No pain, no gain

A family of firewalkers has helped researchers in Cambridge to track down the genetic linchpin that enables us to feel pain. Writing in this weeks Nature, Cambridge Scientist Geoff Woods and his colleagues have uncovered a gene called SCN9a, which plays a critical role in turning on pain pathways. The discovery was made after the scientists heard about members of several Pakistani families who were feted firewalkers, self-impalers and dare-devils. These individuals seemed to be unable to feel pain, although in all other respects they were neurologically normal; they could tell hot from cold and smooth from rough, they were ticklish, and they enjoyed curry, although it didn't burn them in the same way that it would a normal person. By comparing the DNA from six of these people, they pinpointed a region on chromosome 2, and then the SCN9a gene, which had been altered in all of them. The gene codes for a pore which sits on the surface of pain-carrying nerve cells and allows sodium ions to enter and excite the cell when it is activated by a painful stimulus. Since the altered channel doesn't work properly, people with two copies of the altered gene, as was the case in these families, cannot feel pain. The team are hopeful that the discovery will pave the way to a new generation of extremely powerful painkillers with few side effects. "This is as important as the identification of morphine receptors," says UCL pain specialist John Wood.