This is the first time a defect in this gene has been linked with a disease.
Scientists have identified a new gene thought to be critical in the regulation of insulin, an advance that may pave the way for novel treatments for both rare and common forms of diabetes.
In addition to the more common forms of diabetes (type 1 or type 2), in about 1-2 per cent of cases diabetes is due to a genetic disorder, known as maturity onset diabetes of the young (MODY).
A defective gene typically affects the function of insulin-producing cells in the pancreas, known as beta cells.
Researchers from Vanderbilt University in the US, Queen Mary University of London and University of Exeter in the UK studied the unique case of a family where several individuals suffer from diabetes, while other family members had developed insulin-producing tumours in their pancreas.
These tumours, known as insulinomas, typically cause low blood sugar levels, in contrast to diabetes which leads to high blood sugar levels.
"We were initially surprised about the association of two apparently contrasting conditions within the same families – diabetes which is associated with high blood sugar and insulinomas associated with low blood sugar," said Marta Korbonits from Queen Mary University.
"Our research shows that, surprisingly, the same gene defect can impact the insulin-producing beta cells of the pancreas to lead to these two opposing medical conditions," said Korbonits, lead author of the study published in the journal PNAS.
The team also observed that males were more prone to developing diabetes, while insulinomas were more commonly found in females, but the reasons behind this difference are as yet unknown.
"One exciting avenue to explore will be seeing if we can use this finding to uncover new ways to help regenerate beta cells and treat the more common forms of diabetes," said Korbonits.
The researchers identified a genetic disorder in a gene called MAFA, which controls the production of insulin in beta cells.
This gene defect was present in both the family members with diabetes and those with insulinomas, and was also identified in a second, unrelated family with the same unusual dual picture.
This is the first time a defect in this gene has been linked with a disease. The resultant mutant protein was found to be abnormally stable, having a longer life in the cell, and therefore significantly more abundant in the beta cells than its normal version.
"We believe this gene defect is critical in the development of the disease and we are now performing further studies to determine how this defect can, on the one hand, impair the production of insulin to cause diabetes, and on the other, cause insulinomas," said Donato Iacovazzo from Queen Mary.