Type 2 diabetes mellitus (T2DM) affects the majority of people with diabetes, accounting for more than 90% of those with diabetes, and is characterized by insulin secretion defects in pancreatic β-cells and insulin resistance, whereas type 1 DM is caused by autoreactive T cell-mediated destruction of β-cells (Figure 1) (1, 2). The gene discussed is INS; the disease is diabetes mellitus.