## **Core Concept**
Dubin-Johnson syndrome is a rare genetic disorder characterized by an inability to secrete conjugated bilirubin into the bile, leading to its accumulation in the liver and subsequent jaundice. This condition is associated with mutations in a specific gene that encodes for a protein involved in hepatic bilirubin transport.

## **Why the Correct Answer is Right**
The correct answer, **ABCC2**, encodes for a protein known as multidrug resistance-associated protein 2 (MRP2), which plays a crucial role in the transport of conjugated bilirubin from hepatocytes into the bile canaliculi. Mutations in the **ABCC2** gene lead to the absence or dysfunction of MRP2, resulting in the inability to properly transport conjugated bilirubin into the bile, which is a hallmark of Dubin-Johnson syndrome.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While **SLCO1B1** and **SLCO1B3** genes are involved in the transport of organic anions, including bilirubin, into hepatocytes, mutations in these genes are associated with other conditions, such as Rotor syndrome, which presents similarly to Dubin-Johnson syndrome but is caused by different genetic alterations.
- **Option C:** There is no commonly recognized gene associated with Dubin-Johnson syndrome labeled simply as "" in major genetic databases related to this condition.
- **Option D:** Similarly, "" does not directly correspond to a known gene mutation responsible for Dubin-Johnson syndrome.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature of Dubin-Johnson syndrome is the presence of liver discoloration due to the accumulation of melanin and epinephrine metabolites, giving the liver a characteristic black appearance. This condition is also notable for its benign nature, with patients generally having a normal life expectancy and the condition being primarily of concern due to its potential to cause cosmetic jaundice.

## **Correct Answer:** . ABCC2