Our lab has developed a mouse model in which a missense mutation in the JAGGED1 gene was introduced, hereby generating a hypomorphic JAG1 ligand and preventing its binding to the NOTCH receptor on juxtaposed cells. This disruption of the Notch signalling pathway causes multiple organ disorders in these Jag1H268Q/ H268Q or Nodder mice, nicknamed because of their head-nodding phenotype. We discovered that Nodder mice recapitulate the major features of the Alagille syndrome (ALGS), a rare, autosomal dominant genetic disorder affecting eyes, heart, kidney as well as the liver often leading to liver failure and necessitating liver transplantation. ALGS is usually caused by mutations in the gene encoding the ligand JAG1 (~94% of cases) or by mutations in NOTCH2 (~2% of patients). The hepatic defects, observed in both ALGS patients and Nodder mice, include neonatal bile duct paucity and cholestasis but also the spontaneous, and so far, unexplained, recovery of the biliary system in some cases.

As the development of the biliary tract and the formation of the intrahepatic bile ducts are well-conserved processes in rodents and humans, we aim to use the Nodder mice to understand the liver pathology observed in ALGS patients. Poor biliary proliferation, increased cell death, interruption of cholangiocyte fate decision, incomplete terminal differentiation/maturation, defects in tubular organization/elongation, or a combination of these, are amongst the potential mechanisms at the base of ALGS biliary pathology.

AIMS

1) Mapping the protein expression of the components of the NOTCH signalling pathway in embryonic, postnatal and adult mouse liver
2) Unravel the mechanism(s) of bile duct regeneration seen in some Nodder mice

GOALS

1) Get an insight on liver architecture and microscopic cellular organisation
2) Collect pre- and postnatal wild type and Nodder livers (E15.5, E16.5, E17.5, E18.5, P2, P7, P15, 3 and 6 months old) to study the protein expression of Jag1 and its Notch receptors during embryonic development and postnatal maturation with a focus on the portal vein and surrounding mesenchyme, hepatic artery, ductal structures.
3) Assess the timing and location of the appearance of newly formed bile ducts in adult Nodder livers by immunohistochemistry
4) Collection of bile duct fragments by handpicking, culture and passage of mouse and human liver organoids

Methods: As this is a short-term project, you will not be able to have access to the animal facility but you will learn how to handle freshly collected liver tissue and process these samples by fixation and paraffin-embedding, making paraffin sections, performing immunohistochemistry/immunofluorescence, analysis and picture taking. In parallel, you will take part in the generation and maintenance of mouse and human liver organoids.