Search

Background and AimsAlagille syndrome (ALGS) is a pediatric genetic disorder, caused by mutations in the Notch ligandJAGGED1, presenting with cholestasis due to intrahepatic bile duct paucity. Despite chronic liver disease, few patients develop severe fibrosis or liver cancer, compared to other chronic liver diseases. In contrast, about 1/3 of ALGS patients suffer from reoccurring infections. Notch signaling regulates both liver and immune system development, but how immune system defects interact with liver pathology in ALGS to influence disease course is not known. Here, we aimed to determine whether a mouse model of ALGS mimics fibrosis and liver cancer, and whether ALGS immune system compromise could positively modulate inflammation or liver disease course.MethodsWe used single cell RNA sequencing and 25-color flow cytometry to characterize cell populations in embryonic and postnatal liver in an ALGS mouse model (Jag1Ndr/Ndrmice). We analyzed liver cancer prevalence inJag1Ndr/Ndrmice, in a cancer-prone genetic background, and thymic and spleen cell composition using flow cytometry. Finally, to test the functionality of theJag1Ndr/Ndrimmune system we performed adaptive immune cell transfer experiments intoRag1-/mice and assessed inflammatory capacity in an ulcerative colitis model and in a DDC model of hepatocellular damage.ResultsAdultJag1Ndr/Ndrmice do not develop liver tumors (0%) while 45% of control mice do. Interestingly,Jag1Ndr/Ndrmice display ALGS-like chicken-wire hepatocellular fibrosis concomitant with mild inflammation shortly after the onset of liver cholestasis. Comprehensive single cell analysis revealed that liver CD4+and CD8+T cells ofJag1Ndr/Ndrmice are dysregulated in favor of CD4+, and Regulatory T-cells (Tregs) manifest reduced activation. Transplantation experiments show no difference betweenJag1Ndr/NdrandJag1+/+lymphocytes in DDC-induced liver damage. In contrast,Jag1Ndr/Ndrlymphocytes do not mount an inflammatory response to bacterial infection.ConclusionHere we report immune dysregulation and cancer protection in the hypomorphicJag1mouse model of ALGS. Disrupted thymocyte differentiation coincides with limited activation of hepatocytes, blunting the inflammatory response to cholestasis. This may contribute to the pericellular fibrosis and prevent carcinogenesis. These results prompt the question of the relative contribution of Jag1 to liver cell pathology vs immune system in ALGS and highlight the need of future studies focused on dissecting apart how Jag1 modulates susceptibility to infection versus cancer risk.

Using the timely re-activation of WNT signalling in neuralizing human induced pluripotent stem cells (hiPSCs), we have produced neural progenitor cells with a gene expression profile typical of human embryonic dentate gyrus (DG) cells. Notably, in addition to continuous WNT signalling, a specific laminin isoform is crucial to prolonging the neural stem state and to extending progenitor cell proliferation for over 200 days in vitro. Laminin 511 is indeed specifically required to support proliferation and to inhibit differentiation of hippocampal progenitor cells for extended time periods when compared with a number of different laminin isoforms assayed. Global gene expression profiles of these cells suggest that a niche of laminin 511 and WNT signalling is sufficient to maintain their capability to undergo typical hippocampal neurogenesis. Moreover, laminin 511 signalling sustains the expression of a set of genes responsible for the maintenance of a hippocampal neurogenic niche. Finally, xenograft of human DG progenitors into the DG of adult immunosuppressed host mice produces efficient integration of neurons that innervate CA3 layer cells spanning the same area of endogenous hippocampal neuron synapses.