| First Author | Falix FA | Year | 2014 |
| Journal | Dev Biol | Volume | 396 |
| Issue | 2 | Pages | 201-13 |
| PubMed ID | 25446530 | Mgi Jnum | J:218171 |
| Mgi Id | MGI:5616947 | Doi | 10.1016/j.ydbio.2014.10.002 |
| Citation | Falix FA, et al. (2014) Hepatic Notch2 deficiency leads to bile duct agenesis perinatally and secondary bile duct formation after weaning. Dev Biol 396(2):201-13 |
| abstractText | Notch signaling plays an acknowledged role in bile-duct development, but its involvement in cholangiocyte-fate determination remains incompletely understood. We investigated the effects of early Notch2 deletion in Notch2(fl/fl)/Alfp-Cre(tg/-) ("Notch2-cKO") and Notch2(fl/fl)/Alfp-Cre(-/-) ("control") mice. Fetal and neonatal Notch2-cKO livers were devoid of cytokeratin19 (CK19)-, Dolichos-biflorus agglutinin (DBA)-, and SOX9-positive ductal structures, demonstrating absence of prenatal cholangiocyte differentiation. Despite extensive cholestatic hepatocyte necrosis and growth retardation, mortality was only ~15%. Unexpectedly, a slow process of secondary cholangiocyte differentiation and bile-duct formation was initiated around weaning that histologically resembled the ductular reaction. Newly formed ducts varied from rare and non-connected, to multiple, disorganized tubular structures that connected to the extrahepatic bile ducts. Jaundice had disappeared in ~30% of Notch2-cKO mice by 6 months. The absence of NOTCH2 protein in postnatally differentiating cholangiocyte nuclei of Notch2-cKO mice showed that these cells had not originated from non-recombined precursor cells. Notch2 and Hnf6 mRNA levels were permanently decreased in Notch2-cKO livers. Perinatally, Foxa1, Foxa2, Hhex, Hnf1beta, Cebpalpha and Sox9 mRNA levels were all significantly lower in Notch2-cKO than control mice, but all except Foxa2 returned to normal or increased levels after weaning, coincident with the observed secondary bile-duct formation. Interestingly, Hhex and Sox9 mRNA levels remained elevated in icteric 6 months old Notch2-cKOs, but decreased to control levels in non-icteric Notch2-cKOs, implying a key role in secondary bile-duct formation. CONCLUSION: Cholangiocyte differentiation becomes progressively less dependent on NOTCH2 signaling with age, suggesting that ductal-plate formation is dependent on NOTCH2, but subsequent cholangiocyte differentiation is not. |
