In addition to the possibility of the abnormal huntingtin compromising myelin integrity described above, huntingtin may also impact oligodendrocyte function and development through its impact on iron metabolism. Huntingtin is an iron-responsive protein that is involved in brain development and regulates receptors for transferrin, a key iron metabolism protein [108,109]. It could therefore have an indirect role in the striatal iron accumulation observed in this disease (Figure 2) and the neurotoxicity associated with HD as the destructiveness of free radical damage is greatly enhanced by the catalytic effects of iron .
A more severe dysregulation of the iron regulatory function of huntingtin [108,109] may be expected when the CAG repeat number is larger, as occurs in juvenile-onset HD. In these young individuals the toxicity may be more heavily dependent on the risk associated with iron  (see following section).
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