To investigate the physiological function of B7-H4 in pancreatic β cells and whether it is involved in the pathological process of T2D, we generated β-cell-specific B7-H4 knockout (B7-H4 cKO) mice by crossing loxP-flanked B7-H4 fl/fl mice (the targeting strategy is shown in sFigure 2A) with Rip-Cre transgenic mice. The gene discussed is VTCN1; the disease is type 2 diabetes mellitus.