Positions on human embryonic stem-cell research tend to fall into two camps: Either anything goes, or nothing goes. Proponents of the anything-goes position assert that the potential scientific and medical benefits of embryonic stem-cell research override all other considerations--and therefore restrictions on the funding and scope of this research are unwarranted. Proponents of the nothing-goes position assert that no amount of potential medical and scientific usefulness can justify the intentional creation and destruction of nascent human life.
Attempts have been made to bridge this divide by proposing alternative sources of embryonic stem cells for research and therapeutic purposes. In a recent white paper, the President's Council on Bioethics outlined four proposals for obtaining embryonic stem cells without destroying living human embryos: obtaining stem cells from embryos that are clinically dead, removing stem cells without harming the embryo, creating non-embryonic entities that produce usable stem cells, and converting adult cells into embryonic stem cells by a process of genetic reprogramming. Each of these proposals has considerable merit as an alternative to the generation and destruction of embryos for research--yet for each there are also significant questions about scientific feasibility and ethical soundness.
One proposal that has received considerable scientific support has been to generate non-embryonic entities that can serve as a source of stem cells through a process termed Altered Nuclear Transfer (or ANT). This would involve three general steps. First, an adult cell would be removed from a patient and the DNA of that cell altered to control and direct the types of gene expression the nucleus is capable of supporting. Then, the DNA would be removed from an oocyte (an egg cell) and this enucleated oocyte fused to the altered adult cell--creating a new cell that is neither an oocyte nor an adult cell but a hybrid exhibiting the properties programmed into it by the alterations made to the adult-cell nucleus. Finally, the newly generated ANT-cell would be allowed to produce stem cells. These stem cells would be genetically identical to the patient from whom the original adult cell was taken and could be used for research and therapeutic purposes.
This ANT approach could take many possible forms. Some researchers have proposed deleting or disabling key genes that are required for early embryonic development. The cell...