Detection and mapping of 5-methylcytosine and 5-hydroxymethylcytosine with nanopore MspA

Cells attach a methyl group (—CH₃) to certain cytosines in DNA to control gene expression. These methylation patterns change over time and can be related to cell differentiation and diseases such as cancer. Existing methylation detection techniques are not ideal for clinical use. We pulled single-stranded DNA molecules through the biological pore MspA and found that ion currents passing through the pore reveal the methylation sites with high confidence. Hydroxymethylation, which differs from methylation by only one oxygen atom, also produces distinct signals. This technique can be developed into a research tool and may ultimately lead to clinical tests.