A New Variant of an Old Itch: Novel Missense Variant in ABCB4 Presenting with Intractable Pruritus.

We report a novel homozygous missense variant in ABCB4 gene in a Yemeni child born to consanguineous parents, with a significant family history of liver disease-related deaths, resulting in a progressive familial intrahepatic cholestasis (PFIC) type 3 phenotype requiring liver transplantation for intractable pruritus.

Progressive Familial Intrahepatic Cholestasis: A Study in Children From a Liver Transplant Center in India.

Background/Aims: This study aimed to delineate the clinical profile of children diagnosed with progressive familial intrahepatic cholestasis (PFIC). Methods: This study was a retrospective analysis of case records of children in the tertiary care hospital, with the diagnosis of PFIC from January 2017 to January 2020. The diagnosis was made using clinical and laboratory parameters and with genetic testing when available. Medical and surgical management was according to the departmental protocol. Liver transplant was offered to children with end-stage liver disease, intractable pruritus, or severe growth failure. Result: There were 13 identified PFIC cases (familial intrahepatic cholestasis 1 [FIC1] deficiency-4, bile salt export pump (BSEP) deficiency-3, tight junction protein [TJP2] deficiency 3, multidrug-resistant protein 3 [MDR3] deficiency 2 and farnesoid X receptor deficiency-1). PFIC subtypes 1, 2, and 5 presented in infancy, whereas MDR3 presented in childhood. TJP2 deficiency had varied age of presentation from infancy to adolescence. Jaundice with or without pruritus was present in most cases. Genetic testing was carried out in 10 children, of which five had a homozygous mutation, three had a compound heterozygous mutation, and two had a heterozygous mutation. Three children (FIC1-2 and TJP2-1) underwent biliary diversion, of which clinical improvement was seen in two. Six children underwent liver transplantation, which was successful in four. Conclusion: Byler's disease was the most common subtype. A clinicopathologic correlation with molecular diagnosis leads to early diagnosis and management. Liver transplantation provides good outcomes in children with end-stage liver disease.

Human iPSC-derived hepatocyte system models cholestasis with tight junction protein 2 deficiency.

Background & Aims: The truncating mutations in tight junction protein 2 (TJP2) cause progressive cholestasis, liver failure, and hepatocyte carcinogenesis. Due to the lack of effective model systems, there are no targeted medications for the liver pathology with TJP2 deficiency. We leveraged the technologies of patient-specific induced pluripotent stem cells (iPSC) and CRISPR genome-editing, and we aim to establish a disease model which recapitulates phenotypes of patients with TJP2 deficiency. Methods: We differentiated iPSC to hepatocyte-like cells (iHep) on the Transwell membrane in a polarized monolayer. Immunofluorescent staining of polarity markers was detected by a confocal microscope. The epithelial barrier function and bile acid transport of bile canaliculi were quantified between the two chambers of Transwell. The morphology of bile canaliculi was measured in iHep cultured in the Matrigel sandwich system using a fluorescent probe and live-confocal imaging. Results: The iHep differentiated from iPSC with TJP2 mutations exhibited intracellular inclusions of disrupted apical membrane structures, distorted canalicular networks, altered distribution of apical and basolateral markers/transporters. The directional bile acid transport of bile canaliculi was compromised in the mutant hepatocytes, resembling the disease phenotypes observed in the liver of patients. Conclusions: Our iPSC-derived in vitro hepatocyte system revealed canalicular membrane disruption in TJP2 deficient hepatocytes and demonstrated the ability to model cholestatic disease with TJP2 deficiency to serve as a platform for further pathophysiologic study and drug discovery. Lay summary: We investigated a genetic liver disease, progressive familial intrahepatic cholestasis (PFIC), which causes severe liver disease in newborns and infants due to a lack of gene called TJP2. By using cutting-edge stem cell technology and genome editing methods, we established a novel disease modeling system in cell culture experiments. Our experiments demonstrated that the lack of TJP2 induced abnormal cell polarity and disrupted bile acid transport. These findings will lead to the subsequent investigation to further understand disease mechanisms and develop an effective treatment.