Cells in the very early embryo are interchangeable and undergo rapid division. Soon, however, they begin differentiating into more specific types, finally becoming specialized cells like neurons, blood, or muscle. As they differentiate, they should stop dividing and usually become embedded in particular tissues. Some tumor cells are more like stem cells because they are identical, they divide quickly, and in the worst case ?metastasize ?they wander through the body and implant themselves in new tissues.
Specialized cells may die through age or injuries, so the body keeps stocks of stem cells on hand to generate replacements. Usually the stem cell divides into two types: one that is just like the parent, which is kept to maintain the stock, and another that differentiates. This is what happens with neuroblasts. Cell division creates one large neuroblast and a smaller cell that can become part of a nerve. This process is controlled by events that happen prior to division. The parent cell becomes asymmetrical: it collects a set of special molecules, including Prospero and other proteins, in the area that will bud off and become the specialized cell.
"This asymmetry provides the new cell with molecules it needs to launch new genetic programs that tell it what to become," says Cayetano Gonz�lez, whose group began the project at EMBL and has continued the work as they moved to the IRBB-PCB. "The current study investigates what happens when the process of localizi
Source:European Molecular Biology Laboratory