Search for gene 'control switches' begins

A new project that aims to identify the 'on-off' switches that control human genes has begun, scientists announced last week. Researchers at the Wellcome Trust Sanger Centre in the UK and German biotech company 'Epigenomics' hope to complete the work in five years. They say that identifying the chemical markers that affect gene activity will help reveal which genes are switched on in which body tissues. The research, dubbed the Human Epigenome Project (HEP), could also pinpoint changes in gene activity associated with diseased tissues, such as tumours. 'This is an extension of the Human Genome Project' said Stephen Beck of the Sanger Centre.

The Human Genome Project, completed earlier this year, is helping researchers identify the estimated 35,000 different genes contained within the human genetic code. The genes are buried within a DNA sequence made up of around 2.9 billion 'letters': four different chemical bases referred to as A (adenine), T (thymine), C (cytosine) and G (guanine). The new project aims to search through this sequence looking for cytosine units that have a 'methyl' chemical group added - the hallmarks of gene on-off switches. Differences in these methylation patterns are associated with differences in the activity of genes in a particular cell or tissue. And, importantly, many cancers show abnormal methylation patterns. 'One of the first things that will come out of this will be very powerful early tools for the detection of cancers' Alex Olek, chief executive of Epigenomics told the BBC. He said that the company expected to launch a product for the early detection of bowel cancer by 2007.

At the project launch, the group released the results of their pilot study, which provides 'definitive proof' that the cells making up different body tissues have different DNA methylation patterns, says Beck. The group now plans to look at methylation patterns in the entire human genome in 200 DNA samples, one from each of the different human body tissues.