Transcriptional corepressor MTG16 regulates small intestinal crypt proliferation and crypt regeneration after radiation-induced injury

Myeloid translocation genes (MTGs) are transcriptional corepressors implicated in development, malignancy, differentiation, and stem cell function. While MTG16 loss renders mice sensitive to chemical colitis, the role of MTG16 in the small intestine is unknown. Histological examination revealed that Mtg16 −/− mice have increased enterocyte proliferation and goblet cell deficiency. After exposure to radiation, Mtg16 −/− mice exhibited increased crypt viability and decreased apoptosis compared with wild-type (WT) mice. Flow cytometric and immunofluorescence analysis of intestinal epithelial cells for phospho-histone H2A.X also indicated decreased DNA damage and apoptosis in Mtg16 −/− intestines. To determine if Mtg16 deletion affected epithelial cells in a cell-autonomous fashion, intestinal crypts were isolated from Mtg16 −/− mice. Mtg16 −/− and WT intestinal crypts showed similar enterosphere forming efficiencies when cultured in the presence of EGF, Noggin, and R-spondin. However, when Mtg16 −/− crypts were cultured in the presence of Wnt3a, they demonstrated higher enterosphere forming efficiencies and delayed progression to mature enteroids. Mtg16 −/− intestinal crypts isolated from irradiated mice exhibited increased survival compared with WT intestinal crypts. Interestingly, Mtg16 expression was reduced in a stem cell-enriched population at the time of crypt regeneration. This is consistent with MTG16 negatively regulating regeneration in vivo. Taken together, our data demonstrate that MTG16 loss promotes radioresistance and impacts intestinal stem cell function, possibly due to shifting cellular response away from DNA damage-induced apoptosis and towards DNA repair after injury.

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Apoptosis and DNA damage in type 2 alveolar epithelial cells cultured from hyperoxic rats

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1998.274.5.l714 ◽

1998 ◽

Vol 274 (5) ◽

pp. L714-L720 ◽

Cited By ~ 34

Author(s):

Sue Buckley ◽

Lora Barsky ◽

Barbara Driscoll ◽

Kenneth Weinberg ◽

Kathryn D. Anderson ◽

...

Keyword(s):

Dna Damage ◽

Epithelial Cells ◽

Cellular Response ◽

Ex Vivo ◽

Keratinocyte Growth Factor ◽

Alveolar Epithelial Cells ◽

Alveolar Epithelial ◽

Dna Laddering

Apoptosis is a genetically controlled cellular response to developmental stimuli and environmental insult that culminates in cell death. Sublethal hyperoxic injury in rodents is characterized by a complex but reproducible pattern of lung injury and repair during which the alveolar surface is damaged, denuded, and finally repopulated by type 2 alveolar epithelial cells (AEC2). Postulating that apoptosis might occur in AEC2 after hyperoxic injury, we looked for the hallmarks of apoptosis in AEC2 from hyperoxic rats. A pattern of increased DNA end labeling, DNA laddering, and induction of p53, p21, and Bax proteins, strongly suggestive of apoptosis, was seen in AEC2 cultured from hyperoxic rats when compared with control AEC2. In contrast, significant apoptosis was not detected in freshly isolated AEC2 from oxygen-treated rats. Thus the basal culture conditions appeared to be insufficient to ensure the ex vivo survival of AEC2 damaged in vivo. The oxygen-induced DNA strand breaks were blocked by the addition of 20 ng/ml of keratinocyte growth factor (KGF) to the culture medium from the time of plating and were partly inhibited by Matrigel or a soluble extract of Matrigel. KGF treatment resulted in a partial reduction in the expression of the p21, p53, and Bax proteins but had no effect on DNA laddering. We conclude that sublethal doses of oxygen in vivo cause damage to AEC2, resulting in apoptosis in ex vivo culture, and that KGF can reduce the oxygen-induced DNA damage. We speculate that KGF plays a role as a survival factor in AEC2 by limiting apoptosis in the lung after acute hyperoxic injury.

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Telomerase reverse transcriptase protects ATM-deficient hematopoietic stem cells from ROS-induced apoptosis through a telomere-independent mechanism

Blood ◽

10.1182/blood-2010-08-297390 ◽

2011 ◽

Vol 117 (16) ◽

pp. 4169-4180 ◽

Cited By ~ 41

Author(s):

Eriko Nitta ◽

Masayuki Yamashita ◽

Kentaro Hosokawa ◽

MingJi Xian ◽

Keiyo Takubo ◽

...

Keyword(s):

Stem Cell ◽

Reverse Transcriptase ◽

Cell Function ◽

Accelerated Aging ◽

Telomerase Reverse Transcriptase ◽

Protective Mechanisms ◽

Hematopoietic Stem ◽

Induced Apoptosis ◽

Deficient Mice

Abstract Telomerase reverse transcriptase (TERT) contributes to the prevention of aging by a largely unknown mechanism that is unrelated to telomere lengthening. The current study used ataxia-telangiectasia mutated (ATM) and TERT doubly deficient mice to evaluate the contributions of 2 aging-regulating molecules, TERT and ATM, to the aging process. ATM and TERT doubly deficient mice demonstrated increased progression of aging and had shorter lifespans than ATM-null mice, while TERT alone was insufficient to affect lifespan. ATM-TERT doubly null mice show in vivo senescence, especially in hematopoietic tissues, that was dependent on p16INK4a and p19ARF, but not on p21. As their HSCs show decreased stem cell activities, accelerated aging seen in these mice has been attributed to impaired stem cell function. TERT-deficient HSCs are characterized by reactive oxygen species (ROS) fragility, which has been suggested to cause stem cell impairment during aging, and apoptotic HSCs are markedly increased in these mice. p38MAPK activation was indicated to be partially involved in ROS-induced apoptosis in TERT-null HSCs, and BCL-2 is suggested to provide a part of the protective mechanisms of HSCs by TERT. The current study demonstrates that TERT mitigates aging by protecting HSCs under stressful conditions through telomere length-independent mechanisms.

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Doxorubicin Induces Senescence in Intestinal Epithelial Cells

10.1101/2021.01.29.428764 ◽

2021 ◽

Author(s):

Mandy Biraud ◽

Jocsa Cortes ◽

Paul Cray ◽

Guy Kunzmann ◽

Javid Mohammed ◽

...

Keyword(s):

Dna Damage ◽

Epithelial Cells ◽

Intestinal Epithelial Cells ◽

Cell Types ◽

Intestinal Epithelial ◽

Homogeneous Population ◽

Doxorubicin Treatment ◽

Induced Apoptosis

AbstractDoxorubicin treatment induces DNA damage and apoptosis in rapidly dividing cell types like intestinal epithelial cells. This has been demonstrated both in vivo and in vitro. In certain cell types some cells do not undergo DNA damage-induced apoptosis in response to doxorubicin but instead become senescent. Induction of senescence in these cells can lead to dysfunction and chronic inflammation, which can lead to more damage. We questioned whether a single dose of doxorubicin would be able to induce apoptosis and senescence in intestinal epithelial cells in vitro. For these studies, we exposed IEC-6 small intestinal epithelial cells to doxorubicin to evaluate whether senescence is induced in a relatively homogeneous population of intestinal epithelial cells. Although some cells underwent apoptosis, those that did not showed traits of senescence. Our studies showed that doxorubicin treatment increased cell size and increased expression of senescence-associated β-galactosidase. Concomitantly, we observed increased mRNA expression of several genes associated with a senescence-associated secretory phenotype including IL-6, Ptges, Faim2, and Cdkn1a and decreased expression of Sirt1. We also observed release of HMGB1, a cellular alarmin, from treated cells. Together, these data suggest that doxorubicin induces senescence in intestinal epithelial cells. Furthermore, our data indicate that cellular responses to a DNA damaging agent, such as doxorubicin, can differ within a population of cells suggesting differing levels of sensitivity within a relatively homogenous cell population. Further studies are needed to delineate the mechanisms that determine whether a cell moves down an apoptotic or senescent pathway following DNA damage.

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Set1 Targets Genes with Essential Identity and Tumor-Suppressing Functions in Planarian Stem Cells

Genes ◽

10.3390/genes12081182 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1182

Author(s):

Prince Verma ◽

Court K. M. Waterbury ◽

Elizabeth M. Duncan

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Mammalian Cells ◽

Cell Function ◽

Genotoxic Stress ◽

Specific Gene ◽

Cell Identity ◽

Chromatin Signature ◽

Lysine Methyltransferase

Tumor suppressor genes (TSGs) are essential for normal cellular function in multicellular organisms, but many TSGs and tumor-suppressing mechanisms remain unknown. Planarian flatworms exhibit particularly robust tumor suppression, yet the specific mechanisms underlying this trait remain unclear. Here, we analyze histone H3 lysine 4 trimethylation (H3K4me3) signal across the planarian genome to determine if the broad H3K4me3 chromatin signature that marks essential cell identity genes and TSGs in mammalian cells is conserved in this valuable model of in vivo stem cell function. We find that this signature is indeed conserved on the planarian genome and that the lysine methyltransferase Set1 is largely responsible for creating it at both cell identity and putative TSG loci. In addition, we show that depletion of set1 in planarians induces stem cell phenotypes that suggest loss of TSG function, including hyperproliferation and an abnormal DNA damage response (DDR). Importantly, this work establishes that Set1 targets specific gene loci in planarian stem cells and marks them with a conserved chromatin signature. Moreover, our data strongly suggest that Set1 activity at these genes has important functional consequences both during normal homeostasis and in response to genotoxic stress.

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Loss of FancC Function Results in Decreased Hematopoietic Stem Cell Repopulating Ability

Blood ◽

10.1182/blood.v94.1.1.413k03_1_8 ◽

1999 ◽

Vol 94 (1) ◽

pp. 1-8 ◽

Cited By ~ 114

Author(s):

Laura S. Haneline ◽

Troy A. Gobbett ◽

Rema Ramani ◽

Madeleine Carreau ◽

Manuel Buchwald ◽

...

Keyword(s):

Stem Cell ◽

Hematopoietic Stem Cell ◽

Cell Function ◽

Genetic Disorder ◽

Test Cell ◽

Hematopoietic Stem ◽

Murine Homologue ◽

Complex Genetic Disorder

Fanconi anemia (FA) is a complex genetic disorder characterized by progressive bone marrow (BM) aplasia, chromosomal instability, and acquisition of malignancies, particularly myeloid leukemia. We used a murine model containing a disruption of the murine homologue ofFANCC (FancC) to evaluate short- and long-term multilineage repopulating ability of FancC −/− cells in vivo. Competitive repopulation assays were conducted where “test”FancC −/− or FancC +/+ BM cells (expressing CD45.2) were cotransplanted with congenic competitor cells (expressing CD45.1) into irradiated mice. In two independent experiments, we determined that FancC −/− BM cells have a profound decrease in short-term, as well as long-term, multilineage repopulating ability. To determine quantitatively the relative production of progeny cells by each test cell population, we calculated test cell contribution to chimerism as compared with 1 × 105 competitor cells. We determined that FancC −/− cells have a 7-fold to 12-fold decrease in repopulating ability compared with FancC +/+cells. These data indicate that loss of FancC function results in reduced in vivo repopulating ability of pluripotential hematopoietic stem cells, which may play a role in the development of the BM failure in FA patients. This model system provides a powerful tool for evaluation of experimental therapeutics on hematopoietic stem cell function.

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hSSB2 (NABP1) is required for the recruitment of RPA during the cellular response to DNA UV damage

Scientific Reports ◽

10.1038/s41598-021-99355-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Didier Boucher ◽

Ruvini Kariawasam ◽

Joshua Burgess ◽

Adrian Gimenez ◽

Tristan E. Ocampo ◽

...

Keyword(s):

Dna Damage ◽

Cellular Response ◽

Excision Repair ◽

Protein A ◽

Ultraviolet B ◽

Repair System ◽

Uvb Radiation ◽

Exogenous Dna

AbstractMaintenance of genomic stability is critical to prevent diseases such as cancer. As such, eukaryotic cells have multiple pathways to efficiently detect, signal and repair DNA damage. One common form of exogenous DNA damage comes from ultraviolet B (UVB) radiation. UVB generates cyclobutane pyrimidine dimers (CPD) that must be rapidly detected and repaired to maintain the genetic code. The nucleotide excision repair (NER) pathway is the main repair system for this type of DNA damage. Here, we determined the role of the human Single-Stranded DNA Binding protein 2, hSSB2, in the response to UVB exposure. We demonstrate that hSSB2 levels increase in vitro and in vivo after UVB irradiation and that hSSB2 rapidly binds to chromatin. Depletion of hSSB2 results in significantly decreased Replication Protein A (RPA32) phosphorylation and impaired RPA32 localisation to the site of UV-induced DNA damage. Delayed recruitment of NER protein Xeroderma Pigmentosum group C (XPC) was also observed, leading to increased cellular sensitivity to UVB. Finally, hSSB2 was shown to have affinity for single-strand DNA containing a single CPD and for duplex DNA with a two-base mismatch mimicking a CPD moiety. Altogether our data demonstrate that hSSB2 is involved in the cellular response to UV exposure.

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Fully reduced HMGB1 accelerates the regeneration of multiple tissues by transitioning stem cells to GAlert

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1802893115 ◽

2018 ◽

Vol 115 (19) ◽

pp. E4463-E4472 ◽

Cited By ~ 46

Author(s):

Geoffrey Lee ◽

Ana Isabel Espirito Santo ◽

Stefan Zwingenberger ◽

Lawrence Cai ◽

Thomas Vogl ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Tissue Regeneration ◽

Cell Function ◽

Elective Surgery ◽

High Mobility ◽

Underlying Mechanism ◽

Clinical Scenarios ◽

Stem And Progenitor Cells

A major discovery of recent decades has been the existence of stem cells and their potential to repair many, if not most, tissues. With the aging population, many attempts have been made to use exogenous stem cells to promote tissue repair, so far with limited success. An alternative approach, which may be more effective and far less costly, is to promote tissue regeneration by targeting endogenous stem cells. However, ways of enhancing endogenous stem cell function remain poorly defined. Injury leads to the release of danger signals which are known to modulate the immune response, but their role in stem cell-mediated repair in vivo remains to be clarified. Here we show that high mobility group box 1 (HMGB1) is released following fracture in both humans and mice, forms a heterocomplex with CXCL12, and acts via CXCR4 to accelerate skeletal, hematopoietic, and muscle regeneration in vivo. Pretreatment with HMGB1 2 wk before injury also accelerated tissue regeneration, indicating an acquired proregenerative signature. HMGB1 led to sustained increase in cell cycling in vivo, and using Hmgb1−/− mice we identified the underlying mechanism as the transition of multiple quiescent stem cells from G0 to GAlert. HMGB1 also transitions human stem and progenitor cells to GAlert. Therefore, exogenous HMGB1 may benefit patients in many clinical scenarios, including trauma, chemotherapy, and elective surgery.

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