A Slit/miR-218/Robo regulatory loop is required during heart tube formation in zebrafish

MicroRNAs: Impaired vasculogenesis in metal induced teratogenicity

Certain metals have been known for their toxic effects on embryos and fetal development. The vasculature in early pregnancy is extremely dynamic and plays an important role in organogenesis. Nascent blood vessels in early embryonic life are considered to be a primary and delicate target for many teratogens since the nascent blood islands follow a tightly controlled program to form vascular plexus around and inside the embryo for resourcing optimal ingredients for its development. The state of the distribution of toxic metals, their transport mechanisms and the molecular events by which they notch extra-embryonic and embryonic vasculatures are illustrated. In addition, pharmacological aspects of toxic metal induced teratogenicity have also been portrayed. The work reviewed state of the current knowledge of specific role of microRNAs (miRNAs) that are differentially expressed in response to toxic metals, and how they interfere with the vasculogenesis that manifests into embryonic anomalies.

Expression patterns of Slit and Robo family members in adult mouse spinal cord and peripheral nervous system

The secreted glycoproteins, Slit1-3, are classic axon guidance molecules that act as repulsive cues through their well characterised receptors Robo1-2 to allow precise axon pathfinding and neuronal migration. The expression patterns of Slit1-3 and Robo1-2 have been most characterized in the rodent developing nervous system and the adult brain, but little is known about their expression patterns in the adult rodent peripheral nervous system. Here, we report a detailed expression analysis of Slit1-3 and Robo1-2 in the adult mouse sciatic nerve as well as their expression in the nerve cell bodies within the ventral spinal cord (motor neurons) and dorsal root ganglion (sensory neurons). Our results show that, in the adult mouse peripheral nervous system, Slit1-3 and Robo1-2 are expressed in the cell bodies and axons of both motor and sensory neurons. While Slit1 and Robo2 are only expressed in peripheral axons and their cell bodies, Slit2, Slit3 and Robo1 are also expressed in satellite cells of the dorsal root ganglion, Schwann cells and fibroblasts of peripheral nerves. In addition to these expression patterns, we also demonstrate the expression of Robo1 in blood vessels of the peripheral nerves. Our work gives important new data on the expression patterns of Slit and Robo family members within the peripheral nervous system that may relate both to nerve homeostasis and the reaction of the peripheral nerves to injury.

Vegfa Impacts Early Myocardium Development in Zebrafish

Vascular endothelial growth factor A (Vegfa) signaling regulates cardiovascular development. However, the cellular mechanisms of Vegfa signaling in early cardiogenesis remain poorly understood. The present study aimed to understand the differential functions and mechanisms of Vegfa signaling in cardiac development. A loss-of-function approach was utilized to study the effect of Vegfa signaling in cardiogenesis. Both morphants and mutants for vegfaa display defects in cardiac looping and chamber formation, especially the ventricle. Vegfa regulates the heart morphogenesis in a dose-dependent manner. Furthermore, the initial fusion of the bilateral myocardium population is delayed rather than endocardium. The results demonstrate that Vegfa signaling plays a direct impact on myocardium fusion, indicating that it is the initial cause of the heart defects. The heart morphogenesis is regulated by Vegfa in a dose-dependent manner, and later endocardium defects may be secondary to impaired myocardium–endocardium crosstalk.

DCC Confers Susceptibility to Depression-like Behaviors in Humans and Mice and Is Regulated by miR-218

BACKGROUD

Variations in the expression of the Netrin-1 guidance cue receptor DCC (deleted in colorectal cancer) appear to confer resilience or susceptibility to psychopathologies involving prefrontal cortex (PFC) dysfunction.

METHODS

With the use of postmortem brain tissue, mouse models of defeat stress, and in vitro analysis, we assessed microRNA (miRNA) regulation of DCC and whether changes in DCC levels in the PFC lead to vulnerability to depression-like behaviors.

RESULTS

We identified miR-218 as a posttranscriptional repressor of DCC and detected coexpression of DCC and miR-218 in pyramidal neurons of human and mouse PFC. We found that exaggerated expression of DCC and reduced levels of miR-218 in the PFC are consistent traits of mice susceptible to chronic stress and of major depressive disorder in humans. Remarkably, upregulation of Dcc in mouse PFC pyramidal neurons causes vulnerability to stress-induced social avoidance and anhedonia.

CONCLUSIONS

These data are the first demonstration of microRNA regulation of DCC and suggest that, by regulating DCC, miR-218 may be a switch of susceptibility versus resilience to stress-related disorders.

Platelet-derived growth factor (PDGF) signaling directs cardiomyocyte movement toward the midline during heart tube assembly

Communication between neighboring tissues plays a central role in guiding organ morphogenesis. During heart tube assembly, interactions with the adjacent endoderm control the medial movement of cardiomyocytes, a process referred to as cardiac fusion. However, the molecular underpinnings of this endodermal-myocardial relationship remain unclear. Here, we show an essential role for platelet-derived growth factor receptor alpha (Pdgfra) in directing cardiac fusion. Mutation of pdgfra disrupts heart tube assembly in both zebrafish and mouse. Timelapse analysis of individual cardiomyocyte trajectories reveals misdirected cells in zebrafish pdgfra mutants, suggesting that PDGF signaling steers cardiomyocytes toward the midline during cardiac fusion. Intriguingly, the ligand pdgfaa is expressed in the endoderm medial to the pdgfra-expressing myocardial precursors. Ectopic expression of pdgfaa interferes with cardiac fusion, consistent with an instructive role for PDGF signaling. Together, these data uncover a novel mechanism through which endodermal-myocardial communication can guide the cell movements that initiate cardiac morphogenesis.

DOI:http://dx.doi.org/10.7554/eLife.21172.001

In the growing embryo, the heart initially develops in the form of a simple tube. Its outer layer is made up of muscular cells, called myocardial cells, that pump blood through the tube. Before the heart tube develops, two groups of myocardial cells exist – one on each side of the embryo. To assemble the heart, these two populations of cells must move as a group to the middle of the embryo, where they meet and merge through a process called cardiac fusion. This movement of myocardial cells toward the middle of the embryo depends upon interactions with a neighboring tissue called the endoderm. How the endoderm directs the movement of the myocardial cells was not well understood.

The PDGF signaling pathway guides the movement of several different types of cells in the body, but it had not been previously linked to the early stages of heart tube assembly. In this pathway, a molecule called platelet-derived growth factor (PDGF) binds to PDGF receptors that sit on the surface of cells. Using microscopy and genetic analysis to study zebrafish and mouse embryos, Bloomekatz et al. now show that embryos that carry mutations in a gene that encodes a PDGF receptor suffer from defects in heart tube assembly. Further examination of the mutant zebrafish embryos revealed that the myocardial cells were not properly directed toward the middle of the embryo. In fact, many of these cells appeared to move away from the midline.

Bloomekatz et al. also observed that, in normal embryos, the endoderm cells that lie adjacent to the myocardial cells produce PDGF. Therefore, it appears that PDGF produced by the endoderm could interact with PDGF receptors on the myocardial cells to direct these cells toward the middle of the embryo. The next step will be to figure out how this signaling influences the machinery inside the myocardial cells that controls their movement. Ultimately, this knowledge could lead to new ways to identify and treat congenital heart diseases.

DOI:http://dx.doi.org/10.7554/eLife.21172.002

The crucial role and regulations of miRNAs in zebrafish development

To comprehend the events during developmental biology, fundamental knowledge about the basic machinery of regulation is a prerequisite. MicroRNA (miRNAs) act as regulators in most of the biological processes and recently, it has been concluded that miRNAs can act as modulatory factors even during developmental process from lower to higher animal. Zebrafish, because of its favorable attributes like tiny size, transparent embryo, and rapid external embryonic development, has gained a preferable status among all other available experimental animal models. Currently, zebrafish is being utilized for experimental studies related to stem cells, regenerative molecular medicine as well drug discovery. Therefore, it is important to understand precisely about the various miRNAs that controls developmental biology of this vertebrate model. In here, we have discussed about the miRNA-controlled zebrafish developmental stages with a special emphasis on different miRNA families such as miR-430, miR-200, and miR-133. Moreover, we have also reviewed the role of various miRNAs during embryonic and vascular development stages of zebrafish. In addition, efforts have been made to summarize the involvement of miRNAs in the development of different body parts such as the brain, eye, heart, muscle, and fin, etc. In each section, we have tried to fulfill the gaps of zebrafish developmental biology with the help of available knowledge of miRNA research. We hope that precise knowledge about the miRNA-regulated developmental stages of zebrafish may further help the researchers to efficiently utilize this vertebrate model for experimental purpose.

The Robo4 cytoplasmic domain is dispensable for vascular permeability and neovascularization

Vascular permeability and neovascularization are implicated in many diseases including retinopathies and diabetic wound healing. Robo4 is an endothelial-specific transmembrane receptor that stabilizes the vasculature, as shown in Robo4^−/− mice that develop hyperpermeability, but how Robo4 signals remained unclear. Here we show that Robo4 deletion enhances permeability and revascularization in oxygen-induced retinopathy (OIR) and accelerates cutaneous wound healing. To determine Robo4 signalling pathways, we generated transgenic mice expressing a truncated Robo4 lacking the cytoplasmic domain (Robo4ΔCD). Robo4ΔCD expression is sufficient to prevent permeability, and inhibits OIR revascularization and wound healing in Robo4^−/− mice. Mechanistically, Robo4 does not affect Slit2 signalling, but Robo4 and Robo4ΔCD counteract Vegfr2-Y949 (Y951 in human VEGFR2) phosphorylation by signalling through the endothelial UNC5B receptor. We conclude that Robo4 inhibits angiogenesis and vessel permeability independently of its cytoplasmic domain, while activating VEGFR2-Y951 via ROBO4 inhibition might accelerate tissue revascularization in retinopathy of prematurity and in diabetic patients.

Robo4 is a transmembrane protein that regulates vascular permeability. Zhang et al. now reveal the mechanism of Robo4 action and show that Robo4 and UncB are required for VEGF-mediated regulation of vascular barrier by suppressing VEGF-induced phosphorylation of its receptor Vegfr2 on Y949.

POU2F2-oriented network promotes human gastric cancer metastasis

BACKGROUND AND AIMS

Aberrant upregulation of POU2F2 expression has been discovered in metastatic gastric cancer (GC). However, the mechanisms underlying the aberrant upregulation and the potential functions of POU2F2 remain uncertain.

DESIGN

The role and mechanism of POU2F2 in GC metastasis were investigated in gastric epithelial cells, GC cell lines and an experimental metastasis animal model by gain of function and loss of function. Upstream and downstream targets of POU2F2 were selected by bioinformatics and identified by luciferase reporter assay, electrophoretic mobility shift assay and chromatin immunoprecipitation PCR. The influence of miR-218 on its putative target genes (POU2F2, ROBO1 and IKK-β) and GC metastasis was further explored via in vitro and in vivo approaches.

RESULTS

Increased POU2F2 expression was detected in metastatic GC cell lines and patient samples. POU2F2 was induced by the activation of nuclear factor (NF)-κB and, in turn, regulated ROBO1 transcription, thus functionally contributing to GC metastasis. Finally, miR-218 was found to suppress GC metastasis by simultaneously mediating multiple molecules in the POU2F2-oriented network.

CONCLUSIONS

This study demonstrated that NF-κB and the SLIT2/ROBO1 interaction network with POU2F2 as the central part may exert critical effects on tumour metastasis. Blocking the activation of the POU2F2-oriented metastasis network using miR-218 precursors exemplified a promising approach that sheds light on new strategies for GC treatment.

Autophagy is involved in ethanol-induced cardia bifida during chick cardiogenesis

Excess alcohol consumption during pregnancy has been acknowledged to increase the incidence of congenital disorders, especially the cardiovascular system. However, the mechanism involved in ethanol-induced cardiac malformation in prenatal fetus is still unknown. We demonstrated that ethanol exposure during gastrulation in the chick embryo increased the incidence of cardia bifida. Previously, we reported that autophagy was involved in heart tube formation. In this context, we demonstrated that ethanol exposure increased ATG7 and LC3 expression. mTOR was found to be inhibited by ethanol exposure. We activated autophagy using exogenous rapamycin (RAPA) and observed that it induced cardiac bifida and increased GATA5 expression. RAPA beads implantation experiments revealed that RAPA restricted ventricular myosin heavy chain (VMHC) expression. In vitro explant cultures of anterior primitive streak demonstrated that both ethanol and RAPA treatments could reduce cell differentiation and the spontaneous beating of cardiac precursor cells. In addition, the bead experiments showed that RAPA inhibited GATA5 expression during heart tube formation. Semiquantitative RT-PCR analysis indicated that BMP2 expression was increased while GATA4 expression was suppressed. In the embryos exposed to excess ethanol, BMP2, GATA4 and FGF8 expression was repressed. These genes are associated with cardiomyocyte differentiation, while heart tube fusion is associated with increased Wnt3a but reduced VEGF and Slit2 expression. Furthermore, the ethanol exposure also caused the production of excess ROS, which might damage the cardiac precursor cells of developing embryos. In sum, our results revealed that disrupting autophagy and excess ROS generation are responsible for inducing abnormal cardiogenesis in ethanol-treated chick embryos.

The Magnaporthe grisea species complex and plant pathogenesis

TAXONOMY

Kingdom Fungi; Phylum Ascomycota; Class Sordariomycetes; Order Magnaporthales; Family Pyriculariaceae (anamorph)/Magnaporthaceae (teleomorph); Genus Pyricularia (anamorph)/Magnaporthe (teleomorph); Species P. grisea (anamorph)/M. grisea (teleomorph).

HOST RANGE

Very broad at the species level, including rice, wheat, barley, millet and other species of the Poaceae (Gramineae).

DISEASE SYMPTOMS

Can be found on all parts of the plant, including leaves, leaf collars, necks, panicles, pedicels, seeds and even the roots. Initial symptoms are white to grey-green lesions or spots with darker borders, whereas older lesions are elliptical or spindle-shaped and whitish to grey with necrotic borders. Lesions may enlarge and coalesce to eventually destroy the entire leaf.

DISEASE CONTROL

Includes cultural strategies, genetic resistance and the application of chemical fungicides.

GEOGRAPHICAL DISTRIBUTION

Widespread throughout the rice-growing regions of the globe and has been reported in more than 85 countries.

GENOMIC STRUCTURE

Different isolates possess similar genomic sizes and overall genomic structures. For the laboratory strain 70-15: assembly size, 40.98 Mb; number of chromosomes, seven; number of predicted genes, 13 032; G + C composition, 51.6%; average gene contains 451.6 amino acids; mitochondrion genome size, 34.87 kb.

USEFUL WEBSITE

http://www.broadinstitute.org/annotation/genome/magnaporthe_comparative/MultiHome.html.

Discovering miRNA Regulatory Networks in Holt-Oram Syndrome Using a Zebrafish Model

MicroRNAs (miRNAs) are small non-coding RNAs that play an important role in the post-transcriptional regulation of gene expression. miRNAs are involved in the regulation of many biological processes such as differentiation, apoptosis, and cell proliferation. miRNAs are expressed in embryonic, postnatal, and adult hearts, and they have a key role in the regulation of gene expression during cardiovascular development and disease. Aberrant expression of miRNAs is associated with abnormal cardiac cell differentiation and dysfunction. Tbx5 is a member of the T-box gene family, which acts as transcription factor involved in the vertebrate heart development. Alteration of Tbx5 level affects the expression of hundreds of genes. Haploinsufficiency and gene duplication of Tbx5 are at the basis of the cardiac abnormalities associated with Holt–Oram syndrome (HOS). Recent data indicate that miRNAs might be an important part of the regulatory circuit through which Tbx5 controls heart development. Using high-throughput technologies, we characterized genome-widely the miRNA and mRNA expression profiles in WT- and Tbx5-depleted zebrafish embryos at two crucial developmental time points, 24 and 48 h post fertilization (hpf). We found that several miRNAs, which are potential effectors of Tbx5, are differentially expressed; some of them are already known to be involved in cardiac development and functions, such as miR-30, miR-34, miR-190, and miR-21. We performed an integrated analysis of miRNA expression data with gene expression profiles to refine computational target prediction approaches by means of the inversely correlation of miRNA–mRNA expressions, and we highlighted targets, which have roles in cardiac contractility, cardiomyocyte proliferation/apoptosis, and morphogenesis, crucial functions regulated by Tbx5. This approach allowed to discover complex regulatory circuits involving novel miRNAs and protein coding genes not considered before in the HOS such as miR-34a and miR-30 and their targets.

The force within: endocardial development, mechanotransduction and signalling during cardiac morphogenesis

Endocardial cells are cardiac endothelial cells that line the interior of the heart tube. Historically, their contribution to cardiac development has mainly been considered from a morphological perspective. However, recent studies have begun to define novel instructive roles of the endocardium, as a sensor and signal transducer of biophysical forces induced by blood flow, and as an angiocrine signalling centre that is involved in myocardial cellular morphogenesis, regeneration and reprogramming. In this Review, we discuss how the endocardium develops, how endocardial-myocardial interactions influence the developing embryonic heart, and how the dysregulation of blood flow-responsive endocardial signalling can result in pathophysiological changes.

Functions of miRNAs during Mammalian Heart Development

MicroRNAs (miRNAs) play essential roles during mammalian heart development and have emerged as attractive therapeutic targets for cardiovascular diseases. The mammalian embryonic heart is mainly derived from four major cell types during development. These include cardiomyocytes, endocardial cells, epicardial cells, and neural crest cells. Recent data have identified various miRNAs as critical regulators of the proper differentiation, proliferation, and survival of these cell types. In this review, we briefly introduce the contemporary understanding of mammalian cardiac development. We also focus on recent developments in the field of cardiac miRNAs and their functions during the development of different cell types.

S1pr2/Gα13 signaling regulates the migration of endocardial precursors by controlling endoderm convergence

Formation of the heart tube requires synchronized migration of endocardial and myocardial precursors. Our previous studies indicated that in S1pr2/Gα13-deficient embryos, impaired endoderm convergence disrupted the medial migration of myocardial precursors, resulting in the formation of two myocardial populations. Here we show that endoderm convergence also regulates endocardial migration. In embryos defective for S1pr2/Gα13 signaling, endocardial precursors failed to migrate towards the midline, and the presumptive endocardium surrounded the bilaterally-located myocardial cells rather than being encompassed by them. In vivo imaging of control embryos revealed that, like their myocardial counterparts, endocardial precursors migrated with the converging endoderm, though from a more anterior point, then moved from the dorsal to the ventral side of the endoderm (subduction), and finally migrated posteriorly towards myocardial precursors, ultimately forming the inner layer of the heart tube. In embryos defective for endoderm convergence due to an S1pr2/Gα13 deficiency, both the medial migration and the subduction of endocardial precursors were impaired, and their posterior migration towards the myocardial precursors was premature. This placed them medial to the myocardial populations, physically blocking the medial migration of the myocardial precursors. Furthermore, contact between the endocardial and myocardial precursor populations disrupted the epithelial architecture of the myocardial precursors, and thus their medial migration; in embryos depleted of endocardial cells, the myocardial migration defect was partially rescued. Our data indicate that endoderm convergence regulates the medial migration of endocardial precursors, and that premature association of the endocardial and myocardial populations contributes to myocardial migration defects observed in S1pr2/Gα13-deficient embryos. The demonstration that endoderm convergence regulates the synchronized migration of endocardial and myocardial precursors reveals a new role of the endoderm in heart development.

Strategies for analyzing cardiac phenotypes in the zebrafish embryo

The molecular mechanisms underlying cardiogenesis are of critical biomedical importance due to the high prevalence of cardiac birth defects. Over the past two decades, the zebrafish has served as a powerful model organism for investigating heart development, facilitated by its powerful combination of optical access to the embryonic heart and plentiful opportunities for genetic analysis. Work in zebrafish has identified numerous factors that are required for various aspects of heart formation, including the specification and differentiation of cardiac progenitor cells, the morphogenesis of the heart tube, cardiac chambers, and atrioventricular canal, and the establishment of proper cardiac function. However, our current roster of regulators of cardiogenesis is by no means complete. It is therefore valuable for ongoing studies to continue pursuit of additional genes and pathways that control the size, shape, and function of the zebrafish heart. An extensive arsenal of techniques is available to distinguish whether particular mutations, morpholinos, or small molecules disrupt specific processes during heart development. In this chapter, we provide a guide to the experimental strategies that are especially effective for the characterization of cardiac phenotypes in the zebrafish embryo.

Slit-miR-218-Robo axis regulates retinal neovascularization

miR-218 is an important intronic microRNA (miRNA or miR) which is known to regulate angiogenesis in tumors. The present study aimed to investigate the effects of miR-218, as well as its host genes, Slit2 and Slit3, on oxygen-induced retinal neovascularization (RNV) and to explore the associated mechanisms of action. For this purpose, a mouse model of oxygen-induced retinopathy (OIR) was established. The expression levels of miR-218-1 and miR-218-2, as well as those of their host genes, Slit2 and Slit3, were determined by RT-qPCR. Fluorescein angiography was performed on the retinas of the mice with OIR, and RNV was quantified by H&E staining in order to evaluate the effect of pCDH-CMV-miR-218 intravitreal injection on RNV in the mouse model of OIR. Roundabout, axon guidance receptor, homolog 1 (Robo1) expression was detected in mouse retinal vascular endothelial cells expressing high or low levels of miR-218 and in retinal tissues from mice with OIR by western blot analysis. Cell migration was evaluated by a scratch wound assay. We noted that in the mice with OIR, the expression level of miR-218 was significantly downregulated. We also noted that Robo1 expression was suppressed by miR-218. Furthermore, in the mice with OIR, the expression level of miR-218 was significantly downregulated, and that of miR-218-1 and its host gene, Slit2, was concomitantly downregulated as well. The restoration of miR-218 inhibited retinal angiogenesis by targeting Robo1. Taken together, our findings suggest that the Slit2-miR-218-Robo1 axis contributes to the inhibition of retinal angiogenesis and that miR-218 may be a new therapeutic target for preventing RNV.

microRNA-218 Inhibits Oxygen-induced Retinal Neovascularization via Reducing the Expression of Roundabout 1

BACKGROUND

The mechanisms of pathological retinal neovascularization (RNV) remain unknown. Several microRNAs were reported to be involved in the process of RNV. Oxygen-induced retinopathy (OIR) is a useful model to investigate RNV. Our present work explored the expression and the role of microRNA-128 (miR-218) in oxygen-induced RNV.

METHODS

OIR was used to establish RNV model. The expression level of miR-218 in the retina from OIR mice was assessed by quantitative real-time reverse transcriptase polymerase chain reaction. Fluorescein angiography was performed in retinae of OIR mice, and RNV was quantified by hematoxylin and eosin staining to evaluate the effect of pCDH-CMV-miR-218 intravitreal injection on RNV in OIR mice. Roundabout 1 (Robo1) expression was detected by Western blotting in mouse retinal vascular endothelial cells expressing a high or low level of miR-218 and retinal tissues from OIR mice. Cell migration was evaluated by scratch wound assay.

RESULTS

In OIR mice, the expression level of miR-218 was significantly down-regulated (P = 0.006). Retinal Robo1 expression was significantly increased at both mRNA and protein levels (P = 0.001, 0.008; respectively). miR-218 intravitreal injection inhibited retinal angiogenesis in OIR mice, and the restoration of miR-218 in retina led to down-regulation of Robo1.

CONCLUSIONS

Our experiments showed that restoration of miR-218 inhibited retinal angiogenesis via targeting Robo1. MiR-218 contributed to the inhibition of retinal angiogenesis and miR-218 might be a new therapeutic target for preventing RNV.

Human placental multipotent mesenchymal stromal cells modulate placenta angiogenesis through Slit2-Robo signaling

The objective of this study was to investigate whether human placental multipotent mesenchymal stromal cell (hPMSC)-derived Slit2 and endothelial cell Roundabout (Robo) receptors are involved in placental angiogenesis. The hPMSC-conditioned medium and human umbilical vein endothelial cells were studied for Slit2 and Robo receptor expression by immunoassay and RT-PCR. The effect of the conditioned medium of hPMSCs with or without Slit2 depletion on endothelial cells was investigated by in vitro angiogenesis using growth factor-reduced Matrigel. hPMSCs express Slit2 and both Robo1 and Robo4 are present in human umbilical vein endothelial cells. Human umbilical vein endothelial cells do not express Robo2 and Robo3. The hPMSC-conditioned medium and Slit2 recombinant protein significantly inhibit the endothelial cell migration, but not by the hPMSC-conditioned medium with Slit2 depletion. The hPMSC-conditioned medium and Slit2 significantly enhance endothelial tube formation with increased cumulated tube length, polygonal network number and vessel branching point number compared to endothelial cells alone. The tube formation is inhibited by the depletion of Slit2 from the conditioned medium, or following the expression of Robo1, Robo4, and both receptor knockdown using small interfering RNA. Furthermore, co-immunoprecipitation reveals Slit2 binds to Robo1 and Robo4. Robo1 interacts and forms a heterodimeric complex with Robo4. These results suggest the implication of both Robo receptors with Slit2 signaling, which is involved in endothelial cell angiogenesis. Slit2 in the conditioned medium of hPMSCs has functional effect on endothelial cells and may play a role in placental angiogenesis.

MiR218 Modulates Wnt Signaling in Mouse Cardiac Stem Cells by Promoting Proliferation and Inhibiting Differentiation through a Positive Feedback Loop

MiRNA expression was determined in both proliferating and differentiated cardiac stem cells (CSCs) through a comprehensive miRNA microarray analysis. We selected miR218 for functional follow-up studies to examine its significance in CSCs. First, we observed that the expression of miR218 was altered in CSCs during differentiation into cardiomyocytes, and transfection of an miR218 mimic or miR218 inhibitor affected the myocardial differentiation of CSCs. Furthermore, we observed that a negative regulator of Wnt signaling, sFRP2, was a direct target of miR218, and the protein levels of sFRP2 were increased in cells transfected with the synthetic miR218 inhibitor. In contrast, transfection with the miR218 mimic decreased the expression of sFRP2 and potentiated Wnt signaling. The subsequent down-regulation of sFRP2 by shRNA potentiated Wnt signaling, contributing to a gene expression program that is important for CSC proliferation and cardiac differentiation. Specifically, canonical Wnt signaling induced miR218 transcription. Thus, miR218 and Wnt signaling were coupled through a feed-forward positive feedback loop, forming a biological regulatory circuit. Together, these results provide the first evidence that miR218 plays an important role in CSC proliferation and differentiation through the canonical Wnt signaling pathway.

Tinman Regulates NetrinB in the Cardioblasts of the Drosophila Dorsal Vessel

Morphogenesis of the Drosophila dorsal vessel (DV) shares similarities with that of the vertebrate heart. Precursors line up at both sides of the embryo, migrate towards the midline and fuse to form a tubular structure. Guidance receptors and their ligands have been implicated in this process in vertebrates and invertebrates, as have been a series of evolutionarily conserved cardiogenic transcriptional regulators including Tinman, the Drosophila homolog of the transcription factor Nkx-2.5. NetrinB (NetB), a repulsive ligand for the Unc-5 receptor is required to preserve the dorsal vessel hollow. It localizes to the luminal space of the dorsal vessel but its source and its regulation is unknown. Here, using genetics together with in situ hybridization with single cell resolution, we show how tin is required for NetrinB expression in cardioblasts during DV tubulogenesis and sufficient to promote NetB transcription ectopically. We further identify a dorsal vessel-specific NetB enhancer and show that it is also regulated by tin in a similar fashion to NetB.

The role of microRNAs in cardiac development and regenerative capacity

The mammalian heart has long been considered to be a postmitotic organ. It was thought that, in the postnatal period, the heart underwent a transition from hyperplasic growth (more cells) to hypertrophic growth (larger cells) due to the conversion of cardiomyocytes from a proliferative state to one of terminal differentiation. This hypothesis was gradually disproven, as data were published showing that the myocardium is a more dynamic tissue in which cardiomyocyte karyokinesis and cytokinesis produce new cells, leading to the hyperplasic regeneration of some of the muscle mass lost in various pathological processes. microRNAs have been shown to be critical regulators of cardiomyocyte differentiation and proliferation and may offer the novel opportunity of regenerative hyperplasic therapy. Here we summarize the relevant processes and recent progress regarding the functions of specific microRNAs in cardiac development and regeneration.

The emerging role of Slit-Robo pathway in gastric and other gastro intestinal cancers

Gastric cancer remains one of the most common cancers worldwide and one of the leading cause for cancer-related deaths. Due to the high frequency of metastasis, it is still one of the most lethal malignancies in which kinds of signaling pathways are involved in. The Roundabout (ROBO) receptors and their secreted SLIT glycoprotein ligands, which were originally identified as important axon guidance molecules, have implication in the regulation of neurons and glia, leukocytes, and endothelial cells migration. Recent researches also put high emphasis on the important roles of the Slit-Robo pathway in tumorigenesis, cancer progression and metastasis. Herein we provide a comprehensive review on the role of these molecules and their associated signaling pathway in gastric and other gastrointestinal cancers. Improved knowledge of the Slit-Robo signaling pathway in gastric carcinoma will be useful for deep understanding the mechanisms of tumor development and identifying ideal targets of anticancer therapy in gastric carcinoma.

Plasma microRNA profiling of children with idiopathic dilated cardiomyopathy

CONTEXT

Dilated cardiomyopathy (DCM) is the most common cardiomyopathy in children. MicroRNAs (miRNA) are small RNAs which have regulatory functions in many biological processes.

OBJECTIVE

We aimed to determine miRNA expression levels in plasma of children with DCM.

MATERIALS AND METHODS

Plasma expression levels of 379 miRNAs were compared between 23 DCM and 26 healthy children.

RESULTS

The expression levels of miR-618, miR-875-3p, miR-205, miR-194, miR-302a, miR-147, and miR-544 were found decreased. The expression levels of miR-518f and miR-454 were found increased in DCM patients.

DISCUSSION

miRNA level differences may provide the chance of using these miRNAs as new biomarkers.

MicroRNA-29a inhibits mesenchymal stem cell viability and proliferation by targeting Roundabout 1

Secreted Slit glycoproteins and their Roundabout (Robo) receptors have been identified as important axon guidance molecules. The pivotal role of Slit‑Robo signaling is in regulating cell proliferation. MicroRNAs (miRNAs), a class of small non‑coding RNAs, function as critical regulators of gene expression by binding to the 3'‑untranslated region of mRNAs and causing mRNA degradation or translational repression. The present study demonstrated that downregulation of Robo1 using small interfering RNA inhibited mesenchymal stem cell (MSC) proliferation. Additionally, four miRNAs (miR), including miR‑218, miR‑29a, miR‑146 and miR‑148, inhibited the protein expression of Robo1 in the MSCs, with miR‑29 having the most marked effect. A luciferase reporter assay identified Robo1 as a novel target of miR‑29a. Overexpression of miR‑29a suppressed the protein expression levels of Robo1 and Slit2 and inhibited the viability and proliferation of the MSCs. By contrast, overexpression of Robo1 partly rescued these inhibitory effects of miR‑29a on the MSCs confirming that miR‑29a inhibited MSC viability and proliferation, at least partially, by directly targeting Robo1. These results indicated that the miR‑29a/Robo1 axis is crucial for the regulation of MSC viability and proliferation, suggesting that miR‑29a may serve as a potential clinical target for MSC expansion and stem cell transplantation.

Harnessing the microRNA pathway for cardiac regeneration

Mounting evidence over the last few years has indicated that the rate of cardiomyocyte proliferation, and thus the extent of cardiac renewal, is under the control of the microRNA network. Several microRNAs (e.g. miR-1) regulate expansion of the cardiomyocyte pool and its terminal differentiation during the embryonic life; some not only promote cardiomyocyte proliferation but also their de-differentiation towards an embryonic cell phenotype (e.g. the miR-302/367 cluster); a few others are involved in the repression of cardiomyocyte proliferation occurring suddenly after birth (e.g. the miR-15 family); others again are not physiologically involved in the regulation of cardiomyocyte turnover, but nevertheless are able to promote cardiomyocyte proliferation and cardiac regeneration when delivered exogenously (e.g. miR-199a-3p). With a few exceptions, the molecular mechanisms underlying the pro-proliferative effect of these microRNAs, most of which appear to act at the level of already differentiated cardiomyocytes, remain to be thoroughly elucidated. The possibility of harnessing the miRNA network to achieve cardiac regeneration paves the way to exciting therapeutic applications. This could be achieved by either administering miRNA mimics or inhibitors, or transducing the heart with viral vectors expressing miRNA-encoding genes.

The Unc-5 Receptor Is Directly Regulated by Tinman in the Developing Drosophila Dorsal Vessel

During early heart morphogenesis cardiac cells migrate in two bilateral opposing rows, meet at the dorsal midline and fuse to form a hollow tube known as the primary heart field in vertebrates or dorsal vessel (DV) in Drosophila. Guidance receptors are thought to mediate this evolutionarily conserved process. A core of transcription factors from the NK2, GATA and T-box families are also believed to orchestrate this process in both vertebrates and invertebrates. Nevertheless, whether they accomplish their function, at least in part, through direct or indirect transcriptional regulation of guidance receptors is currently unknown. In our work, we demonstrate how Tinman (Tin), the Drosophila homolog of the Nkx-2.5 transcription factor, regulates the Unc-5 receptor during DV tube morphogenesis. We use genetics, expression analysis with single cell mRNA resolution and enhancer-reporter assays in vitro or in vivo to demonstrate that Tin is required for Unc-5 receptor expression specifically in cardioblasts. We show that Tin can bind to evolutionary conserved sites within an Unc-5 DV enhancer and that these sites are required for Tin-dependent transactivation both in vitro and in vivo.

Amotl2a interacts with the Hippo effector Yap1 and the Wnt/β-catenin effector Lef1 to control tissue size in zebrafish

During development, proliferation must be tightly controlled for organs to reach their appropriate size. While the Hippo signaling pathway plays a major role in organ growth control, how it senses and responds to increased cell density is still unclear. In this study, we use the zebrafish lateral line primordium (LLP), a group of migrating epithelial cells that form sensory organs, to understand how tissue growth is controlled during organ formation. Loss of the cell junction-associated Motin protein Amotl2a leads to overproliferation and bigger LLP, affecting the final pattern of sensory organs. Amotl2a function in the LLP is mediated together by the Hippo pathway effector Yap1 and the Wnt/β-catenin effector Lef1. Our results implicate for the first time the Hippo pathway in size regulation in the LL system. We further provide evidence that the Hippo/Motin interaction is essential to limit tissue size during development.

DOI:http://dx.doi.org/10.7554/eLife.08201.001

How do organs and tissues know when to stop growing? A cell communication pathway known as Hippo signaling plays a central role as it can tell cells to stop dividing. It is activated when cells in developing tissues come into contact with each other and causes a protein called Yap1 to be modified, which prevents it from entering the cell nucleus to activate genes that are involved in cell division.

In a zebrafish embryo, an organ called the lateral line forms from a cluster of cells that migrate along the embryo's length. At regular intervals, the cluster deposits small bunches of cells from its trailing end. The resulting loss of cells from the cluster is balanced by cell division at the front of the cluster, which is triggered by another signaling pathway called Wnt signaling. A protein of the ‘Motin’ family called Amotl2a is present in this migrating cluster. Motin proteins form junctions between cells and inhibit the activity of Yap1, but it is not known whether they are involved in regulating the size of organs.

Here, Agarwala et al. used the lateral line as a model to study the control of organ size in zebrafish embryos. The experiments show that when Amotl2a is absent, the migrating cell cluster becomes larger, with the highest levels of cell division occurring at its trailing end. Yap1 and a protein involved in Wnt signaling called Lef1 are also present in the cluster and are required for it to be normal in size. In zebrafish that lack Amotl2a, the additional loss of Yap1 prevents this cluster from becoming too large. From these and other results, it appears that Amotl2a regulates the size of the lateral line cell cluster by restricting the ability of Yap1 and Lef1 to promote cell division.

Agarwala et al.'s findings demonstrate a role for Amotl2a in controlling the size of organs. A future challenge is to understand the details of how it restricts the activities of Yap1 and Lef1.

DOI:http://dx.doi.org/10.7554/eLife.08201.002

Regulation of RPTPα-c-Src signalling pathway by miR-218

Receptor protein tyrosine phosphatase alpha (RPTPα), an activator of Src family kinases, is found significantly overexpressed in human cancer tissues. However, little is known about the regulation of RPTPα expression. miRNAs target multiple genes and play important roles in many cancer processes. Here, we identified a miRNA, miR-218 that binds directly to the 3'-UTR of RPTPα. Ectopic overexpression of miR-218 decreased RPTPα protein leading to decreased dephosphorylation of c-Src and decreased tumour growth in vitro and in vivo. A feedback loop between c-Src and miR-218 was revealed where c-Src inhibits transcription of SLIT2, which intronically hosts miR-218. These results show a novel regulatory pathway for RPTPα-c-Src signalling.

Slit2 signaling through Robo1 and Robo2 is required for retinal neovascularization

Ocular neovascular diseases are a leading cause of blindness. Vascular endothelial growth factor (VEGF) blockade improves vision, but not all individuals respond to anti-VEGF treatment, making additional means to prevent neovascularization necessary. Slit-family proteins (Slits) are ligands of Roundabout (Robo) receptors that repel developing axons in the nervous system. Robo1 expression is altered in ocular neovascular diseases, and previous in vitro studies have reported both pro- and anti-angiogenic effects of Slits. However, genetic evidence supporting a role for Slits in ocular neovascularization is lacking. Here we generated conditional knockout mice deficient in various Slit and Robo proteins and found that Slit2 potently and selectively promoted angiogenesis via Robo1 and Robo2 in mouse postnatal retina and in a model of ocular neovascular disease. Mechanistically, Slit2 acting through Robo1 and Robo2 promoted the migration of endothelial cells. These receptors are required for both Slit2- and VEGF-induced Rac1 activation and lamellipodia formation. Thus, Slit2 blockade could potentially be used therapeutically to inhibit angiogenesis in individuals with ocular neovascular disease.

MiR-218 mediates tumorigenesis and metastasis: Perspectives and implications

MicroRNAs (miRNAs) are a class of small non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. As a highly conserved miRNA across a variety of species, microRNA-218 (miR-218) was found to play pivotal roles in tumorigenesis and progression. A group of evidence has demonstrated that miR-218 acts as a tumor suppressor by targeting many oncogenes related to proliferation, apoptosis and invasion. In this review, we provide a complex overview of miR-218, including its regulatory mechanisms, known functions in cancer and future challenges as a potential therapeutic target in human cancers.

Disrupted Slit-Robo signalling results in membranous ventricular septum defects and bicuspid aortic valves

AIMS

The mesenchymal cushions lining the early embryonic heart undergo complex remodelling to form the membranous ventricular septum as well as the atrioventricular and semilunar valves in later life. Disruption of this process underlies the most common congenital heart defects. Here, we identified a novel role for Slit-Robo signalling in the development of the murine membranous ventricular septum and cardiac valves.

METHODS AND RESULTS

Expression of Robo1 and Robo2 receptors and their ligands, Slit2 and Slit3, was present in or adjacent to all cardiac cushions/valves. Loss of Robo1 or both Robo1 and Robo2 resulted in membranous ventricular septum defects at birth, a defect also found in Slit3, but not in Slit2 mutants. Additionally, Robo1;Robo2 double mutants showed thickened immature semilunar and atrioventricular valves as well as highly penetrant bicuspid aortic valves. Slit2 mutants recapitulated the semilunar phenotype, whereas Slit3 mutants displayed thickened atrioventricular valves. Bicuspid aortic cushions were already observed at E12.5 in the Robo1;Robo2 double mutants. Expression of Notch- and downstream Hey and Hes genes was down-regulated in Robo1 mutants, suggesting that reduced Notch signalling in mice lacking Robo might underlie the defects. Luciferase assays confirmed regulation of Notch signalling by Robo.

CONCLUSION

Cardiac defects in mutants for Robo or Slit range from membranous ventricular septum defects to bicuspid aortic valves. These ligands and receptors have unique functions during development of specific cardiac cushion derivatives, and the Slit-Robo signalling pathway likely enforces its role by regulating Notch signalling, making these mutants a valuable new model to study cardiac valve formation.

Expression quantitative trait loci (eQTLs) in microRNA genes are enriched for schizophrenia and bipolar disorder association signals

BACKGROUND

Schizophrenia (SZ) and bipolar disorder (BD) have substantial negative impact on the quality of human life. Both, microRNA (miRNA) expression profiling in SZ and BD postmortem brains [and genome-wide association studies (GWAS)] have implicated miRNAs in disease etiology. Here, we aim to determine whether significant GWAS signals observed in the Psychiatric Genetic Consortium (PGC) are enriched for miRNAs.

METHOD

A two-stage approach was used to determine whether association signals from PGC affect miRNAs: (i) statistical assessment of enrichment using a Simes test and sum of squares test (SST) and (ii) biological evidence that quantitative trait loci (eQTL) mapping to known miRNA genes affect their expression in an independent sample of 78 postmortem brains from the Stanley Medical Research Institute.

RESULTS

A total of 2567 independent single nucleotide polymorphisms (SNPs) (R2 > 0.8) were mapped locally, within 1 Mb, to all known miRNAs (miRBase v. 21). We show robust enrichment for SZ- and BD-related SNPs with miRNAs using Simes (SZ: p ≤ 0.0023, BD: p ≤ 0.038), which remained significant after adjusting for background inflation in SZ (empirical p = 0.018) and approached significance in BD (empirical p = 0.07). At a false discovery rate of 10%, we identified a total of 32 eQTLs to influence miRNA expression; 11 of these overlapped with BD.

CONCLUSIONS

Our approach of integrating PGC findings with eQTL results can be used to generate specific hypotheses regarding the role of miRNAs in SZ and BD.

Cellular Mechanisms of Drosophila Heart Morphogenesis

Many of the major discoveries in the fields of genetics and developmental biology have been made using the fruit fly, Drosophila melanogaster. With regard to heart development, the conserved network of core cardiac transcription factors that underlies cardiogenesis has been studied in great detail in the fly, and the importance of several signaling pathways that regulate heart morphogenesis, such as Slit/Robo, was first shown in the fly model. Recent technological advances have led to a large increase in the genomic data available from patients with congenital heart disease (CHD). This has highlighted a number of candidate genes and gene networks that are potentially involved in CHD. To validate genes and genetic interactions among candidate CHD-causing alleles and to better understand heart formation in general are major tasks. The specific limitations of the various cardiac model systems currently employed (mammalian and fish models) provide a niche for the fly model, despite its evolutionary distance to vertebrates and humans. Here, we review recent advances made using the Drosophila embryo that identify factors relevant for heart formation. These underline how this model organism still is invaluable for a better understanding of CHD.

Association of microRNA polymorphisms with the risk of myocardial infarction in a Chinese population

MicroRNAs (miRNAs) are involved in the regulation of a variety of biological processes, such as inflammation. Dysregulation of miRNAs have been implicated in many human disease, including cardiovascular diseases. Polymorphisms in miRNA genes may affect the miRNA biogenesis and function, and thus cause changes in the expression of thousands of genes. The aim of this study was to examine whether miRNA polymorphisms (miR-146a rs2910164, miR-149 rs71428439, miR-196a2 rs11614913, miR-218 rs11134527, and miR-499 rs3746444) contribute to the risk for the development of myocardial infarction (MI). Five miRNA polymorphisms were genotyped in a total of 1808 subjects composed of 919 MI patients and 889 control individuals. The GG genotype of rs3746444 was found to be associated with a significantly increased risk of MI (recessive model, adjusted OR = 1.710, 95% CI: 1.058-2.763, P = 0.029). Although the CC genotype of rs2910164 significantly increased the risk of MI under dominant and additive models (P < 0.05), this difference disappeared after adjustment for age, sex, blood pressure, triglycerides, total cholesterol, HDL, LDL and diabetes. In addition, when rs3746444 and rs2910164 were evaluated together by the number of putative high-risk alleles, we found an increased risk of MI for subjects carrying 3-4 risk alleles (3-4 risk alleles vs. 0-1 risk allele, adjusted OR = 1.580, 95% CI: 1.069-2336, P = 0.022; 3-4 risk alleles vs. 0-2 risk allele, adjusted OR = 1.513, 95% CI: 1.031-2.219, P = 0.034). These findings indicate that miR-499 rs3746444 and miR-146a rs2910164 may represent novel markers of MI susceptibility.

microRNA and Cardiac Regeneration

Heart diseases are a very common health problem in developed as well as developing countries. In particular, ischemic heart disease and heart failure represent a plague for the patients and for the society. Loss of cardiac tissue after myocardial infarction or dysfunctioning tissue in nonischemic cardiomyopathies may result in cardiac failure. Despite great advancements in the treatment of these diseases, there is a substantial unmet need for novel therapies, ideally addressing repair and regeneration of the damaged or lost myocardium. Along this line, cardiac cell based therapies have gained substantial attention. Three main approaches are currently under investigation: stem cell therapy with either embryonic or adult stem cells; generation of patient-specific induced pluripotent stem cells; stimulation of endogenous regeneration trough direct reprogramming of fibroblasts into cardiomyocytes, activation of resident cardiac stem cells or induction of native resident cardiomyocytes to reenter the cell cycle. All these strategies need to be optimized since their efficiency is low.It has recently become clear that cardiac signaling and transcriptional pathways are intimately intertwined with microRNA molecules which act as modulators of cardiac development, function, and disease. Moreover, miRNA also regulates stem cell differentiation. Here we describe how miRNA may circumvent hurdles that hamper the field of cardiac regeneration and stem cell therapy, and how miRNA may result as the most suitable solution for the damaged heart.

Cdc42 and formin activity control non-muscle myosin dynamics during Drosophila heart morphogenesis

Cdc42 and the formins dDAAM and Diaphanous play pivotal roles in heart lumen formation through the spatiotemporal regulation of the actomyosin network.

During heart formation, a network of transcription factors and signaling pathways guide cardiac cell fate and differentiation, but the genetic mechanisms orchestrating heart assembly and lumen formation remain unclear. Here, we show that the small GTPase Cdc42 is essential for Drosophila melanogaster heart morphogenesis and lumen formation. Cdc42 genetically interacts with the cardiogenic transcription factor tinman; with dDAAM which belongs to the family of actin organizing formins; and with zipper, which encodes nonmuscle myosin II. Zipper is required for heart lumen formation, and its spatiotemporal activity at the prospective luminal surface is controlled by Cdc42. Heart-specific expression of activated Cdc42, or the regulatory formins dDAAM and Diaphanous caused mislocalization of Zipper and induced ectopic heart lumina, as characterized by luminal markers such as the extracellular matrix protein Slit. Placement of Slit at the lumen surface depends on Cdc42 and formin function. Thus, Cdc42 and formins play pivotal roles in heart lumen formation through the spatiotemporal regulation of the actomyosin network.

Aberrant expression of miR-218 and miR-204 in human mesial temporal lobe epilepsy and hippocampal sclerosis-convergence on axonal guidance

OBJECTIVE

Mesial temporal lobe epilepsy (MTLE) is one of the most common types of the intractable epilepsies and is most often associated with hippocampal sclerosis (HS), which is characterized by pronounced loss of hippocampal pyramidal neurons. microRNAs (miRNAs) have been shown to be dysregulated in epilepsy and neurodegenerative diseases, and we hypothesized that miRNAs could be involved in the pathogenesis of MTLE and HS.

METHODS

miRNA expression was quantified in hippocampal specimens from human patients using miRNA microarray and quantitative real-time polymerase chain reaction RT-PCR, and by RNA-seq on fetal brain specimens from domestic pigs. In situ hybridization was used to show the spatial distribution of miRNAs in the human hippocampus. The potential effect of miRNAs on targets genes was investigated using the dual luciferase reporter gene assay.

RESULTS

miRNA expression profiling showed that 25 miRNAs were up-regulated and 5 were down-regulated in hippocampus biopsies of MTLE/HS patients compared to controls. We showed that miR-204 and miR-218 were significantly down-regulated in MTLE and HS, and both were expressed in neurons in all subfields of normal hippocampus. Moreover, miR-204 and miR-218 showed strong changes in expression during fetal development of the hippocampus in pigs, and we identified four target genes, involved in axonal guidance and synaptic plasticity, ROBO1, GRM1, SLC1A2, and GNAI2, as bona fide targets of miR-218. GRM1 was also shown to be a direct target of miR-204.

SIGNIFICANCE

miR-204 and miR-218 are developmentally regulated in the hippocampus and may contribute to the molecular mechanisms underlying the pathogenesis of MTLE and HS.

Epidermal growth factor receptor-coamplified and overexpressed protein (VOPP1) is a putative oncogene in gastric cancer

MicroRNAs are found to play an important role in gastric cancer. Reduced expression of microRNA-218 (miR-218) is of key interest. The target gene of microRNA-218, epidermal growth factor receptor-coamplified and overexpressed protein (ECOP) encoded by the VOPP1 gene, has been implicated in tumorigenesis. However, few studies on expression and function of ECOP in gastric cancer have been reported. ECOP expression was determined in matched normal and gastric adenocarcinoma tissue specimens by immunohistochemistry and western blot. Subsequently, ectopic overexpression and RNAi-mediated silencing of VOPP1 was effected in the human gastric cancer cell line, AGS. Proliferation and migration of parental, VOPP1 overexpressing and VOPP1-silenced AGS cells were evaluated by cell proliferation assay and scratch wound-healing motility assay. Finally, intracellular localization of ECOP in AGS cells was assessed by green fluorescent protein tagging and fluorescent microscopy. Western blot and immunohistochemistry showed overexpression of ECOP in gastric adenocarcinoma tissues compared to matched normal tissue specimens. Ectopic overexpression and RNAi-mediated silencing of VOPP1 promoted and inhibited, respectively, cell proliferation and migration in AGS cells. Intracellular localization of ECOP in perinuclear lysosomes mimicked colocalization earlier reported for other cancerous cells. VOPP1 is overexpressed in gastric adenocarcinoma, which is involved in promoting cell proliferation and migration and thus might serve as a putative oncogene.

MiRiad Roles for MicroRNAs in Cardiac Development and Regeneration

Cardiac development is an exquisitely regulated process that is sensitive to perturbations in transcriptional activity and gene dosage. Accordingly, congenital heart abnormalities are prevalent worldwide, and are estimated to occur in approximately 1% of live births. Recently, small non-coding RNAs, known as microRNAs, have emerged as critical components of the cardiogenic regulatory network, and have been shown to play numerous roles in the growth, differentiation, and morphogenesis of the developing heart. Moreover, the importance of miRNA function in cardiac development has facilitated the identification of prospective therapeutic targets for patients with congenital and acquired cardiac diseases. Here, we discuss findings attesting to the critical role of miRNAs in cardiogenesis and cardiac regeneration, and present evidence regarding the therapeutic potential of miRNAs for cardiovascular diseases.

Systematic permutation testing in GWAS pathway analyses: identification of genetic networks in dilated cardiomyopathy and ulcerative colitis

Background

Genome wide association studies (GWAS) are applied to identify genetic loci, which are associated with complex traits and human diseases. Analogous to the evolution of gene expression analyses, pathway analyses have emerged as important tools to uncover functional networks of genome-wide association data. Usually, pathway analyses combine statistical methods with a priori available biological knowledge. To determine significance thresholds for associated pathways, correction for multiple testing and over-representation permutation testing is applied.

Results

We systematically investigated the impact of three different permutation test approaches for over-representation analysis to detect false positive pathway candidates and evaluate them on genome-wide association data of Dilated Cardiomyopathy (DCM) and Ulcerative Colitis (UC). Our results provide evidence that the gold standard - permuting the case–control status – effectively improves specificity of GWAS pathway analysis. Although permutation of SNPs does not maintain linkage disequilibrium (LD), these permutations represent an alternative for GWAS data when case–control permutations are not possible. Gene permutations, however, did not add significantly to the specificity. Finally, we provide estimates on the required number of permutations for the investigated approaches.

Conclusions

To discover potential false positive functional pathway candidates and to support the results from standard statistical tests such as the Hypergeometric test, permutation tests of case control data should be carried out. The most reasonable alternative was case–control permutation, if this is not possible, SNP permutations may be carried out. Our study also demonstrates that significance values converge rapidly with an increasing number of permutations. By applying the described statistical framework we were able to discover axon guidance, focal adhesion and calcium signaling as important DCM-related pathways and Intestinal immune network for IgA production as most significant UC pathway.

MicroRNA in teleost fish

MicroRNAs (miRNAs) are transcriptional and posttranscriptional regulators involved in nearly all known biological processes in distant eukaryotic clades. Their discovery and functional characterization have broadened our understanding of biological regulatory mechanisms in animals and plants. They show both evolutionary conserved and unique features across Metazoa. Here, we present the current status of the knowledge about the role of miRNA in development, growth, and physiology of teleost fishes, in comparison to other vertebrates. Infraclass Teleostei is the most abundant group among vertebrate lineage. Fish are an important component of aquatic ecosystems and human life, being the prolific source of animal proteins worldwide and a vertebrate model for biomedical research. We review miRNA biogenesis, regulation, modifications, and mechanisms of action. Specific sections are devoted to the role of miRNA in teleost development, organogenesis, tissue differentiation, growth, regeneration, reproduction, endocrine system, and responses to environmental stimuli. Each section discusses gaps in the current knowledge and pinpoints the future directions of research on miRNA in teleosts.

MicroRNAs in heart failure: Small molecules with major impact

MicroRNAs (miRNAs) have emerged as potent modulators of mammalian gene expression, thereby broadening the spectrum of molecular mechanisms orchestrating human physiological and pathological cellular functions. Growing evidence suggests that these small non-coding RNA molecules are pivotal regulators of cardiovascular development and disease. Importantly, multiple miRNAs have been specifically implicated in the onset and progression of heart failure, thus providing a new platform for battling this multi-faceted disease. This review introduces the basic concepts of miRNA biology, describes representative examples of miRNAs associated with multiple aspects of HF pathogenesis, and explores the prognostic, diagnostic and therapeutic potential of miRNAs in the cardiology clinic.

The combination of transcriptomics and informatics identifies pathways targeted by miR-204 during neurogenesis and axon guidance

Vertebrate organogenesis is critically sensitive to gene dosage and even subtle variations in the expression levels of key genes may result in a variety of tissue anomalies. MicroRNAs (miRNAs) are fundamental regulators of gene expression and their role in vertebrate tissue patterning is just beginning to be elucidated. To gain further insight into this issue, we analysed the transcriptomic consequences of manipulating the expression of miR-204 in the Medaka fish model system. We used RNA-Seq and an innovative bioinformatics approach, which combines conventional differential expression analysis with the behavior expected by miR-204 targets after its overexpression and knockdown. With this approach combined with a correlative analysis of the putative targets, we identified a wider set of miR-204 target genes belonging to different pathways. Together, these approaches confirmed that miR-204 has a key role in eye development and further highlighted its putative function in neural differentiation processes, including axon guidance as supported by in vivo functional studies. Together, our results demonstrate the advantage of integrating next-generation sequencing and bioinformatics approaches to investigate miRNA biology and provide new important information on the role of miRNAs in the control of axon guidance and more broadly in nervous system development.

microRNAs in axon guidance

Brain wiring is a highly intricate process in which trillions of neuronal connections are established. Its initial phase is particularly crucial in establishing the general framework of neuronal circuits. During this early step, differentiating neurons extend axons, which reach their target by navigating through a complex environment with extreme precision. Research in the past 20 years has unraveled a vast and complex array of chemotropic cues that guide the leading tip of axons, the growth cone, throughout its journey. Tight regulation of these cues, and of their receptors and signaling pathways, is necessary for the high degree of accuracy required during circuit formation. However, little is known about the nature of regulatory molecules or mechanisms fine-tuning axonal cue response. Here we review recent, and somewhat fragmented, research on the possibility that microRNAs (miRNAs) could be key fine-tuning regulatory molecules in axon guidance. miRNAs appear to shape long-range axon guidance, fasciculation and targeting. We also present several lines of evidence suggesting that miRNAs could have a compartmentalized and differential action at the cell soma, and within axons and growth cones.

Role of ROBO4 signalling in developmental and pathological angiogenesis

Transmembrane roundabout receptor family members (ROBO1-ROBO4) principally orchestrate the neuronal guidance mechanism of the nervous system. Secreted glycoprotein SLITs are the most appreciated ligands for ROBOs. Recently identified ROBO4 is the key mediator of SLIT-ROBO mediated developmental and pathological angiogenesis. Although SLIT2 has been shown to interact with ROBO4 as ligand, it remains an open question whether this protein is the physiologic partner of ROBO4. The purpose of this review is to summarise how reliable SLIT2 as ligand for ROBO4 is, if not what the other possible mechanisms demonstrated till date for ROBO4 mediated developmental and pathological angiogenesis are. We conclude that ROBO4 is expressed specially in vascular endothelial cells and maintains the vascular integrity via either SLIT2 dependent or SLIT2 independent manner. On the contrary, it promotes the pathological angiogenesis by involving different signalling arm(s)/unknown ligand(s). This review explores the interactions SLIT2/ROBO1, SLIT2/ROBO1-ROBO4, ROBO1/ROBO4, and ROBO4/UNC5B which can be promising and potential therapeutic targets for developmental angiogenesis defects and pathological angiogenesis. Finally we have reviewed the ROBO4 signalling pathways and made an effort to elaborate the insight of this signalling as therapeutic target of pathological angiogenesis.

Roundabout receptors

Roundabout receptors (Robo) and their Slit ligands were discovered in the 1990s and found to be key players in axon guidance. Slit was initially described s an extracellular matrix protein that was expressed by midline glia in Drosophila. A few years later, it was shown that, in vertebrates and invertebrates, Slits acted as chemorepellents for axons crossing the midline. Robo proteins were originally discovered in Drosophila in a mutant screen for genes involved in the regulation of midline crossing. This ligand-receptor pair has since been implicated in a variety of other neuronal and non-neuronal processes ranging from cell migration to angiogenesis, tumourigenesis and even organogenesis of tissues such as kidneys, lungs and breasts.