Bile duct proliferation in Jag1/fringe heterozygous mice identifies candidate modifiers of the alagille syndrome hepatic phenotype

Authors

  • Matthew J. Ryan,

    1. Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA
    2. Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA
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  • Christina Bales,

    1. Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA
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  • Anthony Nelson,

    1. Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA
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  • Dorian M. Gonzalez,

    1. Division of Human Genetics and Molecular Biology, Children's Hospital of Philadelphia, Philadelphia, PA
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  • Lara Underkoffler,

    1. Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA
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  • Michelle Segalov,

    1. Division of Human Genetics and Molecular Biology, Children's Hospital of Philadelphia, Philadelphia, PA
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  • Jeanne Wilson-Rawls,

    1. School of Life Sciences, Arizona State University, Tempe, AZ
    2. Department of Basic Medical Sciences, University of Arizona College of Medicine–Phoenix in Partnership with Arizona State University, Phoenix, AZ
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  • Susan E. Cole,

    1. Department of Molecular Genetics, Ohio State University, Columbus, OH
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  • Jennifer L. Moran,

    1. Genetic Analysis Platform, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA
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  • Pierre Russo,

    1. Department of Pathology and Clinical Laboratories, Children's Hospital of Philadelphia, Philadelphia, PA
    2. Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA
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  • Nancy B. Spinner,

    1. Division of Human Genetics and Molecular Biology, Children's Hospital of Philadelphia, Philadelphia, PA
    2. Department of Pathology and Clinical Laboratories, Children's Hospital of Philadelphia, Philadelphia, PA
    3. Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA
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  • Kenro Kusumi,

    1. Division of Human Genetics and Molecular Biology, Children's Hospital of Philadelphia, Philadelphia, PA
    2. Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA
    3. School of Life Sciences, Arizona State University, Tempe, AZ
    4. Department of Basic Medical Sciences, University of Arizona College of Medicine–Phoenix in Partnership with Arizona State University, Phoenix, AZ
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  • Kathleen M. Loomes

    Corresponding author
    1. Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA
    2. Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA
    • Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, 34th St. and Civic Center Blvd., Philadelphia, PA 19104
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    • fax: 267-426-7814


  • Potential conflict of interest: Nothing to report.

Abstract

Alagille syndrome (AGS) is a heterogeneous developmental disorder associated with bile duct paucity and various organ anomalies. The syndrome is caused by mutations in JAG1, which encodes a ligand in the Notch signaling pathway, in the majority of cases and mutations in the NOTCH2 receptor gene in less than 1% of patients. Although a wide array of JAG1 mutations have been identified in the AGS population, these mutational variants have not accounted for the wide phenotypic variability observed in patients with this syndrome. The Fringe genes encode glycosyltransferases, which modify Notch and alter ligand-receptor affinity. In this study, we analyzed double heterozygous mouse models to examine the Fringe genes as potential modifiers of the Notch-mediated hepatic phenotype observed in AGS. We generated mice that were haploinsufficient for both Jag1 and one of three paralogous Fringe genes: Lunatic (Lfng), Radical (Rfng), and Manic (Mfng). Adult Jag1+/−Lfng+/− and Jag1+/−Rfng+/− mouse livers exhibited widespread bile duct proliferation beginning at 5 weeks of age and persisting up to 1 year. The Jag1+/−Mfng+/− livers showed a subtle, yet significant increase in bile duct numbers and bile duct to portal tract ratios. These abnormalities were not observed in the newborn period. Despite the portal tract expansion by bile ducts, fibrosis was not increased and epithelial to mesenchymal transition was not shown in the affected portal tracts. Conclusion: Mice heterozygous for mutations in Jag1 and the Fringe genes display striking bile duct proliferation, which is not apparent at birth. These findings suggest that the Fringe genes may regulate postnatal bile duct growth and remodeling, and serve as candidate modifiers of the hepatic phenotype in AGS. (HEPATOLOGY 2008;48:1989–1997.)

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