An Evolutionary Tale

Stress leads to genetic changes in laboratory worms

elegans - bwA tiny worm is wiggling its way toward our understanding of evolution and the genetics of aging.

We know that mutations in DNA enable organisms to evolve. But how? Jeremy Northway, an undergraduate in the Oregon State University Honors College, is intent on using this worm, known as C. elegans, to find answers. Few animals are as tough or as unassuming. Specimens of C. elegans survived the 2003 space shuttle Columbia disaster. They have been used in experiments on the International Space Station to investigate the effects of weightlessness on muscles. Technicians on Earth routinely freeze them in liquid nitrogen where they can remain viable for as along as 10 years. On their own, they thrive in compost heaps and garden soil.

Jeremy Northway (Photo: Marissa Solini)

Jeremy Northway (Photo: Marissa Solini)

As a freshman, Northway became interested in research during an introductory biology course. “It was called the phage genomics lab, and the whole concept was that students would go around campus and find their own phage out of an environmental sample,” Northway said. “Phage are viruses that infect bacteria.”

That was where Northway met Professor Dee Denver, a geneticist in the Department of Zoology who studied C. elegans for his doctoral thesis. Denver taught a section of the class on worm genomics.

All Honors College students conduct research and present an undergraduate thesis. Denver helped Northway to frame his research question into a doable project. “Dee is a really good researcher, especially for undergrads and people who haven’t done a lot of research,” Northway said. “He’s really good at the process of scientific discovery and letting you discover yourself.”

Northway received funding through a National Science Foundation grant to Oregon State to study the number of generations it takes for C. elegans to evolve in a new environment. His results could also have implications for the cellular process of aging. The genes he studied help control how cells break down as they age.

Nothing to Hide

The word “worm” evokes images of earthworms or parasites like roundworms. But C. elegans is so tiny that it eats bacteria. And since it is transparent, researchers can watch the developmental process unfold under a microscope.

Evolution can be hard to study in long-lived animals such as humans, but C. elegans speeds things up considerably. It reproduces in only four days, and a group of them can show evolutionary changes in a few weeks.

In Professor Dee Denver's lab, vials of C. elegans are kept at at -112 degrees Fahrenheit (-80 degrees  Celsius). (Photo: Marissa Solini)

In Professor Dee Denver’s lab, vials of C. elegans are kept at at -112 degrees Fahrenheit (-80 degrees Celsius). (Photo: Marissa Solini)

In Denver’s lab, a giant freezer holds the samples with the worms in capped cryogenic vials. The temperature is kept at -112 degrees Fahrenheit. Before Northway is able to pipette worms into a Petri dish and observe them, he must thaw them out for an hour.

Northway’s plan relied on natural selection. He exposed worms to Paraquat, a potent herbicide. Although many worms died, some managed to eke out an existence and reproduce. Those worms were repeatedly dosed with the chemical  for 10 generations. By then, the majority of the worms was resistant to Paraquat. They had evolved to adapt to their environment.

Northway traces the results to changes in the cells of C. elegans. The chemical damages a part of the cell known as mitochondria, a kind of power plant for cellular processes. When mitochondria are damaged, cells die. In Northway’s experiments, the resistant worms may possess an advantage that enabled them to live.

Scientists hypothesize that similar processes are involved in aging, Northway said. Because the worms evolved to resist stress, genes in humans may also function in this manner. Northway’s research could lead to further investigation even if his data don’t turn out to be statistically significant. Analyzing C. elegans genes could provide clues to a long-sought goal in biology: the causes of aging.

Part of the answer could be in the way that genes are regulated. “It would be interesting to see what specific genes are being up- or down-regulated as a result of this stress, and I think that it might be a natural path to look at some kind of human aging diseases like Parkinson’s or Alzheimer’s,” Northway said.

This summer Northway will continue his work with a graduate student on C. elegans genes related to aging.

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