What is Wolfram syndrome?

Wolfram syndrome is a autosomal recessive disorder characterized by juvenile onset diabetes, later followed by various neurological dysfunctions and death from widespread neurodegeneration in the third or fourth decade. Dr. Permutt identified the causative gene named WFS1 in 1998. Dr. Permutt and my groups developed cell and animal models that led to the discovery that WFS1 protein resides in the endoplasmic reticulum (ER) membrane, and that mutant forms predispose β-cells and neurons to ER dysfunction-mediated cell death. A potential link between the diabetes of Wolfram syndrome and type 2 diabetes is supported by recent studies that identified WFS1 single nucleotide polymorphisms (i.e., genetic variations among people) associated with an increased risk for type 2 diabetes. Based on the data accumulated in the past 10 years, we believe that Wolfram syndrome is an endoplasmic reticulum disease. So what is endoplasmic reticulum?