Researchers are making progress in changing cells directly from one type to another: "A research breakthrough has proven that it is possible to reprogram mature cells from human skin directly into brain cells, without passing through the stem cell stage. The unexpectedly simple technique involves activating three genes in the skin cells; genes which are already known to be active in the formation of brain cells at the fetal stage. ... By reprogramming connective tissue cells, called fibroblasts, directly into nerve cells, a new field has been opened up with the potential to take research on cell transplants to the next level. ... We didn't really believe this would work, to begin with it was mostly just an interesting experiment to try. However, we soon saw that the cells were surprisingly receptive to instructions. ... In experiments where a further two genes were activated, the researchers have been able to produce dopamine brain cells, the type of cell which dies in Parkinson's disease. The research findings are therefore an important step towards the goal of producing nerve cells for transplant which originate from the patients themselves. The cells could also be used as disease models in research on various neurodegenerative diseases. Unlike older reprogramming methods, where skin cells are turned into pluripotent stem cells, known as IPS cells, direct reprogramming means that the skin cells do not pass through the stem cell stage when they are converted into nerve cells. Skipping the stem cell stage probably eliminates the risk of tumours forming when the cells are transplanted. "