Scientists have discovered a key protein in the toxic brain pathway that leads to fragile X tremor/ataxia syndrome (FXTAS), an inherited neurodegenerative disorder. The finding, in a Drosophila (fly) model of FXTAS, could help unravel the complex mechanisms of FXTAS and lead scientists to develop therapies to target the protein. The research will be published in the Aug. 16 issue of the journal Neuron.
Fragile X tremor/ataxia syndrome was first recognized several years ago as a neurodegenerative disease caused by a premutation in carriers of the mutated FMR1 gene, the same gene that causes fragile X syndrome--the most common inherited cause of mental retardation. Individuals with the FMR1 premutation (a less exaggerated form of the mutation) do not have retardation, but instead are at risk for developing FXTAS, usually after age 50, causing progressive problems with movement (ataxia), tremor, memory loss, loss of sensation in the lower extremities (peripheral neuropathy), and mental and behavioral changes.
Fragile X syndrome occurs when a region of the FMR1 gene repeats a particular sequence of three DNA basesCGG--causing silencing of the FMRP protein. Called a trinucleotide repeat, this CGG sequence repeats only about 6 to 55 times in normal individuals, but between 200 and 1,000 times in those with fragile X syndrome.
In those with the premutation of the FMR1 gene, CGG repeats between 60 and 100 times.
Scientists estimate the frequency of fragile X syndrome as approximately 1 in 4,000 males and 1 in 8,000 females and the frequency of the FMR1 premutation as 1 in 800 males and 1 in 260 females. Approximately 20 percent of males with the permutation develop FXTAS. Approximately 20 percent of women with the premutation have premature ovarian failure a loss of ovarian function in women younger than 40.
Lead authors of the current study are Peng Jin, PhD, assistant professor of human genetics and Stephen T. Warren, Ph
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