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Nature Biotechnology 27, 361–368 (1 April 2009) | doi:10.1038/nbt.1533

Targeted and genome-scale strategies reveal gene-body methylation signatures in human cells

Madeleine P Ball , Jin Billy Li , Yuan Gao , Je-Hyuk Lee , Emily M LeProust , In-Hyun Park , Bin Xie , George Q Daley & George M Church

Studies of epigenetic modifications would benefit from improved methods for high-throughput methylation profiling. We introduce two complementary approaches that use next-generation sequencing technology to detect cytosine methylation. In the first method, we designed |[sim]|10,000 bisulfite padlock probes to profile |[sim]|7,000 CpG locations distributed over the ENCODE pilot project regions and applied them to human B-lymphocytes, fibroblasts and induced pluripotent stem cells. This unbiased choice of targets takes advantage of existing expression and chromatin immunoprecipitation data and enabled us to observe a pattern of low promoter methylation and high gene-body methylation in highly expressed genes. The second method, methyl-sensitive cut counting, generated nontargeted genome-scale data for |[sim]|1.4 million HpaII sites in the DNA of B-lymphocytes and confirmed that gene-body methylation in highly expressed genes is a consistent phenomenon throughout the human genome. Our observations highlight the usefulness of techniques that are not inherently or intentionally biased towards particular subsets like CpG islands or promoter regions.