UGT1A1 and metabolic disease: Moreover, GPSC-derived hepatocytes may serve as a platform for gene delivery and can partially substitute the diseased liver as in case of metabolic diseases requiring only 5–10% healthy cells for rescue, as in the case, for instance, of Crigler-Najjar syndrome type I for which only 5% of the functional Ugt1a1 enzyme can benefit the patients as well as animal models affected by this disease[35].