Scientists have opened up an important new line of exploration into the causes of many diseases, by producing the first comprehensive map and analysis of the epigenome of a wide variety of human cells and tissue types.
The research could help in efforts to design new treatments to tackle a wide range of illnesses and disorders, including heart disease, cancer, autism and Alzheimer's.
Almost all cells in a person's body contains a complete identical genetic blueprint, which is housed in DNA.
But what makes liver cells different to heart cells and brain cells, for example, is dictated by which genes are switched on and switched off by chemical modifications, and to what extent.
Epigenomes are the patterns of those chemical differences in a person's DNA, which together determine how and when the genes are activated.
The Roadmap Epigenomics programme, a nine-year international collaboration involving 88 research groups across several continents, has taken 111 adult and embryonic tissue and cell types and systematically profiled their epigenome.
By doing so it has created a reference map for each of the tissue and cells types, which has enabled the scientists to say with an unprecedented level of certainty which regions of the DNA are used to control the expression of each gene.
Scientists will now be able to compare different types of cells and tissues at the molecular level to understand what makes them different from each other.
They will also be able to predict the regulators that are responsible for establishing the identity for each cell type.
As a result, the findings should help efforts to identify the control regions that trigger the genetic variations that are associated with different diseases and disorders.
In a series of more than 20 papers published today in the journal Nature and associated publications, the team of researchers has revealed the epigenetic maps associated with 58 traits.
These include evidence of how neural cells develop from stem cells, as well as the signature of multiple sclerosis in immune cells and of blood pressure in heart tissues.
In addition they have discovered how patterns in certain epigenomes are linked to mutations that can cause cancer and that the information can even be used to trace which cell led to the development of the cancerous tumour.
The researchers have also established that the genetic pre-disposition associated with Alzheimer's disease may be primarily associated with the immune system and not the neural system as previously thought.
Although epigenetic marks are stable, they are reversible, and can also be altered by environmental factors like diet, exposure to toxins and ageing.
The work involved the generation of 2,805 genome-wide datasets, encompassing a total of 150 billion sequencing reads, corresponding to 3,174 fold coverage of the human genome.
The maps are to be made freely available to other scientists who wish to use the data to study the area further.
The researchers will not move on to map the epigenetic profiles of individuals to try to understand more about how they vary from person to person.
