Featured Research

from universities, journals, and other organizations

Stem Cell Nuclei Are Soft 'Hard Drives,' Study Finds

Date:
October 15, 2007
Source:
University of Pennsylvania
Summary:
Biophysicists have discovered that the nuclei of human stem cells are particularly soft and flexible, rather than hard, making it easier for stem cells to migrate through the body and to adopt different shapes, but ultimately to put human genes in the correct nuclear "sector" for proper access and expression.

Biophysicists at the University of Pennsylvania have discovered that the nuclei of human stem cells are particularly soft and flexible, rather than hard, making it easier for stem cells to migrate through the body and to adopt different shapes, but ultimately to put human genes in the correct nuclear "sector" for proper access and expression.

Researchers pulled cell nuclei into microscopic glass tubes under controlled pressures and visualized the shear of the DNA and associated proteins by fluorescence microscopy. The study showed that nuclei in human embryonic stem cells were the most deformable, followed by hematopoietic stem cells, HSCs, that generate a wide range of blood and tissue cells. Both types of stem cells lack lamins A and C, two filamentous proteins that interact to stabilize the inner lining of the nucleus of most tissue cells. Lamins A and C stiffen cell nuclei and are expressed in cells only after gastrulation, when most stem cells generate the specific tissues of complex organisms.

The fluid-like character of the nucleus is shown to be set largely by the DNA and the DNA-attached proteins that form chromatin. The extent of deformation of the nucleus is further modulated by the lamina.

"Understanding the sensitivity of stem cells and their nuclei to external stresses has very practical implications in handling these cells as well as in technologies such as cloning in which nuclei are manipulated," said Dennis Discher, a professor in Penn's School of Engineering and Applied Science and the Penn School of Medicine‘―s Cell and Molecular Biology Graduate Group.

The study, published in the Oct. 2 issue of the Proceedings of the National Academy of Sciences, supports the theory that lamin proteins are responsible for much of the genomic "lock-down" within differentiated cells. Differentiated cells, typified by muscle cells, fat cells and bone cells, all arise from stem cells that have committed to these specialized cell types by locking the DNA into a set pattern of gene expression.

To verify that lamin proteins were responsible for nuclear stiffness, the authors created a line of epithelial cells in which lamin filaments had been almost eliminated. Once as stiff as any other differentiated tissue cell derived from stem cells, the cell became as pliable as HSCs.

"Controlling structural proteins within the nucleus might lead to new means for controlling genomic regulatory factors and for generating stem cells from adult tissue cells," J. David Pajerowski, lead author and a graduate student in Penn's School of Engineering and Applied Science, said.

Researchers also found that over time nuclear deformations in stem cells and hematopoietic cells became resistant to returning to their original shape, which provides evidence of plastic flow similar to that of wet clay in the hands of a sculptor. Continued application of force eventually pulled nuclei into irreversible forms in which genes were re-arranged and massaged into new nuclear locations. Researchers literally visualized the flow of chromatin, the structure that carries DNA, and found irreversible distortions occurring on a timescale of minutes, a long time compared to many other cell processes but short compared to the lifetimes of nuclei in our tissue cells.

The research was performed by Pajerowski, Franklin L. Zhong and Discher of the Molecular and Cell Biophysics Laboratory at Penn, Kris Noel Dahl of Carnegie Mellon University and Paul J. Sammak of the University of Pittsburgh.

The research was funded by the National Institutes of Health, the National Science Foundation, an Ashton Fellowship and the Muscular Dystrophy Association.


Story Source:

The above story is based on materials provided by University of Pennsylvania. Note: Materials may be edited for content and length.


Cite This Page:

University of Pennsylvania. "Stem Cell Nuclei Are Soft 'Hard Drives,' Study Finds." ScienceDaily. ScienceDaily, 15 October 2007. <www.sciencedaily.com/releases/2007/10/071011134549.htm>.
University of Pennsylvania. (2007, October 15). Stem Cell Nuclei Are Soft 'Hard Drives,' Study Finds. ScienceDaily. Retrieved April 19, 2014 from www.sciencedaily.com/releases/2007/10/071011134549.htm
University of Pennsylvania. "Stem Cell Nuclei Are Soft 'Hard Drives,' Study Finds." ScienceDaily. www.sciencedaily.com/releases/2007/10/071011134549.htm (accessed April 19, 2014).

Share This



More Health & Medicine News

Saturday, April 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

'Holy Grail' Of Weight Loss? New Find Could Be It

'Holy Grail' Of Weight Loss? New Find Could Be It

Newsy (Apr. 18, 2014) — In a potential breakthrough for future obesity treatments, scientists have used MRI scans to pinpoint brown fat in a living adult for the first time. Video provided by Newsy
Powered by NewsLook.com
Little Progress Made In Fighting Food Poisoning, CDC Says

Little Progress Made In Fighting Food Poisoning, CDC Says

Newsy (Apr. 18, 2014) — A new report shows rates of two foodborne infections increased in the U.S. in recent years, while salmonella actually dropped 9 percent. Video provided by Newsy
Powered by NewsLook.com
Scientists Create Stem Cells From Adult Skin Cells

Scientists Create Stem Cells From Adult Skin Cells

Newsy (Apr. 17, 2014) — The breakthrough could mean a cure for some serious diseases and even the possibility of human cloning, but it's all still a way off. Video provided by Newsy
Powered by NewsLook.com
Obama: 8 Million Healthcare Signups

Obama: 8 Million Healthcare Signups

AP (Apr. 17, 2014) — President Barack Obama gave a briefing Thursday announcing 8 million people have signed up under the Affordable Care Act. He blasted continued Republican efforts to repeal the law. (April 17) Video provided by AP
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