Wnt regulates cellular differentiation and retinoid metabolism genes in the mouse stomach.

Although recognized as a key regulator of gastrointestinal tissues, Wnt signaling pathway function in the stomach is poorly understood. This study aimed to define Wnt functions and identify Wnt-regulated genes in the stomach. Reporter mouse analysis localized Wnt signaling to the base and proliferative region in both the corpus and the antrum. Canonical Wnt inhibition in vivo using Sox2-CreERT2; Ctnnb1fl/fl mice reduced epithelial cell proliferation with loss of gastric stem cells. Wnt-regulated genes and potential effector pathways were studied by bulk RNA sequencing (RNA-Seq) analysis of corpus and antral organoids 24 h after Wnt inhibition in vitro. Cell signature analysis revealed that gastric organoids adopt a surface cell transcriptional profile following Wnt inhibition instead of a basal cell profile. Furthermore, retinoid metabolism terms were differentially expressed after Wnt inhibition, with decreased expression of retinoic acid target genes. Inhibition of retinoic acid signaling in corpus and antral organoids showed a marked increase in surface cell marker expression, consistent with the effects of Wnt inhibition. In the mouse, immunostaining showed differential localization of retinoid metabolic components in luminal pit cells (ALDH3A1) and basal chief/deep mucous cells (STRA6), with expression changes after β-catenin deletion in Sox2-CreERT2; Ctnnb1fl/fl mice, consistent with the Wnt-regulated cell fate changes observed in organoids. Together, these studies showed that Wnt signaling is required for gastric stem cell survival and promotes differentiation of cell types at the gland base. We identified retinoid metabolism as a candidate Wnt-regulated pathway, with cell-specific expression of key components, and regulation of surface cell marker expression by retinoic acid signaling.NEW & NOTEWORTHY Using mouse genetic and organoid models, we show that canonical Wnt signaling promotes gastric epithelial cell proliferation and regulates differentiation along the base-lumen gland axis in the stomach. Transcription profiling of Wnt-inhibited gastric organoids identified retinoic acid signaling as a potential Wnt-regulated effector pathway in the stomach. Accordingly, manipulation of retinoic acid signaling in organoids altered differentiated marker expression consistent with Wnt inhibition, supporting the presence of a Wnt-retinoic acid signaling axis in the stomach.