Nuclear Transfer, Somatic

SOMATIC CELL NUCLEAR TRANSFER (SCNT) is a process that was developed with the intent of producing immunologically compatible pluripo—tent embryonic cells that could be used for treating human diseases. Thus, SCNT was also termed therapeutic cloning. These pluripotent embryonic cells would be able to develop into any type of cell in the human body, and in addition, the technique used for these cells would address two important medical issues: immune system rejection and finding a genetically matching human donor.

The technique of SCNT involves the removal of the nucleus of an unfertilized egg cell (oocyte) and replacing it with the nucleus of a somatic cell. Somatic cells are nongermline cells that make up most cells in the body (e.g., cells found in bone, connective tissue, blood, skin, and internal organs). Ideally, the somatic cell would be obtained from the patient, so that adverse genetic and immunologie sequelae could be averted, thus also eliminating the need for finding a genetically compatible donor. These newly modified cells are then stimulated to divide, and stem cells are extracted five to six days afterward for research or potential therapeutic use.

At present, there is hope that SCNT may be used to treat diseases that are still incurable. Among these diseases are cancer, heart disease, sickle cell disease, psychiatric diseases, and many other medical conditions. SCNT also shows potential for addressing neurological conditions, such as Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, and various types of spinal cord injuries.

The idea of nuclear transfer has been present for many years, beginning with Hans Spemann of Germany, who performed the first such experiment using salamander embryos in the late 1920s and published his results in 1938 in his book Embryonic Development and Induction. Following him were Robert Briggs and Thomas King, who in 1952 cloned northern leopard frogs (Rana pipi—ens), using embryonic blastula nuclei, though by the end of their experiment, they had determined that it was impossible to produce clones from adult differentiated cells. It was Sir John Gurdon of Britain, who in the late 1950s and early 1960s further developed the technique using adult intestinal cells from Xenopus laevis tadpoles to clone 10 tadpoles, who then proved Briggs and Thomas' conclusion to be erroneous. Although some speculate whether Sir Gurdon's experiment was accurately performed, his work did open the way to scientific discussion regarding the ethics of cloning.