'Junk DNA' helps switch on genetic origin of diseases

Thu, Sep 6, 2012, 01:00

OUR UNDERSTANDING of the human genetic blueprint has been turned on its head. Scientists have shown that what they long considered junk DNA is functional and acts like a collection of switches to regulate the genes that give us life.

They have also learned that the genetic origins of many common diseases can be mapped to these switches, providing researchers with a new way of studying the genetic origins of disease.

The announcement, made this morning in four leading research journals, must rank as the greatest DNA discovery since the delivery of the first full human genome in 2003.

The 30 scientific papers presented in the journals offer a detailed map of how the complete genome works, identifying four million of these gene regulators that act like a dimmer switch that turns gene activity up and down as required.

The discovery flows from the Encode (Encyclopaedia of DNA Elements) project launched in 2003. It sought to learn more about the 98 per cent of the genome that seemed to be inactive and unimportant to the workings of the genetic code.

The project identified the genes, the working part of the genome that makes proteins. Now, thanks to Encode, which involves 442 scientists in 32 labs in the UK, US, Spain, Singapore and Japan, researchers have learned that the apparently inactive DNA is central to the genome as a whole, representing the wiring diagram of a human being.

“Our genome is simply alive with switches, millions of places that determine whether a gene is switched on or off,” said Prof Ewan Birney, lead analysis coordinator for Encode at the European Bioinformatics Institute.

The genome project showed what two per cent of the genome did. “With Encode we can see that around 80 per cent of the genome is actively doing something.”

One of the main things the announcement in Nature, Genome Biology, Genome Research and Science will deliver is a new way to approach common disorders.

Researchers have spent years looking for genetic errors associated with disease, focusing their attention on the genes. Many of these delivered gene associations but the information had not got to the source, the DNA regions that actually control the genes.

“It turns out that many of the variants that genetic researchers have tied to various diseases – lupus, Crohn’s disease, metabolic diseases, high cholesterol and much more – sit in these regions that alter how genes are expressed in specific kinds of cells,” said Prof Brad Bernstein, a principal investigator in Encode.