Navigation Links
Stem cell nuclei are soft 'hard drives,' Penn study finds

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 Penns School of Engineering and Applied Science and the Penn School of Medicines 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 Penns 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.


Contact: Jordan Reese
University of Pennsylvania

Related biology news :

1. Nano-Probes Allow an Inside Look at Cell Nuclei
2. Discovery of master switch for the communication process between chloroplast and nuclei of plants
3. Lance Armstrong through a physiological lens: hard training boosts muscle power 8%
4. K-State professors discover enzyme responsible for creation of a beetles hard shell
5. Invasive species harms native hardwoods by killing soil fungus
6. How taste response is hard-wired into the brain
7. Animal brains hard-wired to recognize predators foot movements, Queens study suggests
8. Weighting cancer drugs to make them hit tumors harder
9. Beekeepers work hard for the honey, despite changing tupelo forest
10. Researcher gives hard thoughts on soft inheritance
11. A reason why video games are hard to give up
Post Your Comments:
(Date:5/16/2016)... --  EyeLock LLC , a market leader of iris-based ... IoT Center of Excellence in Austin, Texas ... embedded iris biometric applications. EyeLock,s iris authentication ... with unmatched biometric accuracy, making it the most proven ... platform uses video technology to deliver a fast and ...
(Date:4/28/2016)... First quarter 2016:   , Revenues amounted ... quarter of 2015 The gross margin was 49% (27) ... the operating margin was 40% (-13) Earnings per share ... operations was SEK 249.9 M (21.2) , Outlook   ... M. The operating margin for 2016 is estimated to ...
(Date:4/15/2016)... , April 15, 2016 ... the,  "Global Gait Biometrics Market 2016-2020,"  report to ... ) , ,The global gait biometrics ... of 13.98% during the period 2016-2020. ... angles, which can be used to compute factors ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... DIEGO , June 27, 2016  Sequenom, Inc. ... committed to enabling healthier lives through the development of ... Court of the United States ... courts that the claims of Sequenom,s U.S. Patent No. ... patent eligibility criteria established by the Supreme Court,s Mayo ...
(Date:6/27/2016)... ... June 27, 2016 , ... Newly created 4Sight ... solutions to the healthcare market. The company's primary focus is on new product ... marketing strategies that are necessary to help companies efficiently bring their products to ...
(Date:6/27/2016)... BOSTON , June 27, 2016   Ginkgo ... biology to industrial engineering, was today awarded as ... a selection of the world,s most innovative companies. ... at scale for the real world in the ... organism engineers work directly with customers including Fortune ...
(Date:6/24/2016)... (PRWEB) , ... June 24, 2016 , ... While the ... such as the Cary 5000 and the 6000i models are higher end machines that ... the height of the spectrophotometer’s light beam from the bottom of the cuvette holder. ...
Breaking Biology Technology: