Laminin 511 and WNT signalling sustain prolonged expansion of hiPSC-derived hippocampal progenitors.

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.

Jag1 insufficiency alters liver fibrosis via T cell and hepatocyte differentiation defects.

Fibrosis contributes to tissue repair, but excessive fibrosis disrupts organ function. Alagille syndrome (ALGS, caused by mutations in JAGGED1) results in liver disease and characteristic fibrosis. Here, we show that Jag1Ndr/Ndr mice, a model for ALGS, recapitulate ALGS-like fibrosis. Single-cell RNA-seq and multi-color flow cytometry of the liver revealed immature hepatocytes and paradoxically low intrahepatic T cell infiltration despite cholestasis in Jag1Ndr/Ndr mice. Thymic and splenic regulatory T cells (Tregs) were enriched and Jag1Ndr/Ndr lymphocyte immune and fibrotic capacity was tested with adoptive transfer into Rag1-/- mice, challenged with dextran sulfate sodium (DSS) or bile duct ligation (BDL). Transplanted Jag1Ndr/Ndr lymphocytes were less inflammatory with fewer activated T cells than Jag1+/+ lymphocytes in response to DSS. Cholestasis induced by BDL in Rag1-/- mice with Jag1Ndr/Ndr lymphocytes resulted in periportal Treg accumulation and three-fold less periportal fibrosis than in Rag1-/- mice with Jag1+/+ lymphocytes. Finally, the Jag1Ndr/Ndr hepatocyte expression profile and Treg overrepresentation were corroborated in patients' liver samples. Jag1-dependent hepatic and immune defects thus interact to determine the fibrotic process in ALGS.