Moritz Blumer goes fishing 

If more people knew that a PhD in Computational Genomics could involve spending weeks on end scuba diving in Lake Malawi, there might be more applications than the University could handle. For Moritz Blumer, the fieldwork is a fascinating highlight of his research into the species diversity of the Lake Malawi’s cichlid fish.

 “Malawi cichlids have been studied for their diversity in appearance for more than a century,” the third year Darwin PhD student explains. “In less than a million years, which is a very short time on an evolutionary scale, an estimated 800-1000 species of cichlids evolved from one or a handful of ancestors in Lake Malawi. This makes the system ideal to study speciation. Speciation rates in cichlids are unparalleled by any other vertebrate group. Most interesting to me is that ever since people started to look into Malawi cichlid genetics, it became very clear that their genomes are much less diverse than what one would expect from the extreme variation in physical appearance.”

Even though all species can be crossed in a lab setting and hybridisation is common in the wild, the pronounced differences in appearance and ecology suggest treating them as different species. A significant question in evolutionary biology is how speciation can take place in the face of hybridisation and the absence of geographical barriers.

 “It’s possible now to sequence full genomes at large scale,” says Moritz. “So we’re trying to sequence as many taxa and specimens as possible to understand how this huge phenotypic diversity relates to genetic diversity, and to investigate the basis of explosive speciation. Malawi cichlids are from a genetic point of view a very complex and interconnected system, and frequent hybridisation makes species delimination challenging. One of the most interesting findings so far is the presence of large structural rearrangements within chromosomes, which we suspect are playing a role in speciation and adaptation.”

 This research drew Moritz from his native Germany, where he completed an undergraduate degree in Biological Sciences and a Masters in Ecology and Evolution at Goethe University Frankfurt, followed by a Master thesis at Dresden’s Max Planck Institute of Molecular Cell Biology and Genetics, to Cambridge.

 “I wanted to come specifically to work with Professor Richard Durbin on this project. I remembered the cichlids as textbook examples from high school science classes and was really excited by Professor Durbin’s genomics work. Getting my head around the College system took a bit of time, but once I started researching I really liked for example the fact that Darwin was the first College to admit women and men. And as a biologist, studying at a College named after the Darwin family is very cool!”

 Having previously studied the evolution of vampire bats, the focus on fish has necessitated a change of element.

 “Most of the fieldwork is spent scuba diving and trying to catch the fish, which is fun! Preserving the samples after a long day of fieldwork, and organising their transportation back to Cambridge is the time-consuming part.”

 While in Malawi Moritz and his group work closely with the University of Malawi and the Malawi Fisheries Research Institute. Before his next two-month field trip later this summer, however, he is completing a four-month internship in genomics research at the University of Montana.

 “It couldn’t be more different from Cambridge, in every possible way,” he laughs, gesturing at the mountains in the background of our Zoom call. “But it’s been a great experience.”

Katarina Grobicki catches flies

When Katarina Grobicki was at school, a career spent analysing fruit fly genes wasn’t on her radar.

 “I didn’t know ‘scientist’ was a job,” the Darwin PhD student says now. “My teachers suggested I apply for medicine, because there was an assumption that if you were good at science that was what you did, whilst my mum, who’s a nurse, told me not to go near healthcare!”

 Instead she studied Natural Sciences at Newnham, followed by an MPhil in Genetics. It was during her undergraduate degree that she began to realise that pursuing science for the sake of science was what she wanted to do longer term.

 “The actual practicals were quite formulaic, but talking to the postgraduate demonstrators about their PhD research was really exciting. I also did a summer project at Oxford during my undergraduate degree which really showed me that I enjoyed being in a lab.”

 Katarina made the short transfer down the road from Newnham to Darwin for her PhD, to take advantage of the opportunity to be part of a wholly graduate community. Her research explores the importance of translation in germline development, looking specifically at the ovary of the fruit fly.

 “Proteins are the workhorses of the cell, and translation is the final step of gene expression, which produces the proteins encoded by our genes. I’m looking at ribosomes, the machines within the cells which synthesise all proteins. The earlier stages of gene expression (such as transcription) are very regulated and have been well-researched, while historically ribosomes have been thought not to be particularly regulated. We’re now realising that ribosomes can vary between different tissues, and that regulation of translation and ribosome production is an essential part of the control of processes such as stem cell differentiation.”

 Gene editing technology has transformed the possibilities of this area of research, and Katarina is aware that her experience is unrecognisable when compared with that of her predecessors.

 “I can’t imagine doing science before CRISPR!,” she says. “Over the course of my PhD I’ve mainly been studying 11 different genes, and have made at least 5 mutations in each, plus designed tools to overexpress certain genes or tag them with fluorescent proteins. Flies are brilliant, and compared to other species there are just so many tools available for manipulating their genetics, thanks to them being used as a model for over 100 years, with each generation of scientists producing new tools.”

 During the pandemic, after lockdown, access to the lab was granted according to a strict shift pattern, and Katarina found herself only able to go in after 3pm. She signed up as a virtual volunteer with the Brilliant Club, a charity through which PhD students offer their time to support able but disadvantaged students in secondary schools.

 “I taught them about germline versus somatic genes and gene editing – it was amazing how quickly the students grasped the mechanics of CRISPR-Cas9, and by the end of the term we had a really interesting discussion about the ethical issues surrounding the Chinese CRISPR babies (three children born in 2018-19 whose genes had been edited as embryos).”

 With the end of her PhD now looming, Katarina is looking ahead to the next stage of her academic career.

 “I’m currently madly trying to do as many experiments as I can before I write it up. It’s such a strange world if you’re not familiar with it – when I say to my family that I’m applying for postdocs they say ‘is that another degree?’ The whole system of academia is quite bizarre, but I really love the science.”