SALM4 regulates angiogenic functions in endothelial cells through VEGFR2 phosphorylation at Tyr1175.

Angiogenesis depends on VEGF-mediated signaling. However, the regulatory mechanisms and functions of individual VEGF receptor 2 (VEGFR2) phosphorylation sites remain unclear. Here, we report that synaptic adhesion-like molecule 4 (SALM4) regulates a specific VEGFR2 phosphorylation site. SALM4 silencing in HUVECs and Salm4 knockout (KO) in lung endothelial cells (ECs) of Salm4-/- mice suppressed phosphorylation of VEGFR2 tyrosine (Y) 1175 (Y1173 in mice) and downstream signaling upon VEGF-A stimulation. However, VEGFR2 phosphorylation at Y951 (Y949 in mice) and Y1214 (Y1212 in mice) remained unchanged. Knockdown and KO of SALM4 inhibited VEGF-A-induced angiogenic functions of ECs. SALM4 depletion reduced endothelial leakage, sprouting, and migratory activities. Furthermore, in an ischemia and reperfusion (I/R) model, brain injury was attenuated in Salm4-/- mice compared with wild-type (WT) mice. In brain lysates after I/R, VEGFR2 phosphorylation at Y949, Y1173, and Y1212 were induced in WT brains, but only Y1173 phosphorylation of VEGFR2 was reduced in Salm4-/- brains. Taken together, our results demonstrate that SALM4 specifically regulates VEGFR2 phosphorylation at Y1175 (Y1173 in mice), thereby fine-tuning VEGF signaling in ECs.-Kim, D. Y., Park, J. A., Kim, Y., Noh, M., Park, S., Lie, E., Kim, E., Kim, Y.-M., Kwon, Y.-G. SALM4 regulates angiogenic functions in endothelial cells through VEGFR2 phosphorylation at Tyr1175.

Endothelial Snail Regulates Capillary Branching Morphogenesis via Vascular Endothelial Growth Factor Receptor 3 Expression.

Vascular branching morphogenesis is activated and maintained by several signaling pathways. Among them, vascular endothelial growth factor receptor 2 (VEGFR2) signaling is largely presented in arteries, and VEGFR3 signaling is in veins and capillaries. Recent reports have documented that Snail, a well-known epithelial-to-mesenchymal transition protein, is expressed in endothelial cells, where it regulates sprouting angiogenesis and embryonic vascular development. Here, we identified Snail as a regulator of VEGFR3 expression during capillary branching morphogenesis. Snail was dramatically upregulated in sprouting vessels in the developing retinal vasculature, including the leading-edged vessels and vertical sprouting vessels for capillary extension toward the deep retina. Results from in vitro functional studies demonstrate that Snail expression colocalized with VEGFR3 and upregulated VEGFR3 mRNA by directly binding to the VEGFR3 promoter via cooperating with early growth response protein-1. Snail knockdown in postnatal mice attenuated the formation of the deep capillary plexus, not only by impairing vertical sprouting vessels but also by downregulating VEGFR3 expression. Collectively, these data suggest that the Snail-VEGFR3 axis controls capillary extension, especially in vessels expressing VEGFR2 at low levels.

Sac-1004, a vascular leakage blocker, reduces cerebral ischemia-reperfusion injury by suppressing blood-brain barrier disruption and inflammation.

BACKGROUND: Blood-brain barrier (BBB) breakdown and inflammation are critical events in ischemic stroke, contributing to aggravated brain damage. The BBB mainly consists of microvascular endothelial cells sealed by tight junctions to protect the brain from blood-borne substances. Thus, the maintenance of BBB integrity may be a potential target for neuroprotection. Sac-1004, a pseudo-sugar derivative of cholesterol, enhances the endothelial barrier by the stabilization of the cortical actin ring. RESULTS: Here, we report on the protective effects of Sac-1004 on cerebral ischemia-reperfusion (I/R) injury. Treatment with Sac-1004 significantly blocked the interleukin-1ß-induced monolayer hyperpermeability of human brain microvascular endothelial cells (HBMECs), loss of tight junctions, and formation of actin stress fiber. Sac-1004 suppressed the expression of adhesion molecules, adhesion of U937 cells, and activation of nuclear factor-κB in HBMECs. Using a rat model of transient focal cerebral ischemia, it was shown that Sac-1004 effectively ameliorated neurological deficits and ischemic damage. In addition, Sac-1004 decreased BBB leakage and rescued tight junction-related proteins. Moreover, the staining of CD11b and glial fibrillary acidic protein showed that Sac-1004 inhibited glial activation. CONCLUSIONS: Taken together, these results demonstrate that Sac-1004 has neuroprotective activities through maintaining BBB integrity, suggesting that it is a great therapeutic candidate for stroke.

Gynuella sunshinyii gen. nov., sp. nov., an antifungal rhizobacterium isolated from a halophyte, Carex scabrifolia Steud.

An antifungal bacterial strain, designated YC6258(T), was isolated from the rhizosphere of a halophyte (Carex scabrifolia Steud.) growing in a tidal flat area of Namhae Island, Korea. Cells of the strain were Gram-stain-negative, facultatively anaerobic, moderately halophilic, rod-shaped and motile by a single polar flagellum. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YC6258(T) formed a phyletic lineage distinct from members of the most closely related genera, Saccharospirillum and Reinekea, with less than 91.2 % sequence similarities. The major cellular fatty acids were C18 : 1ω7c, C16 : 0 and Summed feature 3 (C16 : 1ω7c/ C16 : 1ω6c). The quinone system of strain YC6258(T) consisted mainly of ubiquinone Q-8. The polar lipid profile exhibited phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and unknown lipids. The DNA G+C content was 48.9 mol%. Based on the phylogenetic and phenotypic characteristics, strain YC6258(T) should be classified as a representative of a novel species in a novel genus for which the name Gynuella sunshinyii gen. nov., sp. nov. is proposed. The type strain is YC6258(T) (KCCM 43015(T) = NBRC 109345(T)).

Sensititre MYCOTB MIC plate for testing Mycobacterium tuberculosis susceptibility to first- and second-line drugs.

For Mycobacterium tuberculosis, phenotypic methods for drug susceptibility testing of second-line drugs are poorly standardized and technically challenging. The Sensititre MYCOTB MIC plate (MYCOTB) is a microtiter plate containing lyophilized antibiotics and configured for determination of MICs to first- and second-line antituberculosis drugs. To evaluate the performance of MYCOTB for M. tuberculosis drug susceptibility testing using the Middlebrook 7H10 agar proportion method (APM) as the comparator, we conducted a two-site study using archived M. tuberculosis isolates from Uganda and the Republic of Korea. Thawed isolates were subcultured, and dilutions were inoculated into MYCOTB wells and onto 7H10 agar. MYCOTB results were read at days 7, 10, 14, and 21; APM results were read at 21 days. A total of 222 isolates provided results on both platforms. By APM, 106/222 (47.7%) of isolates were resistant to at least isoniazid and rifampin. Agreement between MYCOTB and APM with respect to susceptibility or resistance was ≥92% for 7 of 12 drugs when a strict definition was used and ≥96% for 10 of 12 drugs when agreement was defined by allowing a ± one-well range of dilutions around the APM critical concentration. For ethambutol, agreement was 80% to 81%. For moxifloxacin, agreement was 83% to 85%; incorporating existing DNA sequencing information for discrepant analysis raised agreement to 91% to 96%. For MYCOTB, the median time to plate interpretation was 10 days and interreader agreement was ≥95% for all drugs. MYCOTB provided reliable results for M. tuberculosis susceptibility testing of first- and second-line drugs except ethambutol, and results were available sooner than those determined by APM.

In Vitro Effects of Weissella cibaria CMU and CMS1 on Receptor Activator of NF-κB Ligand (RANKL)-Induced Osteoclast Differentiation.

Excessive osteoclast activity can promote periodontitis-associated bone destruction. The inhibitory mechanisms of Weissella cibaria strains CMU and CMS1 against periodontitis have not yet been fully elucidated. In this study, we aimed to investigate whether heat-killed (HK) W. cibaria CMU and CMS1 or their respective cell-free supernatants (CFSs) inhibit osteoclast differentiation and bone resorption in response to receptor activator of nuclear factor kappa-B ligand (RANKL)-treated RAW 264.7 cells. TRAP (tartrate-resistant acid phosphatase) staining and bone resorption assays revealed that both HK bacteria and CFSs significantly suppressed the number of TRAP-positive cells, TRAP activity, and bone pit formation compared to the RANKL-treated control (p < 0.05). HK bacteria dose-dependently inhibited osteoclastogenesis while selectively regulating certain genes in CFSs (p < 0.05). We found that disrupting the direct interaction between HK bacteria and RAW 264.7 cells abolished the inhibitory effect of HK bacteria on the expression of osteoclastogenesis-associated proteins (c-Fos, nuclear factor of activated T cells c1 (NFATc1), and cathepsin K). These results suggest that dead bacteria suppress osteoclast differentiation more effectively than the metabolites and may serve as beneficial agents in preventing periodontitis by inhibiting osteoclast differentiation via direct interaction with cells.

Hoeflea suaedae sp. nov., an endophytic bacterium isolated from the root of the halophyte Suaeda maritima.

A Gram-negative, aerobic, short rod-shaped bacterium, designated strain YC6898(T), was isolated from the surface-sterilized root of a halophyte (Suaeda maritima) inhabiting tidal flat of Namhae Island, Korea. Strain YC6898(T) grew optimally at 30-37 °C and pH 6.5-7.5. The strain inhibited mycelial growth of Pythium ultimum and Phytophthora capsici. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain YC6898(T) belongs to the genus Hoeflea in the family Phyllobacteriaceae. Its closest relatives were Hoeflea alexandrii AM1V30(T) (96.7% 16S rRNA gene sequence similarity), Hoeflea anabaenae WH2K(T) (95.7%), Hoeflea phototrophica DFL-43(T) (95.5%) and Hoeflea marina LMG 128(T) (94.8%). Strain YC6898(T) contained Q-10 as the major ubiquinone. The major fatty acids of strain YC6898(T) were C18:1ω7c (61.1%), C16:0 (11.9%), 11-methyl C18:1ω7c (9.6%) and C19:0 cyclo ω8c (8.0%). The polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, unknown lipids and an unknown glycolipid. The total genomic DNA G+C content was 53.7 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic analysis, strain YC6898(T) represents a novel species of the genus Hoeflea, for which the name Hoeflea suaedae sp. nov. is proposed. The type strain is YC6898(T) (=KACC 14911(T)=NBRC 107700(T)).

Amorphus suaedae sp. nov., isolated from the root of a tidal flat plant, Suaeda maritima.

A novel bacterial strain, YC6899(T), was isolated from the root of Suaedae maritima growing on a tidal flat of Namhae Island, Korea. Cells were Gram-reaction-negative, rod-shaped, non-motile, slightly halophilic and heterotrophic. Strain YC6899(T) grew optimally at a salinity of 2-4 %, at 25-37 °C and at pH 6.5-8.0. Phylogenetic analysis of 16S rRNA gene sequences demonstrated that strain YC6899(T) was closely related to Amorphus orientalis YIM D10(T) (96.1 % similarity) and Amorphus coralli RS.Sph.026(T) (95.9 %). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unknown aminolipids, an unknown aminophospholipid, an unknown aminoglycolipid, unknown glycolipids and unknown lipids. The major fatty acids of strain YC6899(T) were C19 : 0 cyclo ω8c and C18 : 1ω7c. The G+C content of the genomic DNA was 61.3 mol%. Strain YC6899(T) contained ubiquinone-10 (Q-10) as the major respiratory quinone system. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain YC6899(T) represents a novel species within the genus Amorphus, for which the name Amorphus suaedae sp. nov. is proposed. The type strain is YC6899(T) ( = KACC 14912(T) = NBRC 107845(T)).

Meteorin promotes the formation of GFAP-positive glia via activation of the Jak-STAT3 pathway.

Meteorin is an orphan ligand which has been previously reported to control neuritogenesis and angiogenesis, as well as gliogenesis. However, the precise function of this factor in CNS development and the underlying molecular mechanisms are poorly understood. Here, we demonstrate that meteorin is involved in GFAP-positive glial differentiation through activation of the Jak-STAT3 pathway, by using neurosphere and retinal explant culture systems. During embryonic brain development, meteorin is highly expressed in neural stem and radial glia cells of the ventricular zone and immature neurons outside the ventricular zone but its expression disappears spontaneously as development proceeds except in GFAP-positive astrocytes. In cultured neurospheres, meteorin activates STAT3, and in turn increases the transcriptional activity of GFAP by enhancing the binding of STAT3 to the promoter. By meteorin stimulation, differentiating neurospheres show increased numbers of GFAP-positive cells, but the effect is abrogated by a blockade of the Jak-STAT3 pathway using either a Jak inhibitor or STAT3 siRNA. Furthermore, we expand our findings to the retina, and show that meteorin increases GFAP expression in Müller glia. Together, our results suggest that meteorin promotes GFAP-positive glia formation by mediating the Jak-STAT3 signaling pathway during both cortical stem cell differentiation and retinal glia development.

Nuclear IL-33 is a transcriptional regulator of NF-κB p65 and induces endothelial cell activation.

Interleukin (IL)-33, an IL-1 family member, acts as an extracellular cytokine by binding its cognate receptor, ST2. IL-33 is also a chromatin-binding transcriptional regulator highly expressed in the nuclei of endothelial cells. However, the function of IL-33 as a nuclear factor is poorly defined. Here, we show that IL-33 is a novel transcriptional regulator of the p65 subunit of the NF-κB complex and is involved in endothelial cell activation. Quantitative reverse transcriptase PCR and Western blot analyses indicated that IL-33 mediates the expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 in endothelial cells basally and in response to tumor necrosis factor-a-treatment. IL-33-induced ICAM-1/VCAM-1 expression was dependent on the regulatory effect of IL-33 on the nuclear factor (NF)-κB pathway; NF-κB p65 expression was enhanced by IL-33 overexpression and, conversely, reduced by IL-33 knockdown. Moreover, NF-κB p65 promoter activity and chromatin immunoprecipitation analysis revealed that IL-33 binds to the p65 promoter region in the nucleus. Our data provide the first evidence that IL-33 in the nucleus of endothelial cells participates in inflammatory reactions as a transcriptional regulator of NF-κB p65.

Receptor activator of nuclear factor kappaB ligand is a novel inducer of tissue factor in macrophages.

RATIONALE: Although recent studies have suggested a role for the receptor activator of nuclear factor κB ligand (RANKL) in the late stages of atherosclerosis (eg, plaque destabilization and rupture), the underlying mechanisms and subsequent events are unclear. OBJECTIVE: Because blood clotting is common after plaque rupture, we hypothesized that RANKL influenced tissue factor (TF) expression and activity to initiate the coagulation cascade. METHODS AND RESULTS: RANKL increased the TF mRNA level and procoagulant activity in macrophages, as determined by semiquantitative reverse transcription polymerase chain reaction (semiquantitative RT-PCR) and a chromogenic assay. TF promoter analysis revealed that AP-1 and Egr-1 are responsible for RANKL-induced TF transcription. In addition, RANKL increased phosphorylation of c-Jun NH(2)-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)1/2. RANKL-induced TF expression was attenuated by JNK- and MEK1-specific inhibitors and by small interfering RNA knockdown of c-Jun and Egr-1. CONCLUSION: Our results indicate that RANKL induces TF in macrophages mainly through the cooperative action of AP-1 and Egr-1 via JNK and ERK1/2 pathways. These findings provide strong mechanistic support for the role of RANKL in the thrombogenicity of atherosclerotic plaques.

AKAP12 regulates human blood-retinal barrier formation by downregulation of hypoxia-inducible factor-1alpha.

Many diseases of the eye such as retinoblastoma, diabetic retinopathy, and retinopathy of prematurity are associated with blood-retinal barrier (BRB) dysfunction. Identifying the factors that contribute to BRB formation during human eye development and maintenance could provide insights into such diseases. Here we show that A-kinase anchor protein 12 (AKAP12) induces BRB formation by increasing angiopoietin-1 and decreasing vascular endothelial growth factor (VEGF) levels in astrocytes. We reveal that AKAP12 downregulates the level of hypoxia-inducible factor-1alpha (HIF-1alpha) protein by enhancing the interaction of HIF-1alpha with pVHL (von Hippel-Lindau tumor suppressor protein) and PHD2 (prolyl hydroxylase 2). Conditioned media from AKAP12-overexpressing astrocytes induced barriergenesis by upregulating the expression of tight junction proteins in human retina microvascular endothelial cells (HRMECs). Compared with the retina during BRB maturation, AKAP12 expression in retinoblastoma patient tissue was markedly reduced whereas that of VEGF was increased. These findings suggest that AKAP12 may induce BRB formation through antiangiogenesis and barriergenesis in the developing human eye and that defects in this mechanism can lead to a loss of tight junction proteins and contribute to the development of retinal pathologies such as retinoblastoma.

Functional and developmental analysis of the blood-brain barrier in zebrafish.

The blood-brain barrier (BBB) is essential for maintaining brain homeostasis and protecting the brain from toxic substances. Breakdown of this barrier results in severe brain pathologies, whereas impermeability of the BBB is a major obstacle for drug delivery to the brain. Despite its importance, our understanding of the maturation and modulation of the BBB is limited. Zebrafish (Danio rerio) has emerged as a useful model organism for studying vertebrate development and disease mechanisms, as well as for preclinical drug screening. However, the nature of the BBB has not yet been examined in teleost fish. In this paper, we report that with the exception of the circumventricular organs, the cerebral microvessels in zebrafish are impermeable to sulfo-NHS-biotin and horseradish peroxidase (HRP). Brain endothelial cells show immunoreactivity to Claudin-5 and Zonula Occludens-1 (ZO-1), implying the presence of tight junctions in these cells. The expression of Claudin-5 and ZO-1 was detected in cerebral microvessels from 3 days post-fertilization (dpf), concomitant with maturation of the BBB, as determined by restricted permeability to HRP and various fluorescent tracers. Real-time analysis of fluorescent tracer leakage in embryonic zebrafish suggests that they may be used as an in vivo model for BBB breakdown. Taken together, our results show that the endothelial tight junction-based BBB of zebrafish is similar to that of higher vertebrates and thus, zebrafish may be an excellent genetic and experimental model organism for studying development and maintenance of the BBB.

Protective effect of the green tea component, L-theanine on environmental toxins-induced neuronal cell death.

Several environmental neurotoxins and oxidative stress inducers are known to damage the nervous system and are considered major factors associated with the selective vulnerability of nigral dopaminergic neurons in Parkinson's disease (PD). Gamma-glutamylethylamide (L-theanine), a natural glutamate analog in green tea, has been shown to exert strong anti-ischemic effect. In this study, we investigated the protective effects of L-theanine on neurotoxicity induced by PD-related neurotoxicants, rotenone and dieldrin in cultured human dopaminergic cell line, SH-SY5Y. Our initial experiments revealed that L-theanine (500 microM) attenuated both rotenone- and dieldrin-induced DNA fragmentation and apoptotic death in SH-SY5Y cells. In addition, L-theanine partially prevented both rotenone- and dieldrin-induced heme oxygenase-1 (HO-1) up-regulation. Both rotenone- and dieldrin-induced down-regulation of extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation was significantly blocked by pretreatment with L-theanine. Furthermore, pretreatment with L-theanine significantly attenuated the down-regulation of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) production in SH-SY5Y cells. These results suggest that L-theanine directly provide neuroprotection against PD-related neurotoxicants and may be clinically useful for preventing PD symptoms.

Hippo-YAP/TAZ signaling in angiogenesis.

Angiogenesis is a complex, multistep process involving dynamic changes in endothelial cell (EC) shapes and behaviors, especially in specialized cell types such as tip cells (with active filopodial extensions), stalk cells (with less motility) and phalanx cells (with stable junction connections). The Hippo-Yes-associated protein (YAP)/ transcription activator with PDZ binding motif (TAZ) signaling plays a critical role in development, regeneration and organ size by regulating cell-cell contact and actin cytoskeleton dynamics. Recently, with the finding that YAP is expressed in the front edge of the developing retinal vessels, Hippo-YAP/TAZ signaling has emerged as a new pathway for blood vessel development. Intriguingly, the LATS1/2-mediated angiomotin (AMOT) family and YAP/TAZ activities contribute to EC shapes and behaviors by spatiotemporally modulating actin cytoskeleton dynamics and EC junction stability. Herein, we summarize the recent understanding of the role of Hippo-YAP/TAZ signaling in the processes of EC sprouting and junction maturation in angiogenesis. [BMB Reports 2018; 51(3): 157-162].

Regulation of the HIF-1alpha stability by histone deacetylases.

Histone deacetylase inhibitors (HDACIs) are currently in clinical trials partly due to their potent anti-angiogenic effects. However, the detailed mechanism of their action is unclear. Here, we observed that several HDACIs (TSA, SB, Apicidin, and VPA) dramatically decreased HIF-1alpha protein level and transcriptional activity of HIF-1 in human and mouse tumor cell lines. Furthermore, class I HDACs, HDAC1 and 3 enhanced HIF-1alpha stability and HIF-1 transactivation function in hypoxic conditions. In addition, immunoprecipitation and in vitro binding assays revealed that HDAC1 and 3 directly bind to the oxygen-dependent degradation domain of HIF-1alpha. Collectively, these results suggest that HDAC1 and 3 are considered as a positive regulator of HIF-1alpha stability via direct interaction and may play an important role in HIF-1-induced tumor angiogenesis.

Integrative analysis of DNA methylation and mRNA expression during differentiation of umbilical cord blood derived mononuclear cells to endothelial cells.

Differentiation of umbilical cord blood derived mononuclear cells to endothelial cells is accompanied by massive changes in gene expression. Although methylation and demethylation of DNA likely play crucial roles in regulating gene expression, their interplay during differentiation remains elusive. To address this question, we performed deep sequencing of DNA methylation and mRNA expression to profile global changes in promoter methylation and gene expression during differentiation from mononuclear cells to outgrowing cells. We identified 61 downregulated genes with hypermethylation, including CD74, VAV1, TLR8, and NCF4, as well as 21 upregulated genes with hypomethylation, including ECSCR, MCAM, PGF, and ARHGEF15. Interestingly, gene ontology analysis showed that downregulated genes with hypermethylation were enriched in immune-related functions, and upregulated genes with hypomethylation were enriched in the developmental process and angiogenesis, indicating the important roles of DNA methylation in regulating differentiation. We performed polymerase chain reaction analyses and bisulfite sequencing of representative genes (CD74, VAV1, ECSCR, and MCAM) to verify the negative correlation between DNA methylation and gene expression. Further, inhibition of DNA methyltransferase and demethylase activities using 5'-aza-dc and shRNAs, specific for TET1 and TET2 mRNAs, respectively, revealed that DNA methylation was the main regulator of the reversible expression of functionally important genes. Collectively, our findings implicate DNA methylation as a critical regulator of gene expression during umbilical cord blood derived mononuclear cells to endothelial cell differentiation.

Carbohydrate-binding protein CLEC14A regulates VEGFR-2- and VEGFR-3-dependent signals during angiogenesis and lymphangiogenesis.

Controlled angiogenesis and lymphangiogenesis are essential for tissue development, function, and repair. However, aberrant neovascularization is an essential pathogenic mechanism in many human diseases, including diseases involving tumor growth and survival. Here, we have demonstrated that mice deficient in C-type lectin family 14 member A (CLEC14A) display enhanced angiogenic sprouting and hemorrhage as well as enlarged jugular lymph sacs and lymphatic vessels. CLEC14A formed a complex with VEGFR-3 in endothelial cells (ECs), and CLEC14A KO resulted in a marked reduction in VEGFR-3 that was concomitant with increases in VEGFR-2 expression and downstream signaling. Implanted tumor growth was profoundly reduced in CLEC14A-KO mice compared with that seen in WT littermates, but tumor-bearing CLEC14A-KO mice died sooner. Tumors in CLEC14A-KO mice had increased numbers of nonfunctional blood vessels and severe hemorrhaging. Blockade of VEGFR-2 signaling suppressed these vascular abnormalities and enhanced the survival of tumor-bearing CLEC14A-KO mice. We conclude that CLEC14A acts in vascular homeostasis by fine-tuning VEGFR-2 and VEGFR-3 signaling in ECs, suggesting its relevance in the pathogenesis of angiogenesis-related human disorders.

Cloning and characterization of zebrafish CTCF: Developmental expression patterns, regulation of the promoter region, and evolutionary aspects of gene organization.

CTCF is a nuclear phosphoprotein capable of using different subsets of its 11 Zn fingers (ZF) for sequence-specific binding to many dissimilar DNA CTCF-target sites. Such sites were identified in the genomic DNA of various multicellular organisms, in which the CTCF gene was cloned, including insects, birds, rodents, and primates. CTCF/DNA-complexes formed in vivo with different 50-bp-long sequences mediate diverse functions such as positive and negative regulation of promoters, and organization of all known enhancer-blocking elements ("chromatin insulators") including constitutive and epigenetically regulated elements. Abnormal functions of certain CTCF sites are implicated in cancer and in epigenetic syndromes such as BWS and skewed X-inactivation. We describe here the cloning and characterization of the CTCF cDNA and promoter region from zebrafish, a valuable vertebrate model organism. The full-length zebrafish CTCF cDNA clone is 4244 bp in length with an open reading frame (ORF) of 2391 bp that encodes 797 amino acids. The zebrafish CTCF amino acid sequence shows high identity (up to 98% in the zinc finger region) with human CTCF, and perfect conservation of exon-intron organization. Southern blot analyses indicated that the zebrafish genome contains a single copy of the CTCF gene. In situ hybridization revealed the presence of zebrafish CTCF transcripts in all early stages of embryogenesis. Transfection assays with luciferase reporter-constructs identified a core promoter region within 146 bp immediately upstream of the transcriptional start site of zebrafish CTCF that is located at a highly conserved YY1/Initiator element.

Metastasis-associated protein 1 enhances angiogenesis by stabilization of HIF-1alpha.

Metastasis-associated protein 1 (MTA1) is highly upregulated in cancer cells with metastatic potential; however, the molecular mechanism by which MTA1 increases the metastatic potential of cancer cells is unknown. We characterized the functional consequences of MTA1 overexpression in cancer cells with an emphasis on its potential role as a deacetylator of hypoxia-inducible factor-1alpha (HIF-1alpha). MTA1 increased the expression of HIF-1alpha protein, but did not increase the expression of its mRNA. Glutathione S-transferase pull-down and coimmunoprecipitation assays demonstrated direct interaction of MTA1 with HIF-1alpha both in vitro and in vivo. Immunoprecipitation and acetylation assays also showed that MTA1 has deacetylation activity on HIF-1alpha in vivo. Moreover, MTA1 increased the transcriptional activity of HIF-1alpha and enhanced the expression of vascular endothelial growth factor, a target molecule of HIF-1alpha. Conditioned medium collected from MTA1 transfectants also increased angiogenesis in vitro and in vivo, probably through enhanced HIF-1alpha stabilization. These results indicate that MTA1 enhances angiogenesis by stabilization of the HIF-1alpha protein, which is closely related to the increased metastatic potential of cancer cells with high MTA1 expression.