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Lymphatic endothelial cells, together with Rspo3+Grem1+ fibroblasts, support intestinal stem cells through the production of R-spondin3 in homeostasis and injury [scRNAseq]

ABSTRACT: Intestinal stem cells (ISCs) depend on niche factors for proper function. Here, we focus on RSPO3, an essential ISC niche factor, that engages the Lgr5 receptor on ISCs to potentiate WNT signaling, an interaction that is critical for maintaining intestinal stemness. Leveraging novel Rspo3-GFP and Grem1-tdTomato-CreERT2 genetically engineered mice together with single-cell mRNA profiling, we find that RSPO3 is expressed by lymphatic endothelial cells (LECs) and Rspo3+Grem1+ (RG) fibroblasts in the intestinal stroma where RG fibroblasts surround lymphatics and are in close proximity to Lgr5+ ISCs near the crypt base. Functionally, RG fibroblasts through the production of RSPO3 and GREM1 and LECs through the production of RSPO3 foster intestinal organoid propagation in vitro. Rspo3 loss in either or both of these niche cells in vivo compromises ISC numbers, villi length, and repair after irradiation-induced injury. Mechanistically, irradiation-induced damage expands LEC and RG fibroblast numbers and enhances the latters’ generation of RSPO3 through IL-1 receptor activation. We propose that LECs represent a novel component of the ISC niche, which together with RG fibroblasts, provide essential RSPO3 to sustain ISCs in homeostasis and regeneration.

ORGANISM(S): Mus musculus

PROVIDER: GSE185354 | GEO | 2022/09/08

REPOSITORIES: GEO

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Project description:Background & Aims: Hierarchical organization of intestine relies on their stem cells by self-renew and producing committed progenitors. Although signals like Wnt are known to animate the continued renewal by maintaining intestinal stem cells (ISCs) activity, molecular mechanisms especially E3 ubiquitin ligases that modulate ISCs ‘stemness’ and supportive niche have not been well understood. Here, we investigated the role of Cullin 4B (Cul4b) in regulating ISC functions. Methods: We generated mice with intestinal epithelial-specific disruption of Cul4b (pVillin-cre; Cul4bfn/Y), inducible disruption of Cul4b (Lgr5-creERT2; Cul4bfn/Y, CAG-creERT2; Cul4bfn/Y) and their control (Cul4bfn/Y). Intestinal tissues were analyzed by histology, immunofluorescence, RNA sequencing and mass spectrum. Intestinal organoids deprived from mice with pVillin-Cre; Cul4bfn/Y, Lgr5-Cre; Cul4bfn/Y, Tg-Cul4b and their controls were used in assays to measure intestinal self-renewal, proliferation and differentiation. Wnt signaling and intestinal markers were analyzed by immunofluorescence and immunoblot assays. Differential proteins upon Cul4b ablation or Cul4b-interacting proteins were identified by mass spectrometry. Results: Cul4b specifically located at ISCs zone. Block of Cul4b impaired intestinal homeostasis maintenance by reduced self-renewal and proliferation. Transcriptome analysis revealed that Cul4b-null intestine lose ISC characterization and showed disturbed ISC niche. Mechanistically, reactivated Wnt pathway could recover intestinal dysfunction of Cul4b knockout mice. Analysis of differential total and ubiquitylated proteins uncovered the novel targeting substrate of Cullin-Ring ubiquitin ligase 4b (CRL4b), immunity-related GTPase family M member 1 (Irgm1) in intestine. Decreased Irgm1 rescued abnormally interferon signaling, overemphasized autophagy and downstream phosphate proteins in Cul4b knockout mice. Conclusion: We conclude that Cul4b is essential for ISC self-renewal and Paneth cell function by targeting Irgm1 and modulating Wnt signaling. Our results demonstrate that Cul4b is a novel ISC stemness and niche regulator.

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Lymphatic endothelial cells, together with Rspo3+Grem1+ fibroblasts, support intestinal stem cells through the production of R-spondin3 in homeostasis and injury [scRNAseq]

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