Although genetically identical how can the ES cells differ in phenotype from the iPS cells? In a recent finding by the UCLA researchers, it has been proved that the molecular signatures are distinct. But still tests are pending to reveal the mystery.
After the halt of research related to ES cells, researchers moved towards some solutions to substitute the efficiency of the ES cells. So they developed induced Pluripotent Stem cells, by incorporating the essential embryonic cell genes into normal epithelial cell. The development of these kind of cells, surely promises the success as compared to the ES cells, while avoiding the ethical controversy of the later.
It is a general notion that for similar genetic makeups, the phenotypic expressions must be similar. But this notion is seriously challenged by the new findings which tells:
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.
The results were checked using older methods in UCLA labs too, where integrative viruses were used 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.
This research may seem to be a simpler finding with not much of application, and only based on theoretical interest, it may be said here the conclusion might not be true. The difference between the phenotypic expression with identical genteic makeup, may reveal newer findings, in future which might be more important for application.
Source: Science Daily