Interview Roger Y Tsien The light fantastic The remarkable American biochemist Roger Y Tsien tells us how he made his most famous discovery

n 2008 Roger Y Tsien shared the alone full sized proteins, we would have to Nobel Prize in Chemistry for the adopt the techniques of molecular biology discovery and development of the rather than synthetic chemistry. green fluorescent protein (GFP). I started in around 1988 by discussing a This glowing molecular tool has collaboration with Alexander Glazer revolutionised many areas of on phycobiliproteins, a family of biochemistry research, allowing fluorescent proteins from blue-green algae. Iresearchers to visualise the expression However, these needed a separate partner of certain genes or certain protein to insert the chromophore, molecules within cells. the part of the molecule Molecular biologists have responsible for its colour. since found countless uses for GFP and Why was the similar molecules, fluorescent protein of and fluorescent the jellyfish Aequorea proteins are now an victoria so useful? essential part of In 1992, Douglas biochemists’ Prasher at the Woods molecular toolkit. Bacteria expressing Hole Oceanographic fluorescent proteins used Institution cloned and Before you discovered as ‘paint’ on a petri dish sequenced the gene for GFP GFP, your work involved from Aequorea victoria. looking for dyes that could Although he was unable to help image neuronal activity. What work on GFP any further himself, inspired you to work in this field? he was willing to give samples of its DNA The visual system is the only sensory to requestors, of which there were two: system with the ability to display lots of Martin Chalfie and me. Marty’s lab events in spatiotemporal detail, so one discovered that GFP didn’t need help has to use one’s own visual system to from any other protein in the jellyfish, investigate another creature’s nervous so GFP had both availability and system. From very early on in graduate autonomy. It has taken us almost 30 school, I was attracted to developing more years to engineer an easily techniques for visualising neuronal expressible phycobiliprotein. activity as the best way to resolve many neurons firing simultaneously.

What led you to look at fluorescent I was attracted to proteins and their related genes? developing techniques My colleagues and I had painstakingly built dyes such as Fura-2 and Indo-1 – with for visualising molecular weights near 840 – for recognising neuronal activity as and visualising small calcium ions, whose molecular weight was only 40. So it seemed the best way to resolve that for the more general problem of many neurons firing recognising biochemical messengers such

SIPA PRESS/REX SHUTTERSTOCK PRESS/REX SIPA as cyclic AMP (molecular weight 329), let simultaneously

6 / The Biologist / Biochemistry Supplement Biochemistry Supplement / The Biologist / 7 Interview Interview Roger Y Tsien Roger Y Tsien

We want to use AFTERBEFORE biochemical differences between the tumour and normal tissue to © WENN LTD/ALAMY WENN © Left to right: Nobel Prize winners Paul make the tumour Krugman, Martin Chalfie and Roger Tsien with the then US president George W Bush fluorescent

Did you ever imagine that GFP and its BEFORE derivatives would be used by so many LIGHTING THE WAY researchers in so many different ways? A matched pair of photographs I knew that an autonomously fluorescent showing a tumour about to protein module would be of immense be excised, viewed without value, but I didn’t anticipate it would have and with the aid of tumour quite so many uses. imaging peptides

Do you have a favourite way in which GFP has been used? In this ‘brainbow’ image of a mouse’s It was satisfying when we got a phenomenon brain, different neurons glow with called fluorescence resonance energy different fluorescent proteins, allowing transfer (FRET) working between mutants researchers to visualise brain circuits of GFP. FRET senses the proximity of two fluorophores of different colours and had been a major goal when we set out. fluorescent substrates that are triggered synapses – and thus serve as molecular washed away by the next big wave or high But that’s now long in the past. Aequorea victoria by these enzymes to enter cells and substrates for memory. tide. Perhaps that’s a metaphor for much become trapped, and also to change of my career. How else do you think fluorescence might colour by modulating FRET (the same You hold around 100 or so patents for be used in the future? phenomenon mentioned above). A small various other biotechnology tools. Which You have a long tradition of engineering I can’t foresee a limit to future applications biotech company partly founded by me are you most proud of? in the family. Do you consider yourself a of fluorescence. After all, fluorescence is has just started a clinical trial with such In 1994, we started a biotech company chemist, biologist, bioengineer or what? an unusual and very useful property of molecules, together with the called Aurora Biosciences to use new I’m a muddled mix. When I was applying a small proportion of molecules. Under instrumentation for surgeons to see the fluorescence assays to speed up drug for my first faculty position, several biology the right circumstances it can be observed fluorescence as they operate. screening in the pharmaceutical industry. departments rejected me on the grounds in anything from single molecules to One of the projects Aurora took on was that I was a chemist, and at least one oceans, over nanoseconds to many days, What else is your lab working on to find drugs to help cystic fibrosis. Most chemistry department turned me down using the naked eye to the most at the moment? experts thought Aurora’s chances were as too much of a biologist. Almost all my sophisticated instruments. We are trying to gather evidence for a negligible, as the market for such rare work has been involved with tool building, ‘chromophore’ in the centre – it is new hypothesis for how and where the disease remedies was thought to be too but I have never had a formal engineering Can you tell us a little about fluorescence What is GFP? thought just three amino acids in the brain might store permanent memories small, and gene therapy was considered course or appointment. Fortunately, assisted cancer surgery? GFP stands for green fluorescent protein. protein chain create the fluorescent at the molecular level1. a much more promising approach. However, most forward looking departments In cancer surgery, fluorescence guidance It is a protein that glows green in the ‘chromophore’. It is stable, non-toxic to Previous hypotheses have assigned the Cystic Fibrosis Foundation backed have now adopted a more flexible and would be helpful because tumour tissue presence of UV or blue light, originally most organisms when expressed in cells, the site of memory storage to be various Aurora’s efforts, and fluorescence screening interdisciplinary viewpoint. Personally, doesn’t look any different from normal found in the bioluminescent and and requires only UV/blue light and proteins within synapses, the places at found the drug that was recently lauded by I don’t care much for labels. tissue under ordinary white light fluorescent jellyfish Aequorea victoria. oxygen to emit its eerie glow, making it which neurons communicate with each President Obama as an example of illumination. We want to use biochemical In 1992, the gene for GFP was perfect for in vivo applications. other. The difficulty with these hypotheses ‘precision medicine’. Such a long time is differences between the tumour and normal sequenced by American biologist Douglas Green fluorescent protein has since is that proteins inside synapses undergo required before one knows whether one References tissue to make the tumour fluorescent, so Prasher. The first to express the gene in been used in thousands of different continuous rapid turnover and replacement, has success or not. 1) Tsien, R. Y. Very long-term memories may be stored in the pattern of holes in the perineuronal net. Proc. Natl. that the surgeon can decide where to cut another organism was Martin Chalfie, an ways. Replacing a gene with the gene so that memories would require recopying Acad. Sci. USA 110(30), 12456–12461 (2013). with realtime guidance. American biochemist who shared the for GFP can result in GFP being expressed very many times over an animal or Were you interested in science as a child? Unfortunately, one cannot use GFP or its Nobel Prize with Tsien. He inserted the in the organism only in the places where person’s lifetime. I was always obsessed by pretty colours homologues, because they can be linked to gene for GFP into the bacteria E. coli and the original gene would have been Instead, we are looking at the and by technologies that seem useful. One Roger Y Tsien is professor of pharmacology malignancy only by sophisticated gene nematode worm C. elegans. The resulting expressed, creating a bright visual glycoproteins (proteins plus carbohydrates) of my earliest memories is of a beach that and professor of chemistry and biochemistry at the University of California, therapy that is not practical yet or ethical organisms then glowed green in the pattern of expression. By selectively known to form a coating just outside had a zone of coarse pebbles surrounded by San Diego. After graduating from Harvard, in human patients. Instead, we are presence of UV or blue light. labelling specific proteins, we can create synapses. We are accumulating two zones of sand. I tried to lay down a Tsien also held posts at Cambridge exploiting extracellular enzymes that The protein itself is a barrel shaped images to see exactly where those evidence that this coating, once formed, bridge of sand across the pebbles to make and Berkeley. He is also a noted biochemical inventor who holds more than 100 patents. He are turned on in practically all solid molecule with a colour producing proteins are present. is basically stable but can be locally crossing more comfortable for my tiny bare shared the Nobel Prize in Chemistry in 2008

malignant tumours. We have engineered © LISA WERNER/ALAMY STOCK PHOTO LIVET/WWW.OLYMPUSBIOSCAPES.COM JEAN DR remodelled to strengthen individual feet. Of course, the bridge would have been for his development of GFP.

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