Stem cells research, 2005 : hearing before a Subcommittee of the Committee on Appropriations, United States Senate, One Hundred Ninth Congress, first session, special hearing, October 19, 2005, Washington, DC.
- United States. Congress. Senate. Committee on Appropriations. Subcommittee on Departments of Labor, Health and Human Services, Education, and Related Agencies
- Date:
- 2006
Licence: Public Domain Mark
Credit: Stem cells research, 2005 : hearing before a Subcommittee of the Committee on Appropriations, United States Senate, One Hundred Ninth Congress, first session, special hearing, October 19, 2005, Washington, DC. Source: Wellcome Collection.
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![Cdx2, but once the nucleus is transferred to the egg, the cloned product cannot establish this key lineage. It will develop still to an abnormal blastocyst which collapses because the trophectoderm lin- eage, which will give rise to the placenta, cannot form. The embryonic stem cells derived from this construct are indis- tinguishable in their potential from a normal embryonic stem cell. So the key question for the debate here is: does it generate embryos and how abnormal are they? So I would argue that the ANT, altered nuclear transfer, embryo is already abnormal at the 4- to 8-cell stage molecularly because the gene is then expressed. It is not expressed then. But it becomes morphologically only abnormal within 2 cell divisions. Senator SPECTER. Dr. Jaenisch, could you summarize your testi- mony at this point? Your full statement will be made a part of the record. Dr. JAENISCH. So I will then summarize that the question is can we designate these ANT embryos as normal, these ANT blastocysts as normal embryos. And I would think they are a mass of differen- tiating cells, but they definitely lack the intricate organization of the embryo and its potential. PREPARED STATEMENT I want to emphasize that ANT is a modification, not an alter- native, to nuclear transplantation. It requires additional manipula- tion of the donor cells that may complicate the logistics of an al- ready complex procedure, and this has concerned many scientists. However, our procedure has shown that the procedure is so simple and straightforward that it may be acceptable as a requirement if it would resolve the ethical objections against somatic cell nuclear transfer and allow this research to go ahead. [The statement follows: ] PREPARED STATEMENT OF DR. RUDOLF JAENISCH Mr. Chairman and members of the Subcommittee, my name is Rudolf Jaenisch. I am a founding Member of the Whitehead Institute and Professor of Biology at MIT. Before coming to the Whitehead Institute I was the head of the Department of Tumor Virology at the Heinrich-Pette Institute of the University of Hamburg in Germany. I am privileged to have helped establish the field of transgenic science. Transgenic science deals with the transfer of genes to create mouse models of human disease. My present research focuses on epigenetic gene regulation, on em- bryonic stem cells, and on nuclear cloning. Our focus is understanding the mecha- nisms that bring about reprogramming of a somatic nucleus to an embryonic one after its transfer into the egg. I work with mice and our results have demonstrated that nuclear cloning is inefficient, that most clones die at an early embryonic stage and that the few that survive to birth and beyond harbor serious defects and are not normal. The conclusion from this work is that reproductive cloning of humans is an unsafe technology that should be banned. Our work has shown that somatic cell nuclear transfer (SCNT) can generate “cus- tomized” embryonic stem cells that can be used for the treatment of genetic dis- eases. We have performed a “proof of principle” experiment in mice that carry a spe- cific mutation which causes a defective immune system. Human patients with a cor- responding mutation (designated as Severe Combined Immune Deficiency or SCID) are unable to fight infections and have a grim prognosis. In our proof of principle experiment the nuclei of SCID mouse skin cells were transplanted into enucleated eggs to generate cloned blastocysts (NT-blastocysts) that were then placed into tis- sue culture to derive “customized” cloned embryonic stem cells (NT-ES cells). The genetic mutation was corrected by gene targeting, the “repaired” NT-ES cells were then induced to differentiate into blood stem cells and, when transplanted back into the mutant mouse, restored immune function. I believe that this proof of principle](https://iiif.wellcomecollection.org/image/b32229392_0016.jp2/full/800%2C/0/default.jpg)
