Adult stem cells are not pampered pushovers. O'Reilly et al. report that certain stem cells take charge of their surroundings, molding their environment to control their division and differentiation.
Some stem cells are cosseted like newborns. Neighboring cells cradle them in a structure called the niche. The niche not only nurtures its charges, it also dictates their behavior, determining whether they reproduce and specialize. The standard view is that the niche shapes stem cells, not vice versa.
O'Reilly et al. found evidence for more active stem cells while studying how the cells anchor themselves in the Drosophila ovary.
Previous work indicated that ovary stem cells attach to the niche through the protein E-cadherin. O'Reilly et al. tested whether the stem cells also depend on integrins, cell surface proteins that link molecules in the extracellular matrix to the cytoskeleton.
They found that follicle stem cells (FSC)—one type of ovary stem cell—drifted away from their niche when they carried mutant integrins.
These breakaway cells were abnormally shaped, divided more slowly than normal, and displayed some cancer-like characteristics, such as refusing to stop crawling even after contacting another cell.
Integrins hook onto an extracellular matrix protein called laminin A. FSCs pump out laminin A, and the scientists found that mutant cells that were unable to make the protein broke their moorings and reproduced sluggishly. Two other kinds of stem cells in the ovary—germline stem cells, which spawn the egg, and escort stem cells, which travel along with it—didn't rely on integrins for anchoring, the researchers showed. The team concluded that the interaction between laminin A and integrins ensures that FSCs remain in place, primed to divide. By laying down laminin A, therefore, FSCs help build their own niche.
Citation: O'Reilly, A.M., et al. 2008. J. Cell Biol. doi:10.1083/jcb.200710141.
Source: Rockefeller University
Related stories:
Stem Cell Chicken and Egg Debate Moves to Unlikely Arena: The Testes
Logic says it has to be the niche. As air and water preceded life, so the niche, that hospitable environment that shelters adult stem cells in many tissues and provides factors necessary to keep them young and vital, must have emerged before its stem cell dependents.
Purified stem cells restore muscle in mice with muscular dystrophy
By injecting purified stem cells isolated from adult skeletal muscle, researchers have shown they can restore healthy muscle and improve muscle function in mice with a form of muscular dystrophy. Those muscle-building stem cells were derived from a larger pool of so-called satellite cells that normally associate with mature muscle fibers and play a role in muscle growth and repair.
Japanese encephalitis virus causes 'double trouble' to brain
Japanese encephalitis (JE), commonly known as brain fever, is one of the prevalent mosquito-borne encephalitis in India and entire South East (SE) Asia. Besides resulting in thousand fatalities each year, JE virus (JEV) infection causes prominent neurological sequelae in approximately one-third of the survivors. Even those patients in the good recovery group commonly encounter psychiatric problems, which include mental retardation, learning disabilities, speech and movement disorders and behavioural abnormalities.
Reprogramming Adult Stem Cells in the Brain
In recent years, stem cell researchers have become very adept at manipulating the fate of adult stem cells cultured in the lab. Now, researchers at the Salk Institute for Biological Studies achieved the same feat with adult neural stem cells still in place in the brain. They successfully coaxed mouse brain stem cells bound to join the neuronal network to differentiate into support cells instead.
Stem cells at root of antlers' branching
The ability to regenerate lost body parts is unevenly distributed among higher organisms. Among vertebrates, some amphibians are able to replace lost limbs completely, while mammals are unable to regenerate complex appendages. The only exception to this rule is the annual replacement of deer antlers. The annual regrowth of these structures is the only example of regeneration of a complete, anatomically complex appendage in a mammal, and antlers are therefore of high interest to regeneration biologists.
Researchers find blood stem cells originate and are nurtured in the placenta
Solving a long-standing biological mystery, UCLA stem cell researchers have discovered that blood stem cells, the cells that later differentiate into all the cells in the blood supply, originate and are nurtured in the placenta.
Lab characterizes niche control of stem cell function
The Stowers Institute’s Xie Lab has published findings that begin to characterize the poorly understood interaction among stem cells within their cellular microenvironment, called a niche.
Scientists demonstrate dual intrinsic and extrinsic control of stem cell aging
The Stowers Institute’s Xie Lab has published recent findings that reveal some of the factors underlying the aging of stem cells.