Secondly, treatment of Crigler–Najjar syndrome type 1 with an AAV8 vector expressing UDP-glucuronosyltransferase family 1-member A1 (UGT1A) showed normalization of total serum bilirubin levels in two animal models of the disease, Gunn rats and Ugt1a1-/- mice [105]. This evidence concerns the gene UGT1A1 and Crigler-Najjar syndrome type 1.