With the vision of “Advancing the World Through the Power of Science,” Stellar Science Foundation (SS-F) is dedicated to pursuing the essence of scientific research and elevating its impact to new heights. SS-F values the philosophy of “People-Centric” science—science that is born from people, connects with people, and expands through people—believing that scientific progress emerges from human creativity and collaboration.
In the “Inventor’s Vision” series, we focus on the “Stellar Inventors”—researchers with unparalleled perspectives and imagination who take on ambitious scientific challenges. By delving into their motivations, worldviews, and personal stories, we explore the potential of a “People-Centric” approach to science.
For the second installment, we interviewed Naoko Irie, whose research on the human germline (including germ cells, eggs, sperm, and early embryonic development) seeks to unravel the mysteries of life itself. In January 2025, her groundbreaking work on the early development of human germ cells was recognized with the Japan Society for the Promotion of Science (JSPS) Prize. Her research holds immense potential, not only for advancing assisted reproductive technologies such as in vitro fertilization but also for contributing to broader developments in reproductive science.
“What excites me most is the moment when I feel I am truly uncovering the fundamental mysteries of life,” Irie shares about the allure of her research. She describes how her journey through different fields—including her early studies in an unrelated discipline and the insights gained through international research exchanges—led to unexpected discoveries. From a childhood curiosity to an unconventional change of academic direction, and ultimately to securing a research position in the UK through her own initiative, we trace the path that led Irie to become a researcher exploring the profound mysteries of life.
The “Shock” of The Selfish Gene
— Could you tell us about your journey so far? What kinds of things interested you as a child?
I think I’ve always been drawn to nature from a young age. As a child, I loved catching insects—I would search the entire kindergarten yard for earthworms, gather them all in one place, and then return later to see that they had all disappeared. It fascinated me. It’s funny how, despite loving them so much as a child, I somehow lost the ability to touch them as an adult! (laughs)
I also vividly remember being shocked when I first learned in middle school that DNA duplicates itself precisely before cell division, ensuring that each new cell receives an identical copy. I couldn’t stop thinking: “How is this process so perfectly orchestrated?” Immediately after, I had another burning question—“Why can’t cells first divide in half and then duplicate the DNA separately?” It seemed like a simpler approach, yet biology had evolved in a way that ensured precision and balance. This early curiosity about the intricacies of life has stayed with me ever since.
— But for you, that curiosity didn’t just end there—you actually became a researcher. Why do you think that is?
I’m not sure if there was a direct connection, but there were several experiences that left a strong impression on me. For example, taking a biology class in middle school, reading The Selfish Gene by Richard Dawkins and books by Kumiko Takeuchi, and learning from those books the idea that “DNA is merely a vehicle for life.” That concept was a huge shock to me. I started asking myself, “If DNA is the passenger, then what is the most important vehicle?” Eventually, I came to my own conclusion: “It must be germ cells.”
— I heard that you went on to study Biological Sciences at the School of Science, Kitasato University. Was that decision influenced by your early interests?
Yes, exactly. It was a time when topics like the Human Genome Project, ES cells, and regenerative medicine were making headlines, and molecular biology was experiencing a surge of excitement. The field was evolving rapidly, and I was deeply drawn to the idea of studying biological sciences and molecular biology to explore these groundbreaking advancements firsthand.
“If I’m Going to Do Research, I Want to Fully Explore the Deepest Mysteries”
— What path did you take after graduating from your undergraduate program?
For my master’s and doctoral studies, I researched bone metabolism. I used mice to study the interactions between bone-forming and bone-resorbing cells.
Since I earned my Ph.D. in that field, the natural course would have been to continue pursuing that line of research. However, at the time, I had a strong desire to delve even deeper into the fundamental mysteries of life. I had heard during graduate school that “your Ph.D. research may not necessarily define your future research theme,” so I had already decided that once I earned my Ph.D., I would pursue what truly interested me.
More than anything, I thought, “If I’m going to do research, I want to fully explore the deepest mysteries.” That feeling led me to seriously consider shifting my focus to germ cell research after completing my doctorate.
— After earning your Ph.D., you made a dramatic shift in your research direction! Since this wasn’t a conventional path, I imagine you faced many challenges.
Yes, especially at the beginning—I kept running into walls. People around me told me to quit because it wouldn’t work out, and some labs even turned me away outright. With no one to guide me, I had no choice but to research everything on my own.
Then, one day, I came across the name of Azim Surani, a renowned leader in germ cell research at the University of Cambridge in the UK. I had no prior connections to him or his lab, but I thought, Why not try sending an email? Of course, given the prestige of his lab, I didn’t receive a response right away.
Still, I kept emailing, and eventually, I got a reply: “Our lab space is too small to take on new researchers.” In response, I wrote back, “That’s not a problem. I’m not a huge person, so I can fit into a small space.” (laughs) Somehow, after that, they finally accepted me!
— That’s an incredible story. Most people would have given up.
Maybe they just thought I was being too persistent (laughs). Or perhaps there truly wasn’t enough space, or maybe it was just a polite British-style rejection email… but I feel like I was able to convey my strong desire to pursue germ cell research. The fact that I wasn’t asking for too much space was also pretty genuine (laughs).
Since I had no background or network in germ cell research, I also knew I had to do something unconventional to catch their attention. That’s probably why I never gave up.
In the end, I managed to get into the lab, and looking back, I’m really glad I did. That was around 2011.
A Two-Month Exchange That Led to an Unexpected Breakthrough
— In your 2015 paper, you reported key factors in the development of human germ cells, which gained significant attention. You achieved these results in about four years after moving to the UK.
Yes, but the early days were full of struggles. In Japan, I had almost exclusively worked with mice, so when I first started, I really struggled with culturing human embryonic stem (ES) cells.
Even after six months, I had almost no results to show. No one else in my lab had experience culturing human ES cells either, so I even went to the neighboring lab to ask for guidance.
— So things didn’t go smoothly from the start. Was there a particular turning point for you?
The UK-Israel Research and Academic Exchange Partnership (BIRAX) was just launched, involving Azim Surani from Cambridge University and Jacob Hanna from the Weizmann institute and that became a major turning point for me. As part of a collaboration with a young and dynamic research group in Israel, I was selected as the UK representative and spent about two months there.
This group had developed a specialized method for culturing ES cells, and the technique I learned there later became the key to my work in inducing germ cells. They were also highly skilled in culturing human ES cells and had deep expertise in genetic engineering, which I was able to learn firsthand.
Thanks to that experience, I was able to produce significant results within just four months after returning to the UK. Initially, I was just excited to visit a unique place for the first time, but in hindsight, it was a transformative experience. Beyond research, I was also exposed to a completely different culture, with distinct perspectives on religion and military affairs, which left a strong impression on me. That cultural exchange, my interactions with researchers from diverse backgrounds have been uniquely enriching, yet also incredibly warm. I feel that these experiences have been a major breakthrough for me, both in terms of life experience and scientific research.
— Your two-month exchange experience turned out to be a decisive turning point! After publishing your paper in 2015, why did you decide to return to Japan?
After my publication, I continued research in the UK with substantial funding from Medical Research Council (MRC) for some time. However, due to the pandemic and Brexit, the entire research institute experienced a downturn. Funding was cut, and I realized that I needed to start looking for a new position, so I decided to return to Japan temporarily.
While visiting my alma mater after returning, I happened to meet the director of the research institute where I now work. He invited me to join a new initiative, saying, “We’re transitioning from Keio University School of Medicine to the Central Institute for Experimental Medicine and Life Science (CIEM). Would you like to join us?” He wanted me to establish an entirely new research system for human studies—something that had never been done before. It seemed like a challenging and exciting opportunity, so I decided to take it.
— Now that you’re conducting research in Japan again, do you notice any differences compared to your time in the UK?
To study human early development, it is essential to use human ES cells and human-derived samples. However, in Japan, ethical review processes often feel unclear and ambiguous. There seems to be a prevailing mindset that “if there are no established regulations, research should not proceed.”
In Japan, obtaining approval often requires referencing precedents from similar studies, making it challenging to pioneer cutting-edge research at the global forefront. This can create an environment where new and innovative studies struggle to gain traction simply because no prior research exists to justify them.
By contrast, in the UK, I noticed a starkly different approach—where “if there are no rules, research is permitted” until regulations are put in place. I was particularly shocked when I learned that over 40 years ago, the world’s first “test-tube baby” was conceived under such circumstances, leading to real medical applications before formal regulations were established.
Of course, in recent years, ethical oversight in the UK has become more structured. However, what stands out is the way ethical guidelines are rapidly developed through open discussions—not only among scientists and ethicists but also involving experts from various disciplines and non-scientist members of the public. This inclusive and proactive approach to ethical decision-making allows the UK to advance regulations much faster, creating an environment where scientific progress and ethical considerations evolve together.
Life Passed Down Over Hundreds of Millions of Years: A Mystery Worth Pursuing
— Looking back at your journey, it seems that interactions with researchers from different communities—whether through your time at Cambridge or your exchange program in Israel—have had a major impact on your work.
Yes, absolutely. At the same time, I think my background in an entirely different field—bone research—has also been surprisingly beneficial in many ways.
For example, I discovered that some of the genes I studied in bone research turned out to be crucial in germ cell studies as well. This realization helped me develop new perspectives, leading to innovative ideas like “If this factor functions in this way, then it might also work in this other context.”
In that sense, even what seemed like a detour at the time turned out to be valuable. I’m really glad I had the opportunity to explore bone research as well.
— Changing the direction of your research ended up being a great decision! What do you find most exciting or fulfilling in your work?
What draws me most to this research is the idea that I’m uncovering the fundamental mysteries of life itself. When I make a new discovery about the germline, I think about how it connects to the unbroken continuity of life that has been passed down for hundreds of millions of years. That thought alone gives me a sense of something truly vast and awe-inspiring.
Of course, day-to-day research is a slow and meticulous process. But I also find that steady trial-and-error approach to be deeply enjoyable and rewarding.
For instance, in some of our experiments, we design cells to emit red fluorescence and use a machine to measure the results. When everything goes right, pressing a button suddenly reveals glowing cells on the monitor. Since the experiment often doesn’t work, the moment when it finally does is incredibly exciting. It’s those small yet thrilling moments that make me want to keep exploring science with a sense of wonder.
— Finally, what are your future aspirations?
As a researcher, I want to contribute to improving reproductive technologies and increasing the number of people who can find happiness through advancements in this field. My goal is to establish essential technologies in reproductive science and help create a society where they can be widely utilized.
On a more personal note, one of my dreams is to travel the world collecting reptile and bird eggshells, as well as plant seeds, and comparing them morphologically. So in my retirement, I’d love to embark on a journey around the world for that purpose. Right now, that’s one of the biggest things I’m looking forward to!
[Written by Tomohiro Kurimura, Photography by Kayo Sekiguchi, Interview & Editing by Masayuki Koike]
