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:4/5/2017)... 2017  The Allen Institute for Cell Science today ... one-of-a-kind portal and dynamic digital window into the human ... first application of deep learning to create predictive models ... and a growing suite of powerful tools. The Allen ... future publicly available resources created and shared by the ...
(Date:4/5/2017)... , April 4, 2017 KEY FINDINGS ... to expand at a CAGR of 25.76% during the ... is the primary factor for the growth of the ... MARKET INSIGHTS The global stem ... technology, application, and geography. The stem cell market of ...
(Date:4/3/2017)... 2017  Data captured by IsoCode, IsoPlexis ... a statistically significant association between the potency ... and objective response of cancer patients post-treatment. ... whether cancer patients will respond to CAR-T ... as to improve both pre-infusion potency testing and ...
Breaking Biology News(10 mins):
(Date:10/9/2017)... ... ... The award-winning American Farmer television series will feature 3 Bar Biologics in ... 8:30aET on RFD-TV. , With global population estimates nearing ten billion people by ... feed a growing nation. At the same time, many of our valuable resources are ...
(Date:10/9/2017)... Texas (PRWEB) , ... October ... ... study published on October 5, 2017, in the medical journal, Epilepsia, Brain ... with the gold standard, video EEG, in detecting generalized tonic-clonic seizures (GTCS) ...
(Date:10/7/2017)... , Oct. 6, 2017  The 2017 ... of three scientists, Jacques Dubochet, Joachim Frank ... developments in cryo-electron microscopy (cryo-EM) have ... within the structural biology community. The winners worked ... can now routinely produce highly resolved, three-dimensional images ...
(Date:10/5/2017)... ... October 05, 2017 , ... LabRoots , the ... from around the world, is giving back to cancer research with a month-long promotion ... , Now through October 31, shoppers can use promo code PinkRibbon to get 10 ...
Breaking Biology Technology: