Genetically unique siblings reveal new treatment target for type 1 diabetes

There are lots of genes that are associated with an increased risk of developing type 1 diabetes. Studying these genes can provide researchers with new ideas for treatments for type 1, so the University of Exeter offers free worldwide screening for babies diagnosed with type 1 before they are 9 months old.

A unique genetic difference

New research from University of Exeter, co-funded by JDRF and published in the Journal of Experimental Medicine, studies two siblings who were diagnosed with a rare genetic form of autoimmune diabetes in the first weeks of life. Autoimmunity is where the immune system attacks our body’s own cells – in this case, the insulin-making beta cells.

The changes in their genes (known as a genetic mutation) have not been found in anyone else. The siblings’ mutation is in the gene for a protein called programmed death-ligand 1 (PD-L1) and the researchers think it could be responsible for their very-early-onset autoimmune diabetes.

Insights from cancer therapy

Some cancer patients are treated with a type of immunotherapy that stops PD-L1 from working. These people can develop autoimmune diabetes because of the treatment. We don’t know why only this cancer immunotherapy triggers autoimmune diabetes. The siblings’ genetic mutation results in the same effect as the cancer treatment, shedding new light on the involvement of PD-L1 in type 1 diabetes.

A new research avenue

Study co-author Professor Timothy Tree, from King’s College London, said: “This finding increases our knowledge of how autoimmune forms of diabetes such as type 1 diabetes develop. It opens up a new potential target for treatments that could prevent diabetes in the future. Simultaneously, it gives new knowledge to the cancer immunotherapy field by uniquely providing the results of completely disabling PD-L1 in a person, something you could never manipulate in studies. Reducing PD-L1 is already effective for cancer treatment, and boosting it is now being investigated as a type 1 diabetes treatment – our findings will help accelerate the search for new and better drugs.”

Next steps for the research

“Through studying this one set of siblings – unique in the world to our knowledge – we have found that the PD-L1 gene is essential for avoiding autoimmune diabetes but is not essential for ‘everyday’ immune function. This leads us to the grand question; ‘what is the role of PD-L1 in our pancreas making it critical for preventing our immune cells destroying our beta cells?’ We know that under certain conditions beta cells express PD-L1. However, certain types of immune cells in the pancreas also express PD-L1. We now need to work out the communication between different cell types that is critical for preventing autoimmune diabetes.”

Learn about another of Professor Tim Tree’s JDRF-funded research projects.