Center for Tropical and Emerging Global Diseases
University of Georgia
Professor Emeritus Daniel Colley is the featured guest on the People, Parasites, and Plagues podcast. Learn more about his time spent with the CDC, becoming the director of the Center for Tropical and Emerging Global Diseases at UGA, and the research abroad that sparked his passion for schistosomes in this episode.
Vasant Muralidharan, associate professor in Franklin College‘s Department of Cellular Biology and member of CTEGD, is the featured guest in this episode of People, Parasites, and Plagues. He discusses his work with the Plasmodium parasite and his personal experience with malaria.
by Donna Huber
The parasite that causes malaria was discovered more than 125 years ago, but much is still unknown about this complex, single-celled organism. Researchers in the University of Georgia’s Center for Tropical and Emerging Global Diseases, however, have uncovered the role of one of the parasite’s essential proteins, offering new insights for vaccine and drug development.
Plasmodium falciparum causes the deadliest form of malaria, a disease the World Health Organization estimates killed more than 600,000 people worldwide died in 2022. A large majority of those deaths were children under the age of 5.
Historically, the parasite has been difficult to study due to its complex lifecycle, which includes three stages. One occurs in the mosquito, while the liver and blood stages take place in humans. The blood stage is when the infected person exhibits symptoms of malaria.
In the blood stage, the parasite invades red blood cells (RBCs) where they replicate and can be transmitted to the mosquito. The receptor-ligand complexes that enable RBC invasion have been well-studied and it is one of the targets of anti-malarial vaccines currently in clinical trials. But questions still remain.
“How does the parasite know it has encountered a red blood cell?” asked Vasant Muralidharan, associate professor in Franklin College’s Department of Cellular Biology and leader of the Muralidharan Research Group, where the study took place.
Interested, the team took a closer look at a protein called RON11, which is sent to a pair of unique club-shaped secretory organelles known as the rhoptry (Greek for club) that houses proteins needed to invade the RBC.
“When we knocked out this protein, we found that the parasite could do everything it usually does – create a putative pore in the membrane of the RBC, send proteins needed for parasite invasion through this putative opening into the RBC – but the parasite itself cannot enter the red blood cell,” Muralidharan explained. “If a parasite cannot enter the red blood cell, the life cycle is interrupted and the parasite dies.”
And then things got really interesting.
“We found that the parasites lacking RON11 were only producing half the rhoptry proteins, which are used in invasion,” Muralidharan said.
While it is known that Plasmodium parasites have two rhoptry organelles, they are so teeny-tiny they have been relatively understudied due to a lack of proper tools. However, new tools and techniques are emerging. David Anaguano, a cellular biology graduate student who led the study, traveled on a Daniel G. Colley Training in Parasitology fellowship to the Absalon Laboratory at Indiana University School of Medicine to learn a new tool known as Ultrastructure Expansion Microscopy.
“Electron microscopy is labor intensive, and since it uses thin slices of the parasite you are never sure if what you’re looking for really isn’t there or just not in the slice of the sample you have,” Muralidharan said. “Expansion microscopy is like using light microscopy but with a special gel to expand the cell proportionately in all directions. Thus, you don’t get the distortion you would with just an enlarged cell and you can image the entire infected cell in all dimensions. It has been a real game changer.”
As reported in the PLoS Biology paper, the Muralidharan group generated for the first time a Plasmodium cell with only one rhoptry organelle when they removed RON11 from malaria parasites.
“It’s not unusual for an organism to have a backup copy, but we can see that the parasite can create the first rhoptry just fine – without defect – but the second one that should form during the end of the replication cycle never forms,” Muralidharan said. “Why is that?”
As it appears that this second rhoptry is needed for RBC invasion, understanding the mechanisms that control its development could open up new targets for vaccine and drug treatment discovery as well as answering crucial questions like whether the two rhoptries are identical.
“This has been a long unanswered question,” Muralidharan said. “Now with this RON11 knockout parasite that doesn’t form a second rhoptry, we have the tools to answer it.”
I’m Kaelynn Parker and I’m from Virginia where I received my BS in biology from the University of Mary Washington. I’m a cellular biology Ph.D. student in Deigo Huet‘s laboratory.
What made you want to study science?
I took a genetic course at Germanna Community College as an elective while pursuing an associate’s degree part-time and working as an assistant barn manager. We did an experiment where we transformed E. coli with GFP and I thought it was the coolest thing I had ever done. It was a turning point where I decided I wanted to be in science.
Why did you choose UGA?
I chose UGA because of my undergraduate research advisor, Dr. Swati Agrawal, a CTEGD alum. I fell in love with parasitology (something I never imagined would happen) working with her, which inspired me to continue in the field. She also organized a seminar series featuring graduate students from CTEGD labs. After hearing from the graduate students at CTEGD, UGA was the only place I wanted to go for graduate school.
What is your project and why did you choose this research focus?
My project focuses on understanding interorganellar communication in Toxoplasma gondii through discovery and characterization of membrane contact sites between the ER, mitochondrion, and apicoplast. I am also investigating mitochondrial dynamics and stress response in T. gondii. I came to UGA with the desire to work on T. gondii because my original undergraduate project was supposed to be characterizing proteins important for egress in T. gondii. However, the COVID-19 pandemic put a halt on that plan and I wanted to return to Toxoplasma for graduate school.
What are your career goals?
I would like to remain in academic parasitology.
What do you hope to do for your capstone experience? Is there a collaborator/field site you would like to visit?
For my capstone experience, my plan is to utilize the opportunity to go to another lab to learn techniques to apply to membrane contact site research.
What is your favorite thing about UGA and/or Athens?
I love to go bird watching at the botanical gardens and local parks.
Any advice for a student interested in this field?
Talk to people, take every opportunity to present your work and build connections.
Support trainees like Kaelynn by giving today to the Center for Tropical & Emerging Global Diseases.
Dennis Kyle is the Director of CTEGD and the GRA Eminent Scholar in Antiparasitic Drug Discovery in the Departments of Cellular Biology and Infectious Diseases.
Brain-eating amoeba: Will the warming climate bring more cases? (MSN)
Michael Strand is a Regents Professor in the Department of Entomology and member of the Center for Tropical and Emerging Global Diseases. His mosquito research has recently been featured in a number of news stories.
What drives mosquitoes’ bloodlust? Their hormones (Nature)
The Science Behind What Makes Mosquitoes Bite You! Explained (News 9)
Mosquito bloodlust controlled by two hormones (The Naked Scientists)
My name is Grace Vick and I am a 4th year infectious diseases PhD candidate in Vasant Muralidharan’s lab. I’m originally from North Carolina and received my Bachelor’s of Science in Biology from Western Carolina University. After graduating undergraduate, I completed an internship at the Defense Forensic Science Center doing forensic biology research. After that, I spent 2 years as an ORISE Fellow at the Centers for Disease Control and Prevention, studying and identifying genetic markers of multi-drug resistant strains of Neisseria gonorrhoeae. I came straight to UGA through the ILS program after my fellowship at CDC.
What made you want to study science?
Ever since I was little, I’ve always spent a lot of time being outside in nature and enjoyed figuring out the intricacies of how things work. During my undergraduate, I was able to explore the different areas of science and found the molecular biology of genetics to be an interesting field that is highly translatable and still vastly unknown. After I spent a few years gaining lab experience and an appreciation for the public health concerns of infectious diseases at the CDC, I knew I wanted to pursue a PhD in that field which brought me to UGA.
Why did you choose UGA?
My experience at the CDC offered the opportunity to learn about diseases and public health issues across all sectors and countries, which led me to learn more about parasitic diseases. Previously, I knew nothing about these diseases but as I learned more about their complex and fascinating life cycles and how these diseases of poverty impact people around the world, I was captivated by this research. Because I was really interested in spending my PhD studying infectious and parasitic diseases, I found out about the CTEGD at UGA and that is what brought me here. The CTEGD is a really wonderful environment for trainees to be exposed to exciting and diverse parasitology research, and I’ve really enjoyed my experience here.
What is your research focus and why did you choose it?
Our lab works on the deadliest form of malaria, Plasmodium falciparum. P. falciparum kills over half a million people each year, with the majority of those deaths being children under the age of 5. Our lab is interested in understanding the molecular mechanisms that are essential to asexual blood stage of this parasite. My work specifically focuses on determining the role of previously unknown proteins that we have discovered are essential for asexual stage invasion of merozoites into host red blood cells. Using a combination of genetic engineering, molecular, and cellular biology techniques, I aim to determine the molecular function of these proteins in the human asexual stage invasion of red blood cells.
Have you received any awards or honors?
In addition to receiving the NIH T32 Predoctoral Fellowship, I have been invited to present at multiple national and international conferences such as Molecular Parasitology Meeting in Massachusetts and Molecular Approaches in Malaria in Lorne, Australia where I won a poster award.
What are your career goals?
When I graduate with my doctoral degree, I hope to either join governmental research or the industry sector. If I decided to head into governmental work, I would choose a career at the CDC where I could continue working in the parasitology research field and apply current public health policies to the international parasitology field. If I decide to join the biomedical industry sector, I would want to work in Research and Design at a company that designs therapeutics and diagnostics for disease prevention and treatment.
What do you hope to do for your capstone experience?
I would really love to experience fieldwork in a malaria-endemic region. I think having the experience of meeting people and learning firsthand how this disease affects millions of people every day would be very eye-opening for me since I have only seen the lab side of malaria. The ability to experience fieldwork would give me a broader experience with how malaria is researched and treated outside of the lab environment and in rural lab environments. I would love to visit Africa or South East Asia to conduct fieldwork in a malaria-endemic environment.
What is your favorite thing about Athens?
Obviously, I love the food in Athens! I love going downtown to grab food and drinks on the weekend. Otherwise, I enjoy getting out and exploring the green spaces and parks that Athens has to offer such as Sandy Creek and the North Oconee Greenway with my husband and dog.
Any advice for a student interested in this field?
I would say the best advice is to read and soak up as much as you can about parasitology both before you get into the field and after. A lot of research has overlap between different parasites and it’s helpful to know about other parasitic diseases that might not be your main focus. Plus, parasites are fun! 🙂 My other advice in general for starting graduate school is to always reach out to students in labs you’re interested in joining. Students are pretty much always willing to help give clear insight into lab dynamics, mentorship of the PI, and generally how life working in that lab is. That information is all really helpful to know when choosing which lab to join!
Support trainees like Grace by giving today to the Center for Tropical & Emerging Global Diseases.
By Donna Huber
Tania Rozario, assistant professor in the Department of Genetics and member of the Center for Tropical and Emerging Global Diseases, recently received a seed grant from the Hypothesis Fund to develop a new approach toward advancing tapeworm research. Her natural inquisitiveness and willingness to tackle tough questions has led to this moment.
As a child in Malaysia Rozario was fascinated with the world around her. Her interest was fostered by her grandfather who was an amateur botanist and science teacher. After reading about NASA in a kid’s science magazine, she wrote a letter to them. Their willingness to engage with her inspired her to see science as a real career choice.
“I was exposed to science at an early age,” said Rozario. “But what had the biggest impact on my decision to become a scientist was doing undergraduate research.”
By the time she enrolled in graduate school at the University of Virginia, she knew she wanted to study regeneration. She focused on developmental biology and embryology as she needed a strong foundation in these disciplines to pursue her future research. She returned to regeneration during her post-doctoral training in the Newmark laboratory at the Morgridge Institute for Research. It was then that she started her work in tapeworm regeneration.
“I was drawn to the untapped potential in tapeworms to understand basic biological functions,” she said. “Tapeworms have a complex lifecycle and are difficult to study in the lab – so there’s a challenge there too.”
The mechanisms of regeneration are poorly understood in tapeworms. Stem cells are responsible for regeneration. The Rozario lab wants to know what is special about the stem cells and signals in the “neck” as this tissue is the only tissue capable of regenerating new segments, despite the fact that there are stem cells everywhere in the tapeworm body.
“Tapeworms can grow very large, but regeneration only happens from a tiny part,” explained Rozario. “We want to know what genes are controlling it but right now we don’t have sufficient tools.”
With the gene-editing tool CRISPR/Cas, researchers have been making remarkable strides in understanding genes in many organisms. However, there is no evidence that transgenesis, the process in which genes are inserted into an organism, works in tapeworms.
This is where the seed grant from the Hypothesis Fund comes in.
“They have scouts who are looking for unconventional science – research where although there may be risk or uncertainty that it will work, it could have a transformational effect if it does,” said Rozario.
The Hypothesis Fund provides seed grants for bold ideas at the earliest stage of research, often before any preliminary data have been generated.
“There are a number of barriers to getting CRISPR/Cas to work in an organism,” said Rozario in response to the risk of this project.
She lists three things that are needed to successfully use CRISPR/Cas: the right type of organism, access to an early development stage, and the expertise.
“We are in a good position to make this work,” further explained Rozario.
The Rozario lab has successfully developed a number of tools to better study the tapeworm in the lab. Since tapeworms produce both male and female gametes in every segment there is plenty of early development stage material to work with.
“Thanks to this gift, we are able to bring in post-doctoral researcher Olufemi Akinkuotu from the University of Pennsylvania School of Veterinary Medicine,” said Rozario. “He has specific training in developing gene-editing tools in parasitic nematodes, which are distantly related to tapeworms but share many parallel challenges.”
While there is still a risk that CRISPR/Cas won’t work in tapeworms, if it does the payoff could be huge – not only for understanding the basic biology of tapeworms, but to further our understanding of stem cells in other organisms.
This story first appeared at https://research.uga.edu/news/uga-geneticist-gets-to-take-risks-with-new-seed-grant/
Rick Tarleton, Regents’ Professor in Franklin College‘s Department of Cellular Biology and member of CTEGD, is the featured guest on this episode of People, Parasites, and Plagues. Listen as he discusses his work with Trypanosoma cruzi and Chagas Disease, what transmission looks like here in the U.S., and the important research being done in this area.
