MEF2 transcription factors are key regulators of sprouting angiogenesis

MEF2 and the tumorigenic process, hic sunt leones

While MEF2 transcription factors are well known to cooperate in orchestrating cell fate and adaptive responses during development and adult life, additional studies over the last decade have identified a wide spectrum of genetic alterations of MEF2 in different cancers. The consequences of these alterations, including triggering and maintaining the tumorigenic process, are not entirely clear. A deeper knowledge of the molecular pathways that regulate MEF2 expression and function, as well as the nature and consequences of MEF2 mutations are necessary to fully understand the many roles of MEF2 in malignant cells. This review discusses the current knowledge of MEF2 transcription factors in cancer.

Differential but Complementary HIF1α and HIF2α Transcriptional Regulation

Effective vascular regeneration could provide therapeutic benefit for multiple pathologies, especially in chronic peripheral artery disease (PAD) and myocardial ischemia. The hypoxia inducible factors (HIFs) mediate the cellular transcriptional response to hypoxia and regulate multiple processes that are required for angiogenesis to ultimately restore perfusion and oxygen supply. In endothelial cells, both HIF1α and HIF2α are known to contribute to this role; however, the extent and individual roles of each of these HIFα remain unclear. To characterize the individual roles of HIFα, we sequenced the transcriptional outputs of stabilized forms of HIF1α and HIF2α, where they regulated 701 and 1,454 genes, respectively. HIF1α transcription primarily regulated metabolic reprogramming, whereas HIF2α exerted a larger role in regulating angiogenic extracellular signaling, guidance cues, and extracellular matrix remodeling factors. Furthermore, HIF2α almost exclusively regulated a large and diverse subset of transcription factors and coregulators that contribute to its diverse roles in hypoxia. Further understanding of how HIFs regulate cellular processes in hypoxia and angiogenesis could offer new avenues to modulate physiological angiogenesis to enhance revascularisation in ischemic conditions and other pathologies.

MEF2‑activated long non‑coding RNA PCGEM1 promotes cell proliferation in hormone‑refractory prostate cancer through downregulation of miR‑148a

Prostate cancer gene expression marker 1 (PCGEM1) is a prostate-specific gene overexpressed in prostate cancer cells that promotes cell proliferation. To study the molecular mechanism of PCGEM1 function in hormone-refractory prostate cancer, the interaction between myocyte enhancer factor 2 (MEF2) and PCGEM1 was assessed by a luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay. In addition, the underlying mechanism of PCGEM1 regulating expression of microRNA (miR)-148a in PC3 prostate cancer cells was evaluated. Relative expression levels were measured by reverse transcription-quantitative polymerase chain reaction, and early apoptosis was measured by flow cytometry. PCGEM1 was demonstrated to be overexpressed in prostate cancer tissues compared with noncancerous tissues. Expression levels of PCGEM1 in PC3 cancer cells were demonstrated to be regulated by MEF2, as PCGME1 mRNA was increased by MEF2 overexpression but decreased by MEF2 silencing. MEF2 was also demonstrated to enhance the activity of PCGEM1 promoter and thus promote PCGEM1 transcription. In addition, downregulation of PCGEM1 expression in PC3 cells increased expression of miR-148a. By contrast, overexpression of PCGEM1 decreased miR-148a expression. Finally, PCGME1 silencing by small interfering RNA significantly induced early cell apoptosis but this effect was reduced by a miR-148a inhibitor. In conclusion, the present study demonstrated a positive regulatory association between MEF2 and PCGEM1, and a reciprocal negative regulatory association between PCGEM1 and miR-148a that controls cell apoptosis. The present study, therefore, provides new insights into the mechanism of PCGEM1 function in prostate cancer development.

Identification, molecular characterization and analysis of the expression pattern of SoxF subgroup genes the Yellow River carp, Cyprinus carpio

Sox7, Sox17 and Sox18 are the members of the Sry-related high-mobility group box family (SoxF) of transcription factors. SoxF factors regulate endothelial cell fate as well as development and differentiation of blood cells and lymphatic vessels. There is very less information about the functions of these genes in fish. We obtained the full-length cDNA sequence of SoxF genes including Sox7, Sox17 and Sox18 in Cyprinus carpio, where Sox7 and Sox18 had two copies. The construction of a phylogenetic tree showed that these genes were homologous to the genes in other species. Chromosome synteny analysis indicated that the gene order of Sox7 and Sox18 was highly conserved in fish. However, immense change in genomic sequences around Sox17 had taken place. Numerous putative transcription factor binding sites were identified in the 5_ flanking regions of SoxF genes which may be involved in the regulation of the nervous system, vascular epidermal differentiation and embryonic development. The expression levels of SoxF genes were highest in gastrula, and was abundantly expressed in the adult brain.We investigated the expression levels of SoxF genes in five specific parts of the brain. The expression levels of Sox7 and Sox18 were highest in the mesencephalon, while the expression level of Sox17 was highest in the epencephalon. In carp, the expression patterns of SoxF genes indicated a potential function of these genes in neurogenesis and in vascular development. These results provide new information for further studies on the potential functions of SoxF genes in carp.

RRS1 gene expression involved in the progression of papillary thyroid carcinoma

Background

Papillary thyroid carcinoma (PTC) is one of the most frequent malignancies of the endocrine system, whose mechanisms of pathogenesis, progression and prognosis are still far from being clearly elucidated. Despite an increasing body of evidences highlights ribosome biogenesis regulator homolog (RRS1) as a ribosome biogenesis protein in yeast and plants, little is known about human RRS1 function.

Methods

Proliferation, cell cycle and apoptosis of PTC cells were assessed following the knockdown of RRS1 expression though MTT, colony formation assay, and flow cytometry. Then, transcriptome profiling was conducted to explore pathway changes after RRS1 silencing in PTC cells. Receiver operating characteristic curve and Youden’s index were performed in twenty-four thyroid carcinoma samples to assess their potential clinical diagnostic value.

Results

Firstly, we found that silencing RRS1 significantly reduced cell proliferation, inhibited cell cycle, and promoted apoptosis in PTC cell line. The result also showed that knock-down of RRS1 could up-regulate genes involving apoptosis and metabolism, while, down-regulate genes relative to cell proliferation and blood vessel development. Notably, the present study confirmed the diagnostic value of RRS1 for thyroid carcinoma in both children and adults.

Conclusions

In conclusion, these data afford a comprehensive view of a novel function of human RRS1 by promoting cell proliferation and could be a potential indicator for papillary thyroid carcinoma.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0519-x) contains supplementary material, which is available to authorized users.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

The mechanism and potential targets of class II HDACs in angiogenesis

Angiogenesis refers to the new blood vessels deriving from the existing blood vessels, and it is a complex regulatory process. Angiogenesis is associated with the normal development of the body and tumor growth and migration. The imbalance of histone deacetylase, as an epigenetic modification, could induce the production of diseases, such as cancer, metabolic diseases, etc., and it also plays an important role in angiogenesis. Many researches indicate that class II HDACs nuclear shuttle and its phosphorylation are necessary for the diseases and the protection of the collective itself. This paper will make a review for the relationship between II HDACs and angiogenesis under physiological and pathologic categories, looking forward to the disease treatment in the future.

The endothelial transcription factor ERG mediates Angiopoietin-1-dependent control of Notch signalling and vascular stability

Notch and Angiopoietin-1 (Ang1)/Tie2 pathways are crucial for vascular maturation and stability. Here we identify the transcription factor ERG as a key regulator of endothelial Notch signalling. We show that ERG controls the balance between Notch ligands by driving Delta-like ligand 4 (Dll4) while repressing Jagged1 (Jag1) expression. In vivo, this regulation occurs selectively in the maturing plexus of the mouse developing retina, where Ang1/Tie2 signalling is active. We find that ERG mediates Ang1-dependent regulation of Notch ligands and is required for the stabilizing effects of Ang1 in vivo. We show that Ang1 induces ERG phosphorylation in a phosphoinositide 3-kinase (PI3K)/Akt-dependent manner, resulting in ERG enrichment at Dll4 promoter and multiple enhancers. Finally, we demonstrate that ERG directly interacts with Notch intracellular domain (NICD) and β-catenin and is required for Ang1-dependent β-catenin recruitment at the Dll4 locus. We propose that ERG coordinates Ang1, β-catenin and Notch signalling to promote vascular stability.

Dynamic regulation of VEGF-inducible genes by an ERK/ERG/p300 transcriptional network

The transcriptional pathways activated downstream of vascular endothelial growth factor (VEGF) signaling during angiogenesis remain incompletely characterized. By assessing the signals responsible for induction of the Notch ligand delta-like 4 (DLL4) in endothelial cells, we find that activation of the MAPK/ERK pathway mirrors the rapid and dynamic induction of DLL4 transcription and that this pathway is required for DLL4 expression. Furthermore, VEGF/ERK signaling induces phosphorylation and activation of the ETS transcription factor ERG, a prerequisite for DLL4 induction. Transcription of DLL4 coincides with dynamic ERG-dependent recruitment of the transcriptional co-activator p300. Genome-wide gene expression profiling identified a network of VEGF-responsive and ERG-dependent genes, and ERG chromatin immunoprecipitation (ChIP)-seq revealed the presence of conserved ERG-bound putative enhancer elements near these target genes. Functional experiments performed in vitro and in vivo confirm that this network of genes requires ERK, ERG and p300 activity. Finally, genome-editing and transgenic approaches demonstrate that a highly conserved ERG-bound enhancer located upstream of HLX (which encodes a transcription factor implicated in sprouting angiogenesis) is required for its VEGF-mediated induction. Collectively, these findings elucidate a novel transcriptional pathway contributing to VEGF-dependent angiogenesis.

Endothelial Myocyte Enhancer Factor 2c Inhibits Migration of Smooth Muscle Cells Through Fenestrations in the Internal Elastic Lamina

OBJECTIVE

Laminar flow activates myocyte enhancer factor 2 (MEF2) transcription factors in vitro to induce expression of atheroprotective genes in the endothelium. Here we sought to establish the role of Mef2c in the vascular endothelium in vivo.

APPROACH AND RESULTS

To study endothelial Mef2c, we generated endothelial-specific deletion of Mef2c using Tie2-Cre or Cdh5-Cre-ER^T2 and examined aortas and carotid arteries by en face immunofluorescence. We observed enhanced actin stress fiber formation in the Mef2c-deleted thoracic aortic endothelium (laminar flow region), similar to those observed in normal aortic inner curvature (disturbed flow region). Furthermore, Mef2c deletion resulted in the de novo formation of subendothelial intimal cells expressing markers of differentiated smooth muscle in the thoracic aortas and carotids. Lineage tracing showed that these cells were not of endothelial origin. To define early events in intimal development, we induced endothelial deletion of Mef2c and examined aortas at 4 and 12 weeks postinduction. The number of intimal cell clusters increased from 4 to 12 weeks, but the number of cells within a cluster peaked at 2 cells in both cases, suggesting ongoing migration but minimal proliferation. Moreover, we identified cells extending from the media through fenestrations in the internal elastic lamina into the intima, indicating transfenestral smooth muscle migration. Similar transfenestral migration was observed in wild-type carotid arteries ligated to induce neointimal formation.

CONCLUSIONS

These results indicate that endothelial Mef2c regulates the endothelial actin cytoskeleton and inhibits smooth muscle cell migration into the intima.