New gene discovered

A new gene suspected to contribute to autoimmune diseases such as type 1 diabetes and lupus " a condition in which the body's own immune system attacks organs such as the kidneys and skin " has been discovered by immunologists at the Australian National University.

The researchers found that a mutation in the gene, which they have named Roquin, causes the body's infection fighters " T-cells " to attack their own tissue.

"Before this study, the existence and function of Roquin was not known," said lead researcher Dr Carola Vinuesa, from the John Curtin School of Medical Research (JCSMR) at ANU.

"However, we now know that in the immune system of mammals, the protein Roquin usually suppresses the activity of forbidden T-cells that bind to parts of the body. We found that a single mutation in Roquin causes these T-cells to be abnormally activated, and results in autoimmunity affecting many different parts of the body.

"This could reveal other abnormalities that underpin autoimmunity, and open up opportunities for developing specific treatments and drugs."

Autoimmune disease occurs when the immune system is falsely activated against normal tissue in the body, treating it as if it were a germ, and damaging and destroying the tissue. For example, in type 1 diabetes, an immune response is mounted against the insulin-secreting cells of the pancreas; in lupus, which affects one in 700 women of childbearing age, virtually any part of the body can be attacked by the immune system.

According to Professor Christopher Goodnow, the head of the immunogenomics laboratory at JCSMR and director of the Australian phenomics facility, the discovery hinged upon identifying a single letter change in the DNA code of Roquin.

"Roquin stops T-cells from displaying a stimulatory receptor, ICOS, that may cause the cells to attack normal body tissues. Therefore this gene seems critical in protecting us from autoimmunity "” but it only takes the mutation of one letter in that gene to cripple its function and lead to autoimmune disease."

Studies of the gene are currently underway in patients with lupus and type 1 diabetes to determine whether the same or similar mutations observed in laboratory mice are present in humans.