- Somatic cell nuclear transfer (SCNT): This technique is used to create genetically identical copies of an existing organism. In SCNT, the nucleus of a somatic cell (any cell other than a gamete) is transferred into an enucleated egg (an egg that has had its nucleus removed). The egg is then fertilized, and the resulting embryo develops into a new organism that is genetically identical to the donor of the somatic cell. SCNT has been used to create cloned animals, such as Dolly the sheep.
- Embryonic stem cell nuclear transfer (ESNT): This technique is used to create embryonic stem cells that are histocompatible with a specific individual. In ESNT, the nucleus of a somatic cell is transferred into an enucleated blastocyst (an early-stage embryo that has not yet differentiated into specific cell types). The resulting embryo is allowed to develop until the blastocyst stage, and then the inner cell mass (the part of the embryo that gives rise to the fetus) is removed and cultured. The resulting embryonic stem cells are pluripotent, meaning that they have the potential to develop into any type of cell in the body. ESNT has the potential to be used to treat a variety of diseases and conditions by providing a source of histocompatible stem cells for transplantation.
- Nuclear reprogramming: Nuclear transfer can also be used to reprogram somatic cells into pluripotent stem cells. This is done by transferring the nucleus of a somatic cell into an enucleated egg or zygote (a fertilized egg). The egg or zygote then reprograms the nucleus, causing it to revert to a pluripotent state. Reprogrammed somatic cells have the same potential as embryonic stem cells to develop into any type of cell in the body. Nuclear reprogramming has the potential to be used to create patient-specific stem cells for transplantation, as well as to study the process of cellular differentiation.
