Two new US studies have pinpointed a key gene involved in the ability of adult stem cells to continually produce new body cells, a discovery the scientists say could help develop new disease treatments. A team based at the University of Michigan has shown that a gene called Bmi-1 is crucial in allowing nerve stem cells to carry on growing and multiplying throughout adult life. Another study, carried out by researchers at the Massachusetts General Hospital in Boston, shows that the same gene is also important in blood stem cells. Both groups published their findings in the online edition of Nature last week.
Stem cells are the body's 'master cells', capable of producing many other, more specialised types of cell. For example, blood stem cells, present in the bone marrow, produce a range of different types of blood cell. Ordinary body cells have a limited lifespan - they are genetically programmed to divide a certain number of times, after which time they are replaced. But adult stem cells can divide an unlimited number of times, producing a new stem cell and a new body tissue cell each time. The two new studies suggest that the protein produced by the Bmi-1 gene is crucial to 'overriding' the genes that normally limit a cell's lifespan: 'We now know that Bmi-1 is an important part of the mechanism used by stem cells to persist through adult life' said Sean Morrison of the University of Michigan. He stressed that there were other genes involved, and more research was needed to fully understand the process, but added that 'Bmi-1 is a major key to unlocking this process of self-renewal'.
Morrison said that his team had so far studied three different types of stem cell, and found that Bmi-1 worked in a similar way in each, suggesting that the protein it produces could be the 'universal regulator, controlling self-renewal in all adult stem cells'. The finding might help scientists grow large amounts of adult stem cells in the laboratory, to use in disease treatments. It could also shed light on some cancers, because a malfunctioning Bmi-1 gene could activate excessive cell division (the hallmark of cancer cells), according to Morrison.