Biology subjects

Dale, T. C.

Publications and source records attributed to Dale, T. C..

3 recordsLinked to original sources

bioRxiv2021

Technical advances in the development of zonation liver in vitro systems that incorporate localized Wnt activating signals

A Wnt microenvironment sustained by the hepatic central vein is essential for the segregation of liver functions into zones. Current liver culture systems lack localized Wnt cues and as a consequence fail to maintain the hepatocyte functional heterogeneity that is observed in the intact organ. In this study, organoid models and 2D-culture systems were used to identify cellular sources and Wnt presentation methods that could support the future development of zonated liver in vitro systems. Using soluble ligands, we show that primary hepatocyte (PH)-derived organoids but not bile duct (BD)-derived organoids may be used to recapitulate the resting liver. We provide evidence that differentiation of PH-organoids in the presence of Wnt9b and Rspo3 induce pericentral maturation. Finally, we show that immobilization of Rspo3 onto beads in combination with soluble Wnt9b may be a valid strategy to recreate the central vein Wnt microenvironment in vitro.

cell biology↗

bioRxiv2020

Canonical Wnt signalling is activated during BEC-to-hepatocyte conversion in vivo and modulates liver epithelial cell plasticity in hepatic organoids

While it is recognized that the Wnt/{beta}-catenin pathway orchestrates hepatocyte proliferation in both homeostasis and injury, little is known about the importance of {beta}-catenin in biliary epithelial cell (BEC) plasticity. In this study, the dynamics of activation of the canonical Wnt pathway were investigated during BEC-to-hepatocyte conversion using as a model methionine/choline deficient (MCD)-injured livers where hepatocyte proliferation was compromised by the overexpression of p21. In this model, activation of {beta}-catenin was found an event associated with BEC reprogramming. Using ductal organoids to model BECs transitioning into hepatocytes, we found that activation of the Wnt/{beta}-catenin pathway in these cells promoted partial escape from a biliary fate and triggered the acquisition of progenitor cell features. Our data furthermore support that BECs are source of Wnt ligands and that Rspo proteins potentially act as the limiting factor controlling the activation of {beta}-catenin activation and BEC reprogramming during severe liver damage.

cell biology↗

bioRxiv2019

Developmentally regulated tcf7l2 splice variants mediate transcriptional repressor functions during eye formation

Tcf7l2 mediates Wnt/{beta}-Catenin signalling during development and is implicated in cancer and type-2 diabetes. The mechanisms by which Tcf7l2 and Wnt/{beta}-Catenin signalling elicits such a diversity of biological outcomes are poorly understood. Here, we study alternatively spliced tcf7l2 in zebrafish and show that only splice variants that include exon 5 and an analogous human tcf7l2 variant can effectively provide compensatory repressor function to restore eye formation in embryos lacking tcf7l1a/tcf7l1b function. Knockdown of exon 5 specific tcf7l2 variants in tcf7l1a mutants also compromises eye formation and these variants can effectively repress Wnt pathway activity in reporter assays using Wnt target gene promoters. We show that the repressive activities of exon5-coded variants are likely explained by their interaction with Tle co-repressors. Furthermore, phosphorylated residues in Tcf7l2 coded exon5 facilitate repressor activity. Our studies suggest that developmentally regulated splicing of tcf7l2 can influence the transcriptional output of the Wnt pathway.

developmental biology↗