Researchers at the University of California, San Francisco have pinpointed a protein that is critical for maintaining a stem cell's full potential to self-renew and to differentiate. Stem cells lacking the protein were impaired in their ability to divide and make identical copies of themselves, called self-renewal. These cells also lost their capacity to differentiate into key cell types, such as cardiac muscle. The protein, Chd1, acts to keep chromosome strands loosely wound, which permits widespread gene activation in the cell's nucleus.
Understanding Stem Cell Biology
Researchers at the University of California, Los Angeles have found genetic differences that distinguish induced pluripotent stem (iPS) cells from embryonic stem cells. These differences diminish over time, but never disappear entirely. iPS cells are created when adult cells, such as those from the skin, are reprogrammed to look and behave like embryonic stem cells. But until now, scientists didn't know if the two types of stem cells were actually identical at a molecular level. This latest research shows that iPS and embryonic stem cells differ in which genes they have turned on or off.
Researchers at UC, Santa Barbara, have mapped the role of a genetic signal that puts the breaks on the ability of stem cells to self renew.
Researchers at the Burnham Institute for Medical Research and the Scripps Research Institute have found that a protein known to play an important role in maintaining mouse embryonic stem cells has a similarly crucial job in human embryonic stem cells. This protein, called Shp2, acts as a switch, telling the cells to either divide to make more of themselves â a process called self-renewal â or to mature into different cell types â called differentiation.
Researchers at UC, Los Angeles have found that blood-forming stem cells in mice have their origins in the endothelial cells that line blood vessels during mid-gestation. These cells eventually move to the bone marrow where they generate all the cells of the blood system throughout life. Researchers have long known that blood-forming stem cells arise from the blood vessels, but didn't know exactly which cell type acted as the source. Now that the source is know, the researchers want to learn what signals those endothelial cells to begin producing blood-forming stem cells.
Researchers at UC, San Francisco developed a novel way of finding out the role of DNA-relatives called microRNA. These molecules are known to turn genes on and off and appear to regulate whether embryonic stem cells remain as stem cells or develop into mature cell types, but learning which genes are controlled by each microRNA has been a challenge. Using this screen, the researchers found 14 microRNAs that speed up cell division; of those, five are commonly found in human embryonic stem cells.
Researchers at the The Scripps Research Institute found a new way of classifying the many cell types that fall under the category of "stem cells." The term stem cell refers to tissue specific stem cells found in mature tissues such as blood, brain, or muscle, which are restricted to forming only cells found in those tissues, as well as to embryonic stem cells that are broadly able to form all cells of the body.
Researchers at the Stanford University School of Medicine have found that human embryonic stem cells trigger an immune response much like organ rejection when transplanted into mice. In the past, researchers had thought that transplanted embryonic stem cells might not be rejected the way transplanted organs are. Testing this theory, the team found that after transplanting human embryonic stem cells into normal mice, those cells disappeared within seven to ten days. In mice without an immune system the cells survived and even multiplied.
Researchers at the Salk Institute of Biological Studies discovered that stem cells in the testes of fruit flies are able to generate their own support cells. This work in flies could help guide researchers hoping to understand the environment surrounding resident populations of human stem cells - called the niche. The niche is difficult to study in humans but is an area of great interest because any therapy based on transplanting stem cells into a tissue will require those cells to be paced in a niche where they will thrive.
Researchers at The Scripps Research Institute discovered that human embryonic stem cells have a very specific signature when it comes to the regulators of their genes. MicroRNAs are very small, naturally occurring bits of genetic material. They don't code for specific proteins like genes do, but they regulate the activity of genes and turn on and off their protein production.