Functional Analysis of DNMT3A DNA Methyltransferase Mutations Reported in Patients with Acute Myeloid Leukemia

In mammals, DNA methylation is necessary for the maintenance of genomic stability, gene expression regulation, and other processes. During malignant diseases progression, changes in both DNA methylation patterns and DNA methyltransferase (MTase) genes are observed. Human de novo MTase DNMT3A is most frequently mutated in acute myeloid leukemia (AML) with a striking prevalence of R882H mutation, which has been extensively studied. Here, we investigate the functional role of the missense mutations (S714C, R635W, R736H, R771L, P777R, and F752V) found in the catalytic domain of DNMT3A in AML patients. These were accordingly mutated in the murine Dnmt3a catalytic domain (S124C, R45W, R146H, R181L, P187R, and F162V) and in addition, one-site CpG-containing DNA substrates were used as a model system. The 3-15-fold decrease (S124C and P187R) or complete loss (F162V, R45W, and R146H) of Dnmt3a-CD methylation activity was observed. Remarkably, Pro 187 and Arg 146 are not located at or near the Dnmt3a functional motives. Regulatory protein Dnmt3L did not enhance the methylation activity of R45W, R146H, P187R, and F162V mutants. The key steps of the Dnmt3a-mediated methylation mechanism, including DNA binding and transient covalent intermediate formation, were examined. There was a complete loss of DNA-binding affinity for R45W located in the AdoMet binding region and for R146H. Dnmt3a mutants studied in vitro suggest functional impairment of DNMT3A during pathogenesis

Epigenetic regulation of COL15A1 in smooth muscle cell replicative aging and atherosclerosis

Smooth muscle cell (SMC) proliferation is a hallmark of vascular injury and disease. Global hypomethylation occurs during SMC proliferation in culture and in vivo during neointimal formation. Regardless of the programmed or stochastic nature of hypomethylation, identifying these changes is important in understanding vascular disease, as maintenance of a cells' epigenetic profile is essential for maintaining cellular phenotype. Global hypomethylation of proliferating aortic SMCs and concomitant decrease of DNMT1 expression were identified in culture during passage. An epigenome screen identified regions of the genome that were hypomethylated during proliferation and a region containing Collagen, type XV, alpha 1 (COL15A1) was selected by ‘genomic convergence' for characterization. COL15A1 transcript and protein levels increased with passage-dependent decreases in DNA methylation and the transcript was sensitive to treatment with 5-Aza-2′-deoxycytidine, suggesting DNA methylation-mediated gene expression. Phenotypically, knockdown of COL15A1 increased SMC migration and decreased proliferation and Col15a1 expression was induced in an atherosclerotic lesion and localized to the atherosclerotic cap. A sequence variant in COL15A1 that is significantly associated with atherosclerosis (rs4142986, P = 0.017, OR = 1.434) was methylated and methylation of the risk allele correlated with decreased gene expression and increased atherosclerosis in human aorta. In summary, hypomethylation of COL15A1 occurs during SMC proliferation and the consequent increased gene expression may impact SMC phenotype and atherosclerosis formation. Hypomethylated genes, such as COL15A1, provide evidence for concomitant epigenetic regulation and genetic susceptibility, and define a class of causal targets that sit at the intersection of genetic and epigenetic predisposition in the etiology of complex diseas

Endothelial-to-Mesenchymal Transition in Atherosclerosis: Friend or Foe?

Despite many decades of research, complications of atherosclerosis resulting from the rupture or erosion of unstable plaques remain the leading cause of death worldwide. Advances in cellular lineage tracing techniques have allowed researchers to begin investigating the role of individual cell types in the key processes regulating plaque stability, including maintenance of the fibrous cap, a protective collagen-rich structure that underlies the endothelium. This structure was previously thought to be entirely derived from smooth muscle cells (SMC), which migrated from the vessel wall. However, recent lineage tracing studies have identified endothelial cells (EC) as an essential component of this protective barrier through an endothelial-to-mesenchymal transition (EndoMT), a process that has previously been implicated in pulmonary, cardiac, and kidney fibrosis. Although the presence of EndoMT in atherosclerotic plaques has been shown by several laboratories using EC-lineage tracing mouse models, whether EndoMT is detrimental (i.e., worsening disease progression) or beneficial (i.e., an athero-protective response that prevents plaque instability) remains uncertain as there are data to support both possibilities, which will be further discussed in this review

The effect of ruthenium promotion of the Co/d-Al2O3 catalyst on the hydrogen reduction kinetics of cobalt

The effect of ruthenium content on the reductive activation of the Co/δ-Al2O3 catalyst was investigated using thermal analysis and in situ synchrotron radiation X-ray diffraction. Data of thermal analysis and phase transformations can be described by a kinetic scheme consisting of three sequential steps: Co³⁺ → Co²⁺ → (Co⁰Co²⁺) → Co⁰. The first step is the generation of several CoO clusters within one Co3O4 crystallite followed by their further growth obeying the Avrami–Erofeev kinetic equation (An1) with dimensional parameter n1 < 1, which may indicate the diffusion control of the growth. The second step is the kinetically controlled sequential process of the metallic cobalt phase nucleation (An2), which is followed by the third step of slow particle growth limited by mass transport according to the Jander model (D). Ruthenium promotion of Co/δ-Al2O3 catalysts significantly accelerates the reduction of cobalt. As the ruthenium content is raised to 1 wt%, the characteristic temperature of metal phase formation decreases by more than 200 °C and Ea for An2 step decreases by 25%. For step D, a joint decrease in activation energy and pre-exponential factor in case of ruthenium promotion corresponds to a weaker diffusion impediment at the final step of cobalt reduction. In the case of unmodified Co/δ-Al2O3, the characteristic temperature of the metal phase formation reaches very high values, the metallic nuclei rapidly coalesce into larger ones, and the further process is inhibited by diffusion of the reactants through the product layer. For ruthenium promoted catalysts, each CoO crystallite generates one metal crystallite; thus, ruthenium enhances the dispersion of the active component

The effect of ruthenium promotion of the Co/d-Al2O3 catalyst on the hydrogen reduction kinetics of cobalt

The effect of ruthenium content on the reductive activation of the Co/δ-Al2O3 catalyst was investigated using thermal analysis and in situ synchrotron radiation X-ray diffraction. Data of thermal analysis and phase transformations can be described by a kinetic scheme consisting of three sequential steps: Co³⁺ → Co²⁺ → (Co⁰Co²⁺) → Co⁰. The first step is the generation of several CoO clusters within one Co3O4 crystallite followed by their further growth obeying the Avrami–Erofeev kinetic equation (An1) with dimensional parameter n1 < 1, which may indicate the diffusion control of the growth. The second step is the kinetically controlled sequential process of the metallic cobalt phase nucleation (An2), which is followed by the third step of slow particle growth limited by mass transport according to the Jander model (D). Ruthenium promotion of Co/δ-Al2O3 catalysts significantly accelerates the reduction of cobalt. As the ruthenium content is raised to 1 wt%, the characteristic temperature of metal phase formation decreases by more than 200 °C and Ea for An2 step decreases by 25%. For step D, a joint decrease in activation energy and pre-exponential factor in case of ruthenium promotion corresponds to a weaker diffusion impediment at the final step of cobalt reduction. In the case of unmodified Co/δ-Al2O3, the characteristic temperature of the metal phase formation reaches very high values, the metallic nuclei rapidly coalesce into larger ones, and the further process is inhibited by diffusion of the reactants through the product layer. For ruthenium promoted catalysts, each CoO crystallite generates one metal crystallite; thus, ruthenium enhances the dispersion of the active component

δ -Alumina supported cobalt catalysts promoted by ruthenium for Fischer-Tropsch synthesis

The paper presents the low-temperature nitrogen adsorption, TG, XRD, IR spectroscopy, XPS, TEM and SEM data for ruthenium promoted (0.2–1 wt.%) Сo-δAl2O3 catalysts and characteristics of the catalysts in Fischer-Tropsch synthesis after their activation under the conditions ensuring the reduction of comparable fractions of metallic cobalt. It was shown that cobalt in oxide precursors is a component of the spinel-like Со3-xAlxO4 phase containing the impurity anions СО32−, NO3−, ОН−, and NO in promoted samples, which belong to the thermolysis product of the Ru precursor. Average sizes of Со3-xAlxO4 crystallites are in a range of 5–10 nm. As ruthenium content in the catalyst increases upon reduction, the temperature of metallic phase formation decreases substantially (by more than 150 °C). After the reduction, selectivity of promoted catalysts for α-olefins and high-molecular hydrocarbons was higher in comparison with unpromoted catalysts, without a noticeable decrease in catalytic activity. Therewith, in 0.5–1.0 wt.% catalysts, a part of ruthenium forms individual ultradispersed metallic particles ca. 1 nm in size that are located on the surface of oxide support and are not active in Fischer-Tropsch synthesis. The oxide layer decorating the surface of metallic cobalt particles is also strongly enriched with ruthenium. In the 0.2 wt.% catalyst, the major part of ruthenium resides in metallic cobalt particles. Although the ruthenium-cobalt alloy segregates with enrichment of the surface with cobalt, the presence of ruthenium in the metallic particles and probably in the decorating oxide layer exerts a considerable effect on selectivity of the catalysts