WFS1 and pancreatic insulinoma: To test this hypothesis, we monitored gene expression of PSP/reg in a rat insulinoma (INS-1 832/13) cell line expressing small interfering RNA (siRNA) directed against Wfs1. Consistent with our islet data, cells depleted of Wfs1 expressed a 5-fold increase in Reg1 compared to the control cells (Fig. 1A).