From sharks to mammals

My name is Idoia, I am a PhD student within the Brainshark group at the University of Santiago de Compostela (Spain). I am currently finishing a research stay at the University of Edinburgh (Scotland) funded by the travelling fellowships offered by the Company of Biologists.

It is being four years since I started my predoctoral period. During this time, I have considered several times to carry out an international experience but never found the right moment. Now, just in the final stages of my thesis, I though “now or never”, and here I am, in a wonderful wild place called Scotland.

This stay had involved many changes for me. Language, culture but, most of all, a change in the animal model I work with: from shark to mouse. In our lab in Santiago de Compostela, we use the shark Scyliorhinus canicula (also called lesser-spotted dogfish) as a model for developmental studies of the nervous system. Yes, a shark! Ok, a small one, but still a shark. We are interested in the evolutionary changes that have occurred in the developing and adult nervous system throughout vertebrate phylogeny but also in the analysis of the conserved traits between different animal groups. Analyzing shared and derived features in our model is yielding interesting data like the presence of neuronal tangential migratory routes in the developing telencephalon of sharks homologous to those described in other vertebrates.

I will start by answering the first question that people used to ask me whenever I go to a conference: “why sharks?” Of course, the phylogenetic position of cartilaginous fishes is crucial to assess the ancestral condition of the vertebrate brain. Moreover, in the last decades, there has been an increasing interest in the dogfish as a model for developmental studies. This is due to it presents some advantages with respect to other vertebrate groups which allow a detailed analysis of developmental processes. For example: external egg gestation and transparent eggs (easy accessibility to the embryo to the implementation of different experimental approaches), protracted embryonic development (gestation period from 6 to 8 months), large size of the embryonic brains and availability of embryos at any time of the year. See the eggs in figure 1. Moreover, unlike teleost fish (as zebrafish, the main fish model nowadays), the telencephalon of cartilaginous fish develops by a process of evagination instead of eversion wich allows more reliable comparisons with other vertebrates. In fact, many people cannot distinguish at a glance a shark embryo from a mouse one. Do you want to try? See figure 2.

In the last years, we have been studying the expression patterns of Pax6, a well-conserved transcriptional factor, during forebrain development in sharks. Some open questions in our investigation made us to contact to Dr David Price, in the University of Edinburgh, and propose him a short collaboration. He kindly accepted to having me at least for three months in his lab to check our hypothesis in a different model as well as to help in other aspects of his ongoing project on Pax6.

At the beginning was tricky, working with mice was a big challenge for me; but at the same time was amazing to do research in a species in which several optimized techniques are available. Particularly I enjoyed learning slice culture techniques and I hope to have time to implement them in shark embryos and perform some axon guidance experiments upon my return.

On the other hand, the non-academic experience was also terrific. I loved Scotland, their people, their accent, landscapes, music and traditions. This is a real beautiful corner of the world you have to visit at least once in life. Of course the weather was not the best thing but I have to say that it was way better than I was told.

But maybe the best thing I obtained from this experience is the personal enthusiasm impulse to face the final stage of my predoctoral period. It has been one of the best decisions I have made, without a doubt whatsoever, and I have to sincerely thank to the Company of Biologists for their support.

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