Cloning In the Eyes of the Beholder

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Cloning In the Eyes of the Beholder

• Ida Chow, Ph.D.
• Society for Developmental Biology
• Bethesda, Maryland

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Society for Developmental Biology

• The Society for Developmental Biology
  declares a voluntary five-year moratorium on
  cloning human beings, where cloning human
  beings is defined as the duplication of an
  existing or previously existing human being by
  transferring the nucleus of a differentiated,
  somatic cell into an enucleated human oocyte, and
  implanting the resulting product for intrauterine
  gestation and subsequent birth. Sept. 1997.
  Extended Jan. 2003

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Cloning

• Greek klon twig (cuttings from one original
  plant)
• Molecular biology copies of DNA (gene) fragments
  
• Cell cultures cell multiplication by cell
  division (mitosis)
• Bacterial growth
• Plants budding
• Identical twins
• Identical genetic copies

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Fundamental Question

• How does a single cell, the fertilized egg,
  transform into a complex organism, with many
  different types of cells, tissues and organs?
• - processes?
• - genes?
• - control / regulation?

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• Totipotency Capable of giving origin to all
  the cell types in the organism, person, e.g.,
  fertilized egg developing into a whole organism
• Gradual loss of the capability for
  differentiation with the process of development
  - Pluripotency, multipotency, e.g., superficial
  skin cell from deep layer skin cell

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Definitions

• Somatic cells body cells, full genetic
  complement, 2 sets of chromosomes diploid, 46
  in humans
• Germ cells gametes, oocyte (unfertilized egg)
  and sperm, one half of genetic complement, 1 set
  of chromosomes haploid, 23 in humans
• Fertilization fusion of sperm and oocyte, full
  genetic complement, 1 set of chromosome from egg
  and 1 from sperm, diploid

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Somatic Cell Nuclear Transfer

• Removal of the nucleus containing the genes of an
  unfertilized oocyte
• Fusion of an isolated body cell with the oocyte,
  or injection of the somatic cell nucleus into the
  oocyte
• Stimulation of the oocyte to begin the process of
  cell division and differentiation, producing the
  blastocyst (a hollowed ball with a mass of about
  150 cells)

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Fundamental Questions

• Reprogramming of gene expression How to make
  the adult somatic cell nuclear DNA (genes)
  express the same way as in an embryo, that is,
  following the proper sequence.
• What molecules in the oocyte cytoplasm are
  capable of
• de-differentiating the adult somatic cell
  nucleus?

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Somatic Cell Nuclear Transfer
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Conditions
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Differences

• Embryonic
• unlimited capability for cellular reproduction
• broader pluripotency
• more direct access to stem cells
• large number of available stem cells
• many identified inducing factors

• Adult
• limited capability for cellular reproduction
• limited pluripotency
• difficult access and identification of the stem
  cells
• limited number of available stem cells
• chromosomal defects

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Reproductive Cloning

• Implantation of the blastocyst into a prepared
  womb of a female
• Further differentiation and growth of the cloned
  product
• Delivery of a full-term (or almost) cloned
  individual, with nuclear DNA identical to that of
  the donor of the body cell, and mitochondrial DNA
  identical to that of the oocyte no genetic
  similarity to surrogate female if not oocyte donor

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NO CLONING OF HUMAN BEINGS FOR REPRODUCTIVE
PURPOSES
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• Figures in this presentation are from
  publications by the
• National Institutes of Health (http//www.nih.gov
  )
• Stem Cells a Primer (http//www.nih.gov/news/stem
  cell/primer.htm)
• Stem Cells Scientific Progress and Future
  Research Directions
• (http//www.nih.gov/news/stemcell/scireport.htm)

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Additional Resources

• Society for Developmental Biology (SDB)
  www.sdbonline.org, Focus on Stem Cells
  http//sdb.bio.purdue.edu/publications/focus/index
  .html
• National Institutes of Health (NIH) www.nih.gov,
  Stem Cell Information Index http//www.nih.gov/ne
  ws/stemcell/index.htm
• National Bioethics Advisory Commission Reports
  (NBAC) http//www.georgetown.edu/research/nrcbl/n
  bac/pubs.html. Scrawl done and see the following
  reports Ethical Issues in Human Stem Cell
  Research (Sept. 1999) and Cloning Human Beings
  (June 1997)
• The Presidents Council on Bioethics (PCBE)
  www.bioethics.gov, and see the Cloning Report
  http//www.bioethics.gov/cloningreport/
• The National Academies www.nas.edu. Scientific
  and Medical Aspects of Human Reproductive
  Cloning http//www.nap.edu/catalog/10285.html?se_
  side, Stem Cells and the Future of Regenerative
  Medicine http//www.nap.edu/catalog/10195.html?se
  _side
• Federation of American Societies for Experimental
  Biology (FASEB) www.faseb.org, Cloning, Past,
  Present and the Exciting Future
  http//www.faseb.org/opar/cloning/