'Incurable' disease falls to genetic codebreakers

THE SCIENTIFIC team that helped to break the genetic code of cystic fibrosis added another disease, neurofibromatosis, to its genetic scorecard last week. NF was mistakenly thought to cause Elephant Man’s disease because it disfigures its victims. It is one of the most common genetic diseases of the nervous system, and it is incurable. Francis Collins of the University of Michigan, who helped to locate the principal gene causing cystic fibrosis last year, led one group of researchers. Ray White of the University of Utah led another. Both teams traced the gene for NF1, the most common form, to chromosome 17 by looking for peculiarities in the genes of families with a history of NF. The disease causes benign tumours, called neurofibromas, to form in the sheaths of nerves. Some cases do not progress that far, causing only a profusion of ‘cafe au lait’ spots. In serious cases, however, pillowy tumours form under the skin and can alter the shape of bones. NF usually emerges in adolescents, and many sufferers develop learning disabilities, seizures, complications that require surgery, and cancer. About one in four thousand people a year are born with the gene for NF, more than muscular dystrophy and Huntington’s disease combined. Collins stressed that in many ways the condition had been neglected. Peter Bellerman, president of the National Neurofibromatosis Foundation said: ‘Until six years ago, there was not one organised research programme on NF anywhere in the world.’ Collins found that the gene mutates about a hundred times as much as others that cause inherited disorders. So NF often appears abruptly in a family with no history of it. If someone has the defect, their children have a 50 per cent chance of inheriting it. Collins and White also discovered a new phenomenon: the gene contains other genes within itself. While their purpose is unknown, says White, the other genes may influence the range of symptoms. The teams agree that in NF, a mutation disables the gene, and the researchers surmise that the normal gene restrains cell growth in the nervous system. How such ‘suppressor’ genes keep the cellular barn door locked will provide clues to understanding and controlling diseases such as multiple sclerosis and cancer,
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