Cloning Humans



NEWS ARTICLES


  • Italy Doctor Says Three Cloned Pregnancies Exist April 2002 - Reuters - An Italian fertility specialist who has said he intends to create the world's first human clone told a television show on Wednesday three women were pregnant.
  • Reports Say Italian Claims Success in Human Cloning - April 2002 - Reuters
  • Dozens of human embryos cloned in China New Scientist - March 2002
  • Conceiving a Clone
  • Human Cloning Video and Pictures
  • Clone danger warning - Article
  • Cloning Pros and Cons
  • Ethics of Cloning Humans
  • Human Cloning - How close is it?
  • The Human Cloning Foundation
  • Implications of Human Reproductive Cloning and Germ Line Alteration for Women and Women's Health
  • Human Cloning Foundation Registry
  • Where is the soul in human cloning?


    NEW ARTICLES


    Cloning can turn back the developmental clock

    November 24, 2000 - Eureka Alert

    Settling a hotly debated issue in the field of cloning, a team of researchers from the Whitehead Institute and the University of Hawaii has shown that the egg can reset the developmental clock of a female adult cell, first reversing and then faithfully reproducing an early genetic event called X-inactivation. X-inactivation is a process by which one of two X chromosomes in female embryos is randomly silenced during development.

    The findings, published in Friday�s issue of Science, provide the first molecular evidence for the egg�s ability to reprogram an adult cell back to its embryonic state and show for the first time that the process of X-inactivation in clones occurs in a manner similar to that in normal development.

    Since Dolly was first cloned, researchers have debated whether she has random X-inactivation as normal females do or the same X chromosome inactivated in all her cells (the X that was inactive in the mammary cell nucleus from which she had been cloned). In this study, scientists from Rudolf Jaenisch�s laboratory at the Whitehead Institute and Ryuzo Yanagimachi�s laboratory at the University of Hawaii used their expertise in cloning mice to answer this question. Their results show that X-inactivation is random in the cells of cloned animals. The egg therefore is able to reprogram the X chromosome of an adult cell to a state that is appropriate for an embryonic one.

    "Scientists have suggested that cloning of mammals by nuclear transfer requires reprogramming of the differentiated state of donor cell to an embryonic ground state, but there was no direct molecular evidence for such reprogramming. The process of X-inactivation is an example. It has never been clear whether this process is reversible during cloning," says Jaenisch. Cloning is a very inefficient process, and it is possible that faulty reprogramming contributes to the low success rate. "It will therefore be crucial to determine whether the expression state of other genes of the adult donor cell can be faithfully reset during the cloning process," he says.

    X-inactivation is nature�s way of making sure that males and females have equal numbers of X-linked genes, explains Eggan, the first author on the paper. All human embryos inherit 23 pairs of chromosomes: one pair of sex chromosomes and 22 pairs of non-sex, or autosomal, chromosomes. Embryos that inherit an X chromosome from their mother and a Y chromosome from their father develop into males. Embryos that inherit two X chromosomes (one from each parent) develop into females.

    At the earliest stages of embryonic development, both X chromosomes are active in female embryos, but just before implantation, one chromosome is chosen for inactivation and silenced. The X-inactivation is random in the embryonic tissue, but in the tissue that ultimately becomes the placenta, the inactivation is thought to happen by a process called imprinting in which the paternal X is marked for inactivation.

    All female adult cells therefore have one X chromosome silenced, and the authors wondered whether cloning can reverse it. To do this, they used green fluorescent protein to label a gene on the X chromosome subject to inactivation and followed its course in different lineages of cloned embryos. This allowed them to tell, based on whether the cells were dark or fluorescent green, which X was inactivated and when.

    The researchers then created various populations of donor cells with known X-inactivation states (which could be color coded as dark or green donor cells) and used these donor cells to clone new embryos, transferring the nuclei of these cells into enucleated eggs.

    When researchers analyzed the results they found that X-inactivation is random in the embryonic lineage of cloned mice. "This random inactivation indicates that the epigenetic marks that distinguish the active and inactive X in adult cells can be removed and re-established on either X during the cloning process, resulting in random X-inactivation in the cloned animal," says Eggan.

    In contrast, the epigenetic marks on the active and inactive X in the donor cell are not removed in the early placental tissue of cloned mice and predispose the active X of the donor cell to be active and the inactive X to be inactive. However, just as in normal development, this somatically acquired mark is ignored during early stages of development as both X chromosomes are expressed, says Eggan.

    "Although the egg reprograms some aspects of X-inactivation, for instance, turning on genes in the silent X chromosome, there clearly are other aspects that the egg ignores, namely the marks that lead to imprinted X-inactivation in the placenta,"says Eggan.

    "It is expected that genes on other chromosomes are also reprogrammed to their embryonic state within the egg. If the marks on the genes on the X-chromosome and other chromosomes are faulty in the cell cloned, the egg may not have the ability to fix them, leading perhaps to abnormal development and death of embryos," say Akutsu and Yanagimachi.


    Scientists clone human embryos

    June 17, 1999 - Agence France-Press - Lomdon

    American scientists have cloned the first human embryos, the London Daily Mail reported on Thursday.

    'Nuclear transfer' cloning requires the egg to be hollowed out

    Using methods similar to those which produce Dolly the cloned sheep at Edinburgh's Roslin Institute, they produced a male embryo comprising nearly 400 cells, according to the British tabloid.

    The scientists at the Massachusetts-based Advanced Cell Technology then incinerated it after two days.

    They want to produce human body tissue which can be used to treat patients with various conditions, including nerve damage, diabetes and Parkinson's disease.

    A DNA-loaded nucleus of a human cell was extracted from a skin sample from a man's leg and then inserted into the outer protein of a hollowed out cow's egg under laboratory conditions, said the Mail. The egg was then placed in a laboratory dish and soaked in a chemical solution which fooled it into thinking it was a newly conceived embryo. The cells then began to develop into an embryo, according to the Daily Mail.

    Since the first embryo was cloned last November, the company is thought to have made many more, incinerating them all, in line with U.S. research lines, before they reached the age of 14 days, said the newspaper.


    Cloning gets specific

    June 29, 2000 - BBC

    Scientists have finally published details of an advance in cell technology that has resulted in the creation of the first sheep clones whose genes have been selectively modified.

    The researchers at the Edinburgh (UK)-based biotech company PPL Therapeutics can now introduce a gene into a specific location in an animal's genome.

    Previously, this could only be done randomly. The new technique has several applications, but, primarily, it should make the "pharming" of animals to produce useful drug compounds in their milk far more efficient.

    The work was originally disclosed last year but details were held back because of a patent application.

    Targeted regions

    Those details have now appeared in the journal Nature. They describe the methods that led to the birth of the first genetically modified sheep clones - including two female lambs named Cupid and Diana.

    The team at PPL was closely involved in the creation of Dolly the sheep, the first mammal clone created from an adult cell. Their new research has improved the traditional hit-or-miss technique of gene splicing by getting a "foreign" gene to enter a specific region on a chromosome, one of the structures that bundle up DNA in the nuclei of cells.

    The researchers, led by Dr Alexander Kind, inserted a gene that coded for a human protein into sheep fibroblast cells - the cells that produce collagen. "Flanking" regions of DNA, which are like bookends, marked the beginning and end of the region of DNA that was to be replaced.

    Matching bookends also surrounded the genetic material being inserted - this ensured it only went into the targeted location. Next, using the same method that created Dolly, the modified fibroblast cells were fused with eggs from which the nuclei had been removed. As a result, the eggs acquired the nuclei and genetic instructions of the fibroblasts: they became clones.

    Lung disease

    Surrogate mothers were used to carry the developing embryos to term, but only three survived.

    Among the live births were Diana and Cupid. They now carry a gene that means they produce a human protein called alpha-1-antitrypsin in their milk. Lack of this protein can cause the lung disease familial emphysema.

    Dr Alan Coleman, research director at PPL Therapeutics and a member of the team, said: "The significance of this technique is that you can choose exactly where you want to add a gene, or you could disrupt an existing gene.

    "You could, in principle, eliminate the kind of genes responsible for BSE and scrapie.

    "But cleaning up whole flocks and herds around the world I think would be impossible. There are just too many animals, and you would lose genetic diversity."

    Pig to human transplants

    Alternatively, he said, the technology could be used to make animal models of human illnesses on which new treatments could be tested.

    This is often done in mice but the rodents do not always mimic diseases and symptoms accurately, Dr Coleman said.

    "Mice are used if the model they present is a good one, but often you don't get the same symptoms humans have," said Dr Coleman. "Sheep might be a much better model."

    Dr Coleman said the scientists also hoped to produce selectively modified pig clones within the next year. PPL Therapeutics announced in February that it had succeeded in creating five pig clones - a much harder task than producing sheep.

    Pigs have a gene which triggers a severe rejection response when their tissue is put in humans. If this can be "switch off", it would remove a big obstacle to pig to human transplants, said Dr Coleman.

    
    
    
    
    
    

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