In order to determine the effect of excessive zinc levels in the setting of ATP13A2 deficiency, we exposed hONs cells with compound heterozygous loss-of-function mutations (c.3253delC and c.3176T>G) in ATP13A2 (3), to increasing doses of ZnCl2 and measured the cell viability using the Neutral red uptake assay (33). The gene discussed is ATP13A2; the disease is hyperinsulinemic hypoglycemia, familial, 4.