As the digestive system develops, the gut tube lengthens and convolutes to correctly package the intestine. Intestinal malrotation is a prevalent birth anomaly, but its underlying causes are not well understood. In this new study, Nanette Nascone-Yoder and colleagues show that exposure of Xenopus embryos to atrazine, a widely-used herbicide, can disrupt cellular metabolism in the developing gut tube and lead to intestinal malrotation. We caught up with first author Julia Grzymkowski and corresponding author Nanette Nascone-Yoder, Professor at North Carolina State University, to hear more about the story.
Julia Grzymkowski (left) and Nanette Nascone-Yoder (right)
Nanette, can you give us your scientific biography and the questions your lab is trying to answer?
NNY: I completed my undergraduate degree at a small liberal arts college (Eckerd), where I was fortunate to be involved in a variety of research projects (from fungal metabolism to viral tumorigenesis). It wasn't until my graduate work at Harvard that I fell in love with developmental biology. I was investigating heart morphogenesis and became enamored with Xenopus, a model which allows both assays of gene function and ‘cut and paste’ experiments. This was when I began to study left-right asymmetry (the rightward looping of the heart) and first became intrigued by the tadpole's beautiful counterclockwise intestinal spiral. It was then that I knew that figuring out how such asymmetries arise would be one of the consistent focuses of my scientific career.
Julia, how did you come to work in Nanette's lab?
JG: My undergraduate degree is in Forensic Science and Chemistry, but I discovered a new-found interest in biological research in graduate school (Toxicology programme). This interest grew further when I did a rotation in Nanette's lab, where I was introduced to developmental biology. I had a wonderful rotation experience and really liked the idea of formulating a PhD thesis project/research question that encompassed both developmental biology and toxicology.
What's the background of the field that inspired your work?
NNY: Intestinal malrotation is a very common birth anomaly – affecting as many as 1 in 500 births – but the aetiology of this condition remains poorly understood. Malrotation can result from abnormal left-right patterning but is also often found independently of other laterality anomalies. In human patients, malrotation is associated with decreased intestinal length, but the connection between gut rotation and gut elongation was relatively unexplored.
Can you give us the key results of the paper in a paragraph?
NNY: Julia found that atrazine (ATR), a widely-used herbicide, causes reversed (clockwise) intestinal rotation in tadpole-stage Xenopus, well after the left-right axis has been established and laterality cues have been conveyed to developing organs. Interestingly, ATR-induced malrotation is accompanied by disruption of the cellular events that drive gut tube elongation. Subsequent transcriptomic and metabolomic analyses suggest that the herbicide causes these phenotypes by disrupting central carbon metabolism and inhibiting electron transport reactions. This prevents the gut from undergoing a metabolic shift from glycolysis-driven ATP production to mitochondrial oxidative phosphorylation. Consequently, ATR-induced malrotation elevates reactive oxygen species and, remarkably, can be rescued by treatment with an antioxidant, confirming that the mechanism of action involves redox imbalance. Our results help explain the connection between gut elongation and rotation, and have implications for the role of metabolic perturbation in the aetiology of intestinal malrotation. Our story also suggests that there may be benefits to antioxidant supplementation during pregnancy.
Julia, when doing the research, did you have any particular result or eureka moment that has stuck with you?
JG: Definitely, and Nanette can attest to this as well. We were excited to try the rescue experiments with the antioxidant and those results were, to me, the hardest to wait for. I remember running into her office a few minutes after the first round of data collection and being so excited to go through the results. It was really satisfying to see the story come together with each new piece of data.
It was really satisfying to see the story come together with each new piece of data
A transverse section through the Xenopus tadpole intersects multiple loops of the rotated intestine.
And what about the flipside: any moments of frustration or despair?
JG: The bioenergetic assays using the Seahorse XFp instrument were the most painstaking. At the time, there was no published literature in which someone had performed these types of experiments with late-stage Xenopus embryos: I was the first one to try them in our lab. This period of my research required an immense amount of troubleshooting and optimisation, and I am really proud of the fact that I persevered and helped develop a new tool for future use in the lab.
Why did you choose to submit this paper to Development?
NNY: Our work suggests that intestinal malrotation may not only result from abnormalities in left-right asymmetry but could also be influenced by anomalies in the timing or extent of gut elongation or metabolic dynamics. So, this study provides new avenues to explore the underlying causes of a prevalent birth anomaly and seemed ideal for Development's broad and increasingly interdisciplinary audience.
Julia, what is next for you after this paper?
JG: I really enjoyed communicating about my PhD work, and it turned out that I really excelled at it. I loved writing my thesis, developing figures and giving oral/poster presentations. I have a fond memory from a developmental biology conference where, after I gave a talk, a few undergraduate students approached me and said they found my talk easy to follow and enjoyable despite having no background knowledge on the topic. These are just a few of the reasons why I entered a career in science/medical communication. Currently I am a Medical Writer for MedThink SciCom, where I develop scientific content for publication such as manuscripts, abstracts, posters and oral presentations for industry clients. I hope graduate students reading this will take away that science communication can be a fulfilling career option.
Nanette, where will this story take your lab next?
NNY: With ATR and other metabolic perturbagens as tools in our arsenal, we are now starting to dive deeper into the cellular-level events that coordinate tissue elongation with left-right asymmetric morphogenesis in specific regions of the intestine.
Finally, let's move outside the lab – what do you like to do in your spare time?
NNY: If I hadn't become a scientist, I would probably be an artist. There is something so satisfyingly meditative about the creative process. I especially love painting, but I am also a big fan of the fibre arts, and you will occasionally find me wearing a wrap or sweater that I made myself.
JG: Even though I do so much reading for my job, I still love sitting down with a cup of tea and a good book. In addition, in January 2022, my fiancé and I adopted our black and tan coonhound, Amelia, from North Carolina State University's Veterinary School. She brings so much joy to our lives and we love taking her on hikes or just snuggling on the couch together.
Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA.
E-mail: [email protected]
