First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Dennis Klug is the first author on ‘A synthetic promoter for multi-stage expression to probe complementary functions of Plasmodium adhesins’, published in Journal of Cell Science. Dennis conducted the research in this article while a PhD student in the lab of Prof. Friedrich Frischknecht at Heidelberg Medical School, Germany. He is now a postdoc in Dr Stéphanie Blandin's lab at the IBMC, Strasbourg, France, investigating host–pathogen interactions of the mosquito and the malaria parasite Plasmodium with specific interest in immune components and receptors that support or prevent mosquito infection.
How would you explain the main findings of your paper in lay terms?
When I tell people that I work on malaria, many know about the disease in tropical countries but are less aware that this disease is caused by a single-cell protozoan parasite called Plasmodium. Some Plasmodium species can infect reptiles or birds, some others infect humans. All have in common that transmission occurs by the bite of an infected mosquito. In our lab we study the transmission of the malaria parasite Plasmodium berghei that infects only rodents. We are especially interested in the infective stages of the parasite that initiate colonization of the vector (i.e. the mosquito) and the vertebrate host (e.g. the mouse). At this stage, the parasites are elongated, highly motile cells that are adapted to traverse tissues to reach their final destination, the outside of the mosquito midgut or the liver. In order to be prepared for this task, these stages possess surface proteins called adhesins that form a bridge between the inside of the cell and their environment. Adhesins are believed to make contact with the environment while motor proteins inside the cell move them along the cell membrane. By this process the parasite propels itself forward while the adhesins translocate towards the back end of the cell, similar to a caterpillar moving on its tracks. Interestingly, each stage produces its own adhesin but all share a similar organization and only differ in composition. We wondered if the adhesin expressed in early mosquito stages, called CTRP, can replace the adhesin expressed in late mosquito stages, called TRAP, and the other way around. In order to find out we expressed TRAP in early stages in the absence of CTRP and CTRP in late stages in the absence of TRAP. This way we could show that ‘early’ TRAP supports motility but not colonization of the mosquito midgut, whereas ‘late’ CTRP prevents motility and invasion. Our results support the hypothesis that adhesins have the same mode of action but differ in the recognition of their protein-binding partners or environmental adaptions.
Were there any specific challenges associated with this project? If so, how did you overcome them?
The challenge of this project was the life cycle of Plasmodium. If the adhesin CTRP is not expressed in early mosquito stages, colonization of the mosquito midgut does not take place and none of the later parasite stages that we planned to investigate can develop. To overcome this problem we had the idea to change the CTRP promoter in such a way that it would initiate gene expression in both early and late mosquito stages. Unfortunately, we could not find any promoter in the literature that would fit our needs but we found several publications describing DNA motifs specifically guiding gene expression in early or late mosquito stages. In the end, we tailored the promoter we needed by combining different DNA motifs. By generating parasite lines that express a fluorescent protein under control of this synthetic promoter we could show that it indeed guides gene expression in early and late mosquito stages. Subsequently, we applied our synthetic promoter and exchanged the native promoters of CTRP and TRAP to analyze their expression in both early and late mosquito stages.
When doing the research, did you have a particular result or ‘eureka’ moment that has stuck with you?
“[…] to see that our observations matched our hypothesis was a very joyful and satisfying moment.”
This moment was when I first looked down the microscope at early mosquito stages that expressed ‘early’ TRAP but no CTRP. They were perfectly motile! This was the key experiment of the study, and to see that our observations matched our hypothesis was a very joyful and satisfying moment.
Why did you choose Journal of Cell Science for your paper?
As always, we had a small list of journals with scopes fitting our manuscript, Journal of Cell Science being one of them. Decisive for me was that Journal of Cell Science is published by a nonprofit organization and that peer review is thorough. Moreover, Journal of Cell Science has been able to keep high standards and a very good reputation over more than a century, making it redundant to advertise the much-debated impact factor.
Have you had any significant mentors who have helped you beyond supervision in the lab?
I was very lucky to start my PhD in a growing lab, together with several other highly motivated PhD students, all working on the same model organism but on different topics. As the years passed we formed a very close community; everybody helped each other, and we discussed problems whenever possible. I was also very lucky to have Freddy Frischknecht as supervisor, he gave us a lot of freedom to develop our own projects and always offered his support.
What motivated you to pursue a career in science, and what have been the most interesting moments on the path that led you to where you are now?
I think that I never really made the decision to start a career in science, in fact I am still not sure if I will continue to follow this path. But I have the feeling that I am quite good at what I am doing, and scientific results have always been a big motivation for me. A few years ago I participated in the ‘Biology of Parasitism’ course (insiders just call it BoP) at Woods Hole. This was a great inspiration for me, and I always enjoy remembering it.
Who are your role models in science? Why?
I have always been fascinated by Charles Darwin and how he fitted his observations into a theory that is still valid today. Unfortunately, On the Origin of Species is still on my list of books I have to read.
What's next for you?
I have just started a postdoc working on Anopheles mosquitoes with Stéphanie Blandin and Eric Marois in Strasbourg. The results I will be able to obtain during this time will decide my next steps. But luck and serendipity are always required to be successful. Hopefully I am prepared to grasp these moments.
Tell us something interesting about yourself that wouldn't be on your CV
I used to breed different species of butterflies in my youth and started a little apiary at my parents' place. Nowadays I take care of a few thousand mosquitos, but I hope that I can add some bees again at some point.
Dennis Klug's contact details: Université de Strasbourg, CNRS UPR9022, INSERM U963, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France.