OTC and hyperinsulinemic hypoglycemia, familial, 4: The FRGN chimeric model supports liver humanization and enables repopulation of up to 95% of the liver by human donor hepatocytes.36,56 The recent study by Zabulica et al. demonstrated the transplantation of patient-derived donor human hepatocytes into FRGN mice to generate a humanized model of ornithine transcarbamylase deficiency.39 The weakness of this approach is that the chimeric humanized-liver FRGN mice are immune compromised, which limits the type of experiments that can be conducted.