[Paleopsych] Nature: Biologists come close to cloning primates

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Biologists come close to cloning primates

    [53]Helen Pearson
    Cloned monkey embryos transferred into mothers.

    US biologists have created cloned monkey embryos, and successfully
    transferred them into monkey mothers. Although none of the resulting
    pregnancies lasted more than a month, this is by far the closest
    scientists have come to cloning a primate.
    The study was unveiled yesterday by reproductive biologist Gerald
    Schatten of the University of Pittsburgh, Pennsylvania, at the annual
    meeting of the American Society for Reproductive Medicine in
    Philadelphia. Schatten's group copied a technique used earlier this
    year to clone a human embryo and extract embryonic stem cells.
    If researchers are able to repeat this process in monkeys, it might
    help them to refine the tricky technique without experimenting on
    human eggs and embryos, which are very difficult to obtain and raise a
    host of ethical objections. This in turn might help to resolve whether
    human embryonic stem cells, which can grow into a variety of tissues,
    will prove useful in medicine.
    Previously, Schatten and his colleagues had struggled to create
    healthy monkey embryos by cloning, which involves removing the
    DNA-containing nucleus from an adult cell and inserting it into an egg
    stripped of its own nucleus.
    In a 2003 study published in Science, Schatten suggested that
    extracting the nucleus from a monkey egg also robs it of two proteins
    essential for survival^[54]1. He found that all the resulting embryos
    had fatal chromosomal defects, and speculated that cloning any
    primate, including humans, might be impossible.
    That view proved false in February this year, when scientists from
    South Korea announced in Science that they had successfully cloned
    human embryos, and used them to grow embryonic stem cells capable of
    morphing into numerous different tissue types^[55]2. One aim of such
    research is to grow replacement tissues to fight human disease.
    In the Korean work, the cloned human embryos were allowed to divide in
    culture for just five or six days before being terminated. But, by
    adopting the Koreans' technique, Schatten's team made 135 cloned
    monkey embryos and transferred them into 25 mothers. The team
    experimented with transferring the nuclei from skin cells and from
    cumulus cells, which are found in the ovary.
    Why does it work?
    Schatten says he is not yet sure why the Korean method is so
    successful. Rather than sucking the nucleus out of the recipient eggs,
    the technique involves gently squeezing it out. This may remove less
    of the cell's cytoplasm and leave more of the essential molecules
    needed by the egg to direct embryo development; or it may simply cause
    less damage to the eggs.
    None of the cloned monkey embryos resulted in a pregnancy that lasted
    more than a month. But Schatten says it is too early to say whether
    cloned monkeys will ever be born; it may just take more attempts. It
    is also impossible, he says, to use these results to predict whether a
    cloned human baby could survive long in development.
    Schatten adds that his preliminary attempts to make embryonic stem
    cells from cloned monkey embryos failed. But at least his study
    confirms that the Korean cloning method works, something that has been
    difficult to prove because very few research groups work in such
    areas. "It shows that at least part of the technique is reproducible,"
    he says.

     1. Simerly C., et al. Science, 300. 297
        (2003). | [57]Article | [58]PubMed | [59]ISI |
     2. Hwang W. S., et al. Science, 303. 1669 - 1674
        (2004). | [60]Article | [61]PubMed | [62]ISI | [63]ChemPort |

    [70]UN to debate human cloning
    14 October 2004
    [71]Cloned human embryos yield stem cells
    12 February 2004
    [72]Korea's stem-cell stars dogged by suspicion of ethical breach
    06 May 2004
    [73]Stem-cell research: Crunch time for Korea's cloners
    06 May 2004
    [74]Human clones doomed?
    11 April 2003
    [75]Silence of the clones
    11 March 2003


   53. http://www.nature.com/news/about/aboutus.html#Pearson
   54. http://www.nature.com/news/2004/041018/full/041018-12.html#B1
   55. http://www.nature.com/news/2004/041018/full/041018-12.html#B2
   56. http://www.nature.com/news/2004/041018/full/041018-12.html#top
   57. http://dx.doi.org/10.1126%2Fscience.1082091
   58. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=PubMed&list_uids=12690191&dopt=Abstract
   70. http://www.nature.com/news/2004/041011/full/041011-10.html
   71. http://www.nature.com/news/2004/040209/full/040209-12.html
   72. http://www.nature.com/news/2004/040503/full/429003a.html
   73. http://www.nature.com/news/2004/040503/full/429012a.html
   74. http://www.nature.com/news/2003/030407/full/030407-12.html
   75. http://www.nature.com/news/2003/030310/full/030310-2.html

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