“My thesis was really all about exploring something that was unknown,” said Katie Sullivan ’18 of her research on glycobiology — specifically on glycosylation, a process that allows proteins and cells to be decorated with carbohydrates and sugar motifs.
The biology major and neuroscience minor was inspired to write her thesis, “Investigating the N-Linked Profile of Folded Gastrulation in Drosophila Melanogaster,” on this little-understood field after spending two summers at Stanford University in an immunotherapy and cancer research laboratory with support from the Marian E. Koshland Integrated Natural Sciences Center Summer Scholars Program and the Velay Fellowship.
“Glycosylation is a really, really important part of our biological systems,” said Sullivan. “However, it is rarely talked about. The more I read about glycosylation and glycobiology, the more I thought, ‘Wow, this stuff is really important and I’ve never heard about it before.’ However, we have all heard about glycosylation, or, at least, know about it in some aspects. It is taught ‘secretly’ in most introductory biology classes under the guise of human blood types. Human blood types are all classified based on what type of ‘tags’ or ‘antigens’ you have on your red blood cells. It turns out that the process of glycosylation is responsible for adding these tags to the blood cells.”
What does that mean for you? Think back to the last time you gave or received blood.
“Your blood type is very important for transfusions because it could be very life threatening if you receive the wrong type of blood in an emergency,” said Sullivan. “Since different blood types don’t mix well with each other because the glycosylation patterns do not match, this example demonstrates how important it is for proteins and cells to be glycosylated.”
Sullivan’s thesis advisor was Associate Professor of Biology Rachel Hoang. Sullivan and Hoang first worked together three years ago, when the former worked in the latter’s laboratory the summer after her first year at Haverford.
“Rachel was very encouraging of me thinking about new projects over the summer before my senior year,” Sullivan said. “I was interested in taking a part of the research that I was completing at Stanford that summer and bringing it back to Haverford for my thesis. I also spent a lot of time that summer reading textbooks on glycobiology, so I was hoping to relate some of that information to my senior thesis.”
This fall, Sullivan will begin work as a research specialist in a cardiovascular laboratory at the University of Pennsylvania’s Perelman School of Medicine, where she looks forward to continuing her study of glycosylation.
“Glycosylation also continues to be proven to be a very important and hot topic in cancer biology, rare disease biology, and metabolism biology,” she said. “So much is still yet to be discovered from biological pathways that we only focused on the synthesis steps of proteins.”
How did your advisor help you conduct your research and interpret your results?
We eventually got the ball rolling on a glycosylation project that involved the protein Folded gastrulation (Fog) in Drosophila. Folded gastrulation is a protein that initiates the process of apical cell constriction in Drosophila embryos. This allows for the embryo to form different cells layers. This process is extremely important and integral for the survival of the embryo for any animal. However, the protein Fog is peculiar. It is not well conserved across animals, or insects for that matter. This is very unusual, it is not expected that a protein that is very important for a very conserved biological pathway that every multicellular organism has to complete to survive is evolutionarily not well conserved.
Because of this, Rachel and I were interested in determining if there was some aspect of the Fog protein that can be well conserved without the actual backbone of the protein having to be present in every species of Drosophila. For this, we started to investigate whether or not Fog was glycosylated.
Fog has been predicted to be glycosylated, however, no one has definitely shown that it is. Glycosylation can be predicted by looking at a protein’s amino acid sequence and identifying regions where glycosylation might be likely because of a certain pattern of amino acids. We saw that there are specific sites for predicted glycosylation sites. We hoped to show that these sites were glycosylated by conducting an experiment that analyzes the weight of the protein before and after treating it with enzymes that cleaves the sugar moieties.
What did you learn working on your thesis?
I had just learned about this field of glycobiology that I didn’t explicitly know existed before, and I was really interested in carving out a little corner for myself to explore. What was most surprising to me was that this seemingly very important biological phenomenon, that is usually only taught using that one blood type example, is almost totally forgotten about for the rest of all of the study of biology and biological systems.
Also, my thesis was conducted in tissue culture. This was a process that Rachel and her lab had never done before, so we got to work creating our own tissue culture room. This required buying and borrowing a lot of regents from other laboratories. It was really fun to collaborate with her and other scientists that were generous enough to give me their time and help to get this project going.
Another theme of my thesis project might be persistence. We were having a lot of trouble initially growing our cell cultures and keeping them alive. Many handbooks and published papers had conflicting ideas on the best was to propagate them so it was a little difficult at first trying to figure out what would work best for us. However, once we got that nailed down it was smooth sailing in terms of cell culture growth.
And lastly, another big takeaway was just how much others are willing to help; at Haverford and far from it. I was able to correspond with two scientists, Dr. Stephen Rogers and Dr. Alexey Veraksa, about my project, and they were so willing to help and even send us cells from their own tissue culture stocks when ours were failing. It was very nice of them and I am glad to have been met with such generosity from them.
“What They Learned” is a blog series exploring the thesis work of recent graduates.
Photo: Katie Sullivan in her element. Photo by Holden Blanco ’17