Project description:We previously demonstrated that SRCAP regulates the self-renewal of ESCs and modulates lymphoid lineage commitment. We further validated that SRCAP was mainly distributed in liver, spleen and intestine by Northern blot. SRCAP was also highly expressed in Lgr5+ ISCs. We then sought to explore the physiological role of SRCAP in the regulation of self-renewal maintenance of ISCs.We identified that Srcap deficiency impairs the self-renewal of ISCs and intestinal epithelial regeneration. Through SRCAP ChIP-sequencing, we sough to identify the key gene regulated by SRCAP in ISC self-renewal.
Project description:We previously demonstrated that SRCAP regulates the self-renewal of ESCs and modulates lymphoid lineage commitment. We further validated that SRCAP was mainly distributed in liver, spleen and intestine by Northern blot. SRCAP was also highly expressed in Lgr5+ ISCs. We then sought to explore the physiological role of SRCAP in the regulation of self-renewal maintenance of ISCs.We then generated Srcapflox/flox mice through insertion of loxP sequences flanking at the exon5 of Srcap gene locus. We established Srcapflox/flox;Lgr5GFP-CreERT2 mice through crossing Srcapflox/flox mice with Lgr5GFP-CreERT2 mice. With administration of tamoxifen (TAM), Srcap was completely deleted in Lgr5+ ISCs. We identified that Srcap deficiency impairs the self-renewal of ISCs and intestinal epithelial regeneration. Through RNA-sequencing, we sough to identify the key gene regulated by SRCAP in ISC self-renewal.
Project description:Shavenbaby (Svb) transcription factor is involved in the differenciation of epidermal cells and the homeostasis of intestinal stem cells (ISCs). Svb is produced as a long repressor protein called SvbRepressor (SvbREP). In presence of Pri peptides SvbREP is processed into a shorter activator form (SvbACT) through partial proteasomal degradation of the REP domain. In ISCs, Pri triggers SvbREP to ACT maturation, while SvbREP form accumulates in differentiated enterocytes. The absence of Svb promote the apoptosis of the intestinal stem cells. In ISC, the ectopic expression of SvbREP form promote the differenciation and the SvbACT form overexpression promotes hyperplasia. (Al Hayel, et al 2020) Based on these functional analyses, Svb appears to control ISC survival and behavior, balancing proliferation and differentiation through a molecular switch between its 2 antagonistic isoforms. In this study, we determine the Svb target genes in ISCs. To this aim, we analyze the transcriptomes of ISCs upon modulation of Svb function.
Project description:To examine whether IRF2, a negative regulator of IFN signaling, constitutively represses IFN signaling by binding IFN-inducible gene loci in ISCs, we performed a genome-wide chromatin immunoprecipitation/DNA sequencing (ChIP-Seq) analysis of IRF2 in Lgr5 ISCs. We identified 381 binding peaks in these cells, including well-known IFN-inducible genes. Motif analysis showed significant enrichment of consensus-binding motifs for IRF transcription factors within these peaks. Within IRF2-occupied genes in ISCs, we identified 204 of experimentally validated IFN-inducible genes from Interferome database, and 10.8% of them were overlapped with the genes upregulated by type I IFN stimulation in ISCs. These findings indicated for the first time that IRF2 constitutively bound and repressed the sterile IFN signaling at the level of ISCs.
Project description:The small intestine is a rapidly proliferating organ that is maintained by a small population of Lgr5-expressing intestinal stem cells (ISCs). However, several Lgr5-negative ISC populations have been identified, and this remarkable plasticity allows the intestine to rapidly respond to both the local environment and to damage. The mediators of such plasticity are still largely unknown. Using intestinal organoids and mouse models, we show that upon ribosome impairment (driven by Rptor deletion, amino acid starvation, or low dose cyclohexamide treatment) ISCs gain an Lgr5-negative, fetal-like identity. This is accompanied by a rewiring of metabolism. Our findings suggest that the ribosome can act as a sensor of nutrient availability, allowing ISCs to respond to the local nutrient environment. Mechanistically, we show that this phenotype requires the activation of ZAKɑ, which in turn activates YAP, via SRC. Together, our data reveals a central role for ribosome dynamics in intestinal stem cells, and identify the activation of ZAKɑ as a critical mediator of stem cell identity.
Project description:Intestinal epithelial stem cells (ISCs) are the focus of recent intense study. Current in vitro models rely on supplementation with the Wnt agonist R-spondin1 to support robust growth, ISC self-renewal, and differentiation. Intestinal subepithelial myofibroblasts (ISEMFs) are important supportive cells within the ISC niche. We hypothesized that co-culture with ISEMF enhances the growth of ISCs in vitro and allows for their successful in vivo implantation and engraftment. ISC-containing small intestinal crypts, FACS-sorted single ISCs, and ISEMFs were procured from C57BL/6 mice. Crypts and single ISCs were grown in vitro into enteroids, in the presence or absence of ISEMFs. ISEMFs enhanced the growth of intestinal epithelium in vitro in a proximity-dependent fashion, with co-cultures giving rise to larger enteroids than monocultures. Co-culture of ISCs with supportive ISEMFs relinquished the requirement of exogenous R-spondin1 to sustain long-term growth and differentiation of ISCs. Mono- and co-cultures were implanted subcutaneously in syngeneic mice. Co-culture with ISEMFs proved necessary for successful in vivo engraftment and proliferation of enteroids; implants without ISEMFs did not survive. ISEMF whole transcriptome sequencing and qPCR demonstrated high expression of specific R-spondins, well-described Wnt agonists that supports ISC growth. Specific non-supportive ISEMF populations had reduced expression of R-spondins. The addition of ISEMFs in intestinal epithelial culture therefore recapitulates a critical element of the intestinal stem cell niche and allows for its experimental interrogation and biodesign-driven manipulation. Two samples of intestinal subepithelial myofibroblasts were used in this study.
Project description:Perturbed intestinal epithelial homeostasis demonstrated as decreased Lgr5+ intestinal stem cells (Lgr5 ISCs) and increased secretory lineages were observed in our study where Lkb1 was specfically deleted in Lgr5 ISCs using Lgr5-EGFP-creERT2 (Tamoxifen) deletor. To gain mechanistic insight how Lkb1 maintains intestinal epithelial stem cell homeostasis, Lkb1 deficient ISCs (Lgr5-high cells) and progenitors (Lgr5-low cells) are isolated by flow cytometry and profiled by RNA sequencing to compare with controls (Lkb1 wild type ISCs and progenitors).