“Our paper described a modification of the current NT procedure, which would allow generating ES cells without destroying an embryo.”

The derivation of embryonic stem cells in the US and abroad is very controversial. One potential way to generate "customized" embryonic stem (ES) cells is through nuclear transfer (NT). Our paper described a modification of the current NT procedure, which would allow generating ES cells without destroying an embryo. This is achieved by blocking a gene that is essential for placental-development. The proof of the principle of this approach was demonstrated in a mouse model.

It describes a number of previously described techniques that were combined to achieve the goal of reversibly blocking a gene that is required for the development of the extra-embryonic lineage, which will later form the placenta.

The paper is important, as it describes the first alternative approach ("altered nuclear transfer") that could be used to generate "customized" ES cells without destroying an embryo, as demonstrated in the mouse.

By blocking a gene that is required for the extra-embryonic cells prior to the nuclear transfer, only a disorganized clump of cells develops. This clump, however, still contains the cells that can be expanded into ES cells.

The development of our procedure was only possible through combining a number of recently developed tools. Our lab is one of the few labs that had all the tools in place—nuclear transfer, RNA interference, etc.—and also has a major focus on stem cell biology.

The key issue is whether the "Altered Nuclear Transfer" (ANT) product is an embryo or a biological artifact, as William B. Hurlbut, a physician and consulting professor in the program of human biology at Stanford University, is arguing.

We have now gotten reactions by a number of ethicists, Catholic scholars, and even members of the Bush Administration, that they would not consider the ANT product as an embryo. This may open up funding from NIH for this type of research. Obviously, this is a highly charged political issue and we will have to see where this public discussion goes.