A microscopic worm could reveal how we perceive gravity



While humans rely on gravity for balance and orientation, the mechanisms by which we actually perceive this fundamental force are largely unknown. Oddly enough, the model organism C. elegans, a microscopic worm, can sense the direction of gravity, although there is no known ecological reason for this.

Caenorhabditis elegans, a free-living transparent roundworm, about 1 mm long.

To unravel this mystery and get to the basics of our own sense of gravity, a team of Penn Engineering researchers led by Haim Bau, professor of mechanical engineering and applied mechanics, and David Raizen, associate professor of neurology at Perelman School of Medicine, conducted a series of experiments on this model organism. Lead author Alex Chen, a then visiting PhD student, and co-authors, Hungtang Ko, a then Masters student, and Oswald Chuang, a former postdoctoral fellow, contributed to this work while working in both Bau and Raizen’s laboratories.

Despite its extremely simple physiology, C. elegans shares more than half of its genes with humans, so genetic studies can reveal which genes are responsible for similar traits in humans.

“We did previous research on the hydrodynamics of C. elegans and threw it into the water when we observed that these worms all tended to swim to the bottom of the cuvette,” says Bau. “We asked ourselves whether they react to gravity or are just top-heavy and sink passively.”

Recognizing this as an opportunity to determine molecular pathways responsible for grataxis, or the ability to move in response to gravitational forces, the team initiated the study, which was published in the journal BMC biology.

“We know that dopamine is a very common neurotransmitter that controls many functions in the body. When we turned it off in mutants, the ability to recognize gravity was lost, ”says Bau.

“Interestingly, some of that ability came back when worms were exposed to dopamine supplements in the larval stage and later in the solution, suggesting that pharmaceutical recovery might be possible,” he says.

This link between dopamine and gravity sensing provides insights into human health applications.

This story is from Melissa Pappas. Read more today at Penn Engineering.



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