Keaton Schuster completed his PhD in the lab of Rachel Smith-Bolton at the University of Illinois, USA, investigating Drosophila wing disc regeneration before joining Lionel Christiaen's lab at New York University, USA, for his postdoc studying heart regeneration in the chordate tunicate Ciona robusta (formerly Ciona intestinalis type A). Keaton is part of the second cohort of Development's Pathway to Independence Programme fellows and we spoke to him over Teams to learn more about his career to date and his future plans for starting his own group continuing to use emerging model systems to study cardiac regeneration.

Let's start at the beginning, when did you first become interested in science?

My mom was a teacher and my dad was a medical professional, so while growing up in rural Wisconsin, there was always science and nature around me, but my ‘gateway drug’ for science was probably dinosaurs. I was obsessed with dinosaurs to the point where I would read everything about them in National Geographic, Scientific American, etc. I was a really big nerd for that and it obviously developed into other interests in science. I became interested in development in college. I read a book on EvoDevo (Endless Forms Most Beautiful by Sean Carroll; Carroll, 2005) and I thought it was awesome. This inspired me to take courses in genetics and developmental biology and eventually lead to an undergrad research position in the Ikeda lab at UW (University of Wisconsin). I decided then that wanted to do this for the rest of my life.

Was it at that point you decided to pursue a PhD?

Yes. Growing up, it felt like there were only two things you could do if you were good at science: either become an engineer or a physician. However, once the world of research opened up to me in college, I didn't look back and applied to PhD programs. I developed an interest in regeneration late in my undergraduate studies, and then I knew it was one of the many topics I could be interested in doing. Rachel Smith-Bolton's work was really cool; she was doing a forward genetic approach to identify important genes for regeneration. I joined her lab as her first graduate student. I knew almost immediately that it was what I wanted to do because I had a genetics degree and was also interested in regeneration – it seemed like a perfect fit.

What did you work on during your PhD with Rachel Smith-Bolton at the University of Illinois?

I sought to understand the genes important for patterning and cell fate during regeneration. I identified a regeneration-specific patterning mutant that turned out to be the gene called Taranis, which is essential for posterior cell fate. Taranis mutants, even heterozygotes, undergo posterior-anterior fate transformations during regeneration, resembling classic engrailed mutants. I found that Taranis was essential for protecting Engrailed from becoming misregulated by the wound response induced by JNK signaling (Schuster and Smith-Bolton, 2015). I also discovered that the pioneer transcription factor Zelda is upstream of Taranis, and it has also been shown to be important for other patterning transitions (Bose et al., 2024 preprint). This work is unpublished and has recently been submitted to a journal, so stay tuned for that.

How did you come to join Lionel Christiaen's lab at New York University for your postdoc?

I knew that I wanted to work on an emerging model system for my postdoc, because you can ask questions that are not possible in traditional models. I was interviewed at a bunch of places that, for example, worked on spiny mice, killifish, lamprey, etc. I had to look deep into the literature and find who would be interested in these topics, which led me to Ciona and Lionel. There are two big reasons why I've really liked the Ciona system: First, I knew from learning developmental biology that ascidians are classic models for understanding mosaic development. Much like C. elegans, they have invariant cell lineages and if you ablate a blastomere or any other embryonic cell type, they don't regenerate it back, which is different from what you see in mammals or fish or frogs, where, if you get rid of a cell, it will come back. However, unlike C. elegans, Ciona can regenerate after embryogenesis – it somehow acquires regenerative capacity. This seemed like a cool observation because it raised the question of how an organism can acquire regenerative competence, which was exciting. Second, Ciona are also interesting because they're in a critical evolutionary position. You can learn the origins of vertebrate traits because they are the closest relatives to vertebrates. For about 120 years, people said that Ciona couldn't regenerate its heart largely because of the traumatic method of injury that was used to study their regeneration; if a Ciona is cut in half, it'll regenerate the top, which includes the siphons and brain, but cannot regenerate the bottom half, which contains its heart and other visceral organs. Lionel wrote a review detailing that, although this is the case, there are some reasons to believe that heart regeneration might actually be able to happen (Evans Anderson and Christiaen, 2016). I wanted to go into something where I could really carve my own niche, and the heart has obvious biomedical implications, so I emailed Lionel and asked him if I could interview for a postdoc position to see if Ciona can regenerate its heart. He emailed me within about an hour and invited me to go to New York for the interview. The rest is history.

I knew that I wanted to work on an emerging model system for my postdoc, because you can ask questions that are not possible in traditional models

What did you do during your postdoc?

I asked a simple question: does the Ciona heart regenerate after targeted damage? This first required the development of tools to both damage and visualize the heart before and after damage. Most of what we know in Ciona is about their embryogenesis, and we know almost nothing about what happens after the larval stage in a post-metamorphic animal. I had to find markers that would label the heart. I also had to develop tools to actually study juveniles, because they have a cellulose tunic that makes them more difficult to work with. I adopted the nitroreductase (NTR) and metronidazole (MTZ) genetic ablation system, which is commonly used in zebrafish to ablate various lineages by using NTR to convert MTZ to a toxic byproduct, which kills the cell. I found that, after ablation, Ciona hearts are indeed able to regenerate and, depending on the severity of the injury, they had different responses and different cell types that contribute to regeneration. If you ablate part of the heart, it will regenerate, much like a zebrafish heart, by the proliferation of surviving cardiomyocytes. But, surprisingly, when inducing very severe injuries where the vast majority of the heart, if not the entire heart, is ablated, these hearts often still do regenerate via a contribution from a population of endoderm-derived cells, which we call regenerative de novo cardiogenesis (Schuster and Christiaen, 2023 preprint).

How was your experience of moving from working with a classic model organism like Drosophila to an emerging model system such as Ciona?

You make everything yourself so there's definitely somewhat of a learning curve. In flies, you're used to having the having all these transgenics available to you and everything seems to work on the first try. Ciona sometimes throws some wrenches into the process. Typical techniques that would normally work in Drosophila probably won't work the first time in Ciona. Everything needs to be optimized for the system. One big challenge, for example, is that, due to these animals living in salt water, salt concentration becomes a huge consideration and you have to change many buffers to accommodate more salt. Ciona embryos are liable to burst if the salt concentration is too low. Despite these challenges, the unique discoveries in emerging model systems are incredibly rewarding, which offsets any frustration from technical hurdles.

Where are you in the process of securing an independent position and why did you decide to apply for Development's Pathway to Independence Programme?

I started the process of applying for independent positions last year. It was humbling. This was the impetus for going into this programme. Like most people, I think I heard about it on Twitter (X), but Lionel forwarded an email notification to me encouraging me to apply. I thought it would really help to give me all the feedback and a cohort for support and advice – the mentorship opportunities seemed incredible and I definitely like the idea of elevating my profile.

What are the most important considerations for you when choosing where to start your group?

I'm mostly focused on the USA, but if the right position pops up in Europe, I might take a look at it. I really like living in New York, so I wouldn't mind staying here, but I also recognize the realities of the market; you do have to apply broadly as well. I am always up for the next adventure. I'd like to end up somewhere that has a lot of facilities and has faculty that's collaborative. I need access to a confocal microscope, for example, and having a genomics core where we can do single-cell genomics and other omics-type technologies would be great. Obviously, having an aquatic facility would be great – we don't need it to be as sophisticated as a zebrafish facility; it could be a little bit more humble, such as one large water tank to hold wild-caught Ciona at least. I would like to have stable Ciona transgenics, so I would like to have a small facility with multiple small tanks and equipment to grow algae, which will allow us to maintain those lines over multiple generations.

What excites you most about becoming an independent researcher?

It's exciting to be the leader at the helm and determine the research direction. I also like mentoring students; I've always found that very rewarding. I am also looking forward to teaching lectures. Those allow you to connect to the most students possible and to inspire the next generation of biologists.

And conversely, what do you think will be the most challenging aspect of being a principal investigator and how will you prepare for it?

I think it'd be hard not being able to do my own experiments as much. I love doing bench work, and stepping back from that will probably be hard. Also, being a principal investigator, you have to wear a bunch of different hats and be able to balance all those responsibilities at the same time. There will be a learning curve.

What research questions would you like to address with your own group?

I am interested, broadly speaking, in the origins of regeneration. This can be at the cellular level: what cell types contribute to regeneration and is there any plasticity involved? I'm also interested in the developmental origin of regeneration: how does Ciona acquire regenerative capacity during development? I think my niche is understanding how organisms can acquire regeneration over different timescales, including evolution: how did regeneration evolve in the first place? Ciona will be a workhorse in the lab, but I also want to branch out into other organisms as well because I want to use models that can answer the question most effectively. For example, I am interested in using amphioxus to understand the development and regenerative capacity of the myoepithelial cells that line their blood vessels.

In your opinion, what are some of the most exciting advances in your field?

Regeneration is unique because it lags behind in understanding a lot of molecular mechanisms. This is largely due to many of the experimental models that regenerate well not being genetic model systems. This is improving due to inventions such as CRISPR/Cas9 and laborious establishment of transgenic lines, making non model organisms more experimentally tractable. I am excited by any new mechanistic insight because it's one of the final frontiers of regenerative biology. I'm also excited whenever a new model for regeneration drops. Studies on regeneration have given us surprises, such as reactive oxygen species and senescence actually being critical for a proper regenerative response in various models, where they have previously only been shown to be detrimental in disease models. I expect more unexpected findings like these in the future.

I am excited by any new mechanistic insight because it's one of the final frontiers of regenerative biology

Who have been some of the mentors who've helped you in your career?

There have been a lot (and many were unofficial mentors), all with different perspectives and different strengths. One of my first ‘unofficial’ mentors was the late John Fallon, who studied limb development in chicken embryos. When I was an undergrad, he helped me navigate through the process of applying for a PhD and having deep discussions on developmental biology. Obviously, Rachel and Lionel are huge mentors of mine. I wouldn't be where I am now without them! I would also like to highlight Anna Di Gregorio, Akihiro Ikeda and Brian Freeman as additional mentors throughout the years. Ken Poss is my mentor in this program as well, and I am grateful for the insightful discussions we've had so far. I have always been a big fan of his work.

Tell me more about your interest in diversity, equity and inclusion

I believe it is very important to be aware of these things and be proactive about contributing to these initiatives. For example, I've participated in the Summer Research Program(s), where they bring in students that would not normally get the opportunity to perform research. One of the students I am most proud of was a part of this program and is now a manager at Pfizer. I've been so lucky to work with so many people from different backgrounds, and I want to make my lab a safe and inclusive space for everyone.

What do you get up to outside of the lab?

I believe you need to have a life outside of the lab, finding friends outside science. I really like doing outdoors-y things like canoeing and kayaking. Every year, I go up to Canada with my dad to go on this completely off-the-grid canoe trip. I'm also in this ‘silly’ running club that runs to various bars and into the wilderness, running through woods, swamps and rivers. While it would be nice to live in a place that has easy access to the outdoors, my experience in New York City has shown me that I can be very adaptable.

Keaton Schuster's contact details: New York University, New York, NY 10010, USA.

E-mail: [email protected]

Keaton Schuster was interviewed by Alex Eve, Senior Editor at Development. This piece has been edited and condensed with approval from the interviewee.

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