New Kyurizukai
“It’s incredible that I have been able to maintain my interest in the sea squirt (ascidian, tunicate) for such a long time thus far,” utters Dr. Hotta with an overflowing enthusiasm for this study on his face. Although he was fond of biology as a child, he had long been unsure about developing this fondness in choosing a researcher’s career as a biology specialist, he confesses. In fact, there were a number of occasions in the past when he asked himself, “Will it be possible for me to accomplish this challenge?” Let’s listen to Dr. Hotta on his past thoughts and how he has followed the path of a researcher.

What was your childhood like?
      I was living in Tokai City, Aichi Prefecture up to the time of elementary school first grade. Back in those days, I liked catching insects, drawing pictures and observing living things. What excited me most was when I used a microscope and found water fleas and other plankton moving in the water that I had scooped from a nearby brook. We had a microscope at home that was usually stored in a nicely built wooden box. As a grown-up, I wonder why my father, just an ordinary salaried worker, could afford such a good microscope.
      As a vague memory, I remember a day when I made a clay model of the interior of a “Devil’s (in Japanese, “o-ni”) ” body, which I explained to my grandfather. At the time he told me, “Dear grandson, you will become a scholar when you grow up.”
      I spent my junior and senior high school days in Otsu City, Shiga Prefecture, when I belonged to the Field and Athletic Sports Club and was running daily along the shore of Lake Biwa. Then I entered Hokkaido University and chose the Faculty of Science without hesitation so that I could engage in basic science. Given my fondness of biology, learning veterinary medicine, fisheries science or pharmaceutical faculty may have also suited me.

How did you encounter sea squirts (ascidian, tunicate)?
      At Hokkaido University, I took up a study related to fertilization of frogs as the theme of my graduation thesis. Although my initial plan was to go on to the graduate school, I had to find another university for graduate study because Professor Chiaki Katagiri, my mentor, retired. At the time, I had an opportunity to listen to a special lecture by Professor Nori Satoh of Kyoto University. This served as an impetus for me to make up my mind to study at the Satoh lab. Professor Satoh is the top authority in Japan in the study of sea squirts (ascidian, tunicate). He is credited for enhancing the sea squirt into a model organism.
photo      “What a maniacal creature it is!” – This was my impression when I first heard of the sea squirt because it was little known to us in those days. Thanks to Professor Satoh’s achievements, today there seem to be some high school science textbooks that mention the sea squirt.
      The Satoh lab was a lively place, where I received various kinds of intellectual stimulation. On the following day after I first made my appearance in the lab, I was told to go to Tohoku University’s Asamushi Marine Station in the northern prefecture of Aomori. There, I devoted myself to gathering notochord cells by observing the development of the sea squirt – sitting behind a microscope for as long as one month. Now I know that it was an invaluable opportunity for me to learn the ABCs about the development of organisms. For 15 years since then, I’ve been engaged in sea squirt study.

How has your sea squirt (ascidian, tunicate) study progressed in the past 15 years?
      My sea squirt study has progressed considerably. Just a while ago I said that I had been assigned to the task of gathering notochord cells. It looked like dull, uninteresting work, but beyond it was a big dream of shedding light on the mysteries of the evolution of vertebrate things. A major turning point came after the complete genome sequence of the sea squirt was identified in 2002. At the time, I was assigned to the National Institute of Genetics, engaging in the analysis of sea squirt’s genome. Once the complete genome sequence of the sea squirt was identified, the focus of our research activity now shifted from the former persistent approach of identifying genes one by one to data mining-type approach to look for new discoveries from a mass of comprehensively verified data.
      This genetic study approach has clarified that the sea squirt is not an ancestor of but a “relative” of Homo sapiens and has revolutionized the phylogenetic tree, which I witnessed. Including this development, I have been lucky enough to personally experience more than one historic event.
      Today, research methods are beginning to change even further. Since it has become easy to examine genes comprehensively, the importance is shifting to understanding, at high resolutions, differences between species and between individuals.