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Compared gene expression profile of Lgr5-expressing and deficient stem cells in the intestine

ABSTRACT: The Lgr5 receptor is a marker of intestinal stem cells (ISCs) that regulates Wnt/b-catenin signaling. In this study, phenotype analysis of knockin/knockout Lgr5-eGFP-IRES-Cre and Lgr5-DTReGFP embryos revealed that Lgr5 deficiency during Wnt-mediated cytodifferentiation results in amplification of ISCs and early differentiation into Paneth cells, which can be counteracted by in utero treatment with the Wnt inhibitor LGK974. Conditional ablation of Lgr5 postnatally, but not in adults, altered stem cell fate towards the Paneth lineage. Together, these in vivo studies suggest that Lgr5 is part of a feedback loop to adjust the Wnt tone in ISCs. Moreover, transcriptome analyses revealed that Lgr5 controls fetal ISC maturation associated with acquisition of a definitive stable epithelial phenotype, that depends on the capacity of ISCs to generate their own extracellular matrix. Finally, using the ex vivo culture system, evidences are provided that Lgr5/Rspondin 2 interaction negatively regulates the pool of ISCs in organoids, revealing a sophisticated regulatory process for Wnt signaling in ISC.

ORGANISM(S): Mus musculus

PROVIDER: GSE135362 | GEO | 2020/05/29

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.

Project description:A detailed understanding of intestinal stem cell (ISC) self-renewal and differentiation is required for better treatment options for a variety of chronic intestinal diseases, however, current models of ISC lineage hierarchy and segregation are still under debate. Here we report the identification of Lgr5+ ISCs that express Flattop (Fltp), a Wnt/planar cell polarity (PCP) reporter and effector gene. Functional analysis and lineage tracing revealed that Wnt/PCP-activated Fltp+ ISCs are primed towards either the enteroendocrine or Paneth cell lineage in vivo, while retaining self-renewal and multi-lineage capacity in vitro. Surprisingly, canonical Wnt/beta-catenin- and non-canonical Wnt/PCP-activated Lgr5+ ISCs are indistinguishable by the expression of stem-cell signature or secretory lineage-specifying genes, suggesting that lineage priming and cell-cycle exit is triggered at the post-transcriptional level by polarity cues and a switch of canonical to non-canonical Wnt signalling. Pseudotemporal ordering of targeted single-cell gene expression data allowed us to delineate the ISC differentiation path into enteroendocrine and Paneth cells. Strikingly, both lineages are directly recruited from ISCs via unipotent transition states, excluding the existence of formerly predicted bi- or multipotent secretory progenitors. Transitory cells that mature into Paneth cells are defined by label-retention and co-expression of stem cell and secretory lineage genes, indicating that these cells are the previously described Lgr5+ label-retaining cells (LRCs). Taken together, we identified the Wnt/PCP pathway as a new niche signal and polarity cue regulating stem cell fate. Active Wnt/PCP signalling represents one of the earliest events in ISC lineage priming towards the Paneth and enteroendocrine cell fate, preceding lateral inhibition and expression of secretory lineage-specifying genes. Thus, our findings provide a better understanding of the niche signals and redefine the mechanisms underlying ISC lineage hierarchy and segregation. Here we establish the Wnt/Planar cell polarity (PCP) gene Flattop (Fltp) as a unique marker for intestinal LRCs and their distinct secretory fate. We show that Fltp+ cells are characterized by a combined stem cell and secretory gene signature. A subset of Fltp+ cells is classified by label-retention and predominantly locates at position +4, indicative of quiescent stem cells. Strikingly, Fltp+ LRCs are specified by Wnt/PCP signaling in contrast to actively cycling stem cells that rely on the canonical Wnt/β-catenin pathway. In mice with disturbed Wnt/PCP signaling, the differentiation of enteroendocrine cells from LRCs is impaired. These findings establish Fltp as a novel marker for intestinal LRCs and implicate Wnt/PCP signaling in cell-cycle exit and commitment of ISCs to the secretory lineage. Taken together, we not only provide a marker to study LRCs in homeostatic and diseased conditions, but also identify the Wnt/PCP signaling pathway as a therapeutic target for colorectal cancer and metabolic disease.

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Compared gene expression profile of Lgr5-expressing and deficient stem cells in the intestine

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