Cloning
Cloning, including reproductive and therapeutic cloning, is an emerging technology. In this essay, I focus on the implications of this new polemic technology and how it can influence our lives. As a scientist, who works with stem cells in mice, I have an obligation to contribute to educating the public concerning these technologies and the ethical problems they entail.
From Clones to Dolly
Clones are genetically identical organisms. In other words, organisms with the same DNA or genome. Organisms with asexual reproduction, like many microorganisms, usually have millions of clones because only rare mutations are a cause of genetic change. In mammals such as humans, the existence of clones is limited to divisions of the egg, often called identical or monozygotical twins. Having the same genome does not imply that two animals will be exactly the same. Even identical twins are different to some degree. During development there are always random events, called developmental noise, that are unique to each organism. In addition, changes in education, nurturing, and other environmental factors can lead to noticeable differences between adult organisms with the same genome.
In 1997, Ian Wilmut and colleagues at the Roslin Institute developed an artificial method to obtain mammalian clones from mature organisms and thus permit the first case of asexual reproduction in mammals -- cloning in other species, like frogs, had been done before. Briefly, clones are generated by extracting the nucleus of a mother cell, which in case of Dolly was a mammary cell, and then injecting it into an egg without a nucleus. Precise medium conditions and often an electric shock allow the nucleus to merge with the egg which can then be inserted into a womb and, in some cases, generate a new organism. This way, Dolly, the sheep, featured the same nuclear genome of her mother. In recent years, clones of many other mammalian species have been produced using this or similar techniques: calves, mice, monkeys, pigs, cats, etc. Clones from clones have also been created.
Animal cloning has many applications. Cloning pets is already a reality and some companies offer services in this area. In agriculture, researchers have cloned a disease-resistant bull that had died and the cloning of endangered species is a reliable prospect for conservation efforts. Despite some early setbacks, Pasqualino Loi and his colleagues have been able to clone a mouflon lamb, a member of an endangered species of sheep, using the same somatic cell nuclear transfer technique used to clone Dolly. Even thought cloning animals for human benefit is barely controversial, human cloning has been much attacked.
The Dangers of Human Cloning
The greatest danger human cloning poses is a health risk to babies born through this procedure. Research in animals has shown that while cloning is possible, the majority of animals die in early stages of development or shortly after birth. Moreover, a number of cloned animals are born with defects. Despite anecdotal claims, human cloning has never been performed, but one serious possibility is that human clones would also feature birth defects. One possible cause for defects in clones are epigenomic changes. Succinctly, in addition to the DNA, there is another layer of information in the genome called epigenomics. Genes can be turned on and off through changes at the DNA level such as DNA methylation. Clones derived from adult cells do not have the methylation patterns found in a newly born, and so they could carry defects. For this reason, the majority of researchers, including myself, opposes reproductive human cloning.
Can a mad dictator create an army of elite troops using clones? Sure he can. It is, however, a stupid thing to do because it wouldn't be economically viable. It would require a large amount of resources, not to mention years in research and development. Certainly, it is much easier, quicker, and cheaper to recruit and train adults than to create human clones. To create armies of excellent soldiers, a better idea is to follow the example of dictator Ceausescu of Romania who recruited young orphans to train them for his special forces.
"Cloning may turn out to be less prevalent and less scary than we imagined. Market forces might make reproductive cloning impractical, and scientific advancements may make it unnecessary." — Robin Marantz Henig
Fortunately, the costs of reproductive cloning are prohibitive for most people and with current legislation aiming at preventing human cloning, it is doubtful that many human clones will be born, at least with current technology. It is possible future technological breakthroughs make human cloning a safe and cheap reality, but with improvements in reproductive medicine and genetic engineering, it is unlikely human clones will become widespread any time soon.
Cloning, Stem Cells, and Their Impact on Medicine
"To him that knows to do good and does it not, to him it is sin." — from the Bible
The future of cloning is mostly at a cellular level, called therapeutic cloning. It is possible to obtain blastocysts, also called pre-embryo, which are a mass of undifferentiated cells. In fact, scientists at Advanced Cell Technology have already created human embryos from clones. Each of these cells has the potential to generate an individual, a clone of the patient but that's not the aim. The goal is to use these undifferentiated cells, also called embryonic stem cells, to generate any type of tissue. This stock of stem cells can then be used to treat a myriad of diseases.
Mouse embryonic stem cells derived from the inner mass of the blastocyst. The large aggregates are colonies of cells. These cells can be used to create transgenic mice or they can be differentiated into different types of tissues, including neurons, pancreatic insulin-secreting cells, etc.
Much research is being done in developing therapeutic cloning that can be used against life-threatening disease such as AIDS, Parkinson's disease, Alzheimer's, diabetes, etc. So far, the general strategy involves collecting cells from the patient, creating totipotent cells, differentiating the cells into the necessary tissue type, multiplying the cells, if necessary correcting genetic errors in those cells that are responsible for the disease, and implanting the cells back again. For instance, it may be possible to use cells obtained this way to replace the dying neurons in Alzheimer's disease and thus treating this horrible neurodegenerative disease. Overall, the potential stem cells have is enormous and as engineering problems are progressively solved, this field has the potential to change medicine.
In some cases it is possible to derive stem cells from adults without the need of a blastocyst. These adult stem cells are, however, less powerful than embryonic stem cells and that is why researchers prefer to use embryonic stem cells. Many politicians and bioethics committees have opposed research using embryonic stem cells by drawing parallels between the methods used to derive stem cells and abortion. These comparisons are misleading, though. Unlike in an abortion, an individual is not destroyed to generate embryonic stem cells. The blastocyst is not an embryo, it will not give rise to an individual. Instead, it is a cellular mass that has the potential to yield one, two, three, or more individuals. As such, the blastocyst cannot be considered an individual. Unfortunately, many policy-makers are either unaware of this and continue to confuse stem cell research with abortion or have their own agenda, thus hindering research that can save thousands of lives.
As a conclusion, I'm convinced that human cloning and genetics are going to play a critical role in the future of medicine. I hope I have the opportunities and luck to embark in this exciting journey, and I hope politicians and the public in general see the benefits of stem cell research are much greater than its problems.
Sources and Links
Clonaid; they claim to be the first company to offer human cloning.
Genetic Savings & Clone; for pets.