Scientists regularly use fluorescent proteins as reporter molecules to track proteins and cellular activity (Figure 1). But who discovered and developed these proteins into such valuable tools? Several people were involved, but one person played a crucial role in developing the multicolor proteins that started with the green fluorescent protein (GFP). This article reviews the life, work, and impact of the Nobel Prize winner Roger Yonchien Tsien, who took a single tool and expanded it into the fluorescent protein toolset available to researchers today.

Who was Roger Yonchien Tsien?

Chinese American chemical biologist Roger Yonchien Tsien was born on February 1, 1952 (Figure 2). His father went to MIT and was a mechanical engineer, and his mother was a nurse. Scientific experimentation began early for Tsien. “Some time in elementary school my parents bought a Gilbert chemistry set, but I didn’t find it very interesting because the experiments seemed so tame. Then I discovered a book in the school library that had much better experiments and illustrations,” Tsien described in his Nobel Prize autobiography. In that autobiography, he also detailed some of the experiments involving colorful chemical compounds that sparked his interest in chemistry. It seems fitting that he developed the colorful protein toolset that changed the way scientists visualize living organisms. Doing experiments from a young age—some very dangerous for an 8–15-year-old—helped him learn the rigors and difficulties of research.

Tsien went on to study neurobiology at Harvard, receiving his bachelor’s in 1972, and continued in this field later in his career. In 1977, Tsien received his PhD in Physiology from Cambridge. In his research, he aimed to study neurons in parallel, instead of individually, and thought this could be solved using dyes—he always enjoyed using color to answer biological questions.

During his postdoc at Cambridge from 1977 to 1981, he met his wife Wendy Globe at a Christmas party. Continuing the research path, Tsien took a position at UC Berkeley as a professor from 1982 to 1989 and then at UC San Diego from 1989 until his passing on August 24, 2016.

Figure 1. Fluorescent microscopy of cells expressing proteins labeled with green fluorescent protein. (Jamil Baza, CC BY 4.0, via Wikimedia Commons)
Figure 2. Roger Y Tsien in 2016. (Erin Rod, CC BY-SA 4.0, via Wikimedia Commons; photo cropped to focus on Dr Tsien)

How Fluorescent Proteins Changed Science

Today, many different fluorescent proteins, some with fruit-inspired names like mHoneydew, mOrange, mTomato, mBanana, mCherry, are available to track proteins in real-time. These fluorescent proteins can be attached to another protein of interest and visualized in live cells, such as bacteria, cultured mammalian cells, or even the tissue of study animals. However, it all began with one fluorescent protein called GFP.

What is GFP?

GFP is a green fluorescent protein isolated from the jellyfish Aequorea victoria in 1962 by Osamu Shimomura. This protein will fluoresce in the presence of oxygen under ultraviolet light without the need for substrates. And because the protein itself does not affect biological processes in vivo, it can be used to study live cells over time, which was an important breakthrough. Before the discovery and optimization of this type of fluorescent protein, labelling of proteins or cells required fixing (and killing) the cells. Now, the availability of multiple fluorescent colors allows simultaneous tracking of multiple proteins. Some uses include monitoring gene expression, cellular localization, embryonic development, and cancer progression.

How GFP was Discovered

Tsien learned of GFP through his desire to image cAMP (cyclic adenosine 3ʹ,5ʹ- monophosphate) in a living cell. He wanted to make a fluorescent version of the protein that binds to cAMP to function as a cAMP “sensor” to visualize its binding within a live cell.

So, he began his search and met a researcher named Douglas C Prasher, who was beginning to characterize GFP after cloning it. Prasher shared the protein with Tsien and Martin Chalfie, a researcher from Columbia. Chalfie put GFP into another organism (Escherichia coli and Caenorhabditis elegans) for the first time. With GFP inside a living organism, researchers were able to track the expression of genes and the localization of proteins.

Tsien’s lab then modified GFP to improve its usefulness. He made minor changes to the protein, which created a brighter glowing version as well as slightly different colors. Later, his research group developed other colors from red fluorescent protein (RFP), providing a rainbow of colors. With multiple colors, different cell types can be labeled and tracked. For example, to study cancer, tumor cells and host cells can be labeled with different colors and easily distinguished. Modified GFPs also proved useful in monitoring and imaging calcium in cells, which fulfilled Tsien’s desire to visualize neurons in parallel instead of individually.

Because of the significant impact these researchers made with their discovery and development of GFP, Tsien (optimization of fluorescence and colors), Shimomura (first isolation and description of GFP), and Chalfie (first research use in live organisms) shared the Nobel Prize in Chemistry in 2008.

Tsien’s Scientific Contributions Beyond Academia

Tsien’s work extended beyond fluorescent proteins used in academic research. His name appears on 100 patents; one of them from 1990 describes one of the early next-generation sequencing methods (i.e., base-by-base sequencing on DNA arrays controlled by removable 3ʹ blockers) that was further developed by Illumina.

His scientific research also led to co-founding Aurora Biosciences Corporation, which Vertex Pharmaceuticals subsequently acquired. He also co-founded and served on the scientific advisory board of the company Synomyx, which used his patented technology.

The visual appeal of fluorescent proteins has moved scientists to create art using them. During his presentations, Tsien seemed to enjoy sharing art created in his lab—a California sunset drawn on a Petri dish (Figure 3). Having fluorescent proteins to see the inner workings of living organisms revolutionized the way scientists study life and has provided a beautiful way to do so.

Figure 3. A beach scene drawn with bacterial colonies expressing fluorescent proteins. The proteins are derived from GFP and the red-fluorescent coral protein, dsRed. The colors include BFP, mTFP1, Emerald, Citrine, mOrange, mApple, mCherry, and mGrape. (art, Nathan Shaner/photo, Paul Steinbach, CC BY-SA 3.0, via Wikimedia Commons)

Be sure to explore our products related to cloning and propagating constructs like plasmids with GFP reporters here: