They may have wings, but fruit flies spend plenty of time on their feet. And these insects, also known as Drosophila, are a standard animal model for studying neurodegenerative diseases, such as Parkinson’s and even Alzhiemer’s.
Often, scientists will create fruit flies that contain the same genetic mutations as seen in these disorders to see how the DNA changes affect the insects. Yet, for all the complex genetic tools they employ, the way of measuring the resulting motor defects remain crude: A researcher will knock the flies in a vial down to the bottom with a quick tap, and then wait to see how long it takes for the insects to climb to the top. (For an example, go to 2:28 into this video on LRRK2 animal models of Parkinson’s.)
Now, reporting in eLife, a team at Columbia University in New York has developed a more accurate and sophisticated way to quantify such movement. They first videotape a fly walking, and then, using computer software that can spot the individual footpads of the insect and mark when these each hit the surface. With this data, they can calculate the insects’ walking speed, distance covered and overall gait.
In the paper, the authors looked at sensory-deprived flies and showed that inactivation of sensory neurons in the insects’ legs led to defects in step precision but did not affect coordination between the legs. They call the program FlyWalker.
Similar technology already exists for tracking the movements of lab rodents. But as Ronald Calabrese of Emory University in Atlanta notes in an accompany commentary, “the Columbia team is the first to scale it down to fly-like dimensions.”
With so many metrics being teased apart by the new algorithm, Columbia’s César Mendes, a postdoc in Richard Mann’s lab who led the research, expects scientists who use the technique to discover new things about their diseases of interest, such as how an ailment worsens over time. “This method is good if you want to see a progressive phenotype and to see subtle changes as time goes by and the disease phenotype gets more aggravated,” he says.
“I really foresee that you will see flies that start to have some [movement] defects that have not been seen before, and hopefully we’ll be able to correlate some phenotypes to particular groups of neurons or to particular circuits,” Mendes told Nature Medicine. “I’m very curious to see what we’re going to have in the future.”