Expression of a Novel Murine Type I IFN in the Pancreatic Islets Induces Diabetes in Mice

IFN-κ belongs to a recently identified subclass of type I IFNs. In this study, we report the cloning and preliminary characterization of the murine homologue of IFN-κ. The gene encodes a 200-aa protein which is 38.5% homologous to human IFN-κ. Murine IFN-κ contains four cysteines in analogous positions to those observed in the IFN-α and an additional fifth unique cysteine, C174. The murine gene is located on chromosome 4, where other type I murine IFN genes, IFN-α and IFN-β, are clustered. This region is syntenic with human chromosome 9 where the gene encoding IFN-κ and the type I IFN gene cluster are found. Mouse IFN-κ is expressed at low levels in peritoneal macrophages and its expression is up-regulated by dsRNA and IFN-γ. Similar to previously reported transgenic mice carrying type I and type II IFNs, transgenic mice overexpressing murine IFN-κ in the β cells of the pancreas develop overt diabetes with hyperglycemia. Histological characterization of pancreatic islets from these transgenic mice showed inflammatory infiltrates with corresponding destruction of β cells.