Dr. Shinya Yamanaka, a stem cell researcher at UCSF's Gladstone Institutes who discovered a technique for transforming adult skin cells into "pluripotent" stem cells without resorting to human embryos, has won Japan's $550,000 Kyoto Prize, an international award that honors scientific, cultural and spiritual contributions to human knowledge.

His discovery resulted in a class of much-sought stem cells that scientists can induce to become virtually any other type of functioning human cell that one day might be used to treat varied diseases or injuries.

During their research, Yamanaka and his colleagues altered the genetics of adult skin cells by inserting four specific viral genes that produce proteins known as transcription factors into the cells. Those proteins in turn yielded other genes that reprogrammed the skin cells so they acquired all the characteristics that made them what are now known as induced pluripotent cells.

Before his discovery, those pluripotent human stem cells could only be harvested from human embryos, a source posing such powerful ethical issues that former President George W. Bush banned virtually all embryonic stem cell research eight years ago. The ban remained in force until President Obama reversed it last year.

Yamanaka, 47, who is attending the annual meeting of the International Society of Stem Cell Research in San Francisco this week, was not told of his award until just before midnight Pacific time on Thursday.

The Kyoto Prize is awarded annually by Japan's Inamori Foundation for major discoveries in many fields of advanced technology, and four other Bay Area scientists have won it in recent years.

They are Leonard Herzenberg, a Stanford geneticist and immunologist who developed a revolutionary cell-sorting machine now crucial to advanced biomedical research; Alan Kay, a Silicon Valley pioneer at Hewlett-Packard who led advanced computing technology for 40 years; Donald E. Knuth, a Stanford information technology expert and specialist in computer programming, language analysis and computerized printing and Richard Karp, a UC Berkeley computer scientist and pioneer in computational biology.

In addition to heading his laboratory at the Gladstone Institute for Cardiovascular Research on the Mission Bay campus of UCSF, Yamanaka is also a professor at Kyoto University, where he began his efforts seeking a way of transforming adult cells.

Besides resolving ethical issues by his achievement, Yamanaka's success also means that the pluripotent stem cells needed to treat a patient's disease can be obtained from the ordinary skin cells of a patient's own body - thus making stem cell therapy possible without the hazards involved in immunologic rejection of cells from other people.

Robert Lanza, chief scientific officer of Advanced Cell Technology and an adjunct professor at Wake Forest University's stem cell research center, said recently that Yamanaka's work "is likely to be the most important stem cell breakthrough of all time."

"The ability to generate an unlimited supply of patient-specific stem cells will revolutionize the future of medicine," Lanza said.

This story has been changed since it appeared in print.