While 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 corpus and antrum. Canonical Wnt inhibition in vivo using Sox2-CreER T2 ; Ctnnb1 fl/fl mice reduced epithelial cell proliferation with loss of gastric stem cells. Wnt-regulated genes and potential effector pathways were studied by bulk RNAseq analysis of corpus and antral organoids 24 hours 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 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-CreER T2 ; Ctnnb1 fl/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.
Delgado et al. (Thu,) studied this question.