Evidence of DNA methylation in the neurofibromatosis type 1 (NF1) gene region of 17q11.2

Abstract

Modification of mammalian DNA by the methylation of cytosine in CpG dinucleotides is a complex phenomenon involved in a number of cellular and developmental processes. In a particular, the characteristic hypermutability of CpGs may be a major contributor of point mutations leading to human genetic disease. We have hypothesized that DNA methylation contributes to mutations in the gene causing neurofibromatosis type 1 (NF1), one of the most common genetic disorders in humans and a disease where up to half of all cases are the result of sporadic germline mutations, usually in the paternally-derived allele. We have used two experimental approaches to analyze patterns of DNA methylation at CpG dinucleotides in the NF1 gene region. Southern analyses using isoschizomeric restriction pairs have revealed DNA methylation in areas flanking the NF1 gene region, while PCR-methylation assays have shown that methylation occurs both on genomic sequences flanking the NF1 gene and within the coding region of the gene itself. We suggest that methylated CpG dinucleotides within and around the highly mutable NF1 gene serve as a reservoir within which C-T transitions contribute to the high frequency of spontaneous germline mutations associated with the disease.