RELEVANCE: This marks first time researchers have generated human iPS cells, successfully removed the potentially problematic reprogramming genes, and seen the cells maintain their embryonic stem-cell-like state. Previous methods to reprogram mature cells into iPS cells inserted cancer-causing genes into the cells' DNA. Because the current method removes the cancer-causing genes, the resulting iPS cells' DNA is virtually identical to the DNA of the original adult cells. These iPS cells can be matured into any cell type, allowing for screens of potential drug therapies and study of patient-specific disease at the cellular level.
Whitehead Institute researchers have developed a novel method to remove potential cancer-causing genes during the reprogramming of skin cells from Parkinson's disease patients into an embryonic-stem-cell-like state. Scientists then used the resulting induced pluripotent stem (iPS) cells to derive dopamine-producing neurons, the cell type that degenerates in Parkinson's disease patients.
This marks the first time researchers have generated human iPS cells that have maintained their embryonic stem-cell-like properties after the removal of reprogramming genes. The findings are published in the March 6 edition of the journal Cell.
"Until this point, it was not completely clear that when you take out the reprogramming genes from human cells, the reprogrammed cells would actually maintain the iPS state and be self-perpetuating," says Frank Soldner, a postdoctoral researcher in Whitehead Member Rudolf Jaenisch's laboratory and co-author of the article.
Since August 2006, researchers have been reprogramming adult cells into iPS cells by using viruses to transfer four genes (Oct4, Sox2, c-Myc and Klf4) into the cells' DNA. Although necessary for reprogramming cells, these genes, the known oncogene c-Myc in particular, also have the potential to cause cancer. In addition, the four genes interact with approximately 3000 other genes in the cell, which may change how the cell functions. Therefore, leaving the genes behind in successfully reprogrammed cells may cause unintended alterations that limit the cells' applicability for therapeutic use, for drug screens or to study disease in cell culture.
In the current method, Whitehead researchers used viruses to transfer the four reprogramming genes and a gene coding for the enzyme Cre into skin cells from Parkinson's disease patients. The reprogramming genes were bracketed by short DNA sequences, called loxP, which are recognized by the enzyme Cre.
After the skin cells were reprogrammed to iPS cells, the researchers introduced the Cre enzyme into the cells, which removed the DNA between the two loxP sites, thereby deleting the reprogramming genes from the cells. The result is a collection of iPS cells with genomes virtually identical to those of the Parkinson's disease patients from whom original skin cells came.
Removing the reprogramming genes is also important because of those genes' effect on an iPS cell's gene expression (a measure of which genes the cell is using and how much it's using those genes). When the researchers compared the gene expressions of human embryonic stem cells to iPS cells with and without the reprogramming factors, iPS cells without the reprogramming genes had a gene expression closer to human embryonic stem cells than to the same iPS cells that still contained the reprogramming genes.
"The reprogramming factors are known to bind to and affect the expression of 3,000 genes in the entire genome, so having artificial expression of those genes will change the cell's overall gene expression," Dirk Hockemeyer, who is also a co-author of the Cell article. "That's why the four reprogramming genes can mess up the system so much. From now on, it will be tough for researchers to leave the reprogramming genes in iPS cells."
Jaenisch says that the process to remove the reprogramming genes is very successful, when compared with earlier experiments. "Other labs have reprogrammed mouse cells and removed the reprogramming genes, but it was incredibly inefficient, and they couldn't get it to work in human cells," he says. "We have done it much more efficiently, in human cells, and made reprogrammed, gene-free cells."
After removing the reprogramming genes, the Jaenisch researchers differentiated the cells from the Parkinson's disease patients into dopamine-producing nerve cells. In Parkinson's disease patients, these cells in the brain die or become impaired, causing such classic Parkinson's symptoms as tremors, slowed movement, and balance problems.
Because the cells reside in the patients' brains, researchers cannot easily access them to investigate how the disease progresses at the cellular level, what kills the cells, or what might prevent cellular damage. Therefore, the ability to create patient-specific iPS cells, derive the dopamine-producing cells, and study those patient-specific cells in the lab could be a great advantage for Parkinson's disease researchers.
Although the initial results are extremely promising, Jaenisch acknowledges that the process is far from over. "The next step is to use these iPS-derived cells as disease models, and that's a high bar, a real challenge. I think a lot of work has to go into that."
Nicole Giese | EurekAlert!
Further reports about: > DNA > DNA sequence > DNA sequences > Klf4 > Oct4 > Parkinson > Sox2 > adult cells > c-Myc > cell death > dopamine-producing neurons > embryonic stem > embryonic stem cell > embryonic stem-cell-like state > enzyme Cre > gene-free cells > harmful reprogramming genes > human cells > iPS cells > loxP > oncogene c-Myc > skin cell > stem cells
Transport of molecular motors into cilia
28.03.2017 | Aarhus University
Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences