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Your Environment. Your Health.

Epigenomic Mapping of Human Tissues

Bing Ren, Ph.D.
Ludwig Institute for Cancer Research; University of California, San Diego, School of Medicine
NIEHS Grants R01ES024984, U01ES017166

As part of the Epigenome Roadmap project, an NIEHS grantee and colleagues produced a new atlas of human tissue epigenomes and found that DNA methylation varies greatly among human tissues.

Epigenetic changes influence gene expression without changing the genetic code. Elucidating the mechanisms involved in disease development would require linking genetic information, which is identical in most cells across the body, with epigenetic changes that can vary by tissue. As a starting point, the researchers created a baseline assessment of the epigenome by examining DNA methylation and conducting DNA sequencing of 18 tissue types from four people.

The researchers report widespread differences in the methylation between tissues. Organs extensively differed in the degree of genome-wide methylation. For example, the pancreas had an unusually low level of methylation, while the thymus had high levels of methylation. As expected, less methylation tended to be found around areas of DNA that coded for genes expressed by the type of tissue analyzed. In other words, a cell from muscle tissue had less methylation close to muscle-related genes. One surprising finding was that many tissues exhibited non-CG methylation, a type of methylation previously thought to be widespread only in the brain and stem cells.

Citation: Schultz MD, He Y, Whitaker JW, Hariharan M, Mukamel EA, Leung D, Rajagopal N, Nery JR, Urich MA, Chen H, Lin S, Lin Y, Jung I, Schmitt AD, Selvaraj S, Ren B, Sejnowski TJ, Wang W, Ecker JR. Human body epigenome maps reveal noncanonical DNA methylation variation. Nature 523(7559):212-216.

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