In 2003, the Human Genome Project was successfully completed. For the first time, scientists had mapped all of the DNA that makes up the human body. It took nearly a decade to complete and another decade to become widely applied. Recently President Obama announced an initiative to sequence to the genome of over one million Americans in order to develop ‘precision medicine’ – a bold plan to develop specific medical treatments based on the genes of the patient. However, just knowing the location and function of every piece of DNA may not be enough.

“The only way you can deliver on the promise of precision medicine is by including the epigenome,” said Manolis Kellis of the Massachusetts Institute of Technology. She is referring to the record of chemical changes that differentiate each cell of the body.

Human cells all basically contain the same set of DNA. However, what decides if one cell is a skin cell and another is a brain cell are epigenetic marks. These marks “switch on/off” certain genes within the cell’s DNA. These switches can determine cell types but also the likelihood of major diseases such as cancer and Alzheimer’s.

The system involves over 20,000 genes and is incredibly complicated. Some epigenetic marks are hereditary; some are caused by environmental factors. The task of interpreting all this data can seem impossibly daunting. But scientists at the most elite research facilities around the world have begun to tackle the task. Today, over 20 papers were published in the science journal Nature, the first installment by the international consortium known as The Roadmap Epigenome Project. The studies reveal the DNA differences of 127 tissue and cell types.

A study by the Harvard Medical School focused on the epigenomics of cancer. They discovered that they could determine with 86 percent accuracy the cells where metastatic cancer originated and how many mutations the tumor would have. Currently, on two to five precent of patients know the origin cells of their cancer.

Another study by the Picower Institute for Learning and Memory based in Cambridge, Massachusetts looked at the epigenomic signature of brain cells from people who died of Alzheimer’s disease as well as of brain cells in mice genetically engineered to have Alzheimer’s. They found epigenomic changes in the brain cells’ immune response. Prior to this discovery, Alzheimer’s was not considered to be an immune-system disorder. This opens up a whole new area for research on the disease.

The research was conducted as part of a 10-year program funded by the US government. The program began in 2008. The reports released today barely scratch the surface of the human epigenome. However, one can expect many more breakthroughs to come in the near future.