WFS1 and Leber hereditary optic neuropathy: Furthermore, the CRISPR/Cas9 system was applied to treat Wolfram syndrome (WS), an autosomal recessive disorder which causes childhood-onset diabetes, optic atrophy, neurodegeneration, deafness, etc. WS is caused by mutations in the WFS1 (Wolframin ER transmembrane glycoprotein) gene which leads to chronic endoplasmic reticulum (ER) stress and the impeded folding of proinsulin.