scholarly journals Constitutive loss of DNMT3A causes morbid obesity through misregulation of adipogenesis

2021 ◽  
Author(s):  
Ayala Tovy ◽  
Jaime M Reyes ◽  
Linda Zhang ◽  
Yung-Hsin Huang ◽  
Carina Rosas ◽  
...  
Keyword(s):  
Gene Networks ◽  
Dna Methyltransferase ◽  
Tissue Expansion ◽  
Normal Weight ◽  
Morbidly Obese ◽  
Wild Type ◽  
Dna Hypomethylation ◽  
Hematopoietic Stem ◽  
Fat Depots ◽  
Adipocyte Progenitors

DNA Methyltransferase 3A (DNMT3A) is an important facilitator of differentiation of both embryonic and hematopoietic stem cells. Heterozygous germline mutations in DNMT3A lead to Tatton-Brown-Rahman Syndrome (TBRS), characterized by obesity and excessive height. While DNMT3A is known to impact feeding behavior via the hypothalamus, here we investigated a role in adipocyte progenitors utilizing heterozygous knockout mice that recapitulate cardinal TBRS phenotypes. These mice become morbidly obese due to adipocyte enlargement and tissue expansion. Adipose tissue in these mice exhibited defects in preadipocyte maturation and precocious activation of inflammatory gene networks, including interleukin-6 signaling. Adipocyte progenitor cell lines lacking DNMT3A exhibited aberrant differentiation. Furthermore, mice in which Dnmt3a was specifically ablated in adipocyte progenitors showed enlarged fat depots and increased progenitor numbers, partly recapitulating the TBRS obesity phenotypes. Loss of DNMT3A led to constitutive DNA hypomethylation, such that the DNA methylation landscape of young adipocyte progenitors resemble that of older wild-type mice. Together, our results demonstrate that DNMT3A coordinates both the central and local control of energy storage required to maintain normal weight and prevent inflammatory obesity.

scholarly journals Mutation in DNA Methyltransferase DNMT3A Confers Enhanced Self-Renewal Capacity Onto Multipotent Progenitor Cells and Predisposes to Acute Myeloid Leukemia (AML)

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2569-2569
Author(s):  
Matthew Loberg ◽  
Rebecca Bell ◽  
Tim Stearns ◽  
Leslie Goodwin ◽  
Kira Young ◽  
...  
Keyword(s):  
Myeloid Leukemia ◽  
Dna Methyltransferase ◽  
Hematologic Malignancy ◽  
Selective Advantage ◽  
Wild Type ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Npm1 Mutation ◽  
Clonal Hematopoiesis ◽  
Acute Myeloid

Abstract The clinical significance of clonal hematopoiesis (CHIP or ARCH) remains a barrier to predicting the risk of hematologic malignancy. DNMT3A is a de novo DNA methyltransferase frequently mutated in clonal hematopoiesis, myelodysplastic syndrome and acute myeloid leukemia. Loss of or mutation in DNMT3A has been demonstrated to enhance self-renewal of hematopoietic stem cells (HSCs), suggesting that this is the predominant cell population driving clonal hematopoiesis. How DNMT3A-mutant cells become at risk for transformation is unclear, in part due to our limited understanding of how DNMT3A mutation confers a selective advantage and the cooperating mechanisms required for progression to MDS or AML. To address this gap in knowledge, we generated a cre-inducible Dnmt3a-LSL-R878H mouse model (representing the DNMT3A-R882H mutation commonly found in human AML), in which wild-type Dnmt3a expression is preserved prior to recombination. Heterozygous Dnmt3aR878H mice exhibit an expansion in both HSCs and multipotent progenitor (MPP) cell subsets with distinct kinetics. Transcriptional profiling of sorted HSC and MPP populations by RNA-seq revealed distinct transcriptional signatures indicating that different mechanisms underlie expansion of Dnmt3aR878H/+ HSCs and MPPs. Dnmt3a-mutant HSCs exhibit downregulation of genes important for differentiation, while Dnmt3a-mutant MPPs exhibit upregulation of genes associated with stem cell self-renewal, including Jam2 and Ryk. Functionally, we observe that Dnmt3a-mutant MPPs have enhanced serial replating capacity in in vitro colony assays. These data suggest that mutation in DNMT3A may cause clonal hematopoietic expansion through distinct mechanisms dependent on the cell-of-origin which incurs this mutation. To determine whether clonal hematopoiesis driven by Dnmt3aR878H/+ was sufficient to predispose to a hematologic malignancy, we generated an independent, Flp-inducible Npm1-FSF-cA mouse model (representing the NPM1cA mutation commonly found in human AML), in which wild-type Npm1 expression is preserved prior to recombination. Inducing Npm1cA mutation in hematopoietic stem and progenitor cells carrying Dnmt3aR878H caused development of a fully penetrant myeloproliferative disorder upon transplant into recipient mice. Transplantation of these cells into secondary recipient mice led to a fully penetrant AML with accelerated disease kinetics compared to primary transplant recipients. These data suggest that the combination of DNMT3A mutation followed by NPM1 mutation is sufficient to cause AML. In summary, this study reveals a novel cell context-specificity of how DNMT3A mutation confers a selective advantage and demonstrates that NPM1 mutation can cooperate with DNMT3A mutation to cause AML. This work has implications for predicting individuals at risk of progression from clonal hematopoiesis to AML. Disclosures No relevant conflicts of interest to declare.

scholarly journals Hotspot DNMT3A mutations in Clonal Hematopoiesis and Acute Myeloid Leukemia sensitize cells to Azacytidine via viral mimicry response

2021 ◽  
Author(s):  
Marina Scheller ◽  
Anne Kathrin Ludwig ◽  
Stefanie Göllner ◽  
Christian Rohde ◽  
Stephen Krämer ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Dna Methyltransferase ◽  
Predictive Marker ◽  
Protein Translation ◽  
Dna Hypomethylation ◽  
Hematopoietic Stem ◽  
Clonal Hematopoiesis ◽  
Viral Mimicry ◽  
Acute Myeloid

Abstract Somatic mutations in DNA Methyltransferase 3A (DNMT3A) are among the most frequent alterations in clonal hematopoiesis (CH) and Acute Myeloid Leukemia (AML), with a hotspot in exon 23 at arginine 882 (DNMT3A-R882). Here we demonstrate that DNMT3A-R882H-dependent CH- and AML cells are specifically susceptible to the hypomethylating agent azacytidine (AZA). Addition of AZA to chemotherapy prolonged AML survival solely in patients with DNMT3A-R882 mutation, suggesting its potential as a novel predictive marker for AZA response. AML and CH mouse models confirmed AZA susceptibility specifically in DNMT3A-R882H-expressing cells. Hematopoietic stem and progenitor cells expressing DNMT3A-R882H exhibited cell-autonomous viral mimicry response as a result of focal DNA hypomethylation at retrotransposon sequences. Administration of AZA boosted hypomethylation of retrotransposons specifically in DNMT3A-R882H expressing cells and maintained elevated levels of canonical interferon-stimulated genes (ISGs), thus leading to suppressed protein translation and increased apoptosis.

scholarly journals DNMT3A Regulates Hematopoietic Stem Cell Function Via DNA Methylation-Independent Functions

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 24-24
Author(s):  
Won Kyun Koh ◽  
Hamza Celik ◽  
Jacob Tao ◽  
Jake Fairchild ◽  
Ostap Kukhar ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Dna Methyltransferase ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Ectopic Expression ◽  
Wild Type ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Independent Functions

Abstract The balance between self-renewal and differentiation of hematopoietic stem cells (HSCs) is strictly regulated to sustain blood production throughout adult life. De novo DNA methyltransferase 3-alpha (DNMT3A) is one of the major epigenetic regulators that is essential for efficient HSC differentiation. DNMT3A mutations are prevalent in myeloid diseases that include acute myeloid leukemia (AML; ~22%) and myelodysplastic syndrome (MDS; ~10%) where they act as initiating events However, the precise molecular mechanisms of how DNMT3A regulates normal hematopoiesis and its mutations prime HSCs for leukemic formation are unclear. Although DNMT3A is described as a DNA methyltransferase enzyme, the lack of consistent correlation between changes in DNA methylation and differential gene expression in Dnmt3a-null HSCs in mouse models, and AML patients with DNMT3A mutations undermine the conventional understanding of DNMT3A's canonical role in hematopoietic cells. Hence, we hypothesized that DNMT3A may have novel functions outside of DNA methylation that regulate HSC fate decisions. To answer this question, we first ectopically expressed GFP-labeled Dnmt3a constructs (wild-type Dnmt3a, Dnmt3aE752A; complete DNA methylation dead, and Dnmt3aR832A; reduced DNA methylation target recognition) and empty vector (negative control) in Dnmt3a-null (Vav-Cre: Dnmt3afl/fl = Dnmt3a-/- in hematopoiesis) bone marrow (BM) cells. The result showed that similar to restoring wild-type Dnmt3a, ectopic expression of Dnmt3aE752A as well as Dnmt3aR832A showed a rescue effect of decreased engraftment of transduced cells in the peripheral blood as well as reduced HSC numbers in the BM. Analysis of DNA methylation by whole-genome bisulfite sequencing (WGBS) in transduced cells showed this phenotypic and functional rescue of the Dnmt3a-/- phenotype occurred in the absence of restored DNA methylation patterns. To study the importance of Dnmt3a-mediated DNA methyltransferase activity in a more physiological system, we generated knock-in mice that have one copy of either wild-type Dnmt3a, Dnmt3aE752A, or Dnmt3aR832A (CAGG-Cre-ER T2 = ER T2-Cre: Dnmt3afl/+, Dnmt3afl/E752A, and Dnmt3afl/R832A) to be compared to the Dnmt3a-null group (ER T2-Cre: Dnmt3afl/-). These mice contain one allele with loxP-flanked Dnmt3a that is deleted by tamoxifen-inducible Cre-mediated recombination and one allele of either wild-type Dnmt3a, Dnmt3aE752A, Dnmt3aR832A, or germline knockout Dnmt3anull. 5-weeks post-tamoxifen (~93% floxed allele recombination), competitive transplantation of 250 phenotypically defined test HSCs against with 2.5x10 5 congenic competitor BM cells was performed. Dnmt3a fl/R832A recipients had higher engraftment (35.6 % +/- 6.1) than Dnmt3afl/+ (28.5% +/- 7.2) and Dnmt3afl/- (10.7% +/- 2.79), while Dnmt3afl/E752A had slightly higherengraftment (12.5% +/- 3) than Dnmt3afl/-. Analysis of the BM 18 weeks post-transplant showed that Dnmt3afl/E752A and Dnmt3afl/R832A HSCs phenocopied the HSC self-renewal potential phenotype of heterozygous Dnmt3a fl/+HSCs (Fig. 1). The absolute count of donor-derived HSCs per mouse after the transplant were: ER T2-Cre control (675.7 +/- 299.3), Dnmt3afl/+ (1870 +/- 961.4), Dnmt3afl/- (3546 +/- 1019), Dnmt3afl/E752A (1130 +/- 362.7), and Dnmt3afl/R832A (1184 +/- 344.5) (mean +/- S.E.M.). While the described clonal expansion of Dnmt3a-null HSCs was observed, HSCs with one copy of full-length Dnmt3a but devoid of its methyltransferase capacity mimicked the heterozygous state rather than the homozygous loss-of-function. This is the first evidence to suggest that DNMT3A potentially regulates HSCs by non-canonical (DNA methylation independent) mechanisms. DNA methylation analysis by WGBS is ongoing to determine if Dnmt3afl/E752A and Dnmt3afl/R832A HSCs show a methylome comparable to Dnmt3a-null HSCs whilst having the functional potential of Dnmt3a-heterozygous HSCs, which will be complemented with other molecular analyses including gene expression. Our study opens new avenues for investigations into the molecular mechanisms of DNMT3A function in HSC biology, which could ultimately benefit clinical practice by identifying new therapeutic approaches for the patients with DNMT3A mutations. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

scholarly journals Potential Role of Epigenetic Mechanism in Manganese Induced Neurotoxicity

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Prashant Tarale ◽  
Tapan Chakrabarti ◽  
Saravanadevi Sivanesan ◽  
Pravin Naoghare ◽  
Amit Bafana ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Dna Methyltransferase ◽  
Apoptotic Cell ◽  
Genetic Difference ◽  
Epigenetic Mechanism ◽  
Dna Hypomethylation ◽  
Manganese Neurotoxicity

Manganese is a vital nutrient and is maintained at an optimal level (2.5–5 mg/day) in human body. Chronic exposure to manganese is associated with neurotoxicity and correlated with the development of various neurological disorders such as Parkinson’s disease. Oxidative stress mediated apoptotic cell death has been well established mechanism in manganese induced toxicity. Oxidative stress has a potential to alter the epigenetic mechanism of gene regulation. Epigenetic insight of manganese neurotoxicity in context of its correlation with the development of parkinsonism is poorly understood. Parkinson’s disease is characterized by theα-synuclein aggregation in the form of Lewy bodies in neuronal cells. Recent findings illustrate that manganese can cause overexpression ofα-synuclein.α-Synuclein acts epigenetically via interaction with histone proteins in regulating apoptosis.α-Synuclein also causes global DNA hypomethylation through sequestration of DNA methyltransferase in cytoplasm. An individual genetic difference may also have an influence on epigenetic susceptibility to manganese neurotoxicity and the development of Parkinson’s disease. This review presents the current state of findings in relation to role of epigenetic mechanism in manganese induced neurotoxicity, with a special emphasis on the development of Parkinson’s disease.

Sex differences in white adipose tissue expansion: emerging molecular mechanisms

2021 ◽  
Vol 135 (24) ◽  
pp. 2691-2708
Author(s):  
Simon T. Bond ◽  
Anna C. Calkin ◽  
Brian G. Drew
Keyword(s):  
Sex Differences ◽  
Sexual Dimorphism ◽  
Gene Networks ◽  
Large Scale ◽  
Molecular Mechanisms ◽  
Association Studies ◽  
Tissue Expansion ◽  
Economic Systems ◽  
Genomic Association ◽  
Males And Females

Abstract The escalating prevalence of individuals becoming overweight and obese is a rapidly rising global health problem, placing an enormous burden on health and economic systems worldwide. Whilst obesity has well described lifestyle drivers, there is also a significant and poorly understood component that is regulated by genetics. Furthermore, there is clear evidence for sexual dimorphism in obesity, where overall risk, degree, subtype and potential complications arising from obesity all differ between males and females. The molecular mechanisms that dictate these sex differences remain mostly uncharacterised. Many studies have demonstrated that this dimorphism is unable to be solely explained by changes in hormones and their nuclear receptors alone, and instead manifests from coordinated and highly regulated gene networks, both during development and throughout life. As we acquire more knowledge in this area from approaches such as large-scale genomic association studies, the more we appreciate the true complexity and heterogeneity of obesity. Nevertheless, over the past two decades, researchers have made enormous progress in this field, and some consistent and robust mechanisms continue to be established. In this review, we will discuss some of the proposed mechanisms underlying sexual dimorphism in obesity, and discuss some of the key regulators that influence this phenomenon.

O6-methylguanine-DNA methyltransferase in wild-type and ada mutants of Escherichia coli

1982 ◽  
Vol 152 (1) ◽  
pp. 534-537
Author(s):  
S Mitra ◽  
B C Pal ◽  
R S Foote
Keyword(s):  
Escherichia Coli ◽  
Dna Methyltransferase ◽  
Wild Type ◽  
E Coli ◽  
Methylguanine Dna Methyltransferase ◽  
Synthetic Dna ◽  
In The Wild ◽  
Low Levels ◽  
Enzyme Molecules ◽  
Dna Substrate

O(6)-Methylguanine-DNA methyltransferase is induced in Escherichia coli during growth in low levels of N-methyl-N'-nitro-N-nitrosoguanidine. We have developed a sensitive assay for quantitating low levels of this activity with a synthetic DNA substrate containing 3H-labeled O(6)-methylguanine as the only modified base. Although both wild-type and adaptation-deficient (ada) mutants of E. coli contained low but comparable numbers (from 13 to 60) of the enzyme molecules per cell, adaptation treatment caused a significant increase of the enzyme in the wild type but not in the ada mutants, suggesting that the ada mutation is in a regulatory locus and not in the structural gene for the methyltransferase.

scholarly journals Facilitating Airway Surgery in a Morbidly Obese Patient Using Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE)

2018 ◽  
Vol 2018 ◽  
pp. 1-3 ◽  
Author(s):  
Si-Jia Lee ◽  
Kelvin Howyow Quek
Keyword(s):  
Obese Patient ◽  
Normal Weight ◽  
Morbidly Obese ◽  
Airway Surgery ◽  
Laryngeal Surgery ◽  
Morbidly Obese Patient ◽  
Obese Population ◽  
Obese Subjects ◽  
Difficult Airways ◽  
Surgical Field

Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) is a relatively new noninvasive oxygenation technique with a broad range of applications. It is used in the treatment of type one respiratory failure, as a preoxygenation tool, as a rescue and temporising measure in difficult airways, and as step-down oxygen therapy in patients after extubation. Its use has also been described in laryngeal surgeries, but they mainly involved normal-weight subjects or were used as a bridging oxygenation therapy before definitive airway is secured. The major benefits of using THRIVE in obese subjects undergoing laryngeal surgery include a tubeless and uninterrupted surgical field. This advantage is especially crucial in obese patients as they tend to have limited oropharyngeal space, rendering a shared airway technically challenging for surgeons. However, concerns of potential difficult airway and shorter safe apnoeic time in the obese population limit its use. In this case, we report its use as the sole oxygenation strategy in a morbidly obese patient undergoing airway surgery. Our experience suggests that THRIVE can provide a conducive operating field and adequate oxygenation in short apnoeic laryngeal procedures in the obese population, without causing excessive hypercarbia.

scholarly journals Serum Adiponectin Levels in Advanced-Stage Parkinson's Disease Patients

2011 ◽  
Vol 2011 ◽  
pp. 1-6
Author(s):  
Erica Cassani ◽  
Raffaella Cancello ◽  
Ferruccio Cavanna ◽  
Sabrina Maestrini ◽  
Anna Maria Di Blasio ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Cardiovascular Risk ◽  
Body Weight Loss ◽  
Serum Levels ◽  
Normal Weight ◽  
Morbidly Obese ◽  
Serum Concentrations ◽  
Status Assessment ◽  
Young Subjects

Patients with advanced Parkinson's disease (PD) experience body weight loss and reductions in the most common cardiovascular risk factors. At present, the pathogenetic mechanisms involved have not been elucidated. Increased serum concentrations of adiponectin, which possesses antiatherogenic and anti-inflammatory properties, are associated with a reduction in cardiovascular risk. The objective of this study was to determine adiponectin serum concentrations in PD patients. Thirty PD patients underwent a full nutritional status assessment, including the determination of adiponectin serum concentrations. Mean ± SD adiponectin concentrations were 9.59 ± 5.9 μg/mL (interquartile range: 5.92–12.9 μg/mL). In PD patients, adiponectin serum levels were similar to those in normal-weight, healthy, young subjects and significantly higher than that in an aged-matched group of morbidly obese subjects. Further studies are warranted to establish the role of adiponectin in the management of PD patients.

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