‘A great new environment’

Interview with the new MPIIB research group leader Mark Cronan

March 06, 2020

About one year has passed since the 2019 MPIIB Selection Symposium. Now Mark Cronan, the third new research group leader, is taking up his work at the Institute. Mark spent his postdoc at the lab of David Tobin, studying the granuloma in zebrafish tuberculosis models. He is now bringing his tuberculosis research to the MPIIB. Find out in the interview how zebrafish get to Germany, whether cats can get travelsick and why a disease of the lungs is being researched on an animal with gills.

What motivated you to join the MPIIB?

Compared to the US system, the Max Planck Society offers more support to young investigators­. Being an early career group leader can be difficult in other systems, where there is bigger pressure on publishing early and getting grants continuously. I think the institutional support and core facilities at the MPIIB really enable me to take long-term projects and turn them into something real. I am able to just do science and let the science guide me towards what I really want to do.

More than that, the great community of other researchers focused on infection biology was a huge advantage. It’s particularly exciting that there is a group of younger group leaders coming in at the same time. I think it will be a great new environment.

What are your to-do's for the coming months?

One of the biggest things I have to do is get all my zebrafish over here. There will be a lot of zebrafish related work in the coming months to establish my lab. I already recruited a PhD student who is starting in October and my hope is that by then we will be able to do experiments and not have to worry about this logistical headache anymore.

How do you move zebrafish across continents?

The eggs are tough and you can just ship them in a tube of water. They take a couple of days before they hatch, which means you have some time to ship them. My current strain list is about 40 lines. So I’m going to take over the quarantine space big time at the institute shortly, but I should be able to get all these lines through quarantine fairly quickly.

Is this your first big move from the US?

When I was a kid, my family actually lived in Australia for a year, so I have lived overseas a long, long time ago. But since I've been an adult this is my first big international move. We are excited for being over here for an extended period. Coming over from the states for holidays or conferences is always such a big commitment. You never can see all that you want to see. I would for example love to visit Slovenia and see a lot of Europe that I haven't had the chance yet.

Moving a household from the US to Germany sounds even more complicated than moving some zebrafish.

Yeah the last couple of weeks before we moved are a little bit of a blur, but we managed to ship everything over here. The good news is that people do it all the time, so there's a lot of resources in place for it. What we were most worried about was moving our two cats, but fortunately, they did really well on the plane. They were surprisingly good travellers and managed to do the 14 hours of travel time just fine.

What will be the focus of your research at the MPIIB?

My research is focused on tuberculosis. In particular the granuloma, a structure that forms from immune cells during a tuberculosis infection. I am very interested in understanding how this structure forms and what drives this formation. To study this, we are using zebrafish as a model organism. We infect the fish with one of the closest relatives to tuberculosis, a bacterium called mycobacterium marinum. It is known that this infection leads to granuloma in fish, comparable to human tuberculosis. One of the biggest advantages of zebrafish is that they are optically clear. This is a great situation for microscopy: You can watch the early phases of infections and even the bacteria being chased by immune cells within a live fish.

Your second line of research will be host-directed therapies–what role does the translation of results play in your studies?

One of the things we always run into, given that we work on a disease of the lungs in an animal without lungs, is the question: does it really matter to patients? It’s central for us to show that what we find in fish is also true in humans. Fortunately, zebrafish-mycobacterium marinum models have a good track record of translating into human clinical findings. There are currently several clinical trials based off of data from the zebrafish.

If we see promising things in the fish, we will try to translate these results first into an intermediate mammalian model. However, in the long term we would like to talk to clinical researchers to set up clinical trials where we can directly prove that what we observe in fish translates to patients.

What do you enjoy about science?

One of the things I enjoy most about science is the excitement of it and the notion of being an explorer. It’s very exciting to see something new, to observe a process and then come up with a new set of experiments.

Another thing is the collaborative process to science. Talking to your colleagues to shape your ideas and being able to share your science with a wider community is just as exciting.

One last question: Do you have zebrafish at home?

I do not - I had an aquarium as a kid, but I haven't had one since then. Mostly because the cats would probably get into it. And I see a lot of zebrafish every day anyway.

The Interview was conducted by Christian Denkhaus

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