Ryuzo Yanagimachi
The Modern Laboratory · People
The Modern Laboratory
Ryuzo Yanagimachi
He spent a lifetime watching sperm meet egg, and showed the world how to help them along.
A student of the sea urchin. Ryuzo Yanagimachi was born in 1928 in Ebetsu, Hokkaido, in northern Japan. As a student at Hokkaido University he watched sea urchin eggs being fertilised on field trips to the coast, and the sight stayed with him for life. He earned his doctorate in animal embryology there in 1960.
The hamster workbench. From 1960 to 1964 he worked with the reproductive biologist M. C. Chang at the Worcester Foundation for Experimental Biology in the United States. In 1963 the two reported in Nature that hamster eggs could be fertilised in a dish. The hamster became his favourite partner. Under an ordinary microscope, its sperm showed plainly the changes they go through before fertilisation.
Hawaii. In 1966 he joined the University of Hawaii, where he became professor in 1974 and later founded and directed the Institute for Biogenesis Research. In 1976, with Tsuyoshi Uehara, he injected sperm into hamster eggs and watched male pronuclei form, the first visible step of fertilisation. The Society for the Study of Reproduction calls this the first mammalian ICSI. In the same journal issue his laboratory described how hamster eggs, freed of their outer shell, could be used to test the fertilising ability of human sperm.
From mice to the clinic. He kept asking whether an injected egg could become a living animal. Mouse eggs had always died when injected, until in 1995 he and Yasuyuki Kimura reported ICSI in the mouse. Kimura's piezo-driven method is now widely used by fertility specialists. In 1998 his team reported mice cloned from the nuclei of adult cumulus cells. The first of them, Cumulina, is now kept at the Smithsonian.
Honours. He received the International Prize for Biology in 1996 and was elected to the US National Academy of Sciences in 2001. In 2023 he was awarded the Kyoto Prize. He died on 27 September 2023, aged 95. His typed “Hamster Notes”, a 100-page laboratory guide illustrated with his own drawings, let any newcomer to his laboratory, from any country, begin an experiment.
Also see: Tsuyoshi Uehara, Gianpiero D. Palermo, André Van Steirteghem
About the sources
- Akutsu H, Ogura A. Commentary on the Achievements of the Laureate: Ryuzo Yanagimachi. The 2023 Kyoto Prize Commemorative Lecture, Inamori Foundation, 30 October 2024 (kyotoprize.org PDF): Chang, hamster IVF, Hawaii from age 38, Uehara 1976, Kimura and piezo ICSI, “Hamster Notes”.
- Kyoto Prize laureate page, Ryuzo Yanagimachi (kyotoprize.org): born 1928 in Ebetsu, Hokkaido; DSc Hokkaido University 1960; Worcester Foundation 1960 to 1964; University of Hawaii posts 1966 to 2006; Director, Institute for Biogenesis Research 1999 to 2004; 2023 Kyoto Prize in Advanced Technology.
- Kyoto Prize interview with Ryuzo Yanagimachi (Japanese, kyotoprize.org PDF, October 2023): sea urchin fertilisation seen as a Hokkaido University student.
- Society for the Study of Reproduction. Ryuzo ‘Yana’ Yanagimachi PhD (1928 to 2023), Heritage Honoree 2024 poster (ssr.org): first mammalian ICSI in 1976; International Prize for Biology 1996; National Academy of Sciences 2001.
- University of Hawaiʻi News. In memoriam: Ryuzo Yanagimachi, 28 September 2023: died 27 September 2023 aged 95; joined UH 1966; founded the Institute for Biogenesis Research; cloned mouse Cumulina at the Smithsonian; honours.
- Wakayama T, Perry AC, Zuccotti M, Johnson KR, Yanagimachi R. Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei. Nature 1998;394:369–374. PubMed 9690471.
- Kimura Y, Yanagimachi R. Intracytoplasmic sperm injection in the mouse. Biology of Reproduction 1995;52(4):709–720. PubMed 7779992.
- Yanagimachi R, Yanagimachi H, Rogers BJ. The use of zona-free animal ova as a test-system for the assessment of the fertilizing capacity of human spermatozoa. Biology of Reproduction 1976;15(4):471–476. PubMed 974200.
- Uehara T, Yanagimachi R. Microsurgical injection of spermatozoa into hamster eggs with subsequent transformation of sperm nuclei into male pronuclei. Biology of Reproduction 1976;15(4):467–470. PubMed 974199.
- Yanagimachi R, Chang MC. Fertilization of hamster eggs in vitro. Nature 1963;200:281–282. PubMed 14085061.
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Compiled with AI-assisted research and checked against the original sources. Not yet peer-reviewed. Corrections are warmly welcomed.
