Transferrin gene polymorphism in Alzheimer's disease and dementia with Lewy bodies in humans

Genetic studies in Alzheimer's disease (AD), have indicated that the apolipoprotein E locus (APO E) is a major susceptibility factor, but that it can only account for approximately 50% of AD cases. Several other studies have attempted to identify additional genetic loci associated with disease development, often based on a candidate gene approach. As several lines of evidence indicate that oxidative stress and free radical damage occur in AD, the transferrin gene (TF) has been suggested as a candidate locus for AD since it is the major transport protein for iron, which itself is a major factor in free radical generation. Previous studies have shown elevated TF C2 allele frequencies in AD, this being specifically associated with carriers of the APO E epsilon4 allele. We have therefore determined the influence of the common polymorphisms in TF, C1 and C2, in dementia. The frequency of the C2 allele was not significantly associated with AD. Stratification of cases according to the APO E epsilon4 allele showed a highly significant excess of the C2 allele in AD cases without the e4 allele, contrasting with previous studies. Given the contrasting findings between reports of altered TF C2 allele frequencies, the TF locus would not appear to be a strong risk factor for AD in this population. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.