Navigation Links
Cloned stem cells prove identical to fertilized stem cells

Scientists generally agree that all cloned animals are biologically flawed. But they don't agree about what that means for stem cells derived from cloned embryos, the basis for therapeutic cloning.

Also known as somatic cell nuclear transfer, therapeutic cloning is a promising approach to create individually customized cellular therapies for treating certain disorders. Demonstrated in mice but not in humans, it begins with stem cells derived from a cloned embryo. But if cloned embryos can't produce normal organisms, how can they produce normal stem cells?

Analyzing the complete gene-expression profiles of both cloned and fertilization-derived stem cells in mice, scientists at Whitehead Institute for Biomedical Research now have concluded that the two are, in fact, indistinguishable.

"This paper demonstrates clearly that it doesn't matter if a stem cell has been derived from a cloned embryo or from a fertilized embryo," says Whitehead Member Rudolf Jaenisch, senior author on the paper that will appear in the online the week of January 16 in the Proceedings of the National Academy of Sciences. "Both can be equally good for therapy."

To create a clone, a scientist removes the nucleus from a donor cell, then places it into an egg from which the nucleus has been removed. The researcher then tricks the egg into thinking it's been fertilized. The egg develops into a blastocyst, an early stage embryo consisting of no more than 100 or so cells. The scientist can then either remove the stem cells from this blastocyst, or place it into a uterus where it has the potential to develop into a fetus.

Here's where things get complicated. The original donated nucleus may have come from, say, a skin cell. For a viable fetus to develop, the egg needs to reprogram the genome of the skin cell, shutting off genes specific for skin tissue and turning on genes needed for embryonic development, genes that are normally dormant in tissue-specific cells . In other words, the egg needs to erase all tissue-specific memories from the skin cell and revert it into a genomic blank slate.

But this entire process is almost never perfect, and nearly all cells in a cloned blastocyst retain some memory of their original source. As a result, the developing fetus inevitably has some degree of genetic abnormality. Most clones, in fact, die in utero or at birth. The few clones that make it into adulthood are often plagued by bizarre health complications. This is one reason why scientists generally believe that attempting to clone a human being is morally reprehensible.

But are the cloned embryo's stem cells beleaguered by the same defects?

Studies have demonstrated that a small number of stem cells in the blastocyst appear to be spared this faulty reprogramming. When stem cells from a cloned blastocyst are removed and placed into a dish, most die. A few, however, survive and give rise to an embryonic stem cell line, and these appear to be thoroughly reprogrammed.

Researchers have tried to test the integrity of these surviving stem cells by transplanting them into fertilized blastocysts and then observing the overall health of the resulting animal. Although these animals generated entirely from cloned stem cells appear to be fine, many scientists don't accept this result as definitive.

Tobias Brambrink, a postdoctoral researcher in the Jaenisch lab, tried a different approach, comparing gene expression in cloned and fertilization-derived stem cells. With a series of microarray chips, Brambrink measured which genes were active and which were silent in both kinds of cells. To ensure the accuracy of his results, he compared five lines of cloned stem cells with five fertilization-derived stem cell lines.

"The results are very clear," says Brambrink. "If a gene is active in fertilized stem cells, it's also active in cloned stem cells, and at the same level of activity. The same goes for genes that are silent. There is really no significant molecular difference between both kinds of stem cells."

"In my opinion, these results solidify the argument that while a cloned animal is abnormal, a cloned stem cell is perfectly normal," says Jaenisch.


Source:Whitehead Institute for Biomedical Research

Related biology news :

1. Cloned mice created from fully differentiated cells, a milestone in cloning research
2. Wisconsin scientists grow critical nerve cells
3. Spleen may be source of versatile stem cells
4. Researchers discover way to make cells in the eye sensitive to light
5. Priming embryonic stem cells to fulfill their promise
6. Lack of enzyme turns fat cells into fat burners
7. Poor prenatal nutrition permanently damages function of insulin-producing cells in the pancreas
8. Elusive HIV shape change revealed; Key clue to how virus infects cells
9. Mouse brain cells rapidly recover after Alzheimers plaques are cleared
10. Enzyme allows B cells to resist death, leading to leukemia
11. Scientists rid stem cell culture of key animal cells
Post Your Comments:

(Date:11/18/2015)... , November 18, 2015 ... published a new market report titled  Gesture Recognition Market ... Forecast, 2015 - 2021. According to the report, the global gesture ... is anticipated to reach US$29.1 bn by 2021, at ... North America dominated the global ...
(Date:11/16/2015)... Nov 16, 2015  Synaptics Inc. (NASDAQ: ... solutions, today announced expansion of its TDDI product ... touch controller and display driver integration (TDDI) solutions ... These new TDDI products add to the previously-announced ... TD4302 (WQHD resolution), and TD4322 (FHD resolution) solutions. ...
(Date:11/10/2015)... , Nov. 10, 2015  In this ... the basis of product, type, application, disease ... in this report are consumables, services, software. ... are safety biomarkers, efficacy biomarkers, and validation ... report are diagnostics development, drug discovery and ...
Breaking Biology News(10 mins):
(Date:12/1/2015)... SEATTLE , Dec. 1, 2015 Today ... headquarters in Seattle,s South Lake ... northwest corner of Mercer Street and Westlake Avenue North, ... to the Allen Institute for Brain Science and the ... Allen , philanthropist and founder of the Allen Institute. ...
(Date:12/1/2015)... , Dec. 1, 2015 Oxford Finance LLC ... to life sciences and healthcare services companies, today announced ... loan with MDRejuvena, Inc. ("the Company"). Proceeds from the ... development of the Company,s Rejuvaphyl™ and daily skincare products. ... is the MDRejuvena brand of high potency skincare products ...
(Date:12/1/2015)... , ... December 01, 2015 , ... ... announces Park NX10 SICM Module, an add-on scanning ion conductance microscopy module to ... of SICM to an AFM. , Park SICM benefits virtually all materials characterization ...
(Date:12/1/2015)... Dec. 1, 2015 Cepheid (Nasdaq: CPHD ... at the Piper Jaffray Healthcare Conference in ... Company is reaffirming its outlook for the fourth quarter ... addition to discussing longer term business model expectations. ... Officer.  "We continue to be the fastest growing company ...
Breaking Biology Technology: