Hans Sautter
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 today, 5 August, aged 52. The reasons for Sasais apparent suicide are still not clear but a scandal swirling about two stem-cell papers published in Nature in January had wreaked havoc on his career.
Dr Sasai was a rigorous and innovative scientist and his loss will be deeply felt, says Janet Rossant at 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 Robertis told Nature in 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.
One of Sasais innovations was the discovery in 2007 of 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, says Luc Leyns of 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 a goblet-shaped clump of retinal tissue known as an optic cup and intricate layers of tissue that resembled a cerebral cortex.
Both these discoveries opened the field of in vitro brain 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.
Sasai planned to improve on each of his three-dimensional brain structures, for example creating a pituitary gland with a blood supply. He had an even grander vision of figuring out how all of the different brain parts link up to create the complex networked structure we have.
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Stem-cell scientists mourn loss of brain engineer