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Zebrafish abcb11b mutant reveals strategies to restore bile excretion impaired by bile salt export pump deficiency
Author(s) -
Ellis Jillian L.,
Bove Kevin E.,
Schuetz Erin G.,
Leino Daniel,
Valencia C. Alexander,
Schuetz John D.,
Miethke Alexander,
Yin Chunyue
Publication year - 2018
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.29632
Subject(s) - bile salt export pump , cholestasis , zebrafish , progressive familial intrahepatic cholestasis , biology , multidrug resistance associated protein 2 , mutant , bile acid , atp binding cassette transporter , biochemistry , medicine , endocrinology , transporter , gene , liver transplantation , transplantation
Bile salt export pump (BSEP) adenosine triphosphate–binding cassette B11 (ABCB11) is a liver‐specific ABC transporter that mediates canalicular bile salt excretion from hepatocytes. Human mutations in ABCB11 cause progressive familial intrahepatic cholestasis type 2. Although over 150 ABCB11 variants have been reported, our understanding of their biological consequences is limited by the lack of an experimental model that recapitulates the patient phenotypes. We applied CRISPR/Cas9‐based genome editing technology to knock out abcb11b , the ortholog of human ABCB11 , in zebrafish and found that these mutants died prematurely. Histological and ultrastructural analyses showed that abcb11b mutant zebrafish exhibited hepatocyte injury similar to that seen in patients with progressive familial intrahepatic cholestasis type 2. Hepatocytes of mutant zebrafish failed to excrete the fluorescently tagged bile acid that is a substrate of human BSEP. Multidrug resistance protein 1, which is thought to play a compensatory role in Abcb11 knockout mice, was mislocalized to the hepatocyte cytoplasm in abcb11b mutant zebrafish and in a patient lacking BSEP protein due to nonsense mutations in ABCB11 . We discovered that BSEP deficiency induced autophagy in both human and zebrafish hepatocytes. Treatment with rapamycin restored bile acid excretion, attenuated hepatocyte damage, and extended the life span of abcb11b mutant zebrafish, correlating with the recovery of canalicular multidrug resistance protein 1 localization. Conclusions: Collectively, these data suggest a model that rapamycin rescues BSEP‐deficient phenotypes by prompting alternative transporters to excrete bile salts; multidrug resistance protein 1 is a candidate for such an alternative transporter. (H epatology 2018;67:1531‐1545).