Proliferation of the self-renewing epithelium of the gastric corpus occurs almost exclusively in the isthmus of the glands, from where cells migrate bidirectionally toward pit and base. The isthmus ...is therefore generally viewed as the stem cell zone. We find that the stem cell marker Troy is expressed at the gland base by a small subpopulation of fully differentiated chief cells. By lineage tracing with a Troy-eGFP-ires-CreERT2 allele, single marked chief cells are shown to generate entirely labeled gastric units over periods of months. This phenomenon accelerates upon tissue damage. Troy+ chief cells can be cultured to generate long-lived gastric organoids. Troy marks a specific subset of chief cells that display plasticity in that they are capable of replenishing entire gastric units, essentially serving as quiescent “reserve” stem cells. These observations challenge the notion that stem cell hierarchies represent a “one-way street.”
Display omitted
•A subset of quiescent, differentiated chief cells express Troy•Troy+ chief cells can generate all differentiated lineages of the gastric epithelium•Troy+ chief cells act as “reserve” stem cells upon challenge of tissue homeostasis•Troy+ chief cells can initiate long-term in vitro cultures
Gastric chief cells expressing the marker Troy, although mature and differentiated, can re-enter the cell cycle and ultimately produce all cell lineages of the gastric epithelium, suggesting that they act as reserve stem cells.
The concept that tumors are maintained by dedicated stem cells, the so-called cancer stem cell hypothesis, has attracted great interest but remains controversial. Studying mouse models, we provide ...direct, functional evidence for the presence of stem cell activity within primary intestinal adenomas, a precursor to intestinal cancer. By "lineage retracing" using the multicolor Cre-reporter R26R-Confetti, we demonstrate that the crypt stem cell marker Lgr5 (leucine-rich repeat—containing heterotrimeric guanine nucleotide—binding protein—coupled receptor 5) also marks a subpopulation of adenoma cells that fuel the growth of established intestinal adenomas. These Lgr5 + cells, which represent about 5 to 10% of the cells in the adenomas, generate additional Lgr5 + cells as well as all other adenoma cell types. The Lgr5 + cells are intermingled with Paneth cells near the adenoma base, a pattern reminiscent of the architecture of the normal crypt niche.
The adenomatous polyposis coli (APC) tumor suppressor is mutated in the vast majority of human colorectal cancers (CRC) and leads to deregulated Wnt signaling. To determine whether Apc disruption is ...required for tumor maintenance, we developed a mouse model of CRC whereby Apc can be conditionally suppressed using a doxycycline-regulated shRNA. Apc suppression produces adenomas in both the small intestine and colon that, in the presence of Kras and p53 mutations, can progress to invasive carcinoma. In established tumors, Apc restoration drives rapid and widespread tumor-cell differentiation and sustained regression without relapse. Tumor regression is accompanied by the re-establishment of normal crypt-villus homeostasis, such that once aberrantly proliferating cells reacquire self-renewal and multi-lineage differentiation capability. Our study reveals that CRC cells can revert to functioning normal cells given appropriate signals and provide compelling in vivo validation of the Wnt pathway as a therapeutic target for treatment of CRC.
Display omitted
•Apc suppression in mouse colon recapitulates the molecular features of human CRC•Apc restoration triggers differentiation and restores crypt homeostasis•CRCs harboring Kras and p53 mutations remain strictly dependent on Apc loss•In vivo validation of the Wnt pathway as an effective therapeutic target in CRC
Colorectal cancer cells can revert to functioning normal cells in vivo when Apc levels are restored, even if potent oncogenic insults such as Kras and p53 mutations are present.
High-grade serous ovarian cancer (HG-SOC)-often referred to as a "silent killer"-is the most lethal gynecological malignancy. The fallopian tube (murine oviduct) and ovarian surface epithelium (OSE) ...are considered the main candidate tissues of origin of this cancer. However, the relative contribution of each tissue to HG-SOC is not yet clear. Here, we establish organoid-based tumor progression models of HG-SOC from murine oviductal and OSE tissues. We use CRISPR-Cas9 genome editing to introduce mutations into genes commonly found mutated in HG-SOC, such as Trp53, Brca1, Nf1 and Pten. Our results support the dual origin hypothesis of HG-SOC, as we demonstrate that both epithelia can give rise to ovarian tumors with high-grade pathology. However, the mutated oviductal organoids expand much faster in vitro and more readily form malignant tumors upon transplantation. Furthermore, in vitro drug testing reveals distinct lineage-dependent sensitivities to the common drugs used to treat HG-SOC in patients.
The concept of ‘field cancerization’ describes the clonal expansion of genetically altered, but morphologically normal cells that predisposes a tissue to cancer development. Here, we demonstrate that ...biased stem cell competition in the mouse small intestine can initiate the expansion of such clones. We quantitatively analyze how the activation of oncogenic K‐ras in individual Lgr5+ stem cells accelerates their cell division rate and creates a biased drift towards crypt clonality. K‐ras mutant crypts then clonally expand within the epithelium through enhanced crypt fission, which distributes the existing Paneth cell niche over the two new crypts. Thus, an unequal competition between wild‐type and mutant intestinal stem cells initiates a biased drift that leads to the clonal expansion of crypts carrying oncogenic mutations.
Synopsis
The fate of normal intestinal stem cells is determined through neutral competition. This study shows that when oncogenic K‐Ras mutations arise, biased stem cell competition leads to a drift towards mutant crypt expansion that could be the underlying cause of field cancerization.
Lgr5+ intestinal stem cells obtain a competitive advantage by oncogenic K‐ras mutations
Unequal stem cell competition will induce a biased drift towards crypt clonality
Cancer prone mutations can clonally expand by crypt fission
The fate of normal intestinal stem cells is determined through neutral competition. This study shows that when oncogenic K‐Ras mutations arise, biased stem cell competition leads to a drift towards mutant crypt expansion that could be the underlying cause of field cancerization.
The deubiquitinating enzyme BAP1 is a tumor suppressor, among others involved in cholangiocarcinoma. BAP1 has many proposed molecular targets, while its Drosophila homolog is known to deubiquitinate ...histone H2AK119. We introduce BAP1 loss-of-function by CRISPR/Cas9 in normal human cholangiocyte organoids. We find that BAP1 controls the expression of junctional and cytoskeleton components by regulating chromatin accessibility. Consequently, we observe loss of multiple epithelial characteristics while motility increases. Importantly, restoring the catalytic activity of BAP1 in the nucleus rescues these cellular and molecular changes. We engineer human liver organoids to combine four common cholangiocarcinoma mutations (TP53, PTEN, SMAD4, and NF1). In this genetic background, BAP1 loss results in acquisition of malignant features upon xenotransplantation. Thus, control of epithelial identity through the regulation of chromatin accessibility appears to be a key aspect of BAP1’s tumor suppressor function. Organoid technology combined with CRISPR/Cas9 provides an experimental platform for mechanistic studies of cancer gene function in a human context.
Display omitted
•BAP1 loss affects cell polarity and epithelial organization in human liver tissue•BAP1 controls chromatin accessibility of junctional and cytoskeletal genes•Rescuing BAP1 catalytic activity in the nucleus restores epithelial organization•In an engineered human cancer model, malignant features are induced upon BAP1 loss
Artegiani et al. show that BAP1 mutation in human liver organoids coincides with loss of multiple epithelial characteristics through impairment of chromatin accessibility and gene expression, and this is critical for the acquisition of malignant features in a human model of cholangiocarcinoma.
Most studies on TCF7L2 SNP variants in the pathogenesis of type 2 diabetes (T2D) focus on a role of the encoded transcription factor TCF4 in β cells. Here, a mouse genetics approach shows that ...removal of TCF4 from β cells does not affect their function, whereas manipulating TCF4 levels in the liver has major effects on metabolism. In Tcf7l2−/− mice, the immediate postnatal surge in liver metabolism does not occur. Consequently, pups die due to hypoglycemia. By combining chromatin immunoprecipitation with gene expression profiling, we identify a TCF4-controlled metabolic gene program that is acutely activated in the postnatal liver. In concordance, adult liver-specific Tcf7l2 knockout mice show reduced hepatic glucose production during fasting and display improved glucose homeostasis when maintained on high-fat diet. Furthermore, liver-specific TCF4 overexpression increases hepatic glucose production. These observations imply that TCF4 directly activates metabolic genes and that inhibition of Wnt signaling may be beneficial in metabolic disease.
Display omitted
► Wnt/TCF4 regulates metabolic genes in postnatal and adult liver directly ► TCF4-dependend metabolic program is activated under situations of metabolic demand ► Among other metabolic processes, TCF4 regulates hepatic glucose production
SNPs in TCF7L2, encoding the Wnt effector TCF4, are the strongest genetic risk factors for type 2 diabetes, but surprisingly, the metabolic functions of this protein, as determined in mice, take place in the liver, not in the pancreas.
Intestinal crypts display robust regeneration upon injury. The relatively rare secretory precursors can replace lost stem cells, but it is unknown if the abundant enterocyte progenitors that express ...the Alkaline phosphate intestinal (Alpi) gene also have this capacity. We created an Alpi-IRES-CreERT2 (AlpiCreER) knockin allele for lineage tracing. Marked clones consist entirely of enterocytes and are all lost from villus tips within days. Genetic fate-mapping of Alpi+ cells before or during targeted ablation of Lgr5-expressing stem cells generated numerous long-lived crypt-villus “ribbons,” indicative of dedifferentiation of enterocyte precursors into Lgr5+ stems. By single-cell analysis of dedifferentiating enterocytes, we observed the generation of Paneth-like cells and proliferative stem cells. We conclude that the highly proliferative, short-lived enterocyte precursors serve as a large reservoir of potential stem cells during crypt regeneration.
Display omitted
•Enterocytes in intestinal crypts can dedifferentiate to replace lost Lgr5+ stem cells•Dedifferentiating enterocytes generate proliferative stem cells and Paneth-like cells•Enterocytes with Apc/Kras mutations do not form tumors in vivo•“Stemness” in intestinal crypts is not “hard-wired”
In this article, Tetteh et al. show that enterocyte-lineage progenitors can become stem cells during intestinal regeneration. Additionally, these cells generate Paneth-like cells and turn on genes that promote recovery from injury. In sum, “stemness” in intestinal crypts is not “hard-wired;” many progenitors can regain stemness upon loss of the actual stem cells.
Leucine-rich repeat-containing G-protein coupled receptor 5-positive (Lgr5⁺) stem cells reside at crypt bottoms of the small and large intestine. Small intestinal Paneth cells supply Wnt3, EGF, and ...Notch signals to neighboring Lgr5⁺ stem cells. Whereas the colon lacks Paneth cells, deep crypt secretory (DCS) cells are intermingled with Lgr5⁺ stem cells at crypt bottoms. Here, we report regenerating islet-derived family member 4 (Reg4) as a marker of DCS cells. To investigate a niche function, we eliminated DCS cells by using the diphtheria-toxin receptor gene knocked into the murine Reg4 locus. Ablation of DCS cells results in loss of stem cells from colonic crypts and disrupts gut homeostasis and colon organoid growth. In agreement, sorted Reg4⁺ DCS cells promote organoid formation of single Lgr5⁺ colon stem cells. DCS cells can be massively produced from Lgr5⁺ colon stem cells in vitro by combined Notch inhibition and Wnt activation. We conclude that Reg4⁺ DCS cells serve as Paneth cell equivalents in the colon crypt niche.
The stem cell niche is a specialized environment that dictates stem cell function during development and homeostasis. We show that Dll1, a Notch pathway ligand, is enriched in mammary gland stem ...cells (MaSCs) and mediates critical interactions with stromal macrophages in the surrounding niche in mouse models. Conditional deletion of Dll1 reduced the number of MaSCs and impaired ductal morphogenesis in the mammary gland. Moreover, MaSC-expressed Dll1 activates Notch signaling in stromal macrophages, increasing their expression of Wnt family ligands such as Wnt3, Wnt10A, and Wnt16, thereby initiating a feedback loop that promotes the function of Dll1-expressing MaSCs. Together, these findings reveal functionally important cross-talk between MaSCs and their macrophageal niche through Dll1-mediated Notch signaling.
PDF
