Scientists find genetic key to autoimmune diseases

The discovery of how the gene Roquin suppresses autoimmune diseases like Type 1 diabetes and lupus could open the way for improved treatments for such conditions, scientists propose.

Researchers from the Australian National University (ANU) discovered in 2005 that Roquin can undergo a specific mutation that results in it instructing T-cells to react against the self.

The researchers have now written a report, published in the journal Nature, which shows how a healthy Roquin gene can actually prevent abnormal T-cell behaviour.

“Our findings hinge on the fact that the activities of a normal Roquin gene are orchestrated by parts of the genome until very recently considered to be ‘junk DNA’,” said Dr Vinuesa from the John Curtin School of Medical Research (JCSMR) at ANU.

The discovery centres on some small, non-protein-coding forms of RNA, called microRNAs, which actually induce the decay of messenger RNAs.

“This decay leads to reduction of the expression of proteins such as one called ICOS, that we have now shown can result in autoimmunity when it is over-expressed,” said Dr Di Yu from JCSMR, who performed most of the experiments leading to the discovery.

“This is the first time that microRNAs have been linked to protection from autoimmune diseases.”

Once considered to be genetic junk, microRNAs are now thought to regulate up to 30% of the genome and have been recently shown to play an important role in the development of cancer and other diseases.

“We're learning more and more about how RNAs regulate critical processes related to cell development and the evolution of complex structures like the brain,” said JCSMR’'s Professor Chris Goodnow.

The researchers say their work opens up the possibility of using RNA interference, or the microRNAs themselves, in the treatment of autoimmune diseases.