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Dr. Heidi Elmendorf explains a concept to students in her lab. (Photo: Roland Dimaya)
Dr. Elmendorf's research looks at the structure and function of the Giardia cell. (Photo: Roland Dimaya)
Dr. Elmendorf points to a facet of the Giardia cell's shape to her students. (Photo: Roland Dimaya)

By Megan Weintraub

Dr. Heidi Elmendorf, an associate professor of Biology at Georgetown, is helping to make your high school biology textbook obsolete. Her research on a peculiar single-cell organism called Giardia has yielded fresh insight into properties of cells that scientists have long considered to be givens in the field of biology.

For example, one fascinating insight has come from her studies of gene regulation, the process where cells decide which information that is stored in the DNA will be used. Until recently, scientists believed that only one strand of DNA created all of the cell’s messenger RNA, which is also called “sense RNA” because it relays the information needed to make proteins. However, Dr. Elmendorf identified that an entire 20 percent of the messenger RNA is actually built according to directions from the other DNA strand and is therefore called “antisense.” Dr. Elmendorf’s work on Giardia’s antisense RNA represents a significant finding to the scientific community.

“This is like discovering a new continent in the middle of the Pacific Ocean,” explains Dr. Elmendorf incredulously. “It’s exciting to be a part of this and to be aware of what we can do in science. There is still so much to learn.”

As its name implies, antisense RNA is an upside-down and backwards string of DNA code and it can cause confusion in the process of transmitting messages within the cell. Dr. Elmendorf has found that the Giardia cell makes this antisense RNA, and she is trying to understand not only how that process takes place, but also if the Giardia cell finds it purposeful in some way. More recently, this same abundance of antisense RNA has been found in other cell types--including our own--and research into its functions will have important implications for the ways scientists understand cell behavior.

The World Health Organization (WHO) estimates that 1 billion people, pets, and livestock per year are afflicted with this devastating single-cell intestinal microbe, which lurks in untreated water supplies. While few people die from Giardia, the intestinal distress it causes can inhibit normal functioning and its cumulative effects within a community can weaken local infrastructure. Dr. Elmendorf’s research, which looks at the structure and behavior of the cell itself, serves as a complement to the work of Dr. Steve Singer, a Georgetown professor who examines the host side of the pathogen.

“I find Giardia so fascinating,” she explains. “It’s an unusual member of the microbe family and we’re looking for ways to prevent its deleterious effects.”

One of Giardia’s quirks lies in its structure, which leads it to infect its host using an unusual method of attachment. The pear-shaped cell has a ventral disc on its belly that acts as a suction cup and a mesh-like back made of actin, the same material that allows our muscles to contract. While most intestinal microbes cause infection by using proteins on their surfaces to stick to intestinal cells, Giardia uses its ventral disc to physically cling to its host. Yet despite this understanding, Giardia researchers like Dr. Elmendorf are still puzzled by the way in which this process actually takes place, given that Giardia is merely a single cell and not an entire organism.

“How does this tiny cell summon the energy needed to attach?” asks Dr. Elmendorf. “Our bet is that it compresses its actin-laced backside and squishes itself hard enough against the intestinal wall. So, in the lab, we’re measuring the force of that action.”

To further explore this idea, Dr. Elmendorf and her team of student researchers are working with Dr. Jeffrey Urbach to take pictures of the rapid attachments of the cell to another surface. Once they can pinpoint the way in which the cell attaches, then they can help to develop drugs that prevent the parasite from taking up residence in an individual’s intestine in the first place. Colleen Walls, a fifth-year Ph.D. student, has been working on a drug screening process to create a pharmaceutical that would inhibit Giardia’s ability to attach. Instead, the cell would pass through the digestive tract just like other parasites that flow through our systems every day but fail to cause us intestinal distress.

In addition to her research, Dr. Elmendorf, along with Dr. Anne Rosenwald, has spearheaded the effort to bring a new and important major to the College in the Biology of Global Health. The program emerged from an assessment of the key themes in the Department of Biology. After recognizing that many students in their classes were interested in all aspects of global health, such as epidemiology, law, and policy, Dr. Elmendorf and Dr. Rosenwald created a program to develop these interests in context. While it is still in its infancy, Dr. Elmendorf has already found her work with this program to be extremely rewarding.

“One of the phenomenal things about being a professor is that we get to create bold opportunities for our students,” she says. “This program is hugely fun. And Georgetown students are astonishing. We ask them to do something and they do twice as much.”

Dr. Elmendorf’s appreciation for Georgetown students is evident in her impressive team of student researchers. While their research takes place on a microscopic level, it shows great promise for alleviating systemic problems on a large scale.

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