The sequel to the Human Genome Project, the International Human Epigenome Consortium (IHEC), has arrived and may hold the key to treating intractable diseases such as cancer and obesity. Recent studies mapping epigenetics - chemical modifications of DNA that affect gene expression - have shown how important understanding the epigenome is for health and disease.
IHEC was launched in Paris last week, and has ambitious plans to map 1,000 reference epigenomes within a decade. This will allow researchers to compare their findings with a robust and trustworthy template. According to Peter Jones, University of Southern California, US, speaking for IHEC in Paris, the project was also spurred on by a growing number of publications on epigenetics, which he says is why researchers need to agree now on how to standardise data.
In contrast to mapping the human genome, which is described as 'finite, the human epigenome is almost infinite — the epigenome changes in different states and different tissues', explains Philip Avner of the Pasteur Institute in Paris, a member of IHEC's steering committee. Incidentally, the seemingly epic challenge IHEC has set itself has raised doubts among some scientists at the meeting, according to a Nature news article, and as a result there are concerns the project is premature.
Dr Jones gave his reasons for why science is ready for IHEC: 'But this is exactly the point of launching IHEC now — to avoid confusion and move the field forward more quickly'. A point expanded on by Dr Avner, who said, 'When we have all the references, we'll be able to compare diseased tissue against them', which is a similar model to how we currently locate genetic diseases.
Jeanne Loring of the Scripps Research Institute and her colleagues have shown in a recent Genome Research publication how DNA methylation, a type of epigenetic control, changes during cell differentiation. Their research provides one of the first comprehensive epigenetic maps and indicates the importance of mapping the human epigenome, considering that the control of differentiation is connected to the development of cancer.
Further applications for these findings include using the maps as a reference for what stage of differentiation a cell is at which, for example, is useful as a quality control for induced pluripotent stem cell (iPS cell) production and research. iPS cells, like embryonic stem cells (ES cells), can be used to study differentiation and potentially provide tissue transplants. However, unlike ES cells, iPS cells are originally extracted from a living organism or the patient, which avoids ethical issues and offers greater compatibility for transplant.
In addition to a more advanced understanding of genetic disease, a map of the human epigenome may also pick up the slack from the Human Genome Project. Contrary to previous expectations, genetic variation alone cannot explain the extent of the diversity seen in nature. Whereas an extra layer of heritable information, i.e. the epigenome, could account for the variation seen between species with similar genetic makeup.