The second gene, coding for NF1 protein, increases the activity of RAS proteins. The mutated genes are rarely found together, and scientists now believe that the effect of the mutations are the same, namely that they lead to an increased activity of the RAS, which in turn causes blood cells to divide more rapidly. Researchers at the Sahlgrenska Academy have studied two different mouse models - one carrying the mutated form of RAS and one expressing the mutated NF1. When Bergö and his colleagues took out mice that have mutations in both genes it revealed that they instead developed a highly aggressive form of acute leukemia.
