Mice aid diabetes research

By Damon Shorter

ANU medical researchers are using a sophisticated new genetic technique to help understand the causes of insulin-dependent diabetes, which affects one in 300 Australians.

Using mice predisposed to the disease, the scientists have been able to delete genes from specific tissues in the body and they say the technique may help them clarify the roles particular genes play in causing the disease.

Insulin-dependent diabetes belongs to a group known as autoimmune diseases, in which the body's immune system goes out of control and attacks its own tissue.

Dr Robyn Slattery, a researcher from the John Curtin School of Medical Research (JCSMR), explained that in insulin-dependent diabetes the islet cells in the pancreas, which make insulin, are attacked and destroyed. Sufferers lose the ability to produce insulin and must inject themselves daily with the hormone.

Although the role insulin plays in the body is well understood, the reason why the insulin-producing cells in diabetes patients are attacked remains a mystery.

Dr Slattery's research team is trying to untangle the problem using a new technique called "cre-lox recombination".

The advantage of the system is that it allows genes to be deleted in specific tissues in the body, leaving the other tissues untouched.

All cells in the body have markers on their surface known as MHC molecules, Dr Slattery explained.

These act like traffic lights to the immune system, normally displaying a red signal but giving the green light to attack if a cell becomes infected with a virus.

For a reason which is not understood, the immune system in diabetes patients gets a green signal and attacks insulin-producing cells in the pancreas even when there is no apparent infection, Dr Slattery said.

The aim of her team's work is to understand where the faulty signal is initiated: whether a damaged MHC sends a faulty signal or, alternatively, normal cells are attacked by a faulty immune system.

To find out, her research team is making a mouse which will have no traffic-light MHC molecules on its insulin-producing cells. It will be one of the first times that the new technique has been used in Australia.

Apart from helping to understand diabetes, the work might also provide important insights into the mechanisms of other autoimmune diseases such as multiple sclerosis (MS) and rheumatoid arthritis, Dr Slattery said.

The study could also help research which aims to restore diabetics to health, using transplants of healthy insulin-producing cells, she said.

Dr Slattery presented the results of her study yesterday during a symposium taking place at the JCSMR to promote scientific links between the ANU and Italian medical researchers. The symposium is supported by the Embassy of Italy, the National Research Council of Italy and The Department of Foreign Affairs and Trade.