This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastro Intestinal System, Subject name: Pediatrics
Gene encoding which protein is defective in Dubin Johnson syndrome? 
Select and explain. 
A. JAG1, B. MRP2, C. ATP7A, D. ATP 7B
B: MRP2
Answer: B: MRP2 
Explanation: B. MRP2(Ref: Nelson's 20/e p 1931, 1938)In Dubin Johnson syndrome, ABCC2 gene is affected, that codes for MRP2 protein. Absent function of multiple drug-resistant protein 2 (MRP2), an adenosine triphosphate-dependent canalicular transporter, is the responsible defect, that leads to defective conjugated bilirubin excretion.