Featured Research

from universities, journals, and other organizations

Discredited Korean Embryonic Stem Cells' True Origins Revealed

Date:
August 3, 2007
Source:
Children's Hospital Boston
Summary:
A new report sheds new light on a now-discredited Korean embryonic stem cell line, setting the historical record straight and also establishing a much-needed set of standards for characterizing human embryonic stem cells. DNA analysis finds they were the world's first human embryonic stem cells derived from eggs alone.

A report from researchers at Children's Hospital Boston and the Harvard Stem Cell Institute sheds new light on a now-discredited Korean embryonic stem cell line, setting the historical record straight and also establishing a much-needed set of standards for characterizing human embryonic stem cells.

In 2004, Korean investigators announced the creation of the world's first human embryonic stem cells through somatic cell nuclear transfer, entailing transfer of genetic material from a cell in the body into an egg. Now, research led by Kitai Kim, PhD, and George Q. Daley, MD, PhD, of the Children's Hospital Boston Stem Cell Program demonstrates that the Koreans unwittingly created something entirely different -- the world's first human embryonic stem cell to be derived by parthenogenesis, a process that creates an embryo containing genetic material only from the donor egg.

"We know now that the Koreans' first supposed nuclear transfer-derived stem cell line was actually derived from the woman's egg alone," Daley says.

The Koreans' 2004 paper, published in Science, was retracted by the journal in early 2006 amid evidence that researchers Hwang Woo-Suk et al. had falsified their data. An initial investigation of the Korean group's first embryonic stem cell line suggested it might be parthenogenetic in origin, but the analysis was inconclusive, and the cells' origin, until now, had never been fully explained in a peer-reviewed journal. It has now been explained in a report published online August 2 by the journal Cell Stem Cell.

Kim, Daley and collaborators used sophisticated genetic techniques to compare mouse embryonic stem cells derived from different sources: from embryos produced by natural fertilization; from embryos produced by parthenogenesis (through artificial activation of unfertilized eggs); and from embryos created through somatic cell nuclear transfer (replacing the nucleus of an egg with the nucleus from a cell in the body). They also tested three human embryonic stem cells isolated from fertilized embryos as well as the Korean line of human cells claimed to have been created through nuclear transfer.

They discovered that parthenogenetic embryonic stem cells have a distinct genetic signature that reflects their biological origins. All cells typically contain paired sets of chromosomes, one inherited from the mother and the other from the father. During the process of parthenogenesis, one set of chromosomes is duplicated, resulting in both chromosomes of the pair being of one parental type or the other (a pattern called homozygosity, which has reduced genetic diversity).

Kim and Daley showed previously that because chromosomes often exchange genetic material early in the process of cell division that creates the egg (meiosis), the duplicated chromosomes are not actually identical, but have places where the genes differ between members of the pair (called heterozygosity). In embryonic stem cells of parthenogenetic origin, this occurs especially toward the ends of the chromosomes, which are more likely to exchange genetic material, rather than the middle. In contrast, embryonic stem cells created through nuclear transfer show a consistent pattern of variation through all regions of the chromosome -- thus making them easily distinguishable from parthenogenetic cells.

The Korean cell line displays a genetic pattern that is clearly consistent with a parthenogenetic origin, Kim and Daley now show.

Because mistakes during nuclear transfer can result in parthenogenetic cells, Daley believes that the Hwang group generated parthenogenetic stem cells by accident, and didn't have the tools to conclusively determine what they had created. The first isolation of parthenogenetic stem cells from humans would have been an important contribution, but the Hwang group's attempt to pass off the cells as made by nuclear transfer was instead "a woeful case of misconduct," he says.

Parthenogenesis is a method of reproduction, common in plants and in some animals, in which the female can generate offspring without the contribution of a male. Daley's group has been stimulating parthenogenesis in the laboratory as a way of creating customized embryonic stem cells that can treat disease without being rejected by the immune system.

The team recently demonstrated in mice a feasible technique for generating parthenogenetic embryonic stem cells that were genetically matched to the egg donor at the genes that control tissue typing, and are attempting to create similar cells from humans.  See http://www.sciencedaily.com/releases/2006/12/061215091048.htm.

Daley, who is a member of the executive committee of the Harvard Stem Cell Institute and president of the International Society for Stem Cell Research, notes that scientists now have two powerful tools: human parthenogenesis, which appears to be an efficient means of producing human embryonic stem cells, and genetic screening, which can be used to scan stem cells and help define their origins.

Daley imagines a future in which scientists could create a master bank of parthenogenetic embryonic stem cells with genetically selected cells that could be matched to patients on the genes that control immune rejection. Having all the genetic material come from the mother, as it does in parthenogenesis, reduces tissue compatibility issues.

"There has been an advance in the idea that you can couple parthenogenesis and genetic screening to identify those cell lines that are going to be most helpful," Daley says.

Parthenogenetic embryonic stem cells do not obviate the need to also create embryonic stem cells through nuclear transfer or from human embryos, he adds. "Each of the strategies has its own applications, and there are certain types of research and certain fundamental questions--and major areas of therapy--that can only be accomplished with these other types of stem cells," Daley says.


Story Source:

The above story is based on materials provided by Children's Hospital Boston. Note: Materials may be edited for content and length.


Cite This Page:

Children's Hospital Boston. "Discredited Korean Embryonic Stem Cells' True Origins Revealed." ScienceDaily. ScienceDaily, 3 August 2007. <www.sciencedaily.com/releases/2007/08/070802121026.htm>.
Children's Hospital Boston. (2007, August 3). Discredited Korean Embryonic Stem Cells' True Origins Revealed. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2007/08/070802121026.htm
Children's Hospital Boston. "Discredited Korean Embryonic Stem Cells' True Origins Revealed." ScienceDaily. www.sciencedaily.com/releases/2007/08/070802121026.htm (accessed July 31, 2014).

Share This




More Health & Medicine News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) — Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) — Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) — At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) — The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:  

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile iPhone Android Web
    Follow Facebook Twitter Google+
    Subscribe RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins