Wolfram syndrome (WS) is a rare genetic disease that historically has been thought to occur in approximately 1/200,000 to 1/500,000 people, though more recent data suggests WS may be more common with a spectrum of disease presentation. The classic presentation of WS1, caused by mutations in the WFS1 gene, is insulin dependent diabetes by age 5 to 6, optic nerve atrophy with profound vision impairment or blindness by age 15 to 20. Wolfram syndrome can present with other symptoms including, but not limited to, diabetes insipidus, deafness, and neurodegeneration. Less frequently, mutations in the CISD2 gene can cause Wolfram syndrome type 2 (WS2).
Single, dominant mutations in WFS1, the gene affected in WS type 1, can cause WFS1-related disorder, which often presents as a milder form of Wolfram syndrome. There are numerous mutations of the WFS1 gene that result in Wolfram syndrome or WFS1-related disorder. Each mutation may manifest as a different presentation of the disease with a different level of severity. While some WFS1 mutations are more common than others, there is no single mutation that if corrected, would treat the disease for all WS patients.
The symptoms of WS1 are caused by dysfunctional wolframin, the endoplasmic reticulum (ER) transmembrane protein encoded by the WFS1 gene. Wolframin appears to help fold other proteins properly and maintain proper calcium levels in the ER. Wolframin also appears to communicate with mitochondria, the energy powerhouse of the cell. Without fully functional wolframin the Unfolded Protein Response (UPR) is triggered, misfolded proteins accumulate, calcium leaks into the body of the cell, and ultimately the cell dies. The cells most affected in WS are insulin producing beta cells and neurons.
A second causative gene of WS, CISD2, has been identified in patients with Wolfram syndrome 2 (WS2) resulting in early optic atrophy, diabetes mellitus, deafness, decreased lifespan, but not diabetes insipidus.The CISD2-encoded protein ERIS (endoplasmic reticulum intermembrane small protein) localizes to the ER, but does not interact directly with wolframin.
The diagnosis of Wolfram syndrome can be devastating to patients and families given the numerous life-altering manifestations of the disease. There is new hope for WS patients as there are now treatments in clinical trial that may help slow progression of the disease, and several treatments being studied in the lab to stop disease progression. The ultimate goal for treating WS will be to correct individual mutations within the WFS1 or CISD2 gene and replace or repair damaged tissue. The Power of Wolfram syndrome Although Wolfram syndrome is an ultra-rare genetic disorder, its constituent medical components (e.g. diabetes mellitus, deafness, and retinal degeneration) and underlying ER pathophysiology are individually present in many more common diseases. Consequently, novel treatments designed for WS may have broader implications for more common medical conditions related to ER stress and dysfunction. Thus, by leveraging the tools and therapeutic efforts targeting Wolfram syndrome, researchers may very well identify novel treatment modalities for more prevalent disorders such as diabetes mellitus and neurodegenerative diseases.
