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A Point Mutation R122C in RUNX3 Promotes the Expansion of Isthmus Stem Cells and Inhibits Their Differentiation in the Stomach

ABSTRACT: Background & Aims: RUNX transcription factors play pivotal roles in embryonic development and neoplasia. We previously identified the single missense mutation R122C in RUNX3 from human gastric cancer. However, how RUNX3R122C mutation disrupts stem cell homeostasis and promotes gastric carcinogenesis remained unclear. Methods: To understand the oncogenic nature of this mutation in vivo, we generated the RUNX3R122C knock-in mice. Stomach tissues were harvested, followed by histological and immunofluorescence staining, organoid culture, flow cytometry to isolate gastric corpus isthmal and non-isthmal epithelial cells, and RNA extraction for transcriptomic analysis. Results: The corpus tissue of RUNX3R122C/R122C homozygous mice exhibited a precancerous phenotype such as spasmolytic polypeptide-expressing metaplasia (SPEM). We observed mucous neck cell hyperplasia, massive reduction of pit, parietal, and chief cell populations, as well as a dramatic increase in the number of rapidly proliferating isthmal stem/progenitor cells in the corpus of RUNX3R122C/R122C mice. Transcriptomic analyses of the isolated epithelial cells showed that the cell cycle-related MYC target gene signature was enriched in the corpus epithelial cells of RUNX3R122C/R122C mice compared with the wild-type corpus. Mechanistically, RUNX3R122C mutant protein disrupted the regulation of the restriction point where cells decide to enter either proliferative or quiescent state, thereby driving stem cell expansion and limiting the ability of cells to terminally differentiate. Conclusions: RUNX3R122C missense mutation is associated with the continuous cycling of isthmal stem/progenitor cells, maturation arrest and development of a precancerous state. This work highlights the importance of RUNX3 in prevention of metaplasia and gastric cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE190081 | GEO | 2021/12/05

REPOSITORIES: GEO

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Project description:Background & Aims: Metaplasia and dysplasia in the corpus are reportedly derived from dedifferentiation of chief cells. However, the cellular origin of metaplasia and cancer remained uncertain. Therefore, we investigated whether pepsinogen Ctranscript expressing cells (PGC-transcript expressing cells) represent the cellular origin of metaplasia and cancer using a novel Pgc-specific CreERT2 recombinase mouse model. Methods: We generated a Pgc-mCherry-IRES-CreERT2 (Pgc-CreERT2) knock-in mouse model. Pgc-CreERT2/+ and Rosa-EYFP mice were crossed to generate PgcCreERT2/Rosa-EYFP (Pgc-CreERT2/YFP) mice. Gastric tissues were collected, followed by lineage-tracing experiments, histological and immunofluorescence staining. We further established Pgc-CreERT2;Kras G12D/+ mice and investigated whether PGCtranscript expressing cells are responsible for the precancerous state in gastric glands. To investigate cancer development from PGC-transcript expressing cells with activated Kras, inactivated Apc and Trp53 signaling pathways, we crossed Pgc-CreERT2/+ mice with conditional KrasG12D , Apcflox , Trp53 flox mice. Results: Expectedly, mCherry mainly labeled chief cells in the Pgc-CreERT2 mice. However, mCherry was also detected throughout the neck cell and isthmal stem/progenitor regions, albeit at lower levels. In the Pgc-CreERT2;Kras G12D/+ mice, PGC-transcript expressing cells with Kras G12D/+ mutation presented pseudopyloric metaplasia. The early induction of proliferation at the isthmus may reflect the ability of isthmal progenitors to react rapidly to Pgc-driven Kras G12D/+ oncogenic mutation. Furthermore, Pgc-CreERT2;KrasG12D/+ ;Apc flox/flox mice presented intramucosal dysplasia/carcinoma, while Pgc-CreERT2;KrasG12D/+ ;Apcflox/flox ;Trp53 flox/flox mice presented invasive and metastatic gastric carcinoma. Conclusions: The Pgc-CreERT2 knock-in mouse is an invaluable tool to study the effects of successive oncogenic activation in the mouse corpus. Time-course observations can be made regarding the responses of isthmal and chief cells to oncogenic insults. We can observe stomach-specific tumorigenesis from the beginning to metastatic development.

Project description:Chronic infection with the bacterial pathogen Helicobacter pylori is a risk factor for the development of gastric cancer, yet remains asymptomatic in a majority of individuals. We report here that the C57Bl6 mouse model of experimental infection with the closely related H. felis recapitulates this wide range in host susceptibility. A majority of infected mice develop premalignant lesions such as gastric atrophy, compensatory epithelial hyperplasia and intestinal metaplasia, whereas a minority is completely protected from preneoplasia. Protection is associated with the failure to mount an IFN-gamma response to the infection and an associated high Helicobacter burden. We demonstrate that IFN-gamma is essential for clearance of Helicobacter, but also mediates the formation of preneoplastic lesions. We further provide evidence that IFN-gamma triggers a specific transcriptional program in murine gastric epithelial cells in vitro and in vivo, and induces their preferential transformation to the hyperplastic phenotype. In summary, our data suggest a dual role for IFN-gamma in Helicobacter pathogenesis that could provide an explanation for the differential susceptibility to H. pylori-induced gastric pathology in the human population. Keywords: response to in vitro stimulus / comparison of histopathological states We chose mice for gene expression profiling that following Helicobacter infection had (a) symptoms of gastritis, but no epithelial changes, (b) atrophic gastritis accompanied by corpus gland hyperplasia or (c) atrophic gastritis accompanied by intestinal metaplasia. An uninfected control group was also included in the analysis, as were two groups of mice that lacked mature T- and B-cells due to a deletion mutation in the rag1 gene (Rag-1-/-) and that were either experimentally infected or served as Rag-1-/- uninfected controls. To see the effects of IFNg on murine gastric epithelial cells we analysed an immortalized murine primary gastric epithelial cell line treated with three different concentrations of IFNg in comparison to an untreated control.

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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A Point Mutation R122C in RUNX3 Promotes the Expansion of Isthmus Stem Cells and Inhibits Their Differentiation in the Stomach

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