Complete OATP1B1 and OATP1B3 deficiency underlies human Rotor syndrome.. Homo sapiens

Rotor syndrome is an autosomal recessive disorder characterized by conjugated hyperbilirubinemia, near-absent hepatic uptake of anionic diagnostics, and coproporphyrinuria. The mechanistic basis of other hyperbilirubinemia syndromes is largely understood, but that of Rotor syndrome has remained enigmatic. The existing paradigm of hepatic bilirubin excretion postulates a unidirectional elimination pathway: Uptake of conjugated bilirubin from blood by hepatocytes, glucuronidation of bilirubin, and excretion of conjugated bilirubin into bile by ABCC2, a canalicular bilirubin-glucuronide and xenobiotic export pump. An analogous view holds for drugs conjugated in the liver. Here we demonstrate by molecular-genetic analysis of 8 Rotor-syndrome families that Rotor syndrome is a two-gene disorder, with impaired hepatic re-uptake of bilirubin-glucuronide caused by complete deficiencies in the hepatic organic anion transporting polypeptides OATP1B1 and OATP1B3. Overall design: SNP genotyping was performed on 22 samples - 10 affected and 12 healthy siblings from 8 Rotor-syndrome families. Affymetrix GeneChip Command Console software was used for image processing and CEL files were processed by Affymetrix GTC using the BRLMM-P-Plus algorithm and regional GC correction configuration for Copy Number/LOH analysis. The HapMap270 file supplied by Affymetrix was used as the reference.