Aussie scientists unravel vital role of 'junk' DNA

A piece of DNA, previously considered as 'junk' material by scientists, could be the key to extinguishing fear-related memories for people with post-traumatic stress disorder (PTSD) and phobias, according to a new study led by Australian researchers.

Team leader associate professor Timothy Bredy, a neuroscientist at the Queensland Brain Institute (QBI) which is affiliated with the University of Queensland, said the discovery could ultimately help in the development of a therapy to target areas in the brain that directly modify disturbing memories.

Their findings, published in the journal Cell Reports on Wednesday, are based on a study into the impact of trauma on a genome, which is the complete set of genes or genetic material in a cell, Xinhua news agency reported.

Bredy explained how researchers had tested mice that had been trained to respond to stimuli in a certain way, Xinhua news agency reported.

"We behaviourally train mice and then, immediately following the experience, we examine specific cell types from their prefrontal cortex to see how genes are expressed in response to experience," Bredy said, adding that the results had defied expectations.

"Until recently, scientists thought most of our genes were made up of 'junk' DNA, which essentially didn't do anything," he said. "But when we began to explore these regions, we realised most of the genome is active."

Bredy and his team, including scientists from China and the US, were "very much surprised" by how many long non-coding RNA (lncRNAs) were actively expressed in response to the experience.

He said their breakthrough had been made possible by the use of a powerful new sequencing approach which "shines a very bright light on regions of the genome that one cannot see with standard sequencing methods".

"It is a really interesting way to zero in on sites within the genome that would otherwise be masked," Bredy said. "It's like harnessing the power of the Hubble Telescope to peer into the unknown of the brain."

The technology enabled them to identify 433 lncRNAs from relatively unknown regions of the human genome.

Bredy said a new gene, called ADRAM (which stands for Activity Dependent lncRNA Associated with Memory) acted as a "scaffold for molecules inside the cell" and helped coordinate the formation of fear-extinction memory.

"Our findings suggest that lncRNAs provide a bridge, linking dynamic environmental signals with the mechanisms that control the way our brains respond to fear," he said.

"Our next steps are to continue exploring lncRNA activity in the brain to look at their roles in different compartments of the cell and to harness the selectivity of lncRNAs ... to treat cognitive impairment disorders."