Although the human genome sequence faithfully lists (almost) every single DNA base of the roughly 3 billion bases that make up a human genome, it doesn't tell biologists much about how its function is regulated. Now, researchers at the Salk Institute provide the first detailed map of the human epigenome, the layer of genetic control beyond the regulation inherent in the sequence of the genes themselves. "In the past we've been limited to viewing small snippets of the epigenome," says senior author Joseph Ecker, Ph.D., professor and director of the Genomic Analysis Laboratory at the Salk Institute and a member of the San Diego Epigenome Center. "Being able to study the epigenome in its entirety will lead to a better understanding of how genome function is regulated in health and disease but also how gene expression is influenced by diet and the environment." Their study, published in the Oct. 14, 2009 advance online edition of the journal Nature, compared the epigenomes of human embryonic stem cells and differentiated connective cells from the lung called fibroblasts, revealing a highly dynamic, yet tightly controlled, landscape of chemical signposts known as methyl-groups. The head-to-head comparison brought to light a novel DNA methylation pattern unique to stem cells, which may explain how stem cells establish and maintain their pluripotent state, the researchers say.
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