"From a biological standpoint, what is novel is that this is the first proteomic comparison of embryonic stem cells and IPS cells," says Phanstiel, referring to the study of which proteins a cell produces.
In essence, every cell in the body has the genes to make any protein the body might need, but cells make only the proteins that further their own biological role. Cells regulate the formation and activity of proteins in three ways: first, by controlling the production of RNA, a molecule that transfers the DNA code to protein-making structures; second, by controlling the quantity of each protein made; and third, by adding structures to the protein that regulate when it will be active.
The new study measured each of these activities, Phanstiel says.
"And because we compared four lines of each type of stem cell, and the comparisons were run three times, the statistics are extremely robust," he adds.
The new report, Coon says, suggests that embryonic stem cells and IPS cells are quite similar. According to some measurements, the protein production of an embryonic stem cell was closer to that of an IPS cell than to a second embryonic stem cell.
The ability to measure proteins in such detail emerged from improved ways to measure mass, Coon says.
"New technical developments in both our ability to measure a protein's mass accurate to the third or fourth decimal place and to compare the proteins from up to eight different cell lines at a time -- permitted this important comparison for the first time," says Coon.
The study is not the last word in determining the similarity of the two types of pluripotent stem cells, says Coon, who worked with UW-Madison stem-cell pioneer James Thomson, on the project.
Because clinical uses of either type of stem cells will require that they be transformed into more special
|Contact: Joshua Coon|
University of Wisconsin-Madison