The first SFI patient was a previously healthy 44-year-old California man who developed increasing trouble falling asleep. It then spreads via protein-to-protein contact, with the misshapen version somehow inducing normal proteins to take on the new, indigestible structure. The initial folding error may be induced by a genetic mutation or may occur spontaneously. The different prion disorders all result from gross irregularities in the folding of a particular protein, the normal function of which is not known. Perhaps best known as the cause of "mad cow disease" (bovine spongiform encephalopathy), prions can cause several uncommon human brain disorders such as Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker disease, kuru and FFI, and may even be suspects in more common disorders such as Alzheimer's disease, ALS or Parkinson's disease. This supports the controversial notion, says Mastrianni, that "even in the familial form, it's the prion strain, the precise conformation of the misfolded protein, and not the variation in the gene that ultimately determines the consequences of the disease."įamilial fatal insomnia has been found in only 24 extended families worldwide, but the sporadic version, though still quite rare, may prove somewhat more common, accounting for "most or all cases of pure thalamic dementia," suggest the authors. This indicates that the specific manifestations of the disease are determined not by the abnormal gene or the sequence of amino acids in the protein, but purely by the abnormal shape taken on by the protein. San Francisco, also demonstrate that the sporadic disorder can be transmitted to transgenic animals that have normal copies of the human gene that is mutated in FFI. The researchers, led by Nobel laureate Stanley Prusiner, M.D., a professor of neurology, biochemistry and biophysics at U.C. "Sporadic fatal insomnia is an exact phenocopy, but not a genocopy of fatal familial insomnia." "We found a disease that is indistinguishable from the genetic disorder but lacks the disease gene," said Jim Mastrianni, M.D., Ph.D., assistant professor of neurology at the University of Chicago and lead author of the study. The misfolded protein - called a prion - not only doesn't function, it also cannot be chewed up by enzymes or eliminated from the brain, so it gradually accumulates, causing untreatable sleeplessness, loss of coordination, loss of mental function and death, usually within less than two years.īut SFI, the non-inherited version, occurs without the abnormal gene. FFI is triggered by a tiny mutation in a particular gene that prompts the protein made by that gene to fold into an abnormal shape, like a deformed origami. The symptoms and neuropathology of SFI are identical to an inherited disorder described by Italian scientists in 1986, called fatal familial insomnia (FFI).
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