DNA methylation analysis: a review of current methodologies.

The relationship between levels of DNA methylation and gene activity has been known for some time. Many of the early procedures developed gave only somewhat limited information about methylation patterns, for example, the total level of 5-methyl cytosine in the genome or the frequency of methylation of cytosines within certain restriction sites. However, in the last few years, there has been an explosion of interest in DNA methylation, and with it, many new and powerful techniques have been developed to facilitate its study. In this paper, the key techniques currently available are reviewed and the advantages, disadvantages, and potential artifacts of each are discussed.