An Overview of Somatic Cell Nuclear Transfer


 Administrator    20 Dec 2019 : 06:50
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Understanding Somatic Cell Nuclear Transfer and how it works

Somatic Cell Nuclear Transfer Definition

Somatic cell nuclear transfer is a laboratory technique whereby the nucleus (DNA or genetic material) of a somatic cell (body cell versus an egg or a sperm cell) is injected inside the cytoplasm of an enucleated egg cell from a similar species. Enucleated means a cell with its own nucleus removed. If the egg had not had its nucleus (DNA) removed, there would be 50% more chromosomes in the fertilized egg because each somatic cell has the full number of chromosomes of 46. This would be incompatible with life.

Once inside the ‘nucleus-empty’ egg, the somatic nucleus is reprogrammed and becomes a fertilized egg, called a zygote. The zygote is stimulated by electrical shocks which makes the zygote divide into many cells until it becomes a blastocyst (100 cells). All of these cells are identical to the somatic cell which donated the DNA (nucleus), also known as a clone. Embryonic stem cells (ESC) are derived from the inner portion of the blastocyst and allowed to grow in culture. The blastocyst can be inserted into the uterus of a surrogate mother of the same or similar species. It becomes an embryo, then a fetus, until it arrives as a baby.

Why Use a Somatic Cell?

The reason that a somatic cell is needed for cloning is because the 46 chromosomes in a somatic cell are fixed which will yield a clone or identical individual whereas using two eggs or two sperm would yield completely different individuals with each egg or sperm used. Each egg and sperm in the body has 23 chromosomes but they are not identical in each egg or sperm. In order to get 46 chromosomes, you would need two eggs. Since no two eggs are identical, the offspring cannot be a clone even if the two eggs came from the same individual. If that was the case, then any two people, man and woman, could only make identical children or clones because each sperm and each egg would carry the same exact chromosomes. Fortunately, this is not the case.

Limitations of the nuclear transfer procedure

Although the procedure of Stem Cell Nuclear Transfer has proved effective in many different species, it has several limitations when applied to cattle. It is an inefficient procedure with only a small proportion of reconstructed embryos making it to the birthing process at term (fully developed) and a higher than average post-natal loss ratio. Most losses in the prenatal period occurred within 50 days in a series of tests performed on cattle. Cloned offspring also had a higher incidence of abnormalities. For instance, large babies were a common finding.

Somatic Cell Nuclear Transfer and Effect on Humans

The technique of Somatic Cell Nuclear Transfer is only able to add genes and could not make desired changes to the animals’ own genes. Somatic Cell Nuclear Transfer was believed to be able to make patient-specific embryonic stem cells or pluripotent cells that could be used to repair diseased or damaged tissues.

It is now possible to produce induced pluripotent stem (iPS) cells in chemically defined media suitable for clinical use. A recent study demonstrated a similar incidence of coding mutations in human pluripotent cells derived by somatic cell nuclear transfer and by the introduction of selected transcription factors.

As many clinic testimonials will attest the effectiveness of somatic cell nuclear transfer in the repair of disease and illnesses is showing dramatically positive results. The Stemaid Institute Europe is the only clinic in Europe providing this tremendously positive Stem Cell Treatment option. 

References

  1. Wells DN. et al. 2003. Coordination between donor cell type and cell cycle stage improves nuclear cloning efficiency in cattle. Theriogenology 59, 45–59. (10.1016/S0093-691X(02)01273-6) [PubMed]

  2. Wilmut, I., Bai, Y., & Taylor, J. (2015). Somatic cell nuclear transfer: origins, the present position and future opportunities. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 370(1680), 20140366. doi:10.1098/rstb.2014.0366

  3. Wang H, Yang H, Shivalila CS, Dawlaty MM, Cheng AW, Zhang F, Jaenisch R. 2013. One-step generation of mice carrying mutations in multiple genes by CRISPR/Cas-mediated genome engineering. Cell 153, 910–918. (10.1016/j.cell.2013.04.025) [PMC free article] [PubMed] [CrossRef] [Google Scholar]

  4. Chen G. et al. 2011. Chemically defined conditions for human iPSC derivation and culture. Nat. Methods 8, 424–429. (10.1038/nmeth.1593) [PMC free article] [PubMed] [CrossRef] [Google Scholar]

  5.  Johannesson B. et al. 2014. Comparable frequencies of coding mutations and loss of imprinting in human pluripotent cells derived by nuclear transfer and defined factors. Cell Stem Cell 15, 634–642. (10.1016/j.stem.2014.10.002) [PubMed] [CrossRef] [Google Scholar]




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