DNMT3A
DNA (cytosine-5)-methyltransferase 3A (EC 2.1.1.37) (Dnmt3a) (DNA methyltransferase HsaIIIA) (DNA MTase HsaIIIA) (M.HsaIIIA)
Publications[править]
Hematopoietic stem cells (HSCs) have self-renewal capacity and differentiation potential into all lineages of blood cells throughout the lifetime of an organism. The function of HSCs gradually changes during aging. To date, various stress factors influencing HSC aging have been identified. The increased production of reactive oxygen species and DNA damage responses are causatively attributed to HSC aging. The increased apolarity is a prominent feature of aged HSCs, whereas it is less obvious in young HSCs. The bone marrow (BM) microenvironment niche is a crucial factor for HSC aging. Mesenchymal stem cells show skewed differentiation during aging, which leads to decreased bone formation and increased adipogenesis. The accumulation of adipocytes confers negative effects on hematopoiesis. Loss of sympathetic nerve fibers or adrenoreceptor β3 signaling induces premature HSC and niche aging. Epigenetic regulators such as polycomb group proteins and the sirtuin family of proteins act to prevent premature aging. Targeting these factors, several rejuvenation strategies for aged HSCs have been employed in mice. However, we still do not know whether these strategies can be extrapolated to human HSCs. Aging is frequently accompanied by the development of clonal hematopoiesis, which is called age-related clonal hematopoiesis (ARCH) or clonal hematopoiesis of indeterminate potential (CHIP). Most ARCH/CHIP mutations occur in genes encoding epigenetic regulators including DNMT3A, TET2, and ASXL1, which suggests the relevance of epigenetic drift during the aging process. ARCH/CHIP is a strong risk factor for subsequent hematologic cancer. Notably, it also has an impact on the development of non-malignant disorders such as coronary heart disease. Further studies are warranted to decipher the complete picture of molecular crosstalk that regulates HSC aging.
Keywords
- Age-related clonal hematopoiesis
- Aging
- Clonal hematopoiesis of indeterminate potential
- DNA damage
- Epigenetics
- Hematopoietic stem cell
- Polarity
- Reactive oxygen species
- Senescence
- Stem cell niche
The use of human mesenchymal stem cells (hMSCs) in clinical applications requires large-scale cell expansion prior to administration. However, the prolonged culture of hMSCs results in cellular senescence, impairing their proliferation and therapeutic potentials. To understand the role of microRNAs (miRNAs) in regulating cellular senescence in hMSCs, we globally depleted miRNAs by silencing the DiGeorge syndrome critical region 8 (DGCR8) gene, an essential component of miRNA biogenesis. DGCR8 knockdown hMSCs exhibited severe proliferation defects and senescence-associated alterations, including increased levels of reactive oxygen species (ROS). Transcriptomic analysis revealed that the antioxidant gene superoxide dismutase 2 (SOD2) was significantly downregulated in DGCR8 knockdown hMSCs. Moreover, we found that DGCR8 silencing in hMSCs resulted in hypermethylation in CpG islands upstream of SOD2. 5-aza-2'-deoxycytidine treatment restored SOD2 expression and ROS levels. We also found that these effects were dependent on the epigenetic regulator DNA methyltransferase 3 alpha (DNMT3A). Using computational and experimental approaches, we demonstrated that DNMT3A expression was regulated by miR-29a-3p and miR-30c-5p. Overexpression of miR-29a-3p and/or miR-30c-5p reduced ROS levels in DGCR8 knockdown hMSCs and rescued proliferation defects, mitochondrial dysfunction, and premature senescence. Our findings provide novel insights into hMSCs senescence regulation by the miR-29a-3p/miR-30c-5p/DNMT3A/SOD2 axis.
Keywords
- Cellular senescence
- DNMT3A
- Human mesenchymal stem cells
- Mitochondrial oxidative stress
- SOD2
- microRNAs
The history of clonal hematopoiesis (CH) research is punctuated by several seminal discoveries that have forged our understanding of cancer development. The clever application of the principle of random X-chromosome inactivation (XCI) in females led to the development of the first test to identify clonal derivation of cells. Initially limited by a low level of informativeness, the applicability of these assays expanded with differential methylation-based assays at highly polymorphic genes such as the human androgen receptor (HUMARA). Twenty years ago, the observation that skewing of XCI ratios increases as women age was the first clue that led to the identification of mutations in the TET2 gene in hematologically normal aging individuals. In 2014, large-scale genomic approaches of three cohorts allowed definition of CH, which was reported to increase the risk of developing hematologic cancers and cardiovascular diseases. These observations created a fertile field of investigation aimed at investigating the etiology and consequences of CH. The most frequently mutated genes in CH are DNMT3A, TET2, and ASXL1, which have a role in hematopoietic stem cell (HSC) development and self-renewal. These mutations confer a competitive advantage to the CH clones. However, the penetrance of CH is age dependent but incomplete, suggesting the influence of extrinsic factors. Recent data attribute a modest role to genetic predisposition, but several observations point to the impact of a pro-inflammatory milieu that advantages the mutated clones. CH may be a barometer of nonhealthy aging, and interventions devised at curbing its initiation or progression should be a research priority.
MeSH Terms
- Adult
- Aging
- Biomedical Research
- Chromosomes, Human, X
- DNA-Binding Proteins
- Female
- Hematopoiesis
- Hematopoietic Stem Cells
- History, 20th Century
- History, 21st Century
- Humans
- Male
- Mutation
- Proto-Oncogene Proteins
- Receptors, Androgen
- Repressor Proteins
- X Chromosome Inactivation
DNMT3A R882H, a frequent mutation in acute myeloid leukemia (AML), plays a critical role in malignant hematopoiesis. Recent findings suggest that DNMT3A mutant acts as a founder mutation and requires additional genetic events to induce full-blown AML. Here, we investigated the cooperation of mutant DNMT3A and NRAS in leukemogenesis by generating a double knock-in (DKI) mouse model harboring both Dnmt3a R878H and Nras G12D mutations. DKI mice with both Dnmt3a R878H and Nras G12D mutations were generated by crossing Dnmt3a R878H knock-in (KI) mice and Nras G12D KI mice. Routine blood test, flow cytometry analysis and morphological analysis were performed to determine disease phenotype. RNA-sequencing (RNA-seq), RT-PCR and Western blot were carried out to reveal the molecular mechanism. The DKI mice developed a more aggressive AML with a significantly shortened lifespan and higher percentage of blast cells compared with KI mice expressing Dnmt3a or Nras mutation alone. RNA-seq analysis showed that Dnmt3a and Nras mutations collaboratively caused abnormal expression of a series of genes related to differentiation arrest and growth advantage. Myc transcription factor and its target genes related to proliferation and apoptosis were up-regulated, thus contributing to promote the process of leukemogenesis. This study showed that cooperation of DNMT3A mutation and NRAS mutation could promote the onset of AML by synergistically disturbing the transcriptional profiling with Myc pathway involvement in DKI mice.
MeSH Terms
- Animals
- Apoptosis
- Carcinogenesis
- Cell Differentiation
- DNA (Cytosine-5-)-Methyltransferases
- Disease Models, Animal
- Disease Progression
- Gene Expression Regulation, Neoplastic
- Gene Knock-In Techniques
- Leukemia, Myeloid, Acute
- Longevity
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Monomeric GTP-Binding Proteins
- Mutation
- Phenotype
- Pilot Projects
- Proto-Oncogene Proteins c-myc
- RNA-Seq
- Transcription, Genetic
Keywords
- Acute myeloid leukemia
- DNMT3A mutation
- Myc activation
- Nras G12D
Inflammation and fibroproliferative diseases may be modulated by epigenetic changes. Therefore, we suggest that epigenetic mechanisms could be involved in equine endometrosis pathogenesis. DNA methylation is one of the methods to evaluate epigenetics, through the transcription of methyltransferases (DNMT1, DNMT3A, DNMT3B). The correlation between DNMTs and collagen (COL) transcripts was assessed for the different Kenney and Doig's (Current Therapy in Theriogenology. Philadelphia: WB Saunders; 1986) endometrium categories. Endometrial biopsies were randomly collected from cyclic mares. Histological classification (category I, n = 13; II A, n = 17; II B, n = 12; and III, n = 7) and evaluation of COL1A2, COL3A1 and DNMTs transcripts by qPCR, were performed. Data were analysed by one-way analysis of variance (ANOVA), Kruskal-Wallis test and Pearson correlation. As mares aged, there was an increase in endometrium fibrosis (p < .01), and in DNMT1 mRNA (p < .001). Considering DNMT3B transcripts for each category, there was an increase with fibrosis (p < .05). No changes were observed for DNMT1 and DNMT3A transcripts. However, DNMT3A mRNA levels were the highest in all categories (p < .01). In category I endometrium, a positive correlation was observed for transcripts of all DNMTs in both COLs (p < .01). In category IIA, this correlation was also maintained for all DNMTs transcripts in COL1A2 (p < .05), but only for DNMT3B in COL3A1 (p < .05). In category IIB, there was a positive correlation between DNMT3B and COL3A1 (p < .05). In category III, a positive correlation was only observed between DNMT3B and COL3A1 (p < .05). Our results suggest that there is a disturbance in COLs and DNMTs correlation during fibrosis.
MeSH Terms
- Aging
- Animals
- Collagen
- DNA (Cytosine-5-)-Methyltransferases
- DNA Methylation
- Endometritis
- Endometrium
- Female
- Fibrosis
- Horse Diseases
- Horses
- RNA, Messenger
Keywords
- DNA methylation
- collagen
- endometrium
- epigenetic
- fibrosis
- mare
Age-related clonal haemopoiesis (ARCH) in healthy individuals was initially observed through an increased skewing in X-chromosome inactivation [1]. More recently, several groups reported that ARCH is driven by somatic mutations [2], with the most prevalent ARCH mutations being in the DNMT3A and TET2 genes, previously described as drivers of myeloid malignancies. ARCH is associated with an increased risk for haematological cancers [2]. ARCH also confers an increased risk for non-haematological diseases, such as cardiovascular disease, atherosclerosis, and chronic ischemic heart failure, for which age is a main risk factor [3,4]. Whether ARCH is linked to accelerated ageing has remained unexplored. The most accurate and commonly used tools to measure age acceleration are epigenetic clocks: they are based on age-related methylation differences at specific CpG sites [5]. Deviations from chronological age towards an increased epigenetic age have been associated with increased risk of earlier mortality and age-related morbidities [5,6]. Here we present evidence of accelerated epigenetic age in individuals with ARCH.
MeSH Terms
- Aged
- Aged, 80 and over
- Aging
- Epigenesis, Genetic
- Female
- Hematopoiesis
- Humans
- Longitudinal Studies
- Male
- Risk Factors
- Scotland
Ageing and inflammation strongly drive the risk of cardiovascular disease. Work over the past decade has uncovered a common condition characterized by the positive selection of certain somatic mutations in haematopoietic stem cells in ageing humans. This phenomenon, known as clonal haematopoiesis of indeterminate potential (CHIP), occurs most commonly as a result of mutations in the transcriptional regulators DNMT3A, TET2 and ASXL1. CHIP is associated with a variety of adverse outcomes, including haematological cancer and death. Surprisingly, CHIP is also associated with a doubling of the risk of atherosclerotic cardiovascular disease. Studies in mice support the causality of this relationship. Mutations in TET2, which are among the most commonly found mutations in CHIP, lead to increased expression of inflammatory genes in innate immune cells, potentially explaining the link between mutations and increased cardiovascular risk. Therapies targeting the mutant clones or the increased inflammatory mediators might be useful for ameliorating the risk of cardiovascular disease. We propose that the mutations leading to clonal haematopoiesis contribute to the increased inflammation seen in ageing and thereby explain some of the age-related risk of cardiovascular disease.
MeSH Terms
- Adult
- Age Factors
- Aged
- Aged, 80 and over
- Aging
- Animals
- Cardiovascular Diseases
- DNA (Cytosine-5-)-Methyltransferases
- DNA-Binding Proteins
- Genetic Predisposition to Disease
- Hematopoiesis
- Hematopoietic Stem Cells
- Humans
- Inflammation
- Middle Aged
- Mutation
- Phenotype
- Proto-Oncogene Proteins
- Repressor Proteins
- Risk Assessment
- Risk Factors
Age-related changes in methylation are involved in the occurrence and development of tumors, autoimmune disease, and nervous system disorders, including Alzheimer's disease (AD), in elderly individuals; hence, modulation of these methylation changes may be an effective strategy to delay the progression of AD pathology. In this study, the AD model rats were used to screen the main active extracts from the mushroom, [i]Ganoderma lucidum[/i], for anti-aging properties, and their effects on DNA methylation were evaluated. The results of evaluation of rats treated with 100 mg/kg/day of D-galactose to induce accelerated aging showed that alcohol extracts of [i]G. lucidum[/i] contained the main active anti-aging extract. The effects on DNA methylation of these [i]G. lucidum[/i] extracts were then evaluated using SAMP8 and APP/PS1 AD model mice by whole genome bisulfite sequencing, and some methylation regulators including Histone H3, DNMT3A, and DNMT3B in brain tissues were up-regulated after treatment with alcohol extracts from [i]G. lucidum[/i]. Molecular docking analysis was carried out to screen for molecules regulated by specific components, including ganoderic acid Mk, ganoderic acid C6, and lucidone A, which may be active ingredients of [i]G. lucidum[/i], including the methylation regulators of Histone H3, MYT, DNMT3A, and DNMT3B. Auxiliary tests also demonstrated that [i]G. lucidum[/i] alcohol extracts could improve learning and memory function, ameliorate neuronal apoptosis and brain atrophy, and down-regulate the expression of the AD intracellular marker, Aβ . We concluded that alcohol extracts from [i]G. lucidum[/i], including ganoderic acid and lucidone A, are the main extracts involved in delaying AD progression.
Keywords
- Alzheimer’s disease
- DNA methylation
- Ganoderma lucidum
- active ingredients
- aging
Aging hematopoietic stem cells acquire mutations that sometimes impart a selective advantage. Next-generation DNA sequencing (NGS) can be used to detect expanded peripheral blood progeny of a mutant clone, usually carrying just one cancer-driver mutation, most often in the epigenetic regulator genes, DNMT3A or TET2. This phenomenon is known as clonal hematopoiesis (CH), age-related CH (ARCH) when considering its association with age, and CH of indeterminate potential (CHIP) when the variant allele fraction (VAF) is at least 2% in peripheral leukocytes. CHIP is present in at least 10-15% of adults older than 65 years and is a risk factor for hematological neoplasms and diseases exacerbated by mutant, hyper-inflammatory, monocytes/macrophages, such as atherosclerotic cardiovascular disease. Therefore, the detection of CHIP has important clinical consequences. Herein, we present a protocol for the generation of targeted, amplicon-based, NGS libraries for ion semiconductor sequencing and CHIP detection, using Ion Torrent platforms.
MeSH Terms
- Adult
- Aging
- Atherosclerosis
- Clonal Evolution
- Genome, Human
- Hematopoiesis
- Hematopoietic Stem Cells
- High-Throughput Nucleotide Sequencing
- Humans
- Mutation
- Neoplasms
- Polymerase Chain Reaction
- Risk Factors
- Workflow
Keywords
- Age-related clonal hematopoiesis (ARCH)
- Amplicon
- Clonal hematopoiesis (CH)
- Clonal hematopoiesis of indeterminate potential (CHIP)
- DNMT3A
- Ion Torrent
- Ion semiconductor
- Library
- Next-generation DNA sequencing (NGS)
- Peripheral blood
- TET2
The clonal hematopoiesis when occurring without hematologic abnormalities is defined as clonal hematopoiesis of indeterminate potential (CHIP). Aging causes accumulation of somatic mutations, and hematopoietic stem cells (HSCs) can develop clonal expansion of different lineages by these mutations. CHIP has a correlation with cancer and cardiovascular disease (CVD) through acquired mutations in genes. DNMT3A, TET2, ASXL1, and JAK2 genes as well as other genes are the most common somatic mutations causing CHIP and CVD in an older age. Other factors such as cholesterol level, laboratory tests and indexes also affect CVD. In addition, mutations in adenosine triphosphate-binding cassette transporters and also chronic stress in nervous system can result in HSCs proliferation and CVD. However, laboratory tests and indexes are not sensitive for CVD diagnosis. But the therapeutic interventions can be helpful to prevent CVD cases by targeting somatic mutations, chemokine receptors, and growth factors in HSCs. Also, new drugs can control CVD by targeting of cells and their signaling pathways in HSCs. Therefore, more investigations are needed and more questions should be answered for the relationship between CHIP and CVD as a challenging issue in future.
MeSH Terms
- Aging
- Cardiovascular Diseases
- Cell Lineage
- Clonal Evolution
- DNA (Cytosine-5-)-Methyltransferases
- DNA-Binding Proteins
- Hematopoiesis
- Hematopoietic Stem Cells
- Humans
- Janus Kinase 2
- Mutation
- Proto-Oncogene Proteins
- Repressor Proteins
Keywords
- cardiovascular disease
- clonal hematopoiesis
- genes
- mechanisms
The recent characterization of clonal hematopoiesis in a large segment of the aging population has raised tremendous interest and concern alike. Mutations have been documented in genes associated with hematological cancers and in non-driver candidates. These mutations are present at low frequency in the majority of individuals after middle-age, and principally affect the epigenetic modifiers DNMT3A and TET2. In 10%-40% of cases, the clone will progress to meet the diagnostic criteria for Clonal Hematopoiesis of Indeterminate Potential, which is associated with an increased risk of hematological cancer and cardiovascular mortality. Blood cell parameters appear unmodified in these individuals, but a minority of them will develop a hematologic malignancy. At this time, the factors put forward as potentially influencing the risk of cancer development are clone size, specific gene, specific mutation, and the number of mutations. Specific stress on hematopoiesis also gives rise to clonal expansion. Genotoxic exposure (such as chemotherapy), or immune attack (as in aplastic anemia) selects/provides a fitness advantage to clones with a context-specific signature. Clonal hematopoiesis offers a new opportunity to understand the biology and adaptation mechanisms of aging hematopoiesis and provides insight into the mechanisms underlying malignant transformation. Furthermore, it might shed light on common denominators of age-associated medical conditions and help devise global strategies that will impact the prevention of hematologic cancers and promote healthy aging. Stem Cells 2018;36:1287-1294.
MeSH Terms
- Age Factors
- Cell Transformation, Neoplastic
- Hematopoiesis
- Humans
- Stem Cells
Keywords
- Aging
- Hematologic malignancies
- Hematopoiesis
- Stem cells
Studies on parental aging are a very attractive field, although it is poorly understood how parental age affects embryonic development and adult traits of the offspring. In this study, we used the turquoise killifish Nothobranchius furzeri, as is the vertebrate with shortest captive lifespan and an interesting model. The embryos of N. furzeri can follow two distinct developmental pathways either entering diapause or proceeding through direct development. Thus, this embryonic plasticity allows this model to be used to study different factors that could affect their embryonic development, including parental age. The first goal of the present study was to investigate whether parental aging could affect the embryo development. To do this, we collected F1 embryos from two breeder groups (old parents and young parents). We monitored the duration of embryonic development and analyzed genes involved in dorsalization process. The second goal was to investigate if embryonic developmental plasticity could be modulated by an epigenetic process. To this end, the expression of DNMTs genes was examined. Our data support the hypothesis that diapause, occurring more frequently in embryos from old parents, is associated with increased expression of DNMT3A and DNMT3B suggesting an epigenetic control. Finally, we analyzed whether parental age could affect metabolism and growth during adult life. Morphometric results and qPCR analysis of genes from IGF system showed a slower growth in adults from old breeders. Moreover, a gender-specificity effect on growth emerged. In conclusion, these results may contribute to the better understanding of the complex mechanism of aging.
MeSH Terms
- Aging
- Animals
- Cyprinodontiformes
- Embryo, Nonmammalian
- Embryonic Development
- Epigenesis, Genetic
- Fish Proteins
- Gene Expression Regulation, Developmental
- Longevity
Keywords
- IGF system
- diapause
- embryo development plasticity
- killifish
- transgenerational effects
With ever-increasing elder populations, age-related cognitive decline, which is characterized as a gradual decline in cognitive capacity in the aging process, has turned out to be a mammoth public health concern. Since genetic information has become increasingly important to explore the biological mechanisms of cognitive decline, the search for genetic biomarkers of cognitive aging has received much attention. There is growing evidence that single-nucleotide polymorphisms (SNPs) within the [i]ADAMTS9, BDNF, CASS4, COMT, CR1, DNMT3A, DTNBP1, REST, SRR, TOMM40[/i], circadian clock, and Alzheimer's diseases-associated genes may contribute to susceptibility to cognitive aging. In this review, we first illustrated evidence of the genetic contribution to disease susceptibility to age-related cognitive decline in recent studies ranging from approaches of candidate genes to genome-wide association studies. We then surveyed a variety of association studies regarding age-related cognitive decline with consideration of gene-gene and gene-environment interactions. Finally, we highlighted their limitations and future directions. In light of advances in precision medicine and multi-omics technologies, future research in genomic medicine promises to lead to innovative ideas that are relevant to disease prevention and novel drugs for cognitive aging.
Keywords
- Alzheimer’s diseases
- SNP–SNP interactions
- age-related cognitive decline
- biomarker
- cognitive aging
- gene–gene interactions
- neurodegeneration
- single-nucleotide polymorphisms
Clonal hematopoiesis of aging and indeterminate potential (ARCH or CHIP), driven mainly by mutations in DNMT3A and TET2, is an emerging public health issue, affecting at least 10-15% of adults older than 65 years. CHIP is associated with increased risks of de novo and therapy-related hematological neoplasms and serves as a reservoir for leukemic relapse. CHIP is also associated with increased all-cause mortality and risk of cardio-metabolic disease. The latter association may be explained, at least in part, by the effects of inactivating mutations in TET2 on progeny macrophages. We and others have shown recently that TET2-deficient macrophages are hyperinflammatory and this may exacerbate processes such as atherosclerosis. We postulated an inflammatory state associated with TET2 inactivation and/or unhealthy aging may also favor TET2-mutant hematopoietic stem and progenitor cell (HSPC) expansion. Herein, we demonstrate a clonogenic advantage for Tet2-knockout murine and TET2-mutant human HSPCs in an in vitro environment that contains the proinflammatory cytokine tumor necrosis factor-alpha (TNFα). This phenotype emerges on chronic TNFα exposure and is associated with myeloid skewing and resistance to apoptosis. To our knowledge, this is the first evidence to suggest that TET2 mutations promote clonal dominance with aging by conferring TNFα resistance to sensitive bone marrow progenitors while also propagating such an inflammatory environment. Normalizing the immune environment may present a novel strategy to control or eradicate mutant CHIP clones.
MeSH Terms
- Aged
- Aging
- Animals
- Apoptosis
- DNA-Binding Proteins
- Female
- Humans
- Inflammation
- Macrophages
- Male
- Mice
- Mice, Knockout
- Mutation
- Proto-Oncogene Proteins
- Stem Cell Niche
- Tumor Necrosis Factor-alpha
Recent progress in next-generation sequencing technologies allows us to discover frequent mutations throughout the coding regions of myelodysplastic syndromes (MDS), potentially providing us with virtually a complete spectrum of driver mutations in this disease. As shown by many study groups these days, such driver mutations are acquired in a gene-specific fashion. For instance, DDX41 mutations are observed in germline cells long before MDS presentation. In blood samples from healthy elderly individuals, somatic DNMT3A and TET2 mutations are detected as age-related clonal hematopoiesis and are believed to be a risk factor for hematological neoplasms. In MDS, mutations of genes such as NRAS and FLT3, designated as Type-1 genes, may be significantly associated with leukemic evolution. Another type (Type-2) of genes, including RUNX1 and GATA2, are related to progression from low-risk to high-risk MDS. Overall, various driver mutations are sequentially acquired in MDS, at a specific time, in either germline cells, normal hematopoietic cells, or clonal MDS cells.
MeSH Terms
- Aging
- DEAD-box RNA Helicases
- Genome, Human
- Humans
- Mutation
- Myelodysplastic Syndromes
- Prognosis
Keywords
- Germline mutations
- Myelodysplastic syndromes
- Secondary acute myeloid leukemia
- Somatic mutations
The specific phenotype of mature differentiated beta cells not only depends on the specific presence of genes that allow beta cell function but also on the selective absence of housekeeping genes ("disallowed genes") that would interfere with this function. Recent studies have shown that both histone modifications and DNA methylation via the de novo methyltransferase DNMT3A are involved in repression of disallowed genes in neonatal beta cells when these cells acquire their mature phenotype. It is unknown, however, if the environmental influence of advanced age, pregnancy and the metabolic stress of high fat diet or diabetes could alter the repression of disallowed genes in beta cells. In the present study, we show that islet disallowed genes-which are also deeply repressed in FACS-purified beta cells-remain deeply repressed in animals of advanced age and in pregnant females. Moreover, the stability of this repression was correlated with strong and stable histone repression marks that persisted in islets isolated from 2 year old mice and with overall high expression of Dnmt3a in islets. Furthermore, repression of disallowed genes was unaffected by the metabolic stress of high fat diet. However, repression of about half of the disallowed genes was weakened in 16 week-old diabetic db/db mice. In conclusion, we show that the disallowed status of islet genes is stable under physiological challenging conditions (advanced age, pregnancy, high fat diet) but partially lost in islets from diabetic animals.
MeSH Terms
- Aging
- Animals
- DNA (Cytosine-5-)-Methyltransferases
- DNA Methylation
- Diabetes Mellitus
- Diet, High-Fat
- Female
- Glucose Tolerance Test
- Histone Code
- Insulin
- Insulin-Secreting Cells
- Mice
- Mice, Inbred C57BL
- Mice, Obese
- Pregnancy
- Stress, Physiological
MicroRNA-194 (miR-194), a typical p53 responsive miRNA, serves as a tumor suppressor similar as p53, and has been demonstrated to play an anti-proliferation role in various human cancers. In spite of the pivotal role of p53 during aging process, the knowledge of miR-194's contribution to cellular senescence is limited. We herein sought to explore the role of miR-194 in the replicative senescence and stress-induced senescence of mouse embryonic fibroblasts. Our results unraveled that, compared to young cells, miR-194 is highly expressed in senescent cells, and extra expression of miR-194 significantly triggers the replicative senescence of MEFs and H O -induced senescence of NIH/3T3 cells, while inhibition of miR-194 exhibited the opposite effect. We further unveiled that DNMT3A was a direct and authentic target of miR-194, which has been reported to be closely associated with cellular senescence. Taken together, our data suggest that miR-194 may significantly promote the development of cellular senescence in mouse embryonic fibroblasts, which potentially occurs through inhibiting the DNMT3A expression.
MeSH Terms
- Animals
- Cellular Senescence
- Fibroblasts
- HEK293 Cells
- Human Umbilical Vein Endothelial Cells
- Humans
- Mice
- Mice, Inbred C57BL
- MicroRNAs
- NIH 3T3 Cells
Keywords
- DNMT3A
- cellular senescence
- miR-194
Epigenetic marks, such as histone modifications or DNA methylation, regulate tissue specific gene expression by affecting the structures and accessibility of chromatin or DNA. Epigenetics, the molecular mechanisms regulating the epigenome, would therefore be critically involved in development and cell differentiation versus proliferation. Histone modifications include methylation, acetylation, phosphorylation and ubiquitination of specific lysine, arginine or serine residues on histone tails, and each modification has its own specific effect on gene expressions. Modification of histones is accomplished by multimeric protein complexes including polycomb and trithorax group proteins. Regulation of DNA methylation is another mechanism of epigenetic regulation, which is achieved by DNA methyltransferase (DNMT) and TET family proteins. Methylation of cysteine residues on DNA generally leads to transcriptional repression, and oxidation of methylated cysteines provides another type of molecular mark on DNA that regulates gene expression. Next generation sequencing of tumor genomes has uncovered recurrent somatic mutations of epigenetic genes such as DNMT3A, TET2, and ASXL1 in hematologic malignancies, showing that epigenetic dysregulation is a critical step leading to the transformation of hematopoietic cells. Rigorous integrated functional analyses of mutated epigenetic genes are currently underway, and are anticipated to lead to the development of novel molecularly targeted therapies for hematologic malignancies.
MeSH Terms
- Aging
- Animals
- DNA Methylation
- Epigenesis, Genetic
- Gene Expression Regulation, Neoplastic
- Hematologic Neoplasms
- Histones
- Humans
Lysyl oxidase-like 1 (LOXL1) is an amino-oxidase involved in maturation of elastic fibers. Its downregulation has been associated with elastic fibers repair loss in aging aorta, lung, ligament, and skin. Several evidences of LOXL1 epigenetic silencing by promoter methylation were reported in cancer and cutis laxa syndrome. We hypothesized that this mechanism could be implicated in skin aging process, as far as elastic fibers are also concerned. Anti-DNMT3A chromatin immunoprecipitation was conducted with nuclear extracts from skin fibroblasts isolated from young and elderly individuals, and showed a higher level of DNMT3A protein binding to the LOXL1 promoter in older cells concomitantly to the decrease of LOXL1 mRNA expression and the increase of LOXL1 promoter methylation. Using luciferase reporter assay driven by LOXL1 promoter in HEK293 cells, we demonstrated that LOXL1 transcriptional activity was dramatically reduced when a recombinant DNMT3A was concomitantly overexpressed. LOXL1 promoter transcriptional activity was restored in the presence of a broad-spectrum inhibitor of DNMT activity, 5-aza-2'-deoxycytidine. Finally, to assess whether the interplay between DNMT3A and LOXL1 promoter could be targeted to increase LOXL1 mRNA expression level, an Origanum majorana extract was selected among 43 plant extracts as a new inhibitor of human DNMT3A activity to restore LOXL1 secretion without cytotoxicity in aged skin fibroblasts.
MeSH Terms
- Aging
- Amino Acid Oxidoreductases
- Cellular Senescence
- Child
- Child, Preschool
- DNA (Cytosine-5-)-Methyltransferases
- DNA Methylation
- Female
- Fibroblasts
- HEK293 Cells
- Humans
- Infant
- Origanum
- Plant Extracts
- Promoter Regions, Genetic
- Protein Binding
- Skin
Keywords
- DNA-methyltransferase
- fibroblasts
- lysyl oxidase-like 1
- skin aging
Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders characterized by abnormal cellular differentiation and maturation with variable progression to acute leukemia. Over the last decade, scientific discoveries have unraveled specific pathways involved in the complex pathophysiology of MDS. Prominent examples include aberrations in cytokines and their signaling pathways (such as tumor necrosis factor-alpha, interferon-gamma, SMAD proteins), mutations in genes encoding the RNA splicing machinery (SF3B1, SRSF2, ZRSR2, and U2AF1 genes), mutations in genes disrupting the epigenetic machinery (TET2, DNMT3A, DNMT3B, EZH2, ASXL1). In addition, abnormalities in regulatory T-cell dynamics and atypical interactions between the bone marrow microenvironment, stroma and progenitor cells, and abnormal maintenance of telomeres are also notable contributors to the complex pathogenesis of MDS. These pathways represent potential targets for novel therapies. Specific therapies include drugs targeting aberrant DNA methylation and chromatin remodeling, modulating/activating the immune system to enhance tumor-specific cellular immune responses and reduce anomalous cytokine signaling, and blocking abnormal interaction between hematopoietic progenitors and stromal cells.
MeSH Terms
- Animals
- Bone Marrow
- Cellular Microenvironment
- Cellular Senescence
- Cytokines
- DNA Methylation
- Epigenesis, Genetic
- Gene Expression Regulation
- Gene Silencing
- Genetic Variation
- Humans
- Immune System Diseases
- Molecular Targeted Therapy
- Myelodysplastic Syndromes
- RNA Splicing
- Signal Transduction
- Stromal Cells
- Telomere
Keywords
- bone marrow microenvironment
- cellular senescence
- cytokines
- epigenetic regulation
- immune dysregulation
- myelodysplastic syndromes
- pathogenesis
- targeted therapies
- telomeric erosion
Alterations in DNA methylation have been associated with cognitive decline and Alzheimer's disease. A recent study of mild cognitive impairment (MCI) reported a significant association between annual decline in cognitive function and the rs11887120 SNP located in DNMT3A, a gene implicated in DNA methylation. Here, we aimed to replicate this finding in two independent MCI cohorts (n = 1024); however, no significant association was observed in either cohort or the pooled dataset. In stratified analyses for conversion to Alzheimer's disease status, no association between rs11887120 and cognitive decline was observed in either converters or nonconverters. In conclusion, our analyses provide no support for the hypothesis that genetic variants in DNMT3A are implicated in cognitive performance decline in individuals with MCI.
MeSH Terms
- Aged
- Aged, 80 and over
- Alzheimer Disease
- Case-Control Studies
- Cognition
- Cognitive Dysfunction
- DNA (Cytosine-5-)-Methyltransferases
- Disease Progression
- Female
- Gene Frequency
- Genetic Association Studies
- Humans
- Male
- Polymorphism, Single Nucleotide
Keywords
- Alzheimer's disease
- DNA methylation
- DNA methyltransferase 3a
- DNMT3A
- MCI
- aging
- cognitive decline
- epigenetics
- mild cognitive impairment
- rs11887120
Epigenetic dysregulation has been associated with cognitive decline and Alzheimer's disease. The present study investigated associations between common SNPs in genes regulating DNA methylation and age-related changes in cognitive decline in two independent prospective cohorts of patients suffering from mild cognitive impairment. An association between the rs1187120 SNP in DNMT3A and annual decline in cognitive functioning was discovered and replicated, suggesting that DNMT3A moderates cognitive decline in subjects with mild cognitive impairment.
MeSH Terms
- Aged
- Case-Control Studies
- Cognition
- Cognitive Dysfunction
- DNA (Cytosine-5-)-Methyltransferases
- Female
- Humans
- Male
- Middle Aged
- Polymorphism, Single Nucleotide
Keywords
- DNA methylation
- DNMT3A
- MCI
- SNP
- aging
- epigenetics
- mild cognitive impairment