Could the source of autism be cropping up in our farmer’s fields?

By Nicole Forgione

Farmers and developmental neurobiologists are unlikely collaborators. Not that lab and field don’t mix — farming today is extremely high tech and dependent on science — it’s just that we don’t typically look to soil and crops for answers to early brain development in humans. But two researchers at the University of Guelph are changing that. John Vessey and Scott Ryan are using a New Ideas grant from the Ontario Institute for Regenerative Medicine to investigate the causes of autism spectrum disorder (ASD) — and what they are finding may change how we produce the food we eat.
ASD is defined as a group of developmental disorders that most frequently involve impaired social interaction and communication. This condition is more common than once thought — recent studies estimate it could affect 1 in 68 children. Despite this, we are still largely in the dark about what causes this disorder.
Vessey is a developmental biologist with a keen interest in how neural stem cells build the brain, and Ryan is a neuroscientist who is intrigued by the cellular processes that control neurodegenerative diseases. Their research focuses on a potential link between pesticide exposure during pregnancy and ASD. Before everyone swears off non-organic produce for good, there are a few points to remember: First, this study is still in discovery stages and any correlation between pesticides and ASD will need further research to verify. And second, pesticides are widely used in commercial agriculture to protect against weeds, insects and fungus — in some cases they are used in the production of foods that qualify as organic. Health Canada regulates the use of pesticides, and sets limits for the amount of these chemicals that remain on the food we eat.
Vessey and Ryan are focusing on the role of two specific pesticides, used in Ontario, that have the ability to interfere with the function of a protein known as MEF2C. Ryan explains that the overall goal of the project is to “find a link between environmental triggers that have been associated with autism onset and the genetic triggers that are known to predispose people to developing autism.”
This project is based on fundamental questions that neuroscientists have been asking for centuries: How is the brain formed? How do neurons make the connections that control complex human behaviours? Vessey and Ryan are bringing a new perspective to these old questions by looking at how environmental factors — in this case pesticides — might play a role.
Several lines of research have come together to form their approach to studying this problem. Ryan’s postdoctoral work at the Sanford-Burnham Medical Research Institute in La Jolla, California focused on Parkinson’s disease — a condition that has links to pesticide exposure.
“I was trying to identify commonalities between genetic causes and environmental exposures that are believed to trigger Parkinson’s disease,” says Ryan. Using this approach he identified a pivotal role for MEF2C in the survival and metabolism of neurons in which the protein acts as a “common hub” to regulate the expression of a network of genes.
The next piece in the puzzle came from literature showing that patients with ASD often display changes in the expression of MEF2C regulated genes. This evidence made Ryan wonder if pesticide-induced changes in MEF2C might also have a role in ASD. But he’d need the right partner to find out.
In 2013, that collaboration would begin, as both Ryan and John Vessey were recruited by the University of Guelph as new faculty members. For his part, prior to the move to Guelph, Vessey studied how neural stem cells contribute to the development of the cerebral cortex at the Hospital for Sick Children in Toronto. “It is largely thought that the cortex is where alterations occur in circuitry that lead to the onset of autism,” explains Vessey. So it was a natural jump to question whether altered MEF2C signaling is impacting the ability of neural stem cells to build the cerebral cortex.
To study the possible connection between pesticides and brain development, the research team will mark neural stem cells at very early stages of development in the mouse. Using a technique known as in utero electroporation, a fluorescent green marker will be delivered to neural stem cells. The behaviour of the green neural stem cells can then be tracked in response to pesticide exposure. They are hoping to see if pesticides interfere with the ability of neural stem cells to grow, divide, and form mature cells that are capable of making normal connections in the brain. This experiment — funded by the New Ideas grant — will provide critical preliminary data needed to build a larger research project.
One of the most promising impacts of this work is that it will create the opportunity for increased cross-talk between academic science and the agriculture industry. Ryan says that there is a need for these kinds of interactions. “There seems to be a communication barrier between industry and academia and there doesn’t need to be. In my experience, everyone is really open to the discourse.”
Being in an agriculturally-focused institution like the University of Guelph has provided the environment to foster these relationships. Through a partnership with the Ontario Ministry of Agriculture Food and Rural Affairs researchers can access funds to study how agricultural practices can impact health. Ryan says, “There is a great support network here at Guelph, they really help align you with people in industry that can affect change.”
Improved collaboration between academia and the agricultural industry could have important impacts for the general public.
Vessey says that the most exciting aspect of this work is the potential to create awareness around the influence of environmental factors on health. “If we can show that commonly used pesticides, here in Ontario, might be having adverse effects on health that would be a substantial message that needs to be communicated to the public.”


Photo Credit: "Growth" by TheGiantVermin published under a Creative Commons License on Flickr