Spatial transcriptomics reveals differences among genetic models of disruption in the Wnt‐beta‐catenin signaling in hepatocytes

Abstract

Wnt‐beta‐catenin signaling plays key roles in liver biology. One such role is in regulating the process of metabolic zonation within a liver lobule where Wnt‐beta‐catenin axis controls the expression of many genes expressed in zone‐3 hepatocytes. The cell‐molecule circuitry of the Wnt‐beta‐catenin signaling in this process has been identified and consists of basal expression of Wnt2 and Wnt9b in endothelial cells lining the central vein, which then are secreted by the Wntless (Wls) protein to act in a paracrine manner on Frizzled‐LRP5‐6 co‐receptors on hepatocytes in zone‐3 to activate beta‐catenin. This axis has been revealed through the generation of key genetic knockout (KO) mice including endothelial cell specific Wnt2‐Wnt9b double KO (EC‐Wnt2/9b‐KO), endothelial cell specific Wls KO (prevents secretion of all Wnts from endothelial cells lining central vein) (EC‐Wls‐KO), hepatocyte‐specific‐LRP5‐6 DKO (HC‐LRP5‐6‐DKO) and hepatocyte‐specific‐beta‐catenin KO (HC‐beta‐Cat‐KO). In all 4 genetic mouse models, we have identified notable decrease to complete loss of many zone‐3 genes. However, it remains unclear if all the 4 KO mice are exactly identical in the loss of all well recognized zone‐3 hepatocyte specific targets or are there specific differences since disruption of the pathway occurs at different levels. Likewise, since zonal expression of genes is thought to be dynamic, it is of high interest to determine if loss of zone‐3 target gene expression perturbs the expression of zone‐1 and zone‐2 genes and if that occurs uniformly and similarly in all 4 genetic KO models. Using single cell spatial transcriptomics with Molecular CartographyTM, we are querying the expression of one hundred zonated genes across the hepatic lobule involved in various functions. The current study will allow us to for the first time identify any differences in target genes of Wnt‐beta‐catenin, Wnt‐independent‐beta‐catenin‐dependent, and Wnt‐dependent‐beta‐catenin‐independent target genes. At the same time, we will be able to address if loss of zone‐3 genes in each of the 4 KO models also indirectly perturbs the expression of genes normally expressed in zone‐1 and zone‐2 of the liver. Such novel information will be critical to both liver biologists and pathologists who study alterations in metabolic zonation in many liver pathologies including fatty liver disease and cholestatic liver injury.