Olga F. Sarmento

ePAD, an oocyte and early embryo-abundant peptidylarginine deiminase-like protein that localizes to egg cytoplasmic sheets

Selected for its high relative abundance, a protein spot of MW approximately 75 kDa, pI 5.5 was cored from a Coomassie-stained two-dimensional gel of proteins from 2850 zona-free metaphase II mouse eggs and analyzed by tandem mass spectrometry (TMS), and novel microsequences were identified that indicated a previously uncharacterized egg protein. A 2.4-kb cDNA was then amplified from a mouse ovarian adapter-ligated cDNA library by RACE-PCR, and a unique 2043-bp open reading frame was defined encoding a 681-amino-acid protein. Comparison of the deduced amino acid sequence with the nonredundant database demonstrated that the protein was approximately 40% identical to the calcium-dependent peptidylarginine deiminase (PAD) enzyme family. Northern blotting, RT-PCR, and in situ hybridization analyses indicated that the protein was abundantly expressed in the ovary, weakly expressed in the testis, and absent from other tissues. Based on the homology with PADs and its oocyte-abundant expression pattern, the protein was designated ePAD, for egg and embryo-abundant peptidylarginine deiminase-like protein. Anti-recombinant ePAD monospecific antibodies localized the molecule to the cytoplasm of oocytes in primordial, primary, secondary, and Graafian follicles in ovarian sections, while no other ovarian cell type was stained. ePAD was also expressed in the immature oocyte, mature egg, and through the blastocyst stage of embryonic development, where expression levels began to decrease. Immunoelectron microscopy localized ePAD to egg cytoplasmic sheets, a unique keratin-containing intermediate filament structure found only in mammalian eggs and in early embryos, and known to undergo reorganization at critical stages of development. Previous reports that PAD-mediated deimination of epithelial cell keratin results in cytoskeletal remodeling suggest a possible role for ePAD in cytoskeletal reorganization in the egg and early embryo.

Oxidized Phospholipids Induce Type VIII Collagen Expression and Vascular Smooth Muscle Cell Migration

Phenotypic switching of vascular smooth muscle cells (VSMCs) is known to play a critical role in the development of atherosclerosis. However, the factors present within lesions that mediate VSMC phenotypic switching are unclear. Oxidized phospholipids (OxPLs), including 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine (POVPC), are active components of minimally modified low density lipoprotein and have been previously shown to induce multiple proatherogenic events in endothelial cells and macrophages, but their effects on VSMCs have been largely unexplored until recently. We previously showed that OxPLs induced phenotypic switching of VSMCs, including suppression of SMC differentiation marker genes. The goal of the present studies was to test the hypothesis that OxPLs alter extracellular matrix production and VSMC migration. Results showed that POVPC activated expression of several extracellular matrix proteins in VSMC. POVPC increased expression of type VIII collagen &agr;1 chain (Col8a1) mRNA in cultured VSMCs and in vivo in rat carotid arteries by 9-fold and 4-fold, respectively. POVPC-induced activation of Col8a1 gene expression was reduced by small interfering RNA–mediated suppression of Krüppel-like factor 4 (Klf4) and Sp1, and was abolished in Klf4-knockout VSMCs. POVPC increased Klf4 binding to the Col8a1 gene promoter both in vivo in rat carotid arteries and in cultured VSMCs based on chromatin immunoprecipitation assays. Moreover, POVPC-induced VSMC migration was markedly reduced in Klf4- or type VIII collagen–knockout VSMCs. Given evidence that OxPLs are present within atherosclerotic lesions, it is interesting to suggest that OxPL-induced changes in VSMC phenotype may contribute to the pathogenesis of atherosclerosis at least in part through changes in extracellular matrix composition.

Hbo1 Links p53-Dependent Stress Signaling to DNA Replication Licensing

ABSTRACT Hbo1 is a histone acetyltransferase (HAT) that is required for global histone H4 acetylation, steroid-dependent transcription, and chromatin loading of MCM2-7 during DNA replication licensing. It is the catalytic subunit of protein complexes that include ING and JADE proteins, growth regulatory factors and candidate tumor suppressors. These complexes are thought to act via tumor suppressor p53, but the molecular mechanisms and links between stress signaling and chromatin, are currently unknown. Here, we show that p53 physically interacts with Hbo1 and negatively regulates its HAT activity in vitro and in cells. Two physiological stresses that stabilize p53, hyperosmotic shock and DNA replication fork arrest, also inhibit Hbo1 HAT activity in a p53-dependent manner. Hyperosmotic stress during G1 phase specifically inhibits the loading of the MCM2-7 complex, providing an example of the chromatin output of this pathway. These results reveal a direct regulatory connection between p53-responsive stress signaling and Hbo1-dependent chromatin pathways.

Polycomb Antagonizes p300/CREB-binding Protein-associated Factor to Silence FOXP3 in a Kruppel-like Factor-dependent Manner

Background: Epigenetic regulation of the T regulatory cell transcriptional program remains unclear. Results: Without KLF10, Polycomb permanently silences FOXP3, the master transcription factor of T regulatory cells. Conclusion: Chromatin remodeling events mediated by KLF10 and Polycomb regulate FOXP3 through a Polycomb response element. Significance: Polycomb and KLFs may direct a heritable, broadly applicable regulatory circuit within T cell development. Inducible gene expression underlies the epigenetically inherited differentiation program of most immune cells. We report that the promoter of the FOXP3 gene possesses two distinct functional states: an “off state” mediated by the polycomb histone methyltransferase complex and a histone acetyltransferase-dependent “on state.” Regulating these states is the presence of a Kruppel-like factor (KLF)-containing Polycomb response element. In the KLF10−/− mouse, the FOXP3 promoter is epigenetically silenced by EZH2 (Enhancer of Zeste 2)-mediated trimethylation of Histone 3 K27; thus, impaired FOXP3 induction and inappropriate adaptive T regulatory cell differentiation results in vitro and in vivo. The epigenetic transmittance of adaptive T regulatory cell deficiency is demonstrated throughout more than 40 generations of mice. These results provide insight into chromatin remodeling events key to phenotypic features of distinct T cell populations.

Activation of the pluripotency factor OCT4 in smooth muscle cells is atheroprotective.

Although somatic cell activation of the embryonic stem cell (ESC) pluripotency factor OCT4 has been reported, this previous work has been controversial and has not demonstrated a functional role for OCT4 in somatic cells. Here we demonstrate that smooth muscle cell (SMC)-specific conditional knockout of Oct4 in Apoe−/− mice resulted in increased lesion size and changes in lesion composition that are consistent with decreased plaque stability, including a thinner fibrous cap, increased necrotic core area, and increased intraplaque hemorrhage. Results of SMC-lineage-tracing studies showed that these effects were probably the result of marked reductions in SMC numbers within lesions and SMC investment within the fibrous cap, which may result from impaired SMC migration. The reactivation of Oct4 within SMCs was associated with hydroxymethylation of the Oct4 promoter and was hypoxia inducible factor-1α (HIF-1α, encoded by HIF1A) and Krüppel-like factor-4 (KLF4)-dependent. These results provide the first direct evidence that OCT4 has a functional role in somatic cells, and they highlight the potential role of OCT4 in normal and diseased somatic cells.

The Role of the Histone Methyltransferase Enhancer of Zeste Homolog 2 (EZH2) in the Pathobiological Mechanisms Underlying Inflammatory Bowel Disease (IBD)

Regulatory T (Treg) cells expressing the transcription factor FOXP3 play a pivotal role in maintaining immunologic self-tolerance. We and others have shown previously that EZH2 is recruited to the FOXP3 promoter and its targets in Treg cells. To further address the role for EZH2 in Treg cellular function, we have now generated mice that lack EZH2 specifically in Treg cells (EZH2Δ/ΔFOXP3+). We find that EZH2 deficiency in FOXP3+ T cells results in lethal multiorgan autoimmunity. We further demonstrate that EZH2Δ/ΔFOXP3+ T cells lack a regulatory phenotype in vitro and secrete proinflammatory cytokines. Of special interest, EZH2Δ/ΔFOXP3+ mice develop spontaneous inflammatory bowel disease. Guided by these results, we assessed the FOXP3 and EZH2 gene networks by RNA sequencing in isolated intestinal CD4+ T cells from patients with Crohns disease. Gene network analysis demonstrates that these CD4+ T cells display a Th1/Th17-like phenotype with an enrichment of gene targets shared by FOXP3 and EZH2. Combined, these results suggest that the inflammatory milieu found in Crohns disease could lead to or result from deregulation of FOXP3/EZH2-enforced T cell gene networks contributing to the underlying intestinal inflammation.

A Novel Role for Kruppel-like Factor 14 (KLF14) in T-Regulatory Cell Differentiation

Background & Aims Kruppel-like Factor 14 (KLF14) proteins function as epigenetic reprogramming factors during cell differentiation in many cell populations and in engineered induced pluripotent stem cells. In this study, we determined the function of KLF14 in the regulation of forkhead box protein 3 (FOXP3), a transcription factor critical for T regulatory (Treg) cell differentiation. Methods We studied the effects of KLF14 on FOXP3 expression at the level of the protein and mRNA. We evaluated the functional relevance of KLF14 to FOXP3+ Treg cells in vitro and in vivo through suppression assays and two colitis models. Finally, we analyzed the effect of KLF14 on the epigenetic landscape of the FOXP3 promoter locus through chromatin immunoprecipitation (ChIP) assay. Results KLF14, induced upon activation of naïve CD4+ T cells, segregates to the FOXP3- population and is inversely associated with FOXP3 expression and Treg function. KLF14 knockout (KO) CD4+ cells differentiated into adaptive Tregs more readily in vitro and in vivo. KLF14 KO cells demonstrated an enhanced Treg suppressor function in vitro and in vivo. KLF14 repressed FOXP3 at the level of the mRNA and protein, and by ChIP assay KLF14 was found to bind to the Treg-specific demethylation region (TSDR) enhancer region of FOXP3. Furthermore, loss of KLF14 reduced the levels of H3K9me3, HP1, and Suv39H1at the TSDR. Conclusions These results outline a novel mechanism by which KLF14 regulates Treg cell differentiation via chromatin remodeling at the FOXP3 TSDR. To our knowledge, this is the first evidence to support a role for KLF14 in maintaining the differentiated state of Treg cells, with an outline of a potential mechanism to modify the expression of immune genes such as FOXP3 that are critical to T-cell fate.

Krüppel-like factor KLF10 regulates Transforming growth factor receptor II expression and TGF-β signaling in CD8 + T lymphocytes

KLF10 has recently elicited significant attention as a transcriptional regulator of transforming growth factor-β1 (TGF-β1) signaling in CD4(+) T cells. In the current study, we demonstrate a novel role for KLF10 in the regulation of TGF-β receptor II (TGF-βRII) expression with functional relevance in antiviral immune response. Specifically, we show that KLF10-deficient mice have an increased number of effector/memory CD8(+) T cells, display higher levels of the T helper type 1 cell-associated transcription factor T-bet, and produce more IFN-γ following in vitro stimulation. In addition, KLF10(-/-) CD8(+) T cells show enhanced proliferation in vitro and homeostatic proliferation in vivo. Freshly isolated CD8(+) T cells from the spleen of adult mice express lower levels of surface TGF-βRII (TβRII). Congruently, in vitro activation of KLF10-deficient CD8(+) T cells upregulate TGF-βRII to a lesser extent compared with wild-type (WT) CD8(+) T cells, which results in attenuated Smad2 phosphorylation following TGF-β1 stimulation compared with WT CD8(+) T cells. Moreover, we demonstrate that KLF10 directly binds to the TGF-βRII promoter in T cells, leading to enhanced gene expression. In vivo viral infection with Daniels strain Theilers murine encephalomyelitis virus (TMEV) also led to lower expression of TGF-βRII among viral-specific KLF10(-/-) CD8(+) T cells and a higher percentage of IFN-γ-producing CD8(+) T cells in the spleen. Collectively, our data reveal a critical role for KLF10 in the transcriptional activation of TGF-βRII in CD8(+) T cells. Thus, KLF10 regulation of TGF-βRII in this cell subset may likely play a critical role in viral and tumor immune responses for which the integrity of the TGF-β1/TGF-βRII signaling pathway is crucial.

O-015 YI Alterations in the FOXP3-EZH2 Pathway Associates with Increased Susceptibility to Colitis in Both Mice and Human.

Background:Crohns disease is a common intestinal inflammatory disorder of uncertain etiology and incomplete treatment options. It is characterized by lesions infiltrated by inflammatory CD4+ lymphocytes; yet the mechanism of CD4+ mediated pathophysiology is unclear. Through whole genome approaches on clinical cohorts of CD patients, combined with functional in-vivo and in-vitro murine data, we sought to identify and evaluate aberrant transcriptional gene networks in disease-associated CD4+ cells. Methods:We comparatively studied the expression profile in CD4+ lymphocytes isolated from the Ileum of 21 CD-affected individuals and 12 age/gender matched control individuals. Utilizing RNA-seq, we conducted upstream target analysis to identify top disease associated regulatory networks. Potential coordinated function between FOXP3 and EZH2 was identified, and common gene targets were interrogated for differential expression and pathway analysis.We crossed FOXP3-driven CRE recombinase expressing mice (B6129S-Tg(Foxp3-EGFP/cre)1aJbs/J) with EZH2fl/fl animals to better define the effect of EZH2 ablation on Treg function. Splenocytes were analyzed by cell surface markers for T cell distribution and phenotype. EZH2&Dgr;/&Dgr; FOXP3+ cell function was determined by in-vitro Treg suppressor function assay. Cytokine analyses were performed on supernatants of stimulated EZH2&Dgr;/&Dgr;FOXP3+ splenocytes and serum from 14 to 17 days old FOXP3-CRE;EZH2&Dgr;/&Dgr; mice. FOXP3-CRE;EZH2&Dgr;/&Dgr; or animals treated with EZH2 inhibitors received 3% DSS in an acute model of colitis. Furthermore, RB45high transfer utilizing WT or EZH2&Dgr;/&Dgr;Tregs was used in a chronic model of colitis. Results:Differential expression analysis between CD and CTRL samples revealed 5328 statistically significant Differentially Expressed Genes (DEGs). Principle component analysis, and hierarchical clustering, separated patients from control subjects. Among the DEGs, 83 were well-defined transcription factors (TFs) identified by Master Regulatory Analysis. The transcription factor FOXP3 and its associated regulatory network emerged as a highly differentially expressed pathway in diseased samples by Master Regulatory Analysis, Ingenuity Pathway Analysis, and Gene Set Enrichment Analysis. Additionally, common gene targets for both FOXP3 and EZH2 were concurrently up regulated in disease. Genetic ablation of EZH2 in mouse FOXP3+ cells resulted in Treg cells converted to a TH1/TH17- like effector phenotype, a pattern shared by disease associated CD4+ T cells. These cells exhibited pro-inflammatory cell surface markers, cytokine expression, and reduced in-vitro suppressive capacity. EZH2&Dgr;/&Dgr; Tregs failed to mitigate both DSS and T cell mediated colitis, and mice treated with the EZH2 inhibitor DZNep were also more susceptible to DSS colitis. Conclusions:In conclusion, we compare EZH2/Foxp3 co-regulation of gene networks between Crohns lesions and controls, and in multiple mouse models, to clarify the role of epigenetic regulation in this disease process. Multiple colitis disease models show us that interfering with EZH2 by genetic or pharmaceutical methods results in increased susceptibility to colitis. We postulate the inflammatory milieu found in IBD modulates EZH2 function, thereby making it less able to co-repress non-Treg differentiation programs even in the presence of upregulated FOXP3. Further investigation into EZH2 mutations, signaling cascades and relevant post-translation modifications to the FOXP3-EZH2 gene network may assist to elucidate and predict disease progression and/or severity.

Epigenetics of gastrointestinal diseases: notes from a workshop

ABSTRACT International experts gathered at the Mayo Clinic (Rochester MN, USA) on February 27th-28th, 2017 for a meeting entitled ‘Basic and Translational Facets of the Epigenetics of GI Diseases’. This workshop summarized recent advances on the role of epigenetics in the pathobiology of gastrointestinal (GI) diseases. Highlights of the meeting included recent advances on the involvement of different epigenetic mechanisms in malignant and nonmalignant GI disorders and the epigenetic heterogeneity exhibited in these diseases. The translational value of epigenetic drugs, as well as the current and future use of epigenetic changes (i.e., DNA methylation patterns) as biomarkers for early detection tools or disease stratification were also important topics of discussion.