Model organisms are non-human life forms that scientists study extensively as a way to gain insight into other organisms — including humans.
Thanks to its small size, short life cycle and low cost, Drosophila melanogaster (fruit fly) has been the ideal model organism studied by generations of biologists. With the help of these tiny organisms, scientists around the world have made some major breakthroughs, such as the discovery of biological rhythm that explains why we experience jet lag.
Gaining insight from one organism and applying it to another is a classic tale in biology. Biologists often ask questions about their lab’s organism of choice based on findings from studies in other common model organisms such as worms and mice.
Picking a model organism as the focus of future research projects can be challenging. For Leung, whose interests focus on the neurobiology of behaviour, the decision led the biochemist to choose fruit flies versus other organisms such as worms, mice and rats.
“Drosophila exhibits complex behaviours like courtship and aggression but [is] much simpler than a mammal,” says Leung.
Narsimha Pujari is a PhD student in Leung’s lab at the University of Saskatchewan (USask) who started as a master’s student working on the molecular structure of a protein implicated in psychiatric diseases in humans. He first learned about fruit flies during his undergraduate program.
“When I took an undergraduate genetics course, there were a lot of physiological processes that were discovered in Drosophila,” says Pujari “[After my master’s degree], I also wanted to work with an animal model badly so I could look at how molecules work inside the cell to affect the physiology of the whole animal.”
Leung and Pujari, along with others in Leung’s lab, study how three-dimensional structures of molecules in the nervous system regulate behaviour. Both areas require very different skill sets. Behaviour research involves careful analysis of hours of video footage, dissections and ﬂuorescent microscopes. Studying molecular structures calls for biochemical and biophysical techniques involving the synchrotron at the university’s Canadian Light Source.
But the two areas go hand in hand, and one without the other would leave missing pieces in the puzzle, explains Pujari.
“When we knock [a protein] down and we see a [different behaviour], that means that protein is involved in regulation of proper wing development, or body size, or how much they eat,” says Pujari.
“A protein is made of thousands of atoms — you have to understand at an atomic level to understand how the protein works within the whole nervous system that regulates a behaviour.”
The research all leads back to one goal: the brain — the “final frontier” since researchers are still searching for more knowledge about this critical organ.
“There is not much known about how the brain works and how neural circuits control behaviour,” says Leung, whose research team is focusing on the functions of a group of neurons away from the brain.
“Eventually we will want to look for upstream neurons that are connected to them — that would be the most interesting. The neurons that we have discovered receive signals from the environment – like a keyboard of a computer. Finding upstream neurons is like finding the CPU (central processing unit) of the ‘computer,’” says Leung.
The different behaviours observed by Leung’s team will give clues to where they connect in the brain and what nerves are regulating those behaviours.
Discovering what nerves control what behaviours in fruit ﬂies will allow Leung’s research team to pass the research narrative to another lab that studies more complex model organisms — such as mice or rats — for the basis of their research studies.
And eventually, scientists will have enough hints to piece together the link between certain nerves and behaviours in humans — the most complicated but intriguing model of them all.
Vanessa Browne is a fourth-year biology student in the University of Saskatchewan’s College of Arts and Sciences who worked as a summer research student in 2021. Her story is part of a series of articles written by WCVM summer research students.