New insights into the functioning of stem cells...
Prions may hold key to stem cell function
30 January 2006 - NewScientist.com news service - The curative properties of stem cells may rely on prions, a new study suggests, the type of protein made infamous by mad cow disease.
Prions are a special class of protein that can change the shape and function of other proteins around them. While these are found throughout any mammal’s body, the understanding of their biological role is limited. What is known is that prions that become misshapen, through some unknown process, can result in BSE (bovine spongiform encephalopathy) – mad cow disease – and its equivalents in other animals.
Researchers at the Whitehead Institute in Cambridge, Massachusetts, US, have now found that adult stem cells in bone marrow gradually lose their ability to regenerate without their normal complement of membrane-bound prions. Stem cells are primitive cells which have the potential to divide endlessly, and the ability to differentiate into any cell type in the body – offering hope for future therapies.
Andrew Steele, Cheng Cheng Zhang and colleagues used radiation to deplete the bone marrow of mice genetically engineered to not produce the prion proteins. The animals’ marrow regenerated quickly at first, but eventually slowed to a stop. The marrow also lost its regenerative abilities when transplanted into normal mice.
“For years we’ve wondered why evolution has preserved this protein, what positive role it could possibly be playing,” says Susan Lindquist, one of the team. “With these findings we have our first answer.”
The question of how prions sustain stem cell activity remains unanswered, but the finding is a first step to understanding the destructive streak of misshapen prion proteins, Steele says. Similar tests on neural and lung stem cells are underway.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0510577103)
http://www.newscientist.com/article.ns? ... print=true