane works on insects: It blocks a very specific receptor in the neurons called the GABA receptor. What we proved in our paper has nothing to do with it blocking GABA; it’s something completely different. So we’re showing a new mode of action. We’ve published that research with help from the COE faculty-student grant.
Now that we have this really interesting phenotype, the next question is: Why? Why is it killing motor neurons? What we’re working on right now is trying to figure out this new mode of action. The other thing we’ve done is we’ve expanded our pesticide panel to test other pesticides in the same class as cis-chlordane, so polychlorinated pesticides. One of cis-chlordane’ cousins is DDT, which is the famous pesticide explored in Rachel Carson’s Silent Spring. DDT looks just like cis-chlordane on our motor neurons. So we’re looking into whether it matches all of the other phenotypes we saw in cis-chlordane: Is it interrupting the electrophysiology and interrupting that in the same way? What we’re trying to do is to narrow it down to figure out how cis-chlordane is killing these motor neurons. That’s a big focus. Also, we’re exploring whether the phenotype is unique to cis-chlordane or if there’s a group of these poly-chlorinated pesticides that are doing the same thing. So maybe the phenotype is associated with a class of pesticides. Continuing the electrophysical studies is Aaron Berson ‘24 and with the help of COE funds, I am training a new student on the project, Oliver Clackson ‘25.
How did you get started with this project?
I started this project during my first year at Wesleyan; this is my sixth year. It was my first summer when my lab was just up and running. I was trying to get as many students as possible to stay over the summer to do research, because we were just getting started. I was looking at different ways to get students funded and I saw the COE–which is a perfect match, because 90 percent of ALS has a strong environmental component. So it’s so important to look at these environmental causes.
What do you hope that this research will bring about?
I hope this research will stop the use of certain types of pesticides. I don’t think the noise, the clamor, the protesting, the worry, has been focused enough on neurodegenerative diseases and how these pesticides have long-term effects. We always look at cancer first. Cancer is horrible; I don’t want anyone to get cancer by any means. But we always ask first: Does it cause cancer or not? That’s how we say something’s dangerous. We say that because it’s easier to test for cancer: You feed a rat the chemical and you see if they develop a tumor. With ALS and Alzheimer’s, you also need the genetic risk factors. We don’t even know what those are in a lot of cases. And because these are adult-onset diseases, you also need to make sure that the rat ages. So it’s a hard experiment. I would love to be able to have a set of assays that any new pesticide could go through. We can make motor neurons, for ALS; and cortical neurons, which are the neurons that die in Alzheimer’s; and dopaminergic neurons, which are the kind that die in Parkinson’s. And then we can do the assay that we do here to see if the pesticide is toxic or not. As a hypothetical example, then you could say that not only does glyphosate cause cancer, it also looks like it affects dopaminergic neurons, which means it might be a Parkinson’s causing chemical. We would have that information going forward, as new pesticides are getting ready to come out on the market, and then maybe we wouldn’t be using them.
So, so interesting! Anything else to add?
Just that we’re really thankful to the Bailey COE for their continued support. Stem cell work isn’t cheap! Also, for their support every summer for a student to work on this project. That’s how we’ve gotten all of this important work done!