Professor Tanaka Mikiko of Tokyo Institute of Technology Wins the Saruhashi Prize for Outstanding Women Scientists: Achievements in Research on Vertebrate Limb Development Updated in July 2021

This year's Saruhashi Prize, which honors top female scientists, was presented to Dr. Tanaka Mikiko, a professor at the School of Life Science and Technology, Tokyo Institute of Technology. She researched and achieved results on her perspective of evolution regarding the development of vertebrate limbs. This news was announced by the Association for Bright Future of Women Scientists, chaired by Dr. Ishida Mizuho.

She was awarded for her "study on the development and evolution of vertebrate limbs." Due to "interdigital cell death,” a process which occurs in the womb, human fingers do not have duck-like webs. Interdigital cell death requires reactive oxygen in the environment. She found that this mechanism occurs in animals during the process of habitat transition from sea to land when the animal is exposed to atmospheric oxygen.

The human arm is connected to the body with a single bone, but the pectoral fins of ancient fish that are thought to be the basis of modern arms had multiple bones at the base. Using sharks for comparison because their pectoral fins resemble those of ancient fish, Prof. Tanaka’s team showed how fin-bones may have rearranged themselves into modern forelimbs. The posterior area “widened” significantly, stretching out and forming fingers. The anterior area of the fin spread out comparatively less, forming the thumb. Both areas coalesced into the bones of the arm, resulting in a single bone, the humerus, connecting the limb to the trunk Gradually the multiple bones anchoring the fin to the trunk were integrated into a single bone, approaching the shape of modern forelimbs. What Prof. Tanaka’s team did was to clarify the changes in the genome sequence which caused this evolution.

Free semitendinous muscles which produce the complex muscles of human limbs were said to have first occurred in organisms evolutionarily newer than sharks. Overturning this hypothesis, Prof. Tanaka’s team revealed that sharks’ fin muscles were also made up of cells similar to free semitendinous muscles. This suggests that the origin of limb muscle development goes back way longer than we think.

Prof. Tanaka tackled one of the essential research issues of life phenomena with an original approach, and was praised for her achievements.

Born in Miyagi prefecture, Prof. Tanaka graduated from the Faculty of Science, Osaka City University, and completed the doctoral program at Tohoku University Graduate School, Division of Natural Science. After assuming the position of an associate professor at Tokyo Institute of Technology, she became professor in February 2021.

The Bright Future for Women Scientists Society in Japan was founded by funds contributed by Dr. Saruhashi Katsuko, a geochemist. The year 2021 is the prize’s 41st year since its start in 1981. The presentation ceremony is usually held in Tokyo late May, but this year it was held online on May 22 due to COVID-19.

Prof. Tanaka made the following comments:
"It is a great honor for me to receive the prestigious Saruhashi Prize, and I also feel a great sense of responsibility. This honor has been given to many people around me who have supported me up to now. I would like to thank the remarkable staff and students in the laboratory. Our research is about what points in the development program are liable to change to affect the next generation; I think this is an important issue that tackles fundamental issues in life science. In the future I would like to further contribute to the development of life science, and hope to communicate the importance of exploring the truth and all the joy that comes with the research, so that I can live up to the honor of this prize.”