The Gillis Lab has been making waves on Twitter recently... and so, of course, TFUI Founder Melissa had to reach out to talk to them about their research. Head of the lab, Andrew Gillis, was kind enough to take some time to speak to us! We talk about embryonic development of cartilaginous fishes to understand the origin and early evolution of vertebrates (curious? Keep reading!), chimaeras, and what he hopes for the scientific future of the UK...
The Fins United Initiative: Thank you for your time, Andrew! We're curious to know... did you always want a science job or did another subject peak your interest first?
Andrew Gillis: I was always really interested in science and maths, and I spent a lot of time collecting and observing things outside as a child. As I approached University, I thought that I wanted to become a medical doctor, and I was taking courses with this in mind - until I took a developmental biology course with a man named Prof. Brian Hall. Developmental biology is the field of study that deals with how things grow from a single cell to a complex organisms with different tissues, body parts, etc. I found the subject fascinating - and Brian’s research inspirational - and this led me to think about alternative careers paths - i.e. a career in research.
AG: It soon became clear to me that a career in science, and particularly in the field of "evolutionary developmental biology” (which is the study of how changes during embryonic development can lead to the evolution of anatomy) could allow me to combine my love of wildlife and the outdoors with my new-found love of animal development. It is probably that combination of interests that eventually led me to develop the research programme that is now the basis of my team’s work here at Cambridge.
TFUI: What is your lab currently studying right now?
AG: We study lots of different things in my lab - the embryonic development of jaws, gills, fins, backbones and paired sense organs - but most everything centres around the embryonic development of cartilaginous fishes. The overarching question that motivates our research is: how did the vertebrate body plan evolve?
TFUI: And what does that mean?
AG: Or, in other words, how (on an evolutionary time scale) did vertebrate animals acquire the key structures that set them apart from their invertebrate cousins. It turns out that understanding how cartilaginous fishes build their body is very important for our understanding of vertebrate body plan evolution. We share a common ancestor with cartilaginous fishes very deep in our evolutionary past (probably ~500 million years ago!).
TFUI: Wow! That is fascinating!
AG: So things that we share in common with cartilaginous fishes, like jaws, must have originated at these very early points in vertebrate evolution. So, for example, if we can understand the genetic mechanisms that different kinds of animals use to build their jaws, then we can compare these mechanisms to identify the most basic, shared programmes that were ancestrally used to build these features in our distant ancestors. On the other hand, we can also use this approach to learn about genetic changes that make different kinds of animals unique - for example, why our jaws are built of bone and are fused with our skull, while shark jaws are built of cartilage, and have only a loose connection to their braincase.
TFUI: So, in your opinion, why is your work so important?
AG: Our work is what you would call basic research - i.e. it is done not with the express aim of curing a disease or developing a new product, but rather to gain a fundamental understanding of how biological systems work. It is our hope that by reconstructing the evolutionary history of the vertebrate body, we will come to learn more about ourselves, and about the mechanisms that have led to the incredible diversity of life that we see on earth today. Of course, that is not to say that our research won’t also contribute to cures for diseases or other similar advances. We spend a lot of our time investigating the genetic basis of skeletal development in sharks and skates, and there is a very good chance that discoveries that we make in this area could someday advance cures of skeletal disorders, such as osteoarthritis. Nature has conducted millions of experiments for us, through the evolution of a plethora of species, with countless examples of adaptation to (sometimes rather extreme) challenges. By understanding how animals have evolved ways to solve problems - whether repairing an injured organs, swimming more efficiently or continuously replacing their teeth - we can almost certainly learn new ways to approach the many challenges that humans face our daily lives.
TFUI: Sound important to us! Now, you stated that you spent a few weeks studying elephant fish around the South Island of New Zealand a few years ago. If you can, can you tell the TFUI audience a bit about what you were doing and what you found?
AG: Yes, that was an amazing research experience - and a really fun trip! This actually gets back to an idea that I mentioned [earlier], about natural experiments. One of the questions that we are interested in answering in my lab is how animals can make paired appendages (e.g. fins, limbs) of the right shape and size. Cartilaginous fishes are really interesting for this kind of work, because in addition to their fins, they also have another set of paired appendages called “branchial rays” that extend from their gill arches.
AG: So this presents a really interesting opportunity to see whether different kinds of paired appendages are formed under the control of a common genetic programme, or whether the evolution of a new set of appendages requires the invention of a new genetic programme. As many of your readers will know, there are two major lineages of cartilaginous fishes: the elasmobranchs (which includes the sharks, skates and stingrays) and the holocephalans (which includes the chimaeras). There are some really interesting differences between the skeletons of elasmobranchs and holocephalans, and one of these has to do with their branchial rays: elasmobranchs have five sets of branchial rays, while holocephalans only have one. This means that we can compare the development of the gill skeleton in these two groups, in order to identify developmental features (i.e. genes and cell types) that correlate with the presence or absence of branchial rays.
TFUI: How was this research accomplished?
AG: In order to do this research, we needed to study and compare the embryonic development of elasmobranchs and holocephalans. Elasmobranch embryos are relatively easy to get (as I’ll mention below, there is a species of skate that we have studied extensively for the past several years), but holocephalan embryos are much harder to come by. Most holocephalans spend their entire existence in relatively deep water, making it difficult or impossible to study their embryonic development. However, there is a species called the elephant fish (Callorhinchus milii) that lives off the coast of Australia and New Zealand, and that migrates into shallow bays to lay eggs. So my wife, Kate (who is also a biologist) and I teamed up with some fisheries biologists in Australia and New Zealand, and we spent several weeks diving in bays to collect elephant fish eggs (with financial support from National Geographic, Australian Geographic and the American Museum of Natural History). We ended up collecting quite a few eggs, and we were able to carry out a comparative study of branchial ray development between skates and holocephalans. In the end, we found that expression of an important developmental gene (called, funnily enough, Sonic hedgehog) correlated closely with the presence of branchial rays - and we’ve since gone on to discover that this gene plays a very important role in branchial ray development (you can find some more information about this recent finding here, with some press coverage here).
TFUI: In your opinion, why are chimaeras so important evolution-wise?
AG: People often think of cartilaginous fishes as generally looking very “shark-like” or “ray-like”. The chimaeras offer a nice example of anatomical diversification, and demonstrate that within cartilaginous fishes, we can actually find a whole host of interesting body forms (including the totally whacky-looking elephant fish, complete with a curly proboscis and sharp fin spine!).
TFUI: If you don't mind me asking, your lab is based in Cambridge, UK. Do you think Brexit will have a negative impact on your research?
AG: I don’t expect that anything good will come of Brexit, and I’m very saddened by the result of last year’s referendum. I think that the UK has gained a great deal from being part of a broader European community of scientists and researchers, and while I’m hopeful that many of the links with our European colleagues will survive this unfortunate move, I fear that the collaborative spirit that we have long shared could take a hit (as a consequence of politics - not because scientists want that to happen).
TFUI: Are you seeing this already happening?
AG: I’ve not noticed any impact on our research yet - but one of the great things about being an academic within the UK has been the ease of building networks and teams of colleagues from all over the world. I just hope that people don’t avoid coming to work with us here because of a perceived anti-European sentiment.
TFUI: So, let's forget about all the limitations science has (i.e. lack of funding, space, time, equipment). What is your dream project?
AG: Most of my work on chondrichthyans over the past ten years has focused on the the little skate (Leucoraja erinacea). This species is relatively abundant along the east coast of North America, and it is oviparous (egg-laying), which makes it a really great species for studying embryonic development. Every year, in the summer, my lab relocates to the Marine Biological Laboratory in Woods Hole, where we study the development of the little skate.
TFUI: Sounds fun!
AG: To do this, we capture female skates, and we collect the eggs as they lay them in their tanks. I’ve worked with tens of thousands of skate eggs collected from tanks over the years, but it recently occurred to me that I know absolutely nothing about where these skates live, and how they move around in the wild. When the animal collection teams at the MBL head out to fish skates for me, they always find the adults, but it is very rare to find any juveniles or subadult skates in the wild. In fact, we don’t even really know where they lay their eggs in the wild. I would love to find a way to tag and track (long-term - i.e. for years!) individual skates in the wild, from hatching through to adulthood, to see where their nursery grounds are, how they move around during different phases of their life, and whether/where they migrate. This kind of thing is well outside of my field, and I don’t even know if the technology exists to do these kinds of long-term tracking experiments. It just strikes me as incredible that we can know so much about an animal’s embryonic development in a lab context, but so little about their basic biology in the wild.
TFUI: Do you think people in your country have a good relationship with the ocean environment? If not, what can be done to better it?
AG: This is a great question, and I put it to one of my postdoctoral fellows, Dr. Victoria Sleight, who did her undergraduate degree at Plymouth University, and her PhD at Heriot-Watt University and the British Antarctic Survey - so she’s a proper marine biologist!
TFUI: [laughs] Ooh, what did she say?
AG: Vicky said that her impression is that most people in the UK have either no relationship with the ocean environment, or their relationship is based on the wonderful work of Sir David Attenborough and the Blue Planet documentaries. She thinks that the best way to improve this relationship is through education - i.e. teaching it at school through to A level (i.e high school level). Vicky said that she didn’t learn anything about marine biology until she started her degree in the subject, and she thinks that should change (and I agree with her!).
TFUI: I like her answer-- and we love your series of #SeedorEgg on Twitter! How did that come about?
AG: That actually started thanks to our lab stick insects! My daughter and I collect stick insects, and we keep them in my office at the University of Cambridge. My lab and I have lunch together in my office every day, where we are surrounded by many cages of exotic stick insects (at the moment, we keep 10 different species!). A lot of my stick insects breed quite readily, and lay a lot of eggs - and most of these eggs look remarkably like seeds. At that time, my lab had just recently become active on twitter, and we were trying to come up with some kind of game that would allow us to engage with our followers.
TFUI: We love guessing!
AG: Since we are all developmental biologists, we thought that one fun game might be to post a picture of and egg or a seed each week, and have people guess which it is (and from what species). And from that, #SeedorEgg was born! For the first couple of weeks, we started using some of our stick insect eggs, since they were eggs that looked very seedy. But after that, we started to branch out, and it became a bit of a group activity to come up with ideas fo the next round. We have some keen gardeners in the lab who have collected some really interesting looking seeds, and we are also attached to the University of Cambridge Museum of Zoology (which has some great eggs in its collection). I think one of my favourites so far was the tinamou egg that was collected by Charles Darwin on the HMS Beagle - this amazing specimen is in the collection here in our museum.
TFUI: What is the coolest research you've done so far?
AG: I think that the paper I’m most proud of so far is actually the one on holocephalan gill arch development that I discussed [earlier]. I loved how this project combined an element of fieldwork (diving for elephant fish eggs in Australia and New Zealand) with lab work, to study the molecular mechanisms underlying anatomical difference between different groups of cartilaginous fishes.
TFUI: It does seem like really fascinating results.
AG: More recently, we had another paper out on the embryonic origin of gills in skates, and I think that this was a really cool study, too. There had been a historic debate about whether jawed vertebrates (bony and cartilaginous fishes) and jawless vertebrates (hagfish and lamprey) evolved gills independently from one another. It had been suggested that this was the case because the gills in these groups arise from different embryonic tissues - in jawless vertebrates, gill develop from the skin the lines the inside of the throat, while in jawed vertebrates, it was thought that the gill developed from the skin that forms on the outside of the head. We were interested in testing whether this distinction holds true, so we did an experiment where we labeled the skin that lines the inside of the throat in skate embryos, and followed this tissue through development, until the gills had formed. We found that the skin that lines the inside of the throat actually moves to the outside of the head and gives rise to the gills, just like in jawless vertebrates. This supports the view that gills in jawed and jawless vertebrates are not independently evolved, but actually have a single, common origin very early in vertebrate evolutionary history. I think the cool think about this paper is that it was read with interest not only by other developmental biologists, but also by palaeontologists - so it is a nice example of how findings from one discipline can sometimes help resolve longstanding problems in another.
TFUI: So, What’s next for you?
AG: One area we are just starting to explore in the lab is cartilage repair. In mammals (like ourselves), cartilage is mostly an embryonic tissue, making up the template of the bony skeleton. Most cartilage is replaced by bone early in our life, and the bits that remain (i.e. our joint cartilages) have very limited capacity for repair. Chondrichthyans, on the other hand, have a skeleton that is made entirely of cartilage, and that remains cartilaginous throughout life. We have recently discovered that adult skates have the capacity to repair injured cartilage, and we are investigating the molecular basis of this ability, in hopes that it could shed light on new strategies for cartilage repair in people (i.e. from age-related osteoarthritis, or from sporting injuries).
TFUI: And I have to ask -- what is your favorite Chondrichthyan species and why?
AG: Most of my work over the past ten years has focused on the little skate (Leucoraja erinacea). This is a small species of skate that we work with at the Marine Biological Laboratory in Woods Hole, and we’ve come to understand a lot about this remarkable animal’s embryonic development. So I can say quite confidently that this is my favourite species! Like many cartilaginous fishes, the little skate lays eggs, which allows us to watch and record their embryonic development very easily. You can actually watch a montage of different stages of skate embryo development at this link.
THE FINS UNITED INITIATIVE WOULD LIKE TO THANK andrew FOR HIS TIME AND
TFUI Founder Melissa C. Marquez is author of all animal bios and "Behind the Fins" segments.
SEE MELISSA'S TEDx TALK HERE:
SEARCH BY CATEGORIES