By injecting embryonic stem (ES) cells from a wood mouse into the early embryo of a house mouse, an international team of scientists has produced normal healthy animals made up of a mixture of cells from each of the two distantly related species. This is the first time that stem cells from one mammalian species have been shown to contribute extensively to development when introduced into the embryo of another, very different species.In an advanced online posting on Oct. 3, 2007, in the journal Human Molecular Genetics, scientists from the University of Chicago, Sun Yat-sen University, China, and the University of Liverpool, U.K., describe how they produced a viable “chimera"--a single organism with traits from two different species.
