Genomic Structure of the Canalicular Multispecific Organic Anion–Transporter Gene (MRP2/cMOAT) and Mutations in the ATP-Binding–Cassette Region in Dubin-Johnson Syndrome

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Summary

Dubin-Johnson syndrome (DJS) is an autosomal recessive disease characterized by conjugated hyperbilirubinemia. Previous studies of the defects in the human canalicular multispecific organic anion transporter gene (MRP2/cMOAT) in patients with DJS have suggested that the gene defects are responsible for DJS. In this study, we determined the exon/intron structure of the human MRP2/cMOAT gene and further characterized mutations in patients with DJS. The human MRP2/cMOAT gene contains 32 exons, and it has a structure that is highly conserved with that of another ATP–binding–cassette gene, that for a multidrug resistance–associated protein. We then identified three mutations, including two novel ones. All mutations identified to date are in the cytoplasmic domain, which includes the two ATP-binding cassettes and the linker region, or adjacent putative transmembrane domain. Our results confirm that MRP2/cMOAT is the gene responsible for DJS. The finding that mutations are concentrated in the first ATP-binding–cassette domain strongly suggests that a disruption of this region is a critical route to loss of function.

Dubin-Johnson syndrome
MRP2/cMOAT
Multidrug resistance–associated protein
ATP-binding–cassette transporter
Bilirubin
Exon
ABC transporter (see ATP-binding–cassette transporter)

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