In the fumarylacetoacetate hydrolase (Fah)-knockout mouse model, gRNA libraries codelivered with Fah gene allow hepatocytes expressing Fah (and gRNA) to dominate and regenerate the liver upon withdrawal of NTBC (2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione), a drug that prevent liver damage upon Fah loss induced tyrosinemia by inhibiting tyrosine catabolism. The gene discussed is FAH; the disease is tyrosinemia.