US scientists have found a fault in a newly discovered gene that may explain why some people have type 1 diabetes.
People with type 1 diabetes need to monitor their blood sugar levels
The SUMO-4 gene helps regulate the body's immune system that defends against infection.
Dr Jin-Xiong She and colleagues at the Medical College of Georgia examined nearly 1,000 diabetic families.
The findings are published in the journal Nature Genetics. Other genes have been identified that contribute to type 1 diabetes.
For the last 10 years, Dr She and colleagues have been looking at how the immune system and the environment work together to cause type 1 diabetes.
In diabetes the body cannot convert the glucose in its blood into energy because the hormone insulin, which enables this to take place, is either not produced or does not work properly.
People with type 1 diabetes have to take insulin to correct this.
Dr She and colleagues looked at SUMO-4 because of its action on the immune system.
They found the family members with type 1 diabetes were more likely to have a certain natural mutation of this gene than other non-diabetic family members.
Further studies by the team found when the mutation encountered an environmental trigger, such as a bacterial or viral infection, it threw off the usual well-balanced activity of the body's immune system.
This launched a response from the immune system that would eventually attack the person's own tissue.
This type of self-attack is what causes diseases such as diabetes and rheumatoid arthritis which are known as autoimmune diseases.
The researchers said the mutation made the immune system more reactive to environmental triggers.
SUMO-4 controls the activity of a molecule called NFkB. This, in turn, controls the activity of proteins called cytokines that regulate the intensity and duration of the body's immune response.
It was already known that cytokines have a role in type 1 diabetes and other autoimmune diseases.
What wasn't known was the cause of the excessive cytokines in these conditions.
Dr She said: "It's the first gene for which we know how it contributes to the disease."
The faulty SUMO-4 gene enables more cytokines to be made and directs the revved up immune response at the cells in the pancreas that make insulin.
Dr She said their work should help people with diabetes.
"This helps us understand how type 1 diabetes works and we can use this improved understanding to better predict who will get the disease."
He said this should also enable them to develop new treatments for type 1 diabetes.
Dr Martin Buckley, research fellow at the diabetes centre in Bolton, said: "It's an interesting discovery but obviously more work needs to be done in the future to find out how this could be translated into a potential medical cure for type 1 diabetes."
He said this could be many years away.
Professor Simon Howell, Research Advisor for Diabetes UK said: "This is interesting research and whilst we don't know exactly what causes diabetes we know it is a combination of environmental and genetic factors.
"This research is trying to identify the genes responsible for Type 1 diabetes and may be an important step forward in this area."