The impact of single-nucleotide polymorphisms (SNPs) in OGG1 and XPC on the age at onset of Huntington disease.

The age at onset of Huntington disease (HD) shows a strong, negative correlation with the number of CAG repeats within the huntingtin (HTT) gene. However, this does not account for all the inter-individual variability seen among patients. In order to assess whether single-nucleotide polymorphisms (SNPs) in the OGG1 and XPC genes, both implicated in responses to oxidative stress, are associated with the age of onset of HD, 9 SNPs have been genotyped in 299 individuals with HD and 582 controls. After correction for multiple testing, two OGG1/XPC haplotypes were found to be associated with younger age at onset independently of the number of CAG repeats within the HTT gene. Both haplotypes contain XPC coding variants that would be expected to impact on protein function and/or variants in the 3'UTR that could result in altered protein levels via allele-specific mIR binding. One haplotype also contains the OGG1-326Cys (rs1052133) allele that has been associated with a lower 8-oxoG repair activity and is particularly sensitive to the cellular redox status. These results highlight the potential role of oxidative stress in determining the age at onset of HD.