Somatic cell nuclear transfer
In genetics and developmental biology, somatic cell nuclear transfer (SCNT) is a laboratory strategy for creating a viable embryo from a body cell and an egg cell. The technique consists of taking an enucleated oocyte (egg cell) and implanting a donor nucleus from a somatic (body) cell. It is used in both therapeutic and reproductive cloning. Dolly the Sheep, famous for being the first successfully cloned mammal was created using this process.[1] SCNT has been championed as an answer to the many issues concerning embryonic stem cells (ESC) and the destruction of viable embryos in research. Though questions remain on how homologous the two cell types truly are, SCNT is enthusiastically being utilized in stem cell research, with particular focus in aforementioned "therapeutic cloning", also known as regenerative medicine. The first step in the process of reproductive cloning is accomplished with SCNT.
The process of somatic cell nuclear transplant involves two different cells. The first being a female gamete, known as the ovum (egg/oocyte). In human SCNT experi -ments, these eggs are obtained through consenting donors, many times utilizing ovarian stimulation. The second being a somatic cell, referring to the cells of the human body. Skin cells, fat cells, and liver cells are only a few examples.
The nucleus of the donor egg cell is removed and discarded, leaving it 'deprogra- mmed.' The nucleus of the somatic cell is also removed but is kept, the enucleated somatic cell is discarded. What is left is a lone somatic nucleus and an enucleated egg cell. These are then fused by squirting the somatic nucleus into the 'empty' ovum. After being inserted into the egg, the somatic cell nucleus is reprogrammed by its host egg cell. The ovum, now containing the somatic cell's nucleus, is stimulated with a shock and will begin to divide. The egg is now viable and capable of producing an adult organism containing all the necessary genetic information from just one parent. Development will ensue normally and after many mitotic divisions, this single cell forms ablastocyst (an early stage embryo with about 100 cells) with an identical genome to the original organism (i.e. a clone). Stem cells can then be obtained by the destruction of this clone embryo for use in therapeutic cloning or in the case of reproductive cloning the clone embryo is implanted into a host mother for further development and brought to term.
Somatic cell nuclear transplantation has become a focus of study in stem cell research. The aim of carrying out this procedure is to obtain pluripotent cells from a cloned embryo. These cells genetically matched the donor organism from which they came.This gives them the ability to create patient specific pluripotent cells, which could then be used in therapies or disease research.
Embryonic stem cells are undifferentiated cells of an embryo. These cells are deemed to have a pluripotent potential because they have the ability to give rise to all of the tissues found in an adult organism. This ability allows stem cells to create any cell type, which could then be transplanted to replace damaged or destroyed cells. Controversy surrounds human ESC work due to the destruction of viable human embryos. Leading scientists to seek an alternative method of obtaining stem cells, SCNT is one such method. Another application of SCNT stem cell research is using the patient specific stem cell lines to generate tissues or even organs for transplant into the specific patient. The resulting cells would be genetically identical to the somatic cell donor, thus avoiding any complications from immune system rejection.
