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The Iqgap3-Ras axis drives stem cell proliferation in the stomach corpus during homeostasis and repair [SMART-SeqII]

ABSTRACT: Objective: Tissue stem cells are central regulators of organ homeostasis. We looked for a protein that is exclusively expressed and functionally involved in stem cell activity in rapidly proliferating isthmus stem cells in the stomach corpus. Design: We uncovered the specific expression of Iqgap3 in proliferating isthmus stem cells through immunofluorescence and in situ hybridization. We performed lineage tracing and transcriptomic analysis of Iqgap3+ isthmus stem cells with the Iqgap3-2A-tdTomato mouse model. Depletion of Iqgap3 revealed its functional importance in maintenance and proliferation of stem cells. We further studied Iqgap3 expression and the associated gene expression changes during tissue repair after tamoxifen-induced damage. Immunohistochemistry revealed elevated expression of Iqgap3 in proliferating regions of gastric tumors from patient samples. Results: Iqgap3 is a highly specific marker of proliferating isthmus stem cells during homeostasis. Iqgap3+ isthmus stem cells give rise to major cell types of the corpus unit. Iqgap3 expression is essential for the maintenance of stem potential. The Ras pathway is a critical partner of Iqgap3 in promoting strong proliferation in isthmus stem cells. The robust induction of Iqgap3 expression following tissue damage indicates an active role for Iqgap3 in tissue regeneration. Conclusion: IQGAP3 is a major regulator of stomach epithelial tissue homeostasis and repair. The upregulation of IQGAP3 in gastric cancer suggests that IQGAP3 plays an important role in cancer cell proliferation.

ORGANISM(S): Mus musculus

PROVIDER: GSE161443 | GEO | 2021/03/08

REPOSITORIES: GEO

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Project description:The glandular stomach is comprised of two anatomically and functionally distinct epithelial tissues termed corpus and antrum. While these compartments continuously regenerate to ensure normal organ function, our understanding of the molecular and cellular determinants that maintain these tissues remains incomplete. Here, we established an unbiased account of all gastric epithelial cells of the mouse corpus and antrum using single cell RNA-sequencing, allowing us to compare these adjacent epithelia and their stem cell compartments. Our data reveals that epithelial cell types with equivalent functional roles in the corpus and antrum utilize similar transcriptional programs, and our results support the existence of two discernible stem cell populations within the gland base and isthmus regions of these tissues. To study isthmus stem cells, typically underrepresented in conventional, gland base-enriched organoid cultures, we developed a novel 2D monolayer culture system to propagate mouse and human gastric epithelia. These 2D cultures expand indefinitely via Lgr5- isthmus-like cells and maintain the ability to differentiate into diverse gastric cell types. While 2D corpus and antrum cultures were transcriptionally similar, they retained a molecular memory and differentiation bias that mirrored their tissue of origin. Furthermore, gastric 2D cultures could be readily and reversibly converted into conventional 3D organoids, highlighting the remarkable plasticity of undifferentiated stomach epithelial cells. Finally, we utilized the 2D culture system to show that rare primary epithelial cells with high levels of Sox2 expression, previously hypothesized to be gastric stem cells, most closely resembled enterochromaffin (EC) cells and Sox2 is both necessary and sufficient to generate EC cells in vivo. Together, our data (i) provide important insights into the basis of gastric epithelial regeneration and differentiation, (ii) establish a tractable 2D culture system to capture and manipulate primary gastric isthmus stem cells in vitro and (iii) uncover a role for the stem cell factor Sox2 during EC cell specification.

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The Iqgap3-Ras axis drives stem cell proliferation in the stomach corpus during homeostasis and repair [SMART-SeqII]

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