Teams of biologists in Japan and Wisconsin discovered new methods for transforming human skin cells into “induced pluripotent stem cells.” Both techniques employ a retrovirus to inject the cells with four “master regulator” genes that reprogram the cells’ function. The Wisconsin team, directed by James A. Thompson, who pioneered the harvesting of embryonic stem cells, culled its skin cells from foreskins. The Japanese team conducted their preliminary research on mice, with a cancer gene among the regulators, and created in the process a mischief of clone mice, 20 percent of which developed cancer. President George W. Bush was said to …



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