A new breakthrough in stem cell research has occurred, thanks to scientists at the Children's Medical Center Research Institute at UT Southwestern Medical Center in Dallas, Texas.
The researchers claim that protein synthesis - an essential biological process - can be studied in adult stem cells. This is something that scientists have been previously unable to accomplish.
It is believed that many degenerative diseases and some cancers are linked with mutations that affect the process of protein synthesis. But experts have been unable to pinpoint why this happens.
Therefore, the team's discovery is important in improving understanding of protein synthesis and why changes in the process are linked with the development of disease.
The research built on previous work that used a modified antibiotic, called puromycin, to make it possible to see and measure the amount of protein that is being synthesized in the body.
Stem cells require a regulated rate of protein synthesis
When the ribosomal mutant mice and the Pten mutant mice were bred together, stem cell function returned to normal and the development of leukemia was greatly delayed.
Using this reagent, the team at the Children's Medical Center Research Institute (CRI) found that different types of blood cells produce different amounts of protein per hour. Also, stem cells synthesize much lower amounts of protein than other blood-forming cells.
The paper's senior author, CRI director Dr. Sean Morrison, says this discovery "suggests that blood-forming stem cells require a lower rate of protein synthesis as compared to other blood-forming cells."
The researchers tested their findings using mice. They found that when a genetic mutation in a component of the machinery that makes proteins - called the ribosome - was present, protein production in stem cells was reduced by 30%.
In another group of mice, the scientists tried to increase the rate of protein synthesis by deleting the tumor suppressor gene Pten in blood-forming stem cells. This had the effect of impairing stem cell function.
These observations confirm that blood-forming stem cells require a highly regulated rate of protein synthesis. Therefore, any increase or decrease in the rate of synthesis caused the stem cells to work less effectively.
'It was as if two wrongs made a right'
But there was one further twist. Dr. Morrison explains:
"Amazingly, when the ribosomal mutant mice and the Pten mutant mice were bred together, stem cell function returned to normal, and we greatly delayed, and in some instances entirely blocked, the development of leukemia.
All of this happened because protein production in stem cells was returned to normal. It was as if two wrongs made a right."
"Many people think of protein synthesis as a housekeeping function, in that it happens behind the scenes in all cells," says Dr. Robert A.J. Signer, a postdoctoral research fellow and first author of the study.
"The reality is that a lot of housekeeping functions are highly regulated," Dr. Signer adds, "they have just not been studied enough to recognize the difference among cells. I think what we are seeing with this study is just the tip of the iceberg, where the process of protein production is probably quite different in distinct cell types."
Dr. Morrison says the team's findings have uncovered new areas of cellular biology that no one has seen before, adding that:
"No one has ever studied protein synthesis in somatic stem cells. This finding not only tells us something new about stem cell regulation, but opens up the ability to study differences in protein synthesis between many kinds of cells in the body."
"We believe there is an undiscovered world of biology that allows different kinds of cells to synthesize protein at different rates and in different ways, and that those differences are important for cellular survival."
Written by David McNamee