In genetics and developmental biology, somatic cell nuclear transfer (SCNT) is a technique for creating an ovum with a donor nucleus (see process below) . It can be used in embryonic stem cell research, or in regenitive medicine where it is sometimes refered to "therapeutic cloning." It can also be used in reproductive cloning. The term cloning in conjunction with SCNT is controversial and somewhat misleading as SCNT itself does not result in a clone of the donor ovum or somatic cell.

In SCNT the nucleus, which contains the organism's DNA, of a somatic cell (a body cell other than a sperm or egg cell) is removed and the rest of the cell is discarded. At the same time, the nucleus of an egg cell is removed. The nucleus of the somatic cell is then inserted into the enucleated egg cell. After being inserted into to the egg, the somatic cell nucleus is reprogrammed by the host cell. The egg, now containing the nucleus of a somatic cell, is stimulated in such a way that it begins to divide. After many mitotic divisions in culture, this single cell forms a blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to the original organism.

Some researchers use SCNT in stem cell research. The aim of carrying out this procedure is to obtain stem cells that are genetically matched to the donor organism. Presently, no human stem cell lines have been derived from SCNT research.

A potential use of genetically customized stem cells would be to create cell lines that have any genes linked to a particular disease. For example, if a person with Parkinson's disease donated his or her somatic cells, then the stem cells resulting SCNT would have any genes which contribute to Parkinson's disease. In this scenario, the disease-specific stem cell lines would be studied in order to better understand the disease, and perhaps develop treatments using more tradition research techniques.

In another scenario, the genetically customized stem cell lines would be generated for cell-based therapies to transplant to the patient. The resulting cells would be genetically identical to the somatic cell donor, allowing doctors to tailor stem cell treatments to patients, avoiding any complications from immune system rejection.

Only a handful of the labs in the world are currently using SCNT techniques in human stem cell research. In the United States, scientists at the Harvard University Stem Cell Institute, the University of California San Francisco, and possibly Advanced Cell Technology are currently researching a technique to use somatic cell nuclear transfer to produce embryonic stem cells. ^[1] In the United Kingdom, the Human Fertilisation and Embryology Authority has granted permission to labs at the Roslin Institute and the Newcastle Centre for Life.^[2] SCNT may also be occurring in China.^[3]

In 2005, a South Korean research team led by Professor Hwang Woo-suk, published claims to have derived stem cell lines via SCNT, but supported those claims with fabricated data.

This technique is currently the basis for cloning animals, such as the famous Dolly the sheep, and could theoretically be used to clone humans. Although most researchers agree that Cloning a Human that will develop to term is not possible for the foreseeable future using this technique. In late 2006, Iranian scientists cloned successfully a sheep, by somatic cell nuclear transfer, at the Rouyan research centre in Isfahan. [1]

The stresses placed on both the egg cell and the introduced nucleus are enormous, leading to a high loss in resulting cells. As the procedure currently cannot be automated, but has to be performed surprisingly manually under a microscope, SCNT is very resource intensive.

The biochemistry involved in "activating" the recipient egg is far from understood.

Not all of the donor cell's genetic information is transferred. DNA of organelles (mostly mitochondria) is left behind, with the resulting cells retaining those structures which originally belonged to the egg. This may be advantageous or disadvantageous depending on the quality, although evolution not having selected for the combination of mitochondria and DNA, it would be safe to assume it would be of less synchronity.

Whether or not the mitochondrial DNA divides based on the matriarchal line of the donor stem cell, or whether it is reconfigured based on the data in the DNA, is not identified here.

The health of the DNA used from somatic lines is also at risk, as it does not select against mutations, nor telomere count, as does the germ line. This is why germ cell nuclear transfer is a more ideal, though difficult to implement, procedure.

Proposals to use Nucleus Transfer techniques in human stem cell research raise a set of concerns beyond the moral status of any created embryo. These have led to some individuals and organizations who are also opposed to human embryonic stem cell research to be concerned about, or opposed to, SCNT research.

One concern is that blastula creation in human stem cell research will lead to the reproductive cloning of humans. Both processes use the same first step: the creation of a nuclear transferred embryo, most likely via SCNT. Those who hold this concern often advocate for strong regulation of SCNT to preclude implantation of any derived products for the intention of human reproduction. ^[4], or its prohibition.^[5]

A second concern is the appropriate sourcing of the eggs that are needed. SCNT requires human eggs, which can only be obtained from women. The most common source of these eggs today are eggs that are produced and in excess of the clinical need during IVF treatment. This is a minimally invasive procedure, but it does carry some health risks, such as ovarian hyperstimulation syndrome, and in very rare instances even death.

SCNT is currently legal for research purposes in the United Kingdom, having been incorporated into the 1990 Human Fertilisation and Embryology Act in 2001.^[6] Permission must be obtained from the Human Fertilisation and Embryology Authority in order to perform attempt SCNT.

In the United States, the practice remains legal, as it has not been addressed by federal law. ^[7]Kristen Philipkoski,

In 2005, the United Nations adopted against proposal submitted by Costa Rica, calling on member states to "prohibit all forms of human cloning inasmuch as they are incompatible with human dignity and the protection of human life." ^[8] This phrase may include SCNT, depending on interpretation.

The Council of Europe's Convention on Human Rights and Biomedicine and its Additional Protocol to the Convention for the Protection of Human Rights and Dignity of the Human Being with regard to the Application of Biology and Medicine, on the Prohibition of Cloning Human Being appear to ban SCNT. Of the Council's 45 member states, the Convention has been signed by 31 and ratified by 18. The Additional Protocol has been signed by 29 member nations and ratified by 14.^[9]

• Stem cell research
• Stem cell controversy
• Embryogenesis
• In vitro fertilisation
• Cloning
• New Jersey legislation S1909/A2840
• Rejuvenation

• The Century Foundation, The Basics: Stem Cells and Public Policy, June 2005
• Center for Genetics and Society, "Research Cloning Basic Science," (Last modified October 4, 2004, retrieved October 6, 2006)
• Center for Genetics and Society,