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Hi Everyone,

My name is Kristen Hirter, and I am a master’s student in ������’s anthropology department. This summer I have been awarded the incredible opportunity to travel to Japan and study at the . Here, I’ve joined Dr. Hiroo Imai’s molecular biology research team in their investigation of bitter taste receptor genes in Japanese macaque monkeys. In these weekly blog posts, I will be updating you on my scientific and cultural experiences during my stay in Japan. Before I begin, I would like to extend my deepest gratitude to Dr. Tosi, Kent State’s Giving Tuesday donors, Kent State Graduate Student Senate, and my family for making this internship possible.

Arrival Destination: Japan

My travels began with a quick layover in Toronto, Canada where I then started the long journey to Japan. After 16 hours of travel by air and train, it is an understatement that I was happy to see Imai-sensei waiting for me at Inuyama Station. After exchanging introductions, (which included both of us laughing at me getting into the car on the wrong side; cars drive on the left side of the road here and the driver’s seat is on the right), we were on our way to the institute. After dropping my things off in the dormitory, Imai-sensei, and two of the laboratory graduate students, Mita-san and Misa-san, took me to sushiro (スシロー), a restaurant with delicious sushi brought out on a conveyor belt next to our table. It was a relaxing end to a long day of travel.

Inuyama Castle and Town Tour

The next day, Mita-san graciously offered to show me the town of Inuyama. We began our exploration on bike and ate delicious rice bowls at a nearby restaurant. After lunch, she took me to the old part of town where Inuyama Castle is located. Riding through this part of town made me very happy; it was lively with many people and shops. The castle was breathtaking and unlike anything I have seen before. It is one of the oldest castles in Japan, with original construction completed in 1440! The grounds were lined with torii (traditional Japanese gates marking sacred lands) and the panoramic view from the top level of the castle was absolutely stunning. After grabbing some matcha (green tea) for refreshment, we headed back to the PRI.

First days at the Primate Research Institute

The PRI is an incredible facility. Established in 1967, it is a true powerhouse in primatological and anthropological research. From ecology, to brain sciences, to molecular biology, to morphology, the PRI takes a multi-disciplinary approach in studying the Primate Order. Groups of several different primates are on the premises, including chimpanzees, various macaque species, and a number of South American monkeys. Moreover, their many laboratories offer a wide range of scientific techniques to examine questions in all aspects of primate biology. The PRI places great importance on an international approach to science. Faculty and students from all over the world come together here to study, making this an exciting and wonderfully collaborative research center.

Every Monday morning the molecular biology section, led by Dr. Imai, starts their week with a seminar. Here, I met all of the student researchers and faculty and introduced myself. Afterward, Dr. Imai showed me around the institute and explained to me one of his on-going projects concerning bitter taste receptors in Japanese macaques (Macaca fuscata). These macaques are found through most of Japan (excluding the island of Hokkaido), and no other primate lives in a more northern, colder climate, which is why these animals are also known as “snow monkeys”. In snow monkeys and other mammals, bitter taste is mediated by a group of genes for taste-2 receptors (TAS2R). These are transmembrane G protein-couple receptors (GPCR), receptors that detect molecules outside the cell and then activate signal pathways inside of the cell (many modern medicines target GPCRs). When a ligand, in this case a bitter compound, binds to the receptor, the receptor changes shape and activates another protein. This can then affect other intracellular proteins and create a cellular response (see graphic below). Some studies suggest bitter-taste sensitivities evolved independently in different primate species to adapt to the food items they consume, as significant intra- and interspecies variability has been found.

One of the most studied bitter taste receptors is TAS2R38; this receptor recognizes the substance phenylthiocarbamide (PTC) and is the focus of my research as part of Dr. Imai’s laboratory group. In humans, some individuals can taste the bitterness of PTC, while others taste nothing at all, depending on their unique genetic make-up. This genetic variation is called a polymorphism, and it relates directly to dietary choices.  If you dislike cabbage or broccoli, it could be because these plants contain compounds similar to PTC.

Japanese macaques also have variation (even more so than humans!) in the TAS2R38 gene, and I will study how this variation affects sensitivity to bitter taste through functional analysis. The goal is to better understand the relationship between the TAS2R38 genes and proteins. Genes consist of DNA, which is transcribed to RNA and finally translated to proteins. Fluctuations in the genetic code can result in changes in the protein product, or no protein product at all. Although most mutations in the genetic code do not result in protein changes, we believe several do in the TAS2R38 gene. To investigate this, the TAS2R38 gene sequence is targeted and amplified using the Polymerase Chain Reaction (PCR). Next, an essential part of functional analysis in Dr. Imai’s lab is cell culture, the process by which cells (HEK293T, human embryonic kidney cells, to be exact) are grown under controlled conditions outside of their natural environment. Then, our gene of interest, TAS2R38, will be transferred into the cells. This will cause the cells to express the TAS2R38 gene. Finally, we add a series of PTC concentrations to the receptor and examine the response using a calcium imaging method. If you are scratching your head at this point, don’t worry, I will be covering each of these steps in more detail in the coming weeks.

This week I began changing the media for the cells, a regular maintenance that provides essential nutrients to keep them healthy and functional. Next week, I will transfer to the cells a variant receptor haplotype – found among the Shimokita (SMK) population of Japanese macaques – to examine its response to PTC compared to the human TAS2R38 gene.

As my stay here in Japan continues, I will elaborate on each step of this unique and exciting scientific method as well as update you on the amazing places I visit. My first week here at the PRI has been absolutely incredible! The molecular biology department has welcomed me in the warmest of fashions, and I have felt very much at home despite being over 6,000 miles away.

Well, that is it for my first week at the PRI. Thank you for reading and for taking an interest in my research and cultural experiences during my internship here in Japan!  Check this website next week for blog post #2!

 Matane (see you later),