SLC30A8 and type 2 diabetes mellitus: ZnT8, which is expressed in pancreatic β cells, is essential for packaging insulin crystals (Bosco et al, 2010; Hardy et al, 2011), and variants in the SLC30A8/ZnT8 gene are associated with an increased risk for type 2 diabetes (Xu et al, 2012; Tamaki et al, 2013).