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One Step Forward in Human Cloning

By Edited Jun 19, 2014 1 2

New research was published on the 15th May 2013[1] that validates the work done in other species (see Dolly the sheep) at a small scale in humans. The genetic material of skin cells of a donor was implanted into a human egg and developed into the initial stages of an embryo (blastocyst).

What is cloning?

Cloning can be defined as the technical process by which an individual can be exactly replicated from a single cell of his body, asexually. The new being has the same genetic material as the original one.

Clone
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Why cloning?

There are two potential areas where cloning could be beneficial: reproductive cloning and therapeutic cloning.

Reproductive cloning addresses the issue of couples where one of the individuals is sterile or in homosexual couples. It tries to create a new (identical) human being by the use of DNA material from exclusively one of the two parents. It is a topic that creates deep controversies and that has arisen critics and the creation of new laws in several countries.

Therapeutic cloning aims at curing diseases that would require healthy cells from the same patient to be injected in replacement for the damaged ones. This would involve the cloning of a subtype of cells from the individual specifically for this purpose, and not for the creation of a new human being. The main problem with cellular therapies at the moment is that they tend to come from donors, which results in future problems of cell rejection.

How does it work?

For years we know that all cells of an adult organism contain essentially the same genetic material in their nucleus.

Somatic Cell Nuclear Transfer or SCNT basically involves introducing the nucleus of a somatic donor, i.e. a cell from any non-sexual tissue or organ, into an egg from which the nucleus has been previously extracted. Once combined, cell division is stimulated and the whole is then implanted into the uterus of the egg donor animal for the development of the embryo. This is called nuclear transfer, because the nucleus of a cell is transferred into the cytoplasm of an enucleated (nucleus free) egg. It is therefore a process of asexual reproduction, meaning that sexual cells are not involved in it. By contrast, sexual reproduction is the one that happens naturally in humans and other mammals when an egg and a spermatozoid meet.

The nuclear transfer technique was the one used in the case of Dolly the sheep.

What did they do?

Mitalipov, S. et al. from the Oregon Health & Science University gave one step forward in human cloning, as published in their paper in the journal Cell on the 15th May 2013. They present their results optimized in non-human (primate) cells and the application of the same practice to human cells.

Cloning primates

The researchers initially faced a problem when putting together the donor DNA with the receptor’s egg: the cell stopped being in meiosis prematurely (the stage at which eggs and sperm are before giving rise to a single, unique being). They developed a method by which they could keep them a bit longer (by adding the envelope of a viral inactivated agent). In addition, they employed an electropulse method to stimulate the donor DNA to be reprogrammed as embryo DNA.

This method has been tried in later stages, by implanting the “fertilized” eggs into the uterus of female primates, but unsuccessfully, as in only one among 67 attempts the fetus developed correctly, but finally resulted in an abortion.

Towards cloning humans (or clone therapies)

The Oregon research group basically proceeded in the same ways with human cells. The results show that most embryos (61%) reached the stage where 8 daughter cells directly born to the initial clone could be seen. However, only 11% transformed into blastocysts (cell “balls” composed of between 70-100 cells). But by stimulating the eggs with varying caffeine concentration, this value could be increased to 23.5%. It is considered that after the 8 cell stage, the cell aggregate effectively transcribes the genetic material of the new individual and activates the embryo’s genes. Therefore, the blastocyst stage proves that this has been possible, at least at a very basic level. Nevertheless, there are many technical difficulties to overcome, mainly involving the quality of the embryos produced.

Human cloning and ethics

Apart from the technical difficulties, cloning presents a number of drawbacks or ethical and moral dilemmas.

Skeptics argue that the cloning of a human being could cause damage to the single individual, mainly on his physical and mental health. But they also highlight the damages that could mean for the human species. The main arguments in this regard are:

  • Responsibility to protect the integrity of the human species, as well as the integrity and diversity of the gene pool.
  • “Human beings should not be involved in the creation or alteration of their own life.”
  • The concern that "custom children" would be selectively created with certain physical or intellectual advantages, which might give rise to a social movement to create a “superior” human race.
  • The essence of humanity lies in the unique character of each of its members and the unpredictability of development.
  • Real secondary effects of the cloning that in most of the cases will impair the child (early death, excessive growth problems).
  • Adverse effects on natural selection and limited adaptability of the human species to an uncertain future.
Cloning: A Beginner's Guide (Beginner's Guides)
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Gene Cloning and DNA Analysis: An Introduction
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After Dolly: The Promise and Perils of Cloning
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Comments

May 20, 2013 6:23am
MrRooibos
Very informative article, great read
May 20, 2013 6:31am
mariuski
Glad you liked it - as a researcher I try to keep up with the (innumerable) progresses in science and this one striked me especially
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Bibliography

  1. Masahito Tachibana, Paula Amato, Michelle Sparman, Nuria Marti Gutierrez, Rebecca Tippner-Hedges, Hong Ma, Eunju Kang, Alimujiang Fulati, Hyo-Sang Lee, Hathaitip Sritanaudomchai, Keith Masterson, Janine Larson, Deborah Eaton, Karen Sadler-Fredd, David Bat "Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer." Cell. (2013): 1-11.

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