WFS1 and diabetes mellitus: Moreover, it was also demonstrated that WFS1 regulates secretory granule acidification in β-cells and neurons (Gharanei et al., 2013; Sutt et al., 2015) and that the ER dysfunction caused by WFS1 deficiency is accompanied by altered mitochondrial function in β-cells and neurons contributing to diabetes and neurodegeneration (Cagalinec et al., 2016; Maxwell et al., 2020).