To get a deeper insight into the molecular processes underlying bilirubin-induced neuronal injury in vivo, we used a mouse strain bearing a targeted mutation in the Ugt1 gene.19 Mutant mice developed hyperbilirubinemia within 36 h after birth as evident by the yellow staining of their skin (Figure 1a, pup on the top). Here, UGT1A1 is linked to Hyperbilirubinemia.