The mutant mice didnt make sense. Josef M. Penninger of the University of Toronto and his colleagues had disabled a rodent gene that they thought controlled another gene, one involved in the immune system. Yet the mice had no immune defects or any other obvious problems. The more we went into the project the more confused we got, recalls Penninger.
When the mice were subjected to an array of behavioral tests, however, the scientists noticed that the rodents werent as sensitive to acute and chronic forms of pain, including pain caused by heat, toxic substances, and nerve damage. The gene that Penningers team had mutated encodes a protein called DREAM (downstream regulatory element antagonistic modulator), which is a so-called transcription factor. As such, it binds to DNA and regulates the activity of genes.