The body is a battle zone. Cells constantly compete with one another for space and dominance. Though the manner in which some cells win this competition is well known to be the survival of the fittest, how stem cells duke it out for space and survival is not as clear. A study on fruit flies published in the October 2 issue of Science by Johns Hopkins researchers describes how stem cells win this battle by literally sticking around.
"Our work exemplifies how one signal coordinately maintains two types of stem cells in a single niche, or microenvironment," says Erika Matunis, Ph.D., associate professor of cell biology at the Johns Hopkins School of Medicine. "What we found may emerge as common themes of mammalian stem cell niches as they become better characterized."
To tackle the stem cell competition quandary, the team looked at fruit fly testes where two different stem cells exist: germline stem cells which give rise to sperm, and somatic stem cells which develop into non-reproductive cell types.
Using genetics, the researchers grew flies lacking the SOCS protein, which controls other molecules that promote stem cell growth. SOCS normally ensures that the right numbers of stem cells are present in the stem cell niche, a region at the far end of the fly testis where new cells are born. In a normal testis, the germline stem cells are surrounded by somatic stem cells at a ratio of about one germline stem cell for every two somatic stem cells.
The researchers isolated testes from flies lacking SOCS and, under a microscope, counted the number of germline stem cells and somatic stem cells. They found that nearly half of the germline stem cells were gone and the somatic stem cells appeared to be occupying that space.
"The somatic stem cells almost look like they've invaded the niche area," says Melanie Issigonis, a graduate student in the Biochemistry, Cellular, and Molecular Biology graduate program at Johns Ho
|Contact: Audrey Huang|
Johns Hopkins Medical Institutions