The data from the study suggest that embryonic stem cells and the reprogrammed cells, known as induced pluripotent stem (iPS) cells, have overlapping but still distinct gene expression signatures.
The differing signatures were evident regardless of where the cell lines were generated, the methods by which they were derived or the species from which they were isolated, said Bill Lowry, a researcher with the Broad Stem Cell Research Center and a study author.
"We need to keep in mind that iPS cells are not perfectly similar to embryonic stem cells," said Lowry, an assistant professor of molecular, cell and developmental biology. "We're not sure what this means with regard to the biology of pluripotent stem cells. At this point our analyses comprise just an observation. It could be biologically irrelevant, or it could be manifested as an advantage or a disadvantage."
The study appears in the July 2, 2009 issue of the journal Cell Stem Cell.
The iPS cells, like embryonic stem cells, have the potential to become all of the tissues in the body. However, iPS cells don't require the destruction of an embryo.
The study was a collaboration between the labs of Lowry and UCLA researcher Kathrin Plath, who were among the first scientists and the first in California to reprogram human skin cells into iPS cells. The researchers performed microarray gene expression profiles on embryonic stem cells and iPS cells to measure the expression of thousands of genes at once, creating a global picture of cellular function.
Lowry and Plath noted that, when the molecular signatures were compared, it was clear that certain genes were expressed differently in embryonic stem cells than they were in iPS cells. They then compared their data to that stored on a National Institutes of Health data base, submitted by laboratories worldwide. They analyzed that data to see if the genetic profiling conducted in other labs validated their findings, and again they found overlapping but distinct differences in gene expression, Lowry said.
"This suggested to us that there could be something biologically relevant causing the distinct differences to arise in multiple labs in different experiments," Lowry said. "That answered our first question: Would the same observation be made with cell lines created and maintained in other laboratories?"
Next, UCLA researchers wanted to confirm their findings in iPS cell lines created using the latest derivation methods. The cells from the UCLA labs were derived using an older method that used integrative viruses to insert four genes into the genome of the skin cells, including some genes known to cause cancer. They analyzed cell lines derived with newer methods that do not require integration of the reprogramming factors. Their analysis again showed different molecular signatures between iPS cells and their embryo-derived counterparts, and these signatures showed a significant degree of overlap with those generated with integrative methods.
To determine if this was a phenomenon limited to human embryonic stem cells, Lowry and Plath analyzed mouse embryonic stem cells and iPS lines derived from mouse skin cells and again validated their findings. They also analyzed iPS cell lines made from mouse blood cells with the same result
"We can't explain this, but it appears something is different about iPS cells and embryonic stem cells," Lowry said. "And the differences are there, no matter whose lab the cells come from, whether they're human or mouse cells or the method used to derive the iPS cells. Perhaps most importantly, many of these differences are shared amongst lines made in various ways."
Going forward, UCLA researchers will conduct more sophisticated analyses on the genes being expressed differently in the two cell types and try to understand what is causing that differential expression. They also plan to differentiate the iPS cells into various lineages to determine if the molecular signature is carried through to the mature cells. In their current study, Lowry and Plath did not look at differentiated cells, only the iPS and embryonic stem cells themselves.
Further study is crucial, said Mark Chin, a postdoctoral fellow and first author of the study.
"It will be important to further examine these cells lines in a careful and systematic manner, as has been done with other stem cell lines, if we are to understand the role they can play in clinical therapies and what effect the observed differences have on these cells," he said.
The stem cell center was launched in 2005 with a UCLA commitment of $20 million over five years. A $20 million gift from the Eli and Edythe Broad Foundation in 2007 resulted in the renaming of the center. With more than 150 members, the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research is committed to a multi-disciplinary, integrated collaboration of scientific, academic and medical disciplines for the purpose of understanding adult and human embryonic stem cells. The center supports innovation, excellence and the highest ethical standards focused on stem cell research with the intent of facilitating basic scientific inquiry directed towards future clinical applications to treat disease. The center is a collaboration of the David Geffen School of Medicine, UCLA's Jonsson Cancer Center, the Henry Samueli School of Engineering and Applied Science and the UCLA College of Letters and Science.
20.11.2017 | Washington University in St. Louis
Carefully crafted light pulses control neuron activity
20.11.2017 | University of Illinois at Urbana-Champaign
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
20.11.2017 | Earth Sciences
20.11.2017 | Earth Sciences
20.11.2017 | Life Sciences