The stem-cell research community reels after Yoshiki Sasai, a famous name in regenerative medicine, is found dead on August 5

Yoshiki Sasai. Credit: Nick Higgins

Scientists around the world are struggling to get to grips with the loss of one of the brightest stars in stem-cell science. Yoshiki Sasai of the RIKEN Center for Developmental Biology (CDB) in Kobe brought excitement and rigour to the field but died yesteday, August 5, aged 52. The reasons for Sasais apparent suicide are still not clear but a scandal swirling about two stem-cell papers published inNaturein January had wreaked havoc on his career.

Dr. Sasai was a rigorous and innovative scientist and his loss will be deeply felt, saysJanet Rossantat the Hospital for Sick Children in Toronto, Canada, a former head of the International Society for Stem Cell Research. His most important contributions to the stem-cell field came from his background in developmental biology.

Sasais research spanned developmental biology, stem cells, organogenesis and tissue engineering. His success was built on his painstaking efforts to understand exactly which factors needed to be added or removed to cell cultures to guide embryonic stem cells as they differentiated to mature cell types,especially neuronal cells.

He sees things that others dont see,Eddy De Robertistold Naturein a 2012 interview. De Robertis, a developmental biologist at the University of California, Los Angeles, who supervised Sasais postdoctoral work in the mid 1990s, recalled Sasai once retyping a manuscript lost in a computer from memory with word-for-word perfection. Id never seen anything like that, he said.

Lab-grown cortex One of Sasais innovations was thediscovery in 2007of a pharmacological compound that kept embryonic stem cells from dying when separated from each other. Previously, embryonic stem cells had to be manually cut with a cumbersome method and transferred as partial colonies, which resulted in experimental variation. His paper solved that overnight, saysLuc Leynsof the Vrije Universiteit in Brussels.

But Sasai's show-stoppers came shortly after that. Based on his success in differentiating neurons, Sasai started mimicking embryonic development with such fidelity that his cells would organize themselves into three-dimensional structures, including agoblet-shaped clump of retinal tissue known as an optic cupandintricate layers of tissue that resembled a cerebral cortex.

Both these discoveriesopened the field ofin vitrobrain organogenesis. Finally, we have easy access to the developing brain without having to micro dissect embryos, says Leyns. Leyns says he uses Sasais papers to show masters students how a modern scientific discovery is made and progressively built-up to a climax.

Sasais work was inspirational, says Pete Coffey of University College London, where Sasai presented the optical cup research last November. The clarity of his presentation, the excitement and post lecture discussions with fellows and students are still discussed today. He had a major impact on my group, says Coffey. Sasais research will probably contribute to treatments for various disorders, such as macular degeneration. His findings galvanized the ophthalmology community in truly developing a cell therapy for blinding disorders, says Coffey.

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