PRKD2 and hyperinsulinism: To delineate the mechanism underlying PRKD2 deficiency-induced hyperinsulinemia, we analyzed the islet morphology and found no overt difference between PRKD2−/− and WT mice in terms of islet size or the proportion of β-cells within islets (Fig. 5a–d), indicating that PRKD2 deficiency does not affect islet structure.