, Volume 21, Issue 2, pp 79–83 | Cite as

Ethics and Embryonic Stem Cell Research

Altered Nuclear Transfer as a Way Forward
  • William B. Hurlbut
Current Opinion


Ethical controversy in stem cell research arises because current methods to produce embryonic stem cell lines require the destruction of living human embryos. For this reason, there is increasing interest in developing alternative, non-embryonic sources of pluripotent stem cells. This effort is especially important in the US due to the prevailing policy against federal funding of embryo-destructive research.

Altered nuclear transfer (ANT) is one of several potential methods to develop alternative sources of pluripotent stem cells. This approach employs the technique of somatic cell nuclear transfer, but the somatic cell nucleus or egg cytoplasm (or both) are first altered before the somatic cell nucleus is transferred into the oocyte. This alteration precludes the coordinated organization and developmental potential that is necessary for the resulting biological entity to be an embryo, but it still allows the entity to generate pluripotent stem cells.

Proof-of-principle for one variant of ANT has been established in mice by silencing the functional expression of the gene Cdx2 in the somatic cell nucleus prior to its transfer into an enucleated egg. From the resulting non-embryonic laboratory construct, fully functional pluripotent stem cells were procured. Other more recent studies have suggested the possibility of achieving the same results by preemptively silencing maternally derived Cdx2 messenger RNA in the egg before the act of nuclear transfer. The procedure would produce the equivalent of a tissue culture of pluripotent stem cells.

In contrast to the use of embryos ‘left over’ from clinical in vitro fertilization, ANT could produce pluripotent stem cell lines with an unlimited range of specifically selected and controlled genotypes. Such flexibility would greatly facilitate the study of disease, drug development, and toxicology testing, and may allow the production of therapeutically useful pluripotent stem cells that are immune-compatible. If developed to the point of scientific reliability, ANT would be a valuable research tool for the study of other aspects of cell development and differentiation, including gene expression patterns, imprinting, and cell-cell signaling. ANT would also help to clarify definitions and boundaries that distinguish true organisms from ‘biological artifacts’ and, thereby, provide moral precedent to guide future progress in developmental biology.


Pluripotent Stem Cell Human Embryo Stem Cell Research Nuclear Transfer Somatic Cell Nuclear Transfer 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



No sources of funding were used to assist in the preparation of this article. The author has no conflicts of interest that are directly relevant to the content of this article.


  1. 1.
    President’s Council on Bioethics. White paper: alternative sources of human pluripotent stem cells. Washington, DC: President’s Council of Bioethics, 2005 [online]. Available from URL: [Accessed 2007 Feb 23]
  2. 2.
    United States Congress 2006 Section 506. In: Labor, HHS, and Education and Related Agencies Appropriations Act, 2006, HR3010. In: H Rept 109-143Google Scholar
  3. 3.
    More Americans than ever support embryonic stem cell research. Virginia Commonwealth University Life Sciences Poll, October 24, 2005 [online]. Available from URL: [Accessed 2006 Sep 14]
  4. 4.
    United States Conference of Catholic Bishops. New poll: Americans continue to oppose funding stem cell research that destroys human embryos [online]. Available from URL: http://usccb.Org/comm./archives/2006/06-109.shtml [Accessed 2006 Sep 11]
  5. 5.
    Campo-Flores A. Split remains [online]. Available from URL: [Accessed 2006 Sep 11]
  6. 6.
    Hurlbut WB. Framing the future: embryonic stem cells, ethics, and the emerging era of developmental biology. Pediatr Res 2006 Apr; 59 (4 Pt 2): 4R–12RPubMedCrossRefGoogle Scholar
  7. 7.
    Meissner A, Jaenisch R. Generation of nuclear-transfer derived pluripotent ES cells from cloned Cdx2-deficient blastomeres. Nature 2006; 439: 212–21PubMedCrossRefGoogle Scholar
  8. 8.
    Deb K, Sivaguru M, Yong HY, et al. Cdx2 gene expression and trophectoderm lineage specification in mouse embryos. Science 2006 Feb 17; 311(5763): 992–6PubMedCrossRefGoogle Scholar
  9. 9.
    Schöler H. Testimony to the President’s Council on Bioethics. Session 1, stem cell research update, November 16, 2006 [online]. Available from URL: [Accessed 2006 Nov 29]
  10. 10.
    Jaenisch R. Testimony of Rudolf Jaenisch, M.D. Hearing on ‘An alternative method for obtaining embryonic stem cells’. Committee on Appropriations, Subcommittee of Labor, Health and Human Services, Education, United States Senate, 2005 Oct 19Google Scholar

Copyright information

© Adis Data Information BV 2007

Authors and Affiliations

  1. 1.Neuroscience Institute at StanfordStanford University Medical CenterStanfordUSA

Personalised recommendations