As we age, iron accumulates in various regions of our brains, and an excess of iron is usually found in the parts of the brain that degenerate in disorders such as Parkinson and Alzheimer diseases. Because some level of higher-than-normal iron concentrations tends to accompany the aging process, it is difficult to say whether there is any pathological effect produced by excess iron in brain.
Work by two groups of researchers Nature Genetics (Vol. 28, pp. 327-334) has now revealed that defects in iron metabolism do in fact cause some neurodegenerative disorders. John Burn (of the Institute of Human Genetics) and colleagues found that one of the two genes required to make the ferritin protein-which acts as a storage depot for iron-is mutated in a number of individuals suffering from neurodegeneration. The mutation seems to make the protein less stable, and so perhaps less iron is stored in the ferritin complex and more iron accumulates.
In a second study, of a population of Amish individuals, Susan Hayflick (of Oregon Health and Sciences University) and colleagues find that a condition called Hallervorden-Spatz syndrome-characterized by the most profound accumulations of excess iron in the brain of any neurodegenerative disorder-results from mutation of another gene, PANK2. This gene encodes a factor, expressed specifically in the brain, that may modulate iron levels by a secondary mechanism involving the amino acid cysteine.
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