Project description:Mutated cells undergo changes in chromatin accessibility and gene expression, resulting in aberrant proliferation and differentiation, although how this occurs is unclear. HMGA1 chromatin regulators are abundant in stem cells and oncogenic in diverse tissues; however, their role in colon tumorigenesis is only beginning to emerge. Here, we uncover a previously unknown epigenetic program whereby HMGA1 amplifies Wnt signaling during colon tumorigenesis driven by inflammatory microbiota and/or Adenomatous polyposis coli (Apc) inactivation. Mechanistically, HMGA1 “opens” chromatin to up-regulate the stem cell regulator, Ascl2, and downstream Wnt effectors, promoting stem and Paneth-like cell states while depleting differentiated enterocytes. Loss of just one Hmga1 allele within colon epithelium restrains tumorigenesis and Wnt signaling driven by mutant Apc and inflammatory microbiota. However, HMGA1 deficiency has minimal effects in colon epithelium under homeostatic conditions. In human colon cancer cells, HMGA1 directly induces ASCL2 by recruiting activating histone marks. Silencing HMGA1 disrupts oncogenic properties, whereas re-expression of ASCL2 partially rescues these phenotypes. Further, HMGA1 and ASCL2 are co-expressed and up-regulated in human colorectal cancer. Together, our results establish HMGA1 as an epigenetic gatekeeper of Wnt signals and cell state under conditions of APC inactivation, illuminating HMGA1 as a potential therapeutic target in colon cancer.
Project description:Mutated cells undergo changes in chromatin accessibility and gene expression, resulting in aberrant proliferation and differentiation, although how this occurs is unclear. HMGA1 chromatin regulators are abundant in stem cells and oncogenic in diverse tissues; however, their role in colon tumorigenesis is only beginning to emerge. Here, we uncover a previously unknown epigenetic program whereby HMGA1 amplifies Wnt signaling during colon tumorigenesis driven by inflammatory microbiota and/or Adenomatous polyposis coli (Apc) inactivation. Mechanistically, HMGA1 “opens” chromatin to up-regulate the stem cell regulator, Ascl2, and downstream Wnt effectors, promoting stem and Paneth-like cell states while depleting differentiated enterocytes. Loss of just one Hmga1 allele within colon epithelium restrains tumorigenesis and Wnt signaling driven by mutant Apc and inflammatory microbiota. However, HMGA1 deficiency has minimal effects in colon epithelium under homeostatic conditions. In human colon cancer cells, HMGA1 directly induces ASCL2 by recruiting activating histone marks. Silencing HMGA1 disrupts oncogenic properties, whereas re-expression of ASCL2 partially rescues these phenotypes. Further, HMGA1 and ASCL2 are co-expressed and up-regulated in human colorectal cancer. Together, our results establish HMGA1 as an epigenetic gatekeeper of Wnt signals and cell state under conditions of APC inactivation, illuminating HMGA1 as a potential therapeutic target in colon cancer.
Project description:Wnt signals control three functions of intestinal crypts: maintenance of Lgr5 stem cells, proliferation of transit-amplifying daughters and formation of Paneth cells. Here, we study how the Wnt effector β-catenin/Tcf4 cooperates with the Wnt-activated transcription factor Ascl2 to control a stem cell transcription program. DNA elements that are co-occupied and synergistically regulated by Ascl2 and Tcf4 specifically map to stem cell genes. In vitro, Tcf4-/- mini-guts are rescued by Ascl2 expression, while Ascl2-/- organoids are rescued by Wnt signaling. A direct auto-activatory loop leads to an on/off expression pattern of Ascl2 with a threshold that depends on the previous state. Wnt/R-spondin1 activates this loop. This mechanism interprets Wnt levels in crypts and translates this continuous signal into a discrete Ascl2 âonâ or âoffâ decision. In turn Ascl2, together with β-catenin/Tcf, activates stem cell genes. Thus, Ascl2 forms a transcriptional 'stemness switch' that is both Wnt-responsive and Wnt-dependent Examination of Tcf4, B-catenin and Ascl2 DNA occupancy in murine intestinal organoids and human colorectal cancer cell lines *** Original raw files unavailable due to loss during backup ***
Project description:Wnt signals control three functions of intestinal crypts: maintenance of Lgr5 stem cells, proliferation of transit-amplifying daughters and formation of Paneth cells. Here, we study how the Wnt effector β-catenin/Tcf4 cooperates with the Wnt-activated transcription factor Ascl2 to control a stem cell transcription program. DNA elements that are co-occupied and synergistically regulated by Ascl2 and Tcf4 specifically map to stem cell genes. In vitro, Tcf4-/- mini-guts are rescued by Ascl2 expression, while Ascl2-/- organoids are rescued by Wnt signaling. A direct auto-activatory loop leads to an on/off expression pattern of Ascl2 with a threshold that depends on the previous state. Wnt/R-spondin1 activates this loop. This mechanism interprets Wnt levels in crypts and translates this continuous signal into a discrete Ascl2 “on” or “off” decision. In turn Ascl2, together with β-catenin/Tcf, activates stem cell genes. Thus, Ascl2 forms a transcriptional 'stemness switch' that is both Wnt-responsive and Wnt-dependent.
Project description:Wnt signals control three functions of intestinal crypts: maintenance of Lgr5 stem cells, proliferation of transit-amplifying daughters and formation of Paneth cells. Here, we study how the Wnt effector β-catenin/Tcf4 cooperates with the Wnt-activated transcription factor Ascl2 to control a stem cell transcription program. DNA elements that are co-occupied and synergistically regulated by Ascl2 and Tcf4 specifically map to stem cell genes. In vitro, Tcf4-/- mini-guts are rescued by Ascl2 expression, while Ascl2-/- organoids are rescued by Wnt signaling. A direct auto-activatory loop leads to an on/off expression pattern of Ascl2 with a threshold that depends on the previous state. Wnt/R-spondin1 activates this loop. This mechanism interprets Wnt levels in crypts and translates this continuous signal into a discrete Ascl2 “on” or “off” decision. In turn Ascl2, together with β-catenin/Tcf, activates stem cell genes. Thus, Ascl2 forms a transcriptional 'stemness switch' that is both Wnt-responsive and Wnt-dependent
Project description:Metabolic reprogramming is a typical feature of tumors, in which biological macromolecules and energy produced in abnormal metabolism meet the requirements of highly proliferative tumor cells and participate in multiple stages of tumor development. High mobility group A1 (HMGA1) is a structural transcription factor, which plays a carcinogenic role in regulating the transcription of oncogenes. Bioinformatics analysis showed that HMGA1 was overexpressed in human CRC. However, the mechanisms by which HMGA1 promotes the tumorigenesis of CRC remains unknown. Herein, we applied intestinal epithelium conditional knockout (Hmga1△IEC) and knock-in (Hmga1IEC-OE/+) mice of HMGA1 to induce CRC, and identified that HMGA1 promotes colorectal cancer growth by increasing lipid synthesis. Single-cell sequencing (scRNA seq) and immunohistochemical staining showed that HMGA1 was highly expressed in the epithelial cells of CRC. HMGA1 promoted the CRC cell proliferation and accelerated CRC development in HMGA1-knock-in (Hmga1IEC-OE/+) mice. Knockout of HMGA1 (Hmga1△IEC) in intestinal epithelial cells of mice reduced the lipid accumulation and inhibited the occurrence and development of CRC. We further characterized that HMGA1 upregulated the level of fatty acid synthase (FASN) through enhancing the transcriptional binding of sterol regulatory element-binding protein 1 (SREBP1) to the promoter of FASN, leading to an increase in lipid synthesis in intestinal epithelial cells. High fat diet (HFD) aggravated the malignant progression of CRC in Hmga1△IEC mice and reversed the inhibitory effect of HMGA1 depletion on CRC. Administration Orlistat (50 mg/kg), an inhibitor of FASN-mediated lipid synthesis, into Hmga1-knock-in (Hmga1IEC-OE/+) mice markedly reduced lipid accumulation in intestinal epithelial cells and decreased the tumorigenesis of CRC. Taken together, our data suggest that HMGA1 promotes the tumorigenesis of colorectal cancer by up-regulating FASN-mediated de novo fatty acid synthesis. Our findings provide strong evidence supporting therapeutic intervention of lipid accumulation for the prevention and treatment of CRC
Project description:Invasive trophoblast cells are critical to spiral artery remodeling in hemochorial placentation. Insufficient trophoblast invasion and vascular remodeling can lead to pregnancy disorders including preeclampsia, preterm birth, and intrauterine growth restriction. Previous studies in the mouse identified achaete-scute homolog 2 (ASCL2) as essential to extraembryonic development. We hypothesized that ASCL2 is a critical and conserved regulator of invasive trophoblast lineage development. In contrast to the mouse, the rat possesses deep intrauterine trophoblast cell invasion and spiral artery remodeling similar to human placentation. In this report, we investigated invasive/extravillous trophoblast (EVT) cell differentiation using human trophoblast stem (TS) cells and a loss-of-function mutant Ascl2 rat model. ASCL2 transcripts are expressed in the EVT column and junctional zone, which represent tissue sources of invasive trophoblast progenitor cells within human and rat placentation sites, respectively. Differentiation of human TS cells into EVT cells resulted in significant upregulation of ASCL2 and several other transcripts indicative of EVT cell differentiation. Disruption of ASCL2 impaired EVT cell differentiation as indicated by cell morphology and transcript profiles. RNA sequencing analysis of ASCL2-deficient trophoblast cells identified both downregulation of EVT cell-associated transcripts and upregulation of syncytiotrophoblast-associated transcripts, indicative of dual activating and repressing functions. ASCL2 deficiency in the rat impacted placental morphogenesis resulting in junctional zone dysgenesis and failed intrauterine trophoblast cell invasion. ASCL2 acts as a critical and conserved regulator of invasive trophoblast cell lineage development and a species-specific modulator of the syncytiotrophoblast lineage.