Serena Dai

Wild Sand Rat Researcher

My Story

I moved frequently with my family – I was born in a rural town in China and by the age of 12 had lived in Shanghai, Texas, New York and Beijing. As a child, I was deeply interested in animals and plants. I remember getting a set of encyclopaedias for my 6th birthday, and I read the biology section so many times the pages fell out. In New York City, where I attended primary school, I was always eager to present at the annual school science fair – my chosen topics included chlorophyll, butterfly metamorphosis, and DNA structure.

By the time I entered secondary school in Beijing, I didn’t really think about studying biology at university – until I joined a biology interest group in 10th grade. I was really lucky because that year a research group in the Institute of Microbiology opened its doors to us and allowed us to visit their labs and conduct small research experiments with their graduate students there. This gave me a taster of working in a molecular biology lab and introduced me to technology that wasn’t in our biology textbooks – and I loved it.

I went for a degree in Molecular Biotechnology when I entered university – I wanted to learn more about the things happening at the molecular level and how people were studying these tiny molecules. One of the professors at my university, Dr. Lam, was extremely interested in DNA and the process of soybean domestication. Domesticated soybeans are quite sensitive to increased saline content in the soil, while their wild soybean cousins can thrive in saline-affected land. Dr. Lam aimed to find out what enabled wild soybean plants to survive in high salt conditions using a combination of DNA sequencing technology and genomic studies, and one of the main aims of his research was to breed plants that could be cultivated even in suboptimal soil conditions. His passion for using molecular biology to solve questions influenced me to pursue a PhD in molecular evolution.

I wanted to do a PhD because I realised I loved asking questions about DNA and trying different methods to test my hypotheses. However, when I shared this idea with others, the reply was sometimes a warning: I was told that PhDs were difficult for girls, and there was the prevailing idea that girls would naturally struggle with science subjects. Comments like this really disheartened me, but fortunately I had very supportive parents, friends and mentors, who encouraged me to believe in myself and apply to graduate school. Here in Oxford, I am doing a DPhil in the Department of Zoology, and my project focuses on the genome of the fat sand rat (Psammomys obesus), a rodent with some very “weird” genes.

My research on wild sand rats

Wild sand rats look pretty normal – they’re a common rodent found in desert areas around the Middle East and North Africa. In fact, they have a close relative, the Mongolian gerbil, that is often sold as a pet. So why is it named P. obesus? It all started when some researchers tried to keep these animals in the lab. After two to three weeks of feeding the sand rats rodent chow (which are like standard food pellets that you can get at the pet shop) the researchers noticed that some of the animals became very obese, and blood tests showed that their blood glucose levels were abnormally high! Further investigation showed that the laboratory rodent chow had slightly higher calorie levels compared to the sand rat’s natural diet, which mainly consists of desert plants, and some sand rats were developing type 2 diabetes just after two to three weeks of eating the chow diet. Something was causing these animals to be very prone to diet-induced diabetes, but what was the cause? Would this help us understand how type 2 diabetes develops?

One of the techniques we can use to understand an organism better is DNA sequencing. This can tell us what genes this organism possesses and allow us to reconstruct this organism’s genome (its entire DNA sequence consisting of four different types of ‘building block’ (or bases) – A, T, G, and C). DNA sequencing revealed something extremely interesting in the sand rat genome – sand rats have highly GC-rich regions where >75% of the DNA sequence consists of GC pairs. Normally we expect AT and GC pairs to each make up 50%, so this abnormal GC skew was very unexpected. What came across as even more surprising was the changes that were caused by this unexpected GC increase: lots of conserved genes were affected, resulting in “weird” genes with changes not found in any other vertebrate lineage!

My DPhil project focuses on finding out what these “weird” genes and their unusual protein products do. Do they have the same properties and function as their conserved counterparts? I use different molecular biology techniques to study this, and one of the key methods I use is expressing genes from different origins in cells that I culture in a dish. Most animals share common mechanisms in their cells that allow them to ‘read’ the information stored inside a gene and build protein molecules based on the instructions stored in the gene. This means that rat cells that I keep inside a culture dish will be able to build sand rat proteins based on information stored in sand rat genes. Working with cells also lets me use fluorescent chemicals to help me tag different proteins, which allows me to do things like seeing where these proteins are located and measuring how long it takes for them to be broken up and recycled inside the cell. It amazes me every time how assorted techniques can help us understand things happening at the molecular level!

Another amazing aspect of being a biologist is having so many opportunities to meet people from different places and with different research interests – whether it is in the department kitchen or at a conference venue. During my DPhil, I’ve had many opportunities to travel to different places, for example Strasbourg, France and Washington D.C., USA, to talk to fellow researchers at meetings or to share ideas with school students – studying molecular biology is definitely not just about working in the lab!