Cardiac miRNAs were involved in the regulation of pathophysiological mechanisms underlying HF in pediatric patients after ventricular assist device implantation

Background

VAD use in heart failure (HF) children have undergone rapid progress in the last three decades through pump technological innovation and improvement of perioperative care. Studies in HF adults showed that VAD put native heart at rest and lead to molecular changes in cardiac muscle, including at microRNA (miRNA) level. However, little is known on changes induced by VAD implant in cardiac miRNA expression and their putative targets in HF children.

Purpose

The aims of this study were to evaluate: 1) modification of miRNA expression in cardiac muscle from HF children after VAD support; 2) the putative targets of selected miRNAs by in silico analysis; 2) the role of the identify miRNAs on putative targets by in vitro study.

Methods

Cardiac biopsies were collected from HF children at the moment of VAD implant [n=8; 20 (7.5–64.5) months, 2 males; 19 (15.75–32.25) LVEF%] and at the time of heart transplant after VAD support [n=5; 32 (5–204) months; 4 males; 13.5 (10–18) LVEF%]. Cardiac miRNA expression was evaluated by NGS. The potential miRNA targets were identified by bioinformatics analyses and their cardiac expression by real-time PCR was evaluated. HL-1 cell line was used for testing the regulatory role of selected miRNA on predicted targets by miRNA mimic transfection study.

Results

At NGS, 465 miRNA were found on average in each sample and the cardiac expression levels of miR19a-3p, miR-1246 and miR-199b-5p decreased in HF children after VAD support compared to pre-implant (Fig. 1A-B). In silico analysis showed that more than 5000 potential gene targets regulated by miR-19a-3p, miR-1246 and miR-199b-5p. Among them, adiponectin receptors (AdipoR1, AdipoR2, T-CAD) were identified as common targets for 3 miRNAs. Real-time PCR data showed that levels of all adiponectin receptors increased significantly whilst the expression of 3 miRNAs decreased after VAD support (Fig. 1C). Moreover, AdipoR2 and T-CAD were inversely related to miRNA levels (Fig. 1D). In vitro studies confirmed the regulatory role of miR-1246 and miR-199b-5p on AdipoR2 (Fig. 1E-F), whilst only miR-199b-5p reduced the expression of T-CAD (Fig. 1G). Finally, AdipoR1 expression levels are not modified compared to control by miRNAs mimic transfection (data not shown).

Conclusion

In HF children the use of VAD could modify the expression of several miRNAs potentially involved in the regulation of several pathophysiological mechanisms underlying HF. Specifically, the reductions of miR-1246, mir-19a-3p, miR-199b-5p were associated with an increase of the adiponectin receptors AdipoR2 and T-CAD mRNA, suggesting the existence of a miRNAs related fine tuning of the adiponectin system at cardiac tissue level by VAD implant, able to favour the protective effect of adiponectin in HF cardiac muscle.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): FP7-ICT-2009 Project, Grant Agreement 24863 Figure 1

Thyroid disrupting effects of low-dose dibenzothiophene and cadmium in single or concurrent exposure: New evidence from a translational zebrafish model

Thyroid hormones (THs) are major regulators of biological processes essential for correct development and energy homeostasis. Although thyroid disruptors can deeply affect human health, the impact of exogenous chemicals and in particular mixture of chemicals on different aspects of thyroid development and metabolism is not yet fully understood. In this study we have used the highly versatile zebrafish model to assess the thyroid axis disrupting effects of cadmium (Cd) and dibenzothiophene (DBT), two environmental endocrine disruptors found to be significantly correlated in epidemiological co-exposure studies. Zebrafish embryos (5hpf) were exposed to low concentrations of Cd (from 0.05 to 2 μM) and DBT (from 0.05 to 1 μM) and to mixtures of them. A multilevel assessment of the pollutant effects has been obtained by combining in vivo morphological analyses allowed by the use of transgenic fluorescent lines with liquid chromatography mass spectrometry determination of TH levels and quantification of the expression levels of key genes involved in the Hypothalamic-Pituitary-Thyroid Axis (HPTA) and TH metabolism. Our results underscore for the first time an important synergistic toxic effect of these pollutants on embryonic development and thyroid morphology highlighting differences in the mechanisms through which they can adversely impact on multiple physiological processes of the HPTA and TH disposal influencing also heart geometry and function.

4180Expression profile of microRNAs in cardiac tissue from pediatric patients with heart failure (HF) supported by Ventricular Assist Device and their involvement in pathophysiological mechanisms of HF

Background

Ventricular Assist Device (VAD) has been increasingly used as bridge to transplantation for the treatment both of adult and pediatric patients with end-stage Heart Failure (HF). Several studies reported that VAD support could affect cardiac molecular mechanisms, including miRNA expression, in HF adult patients. However, little is known about the miRNA profile in pediatric HF patients supported by VAD.

Purpose

Aim of this study was to evaluate the effects of VAD support on expression profile of miRNAs in cardiac tissue from pediatric patients with HF, and to enrich the analysis by an in silico exploration of their potential functions and pathways.

Methods

Cardiac biopsies from HF children collected at the time of VAD implant [8 HF children; 57±33 (mean±SD) months; 2 males; 14.2±13.5 weight; 29±8 LVEF%] and at the time of heart transplantation after 155±33 days of VAD support [5 children; 90±46 months; 4 males; 30±15.8 weight; 38±3.9 LVEF%] were used for profiling miRNA expression by Next Generation Sequencing (NGS). Bioinformatic analyses were performed to identify the differentially expressed miRNAs in cardiac tissues after VAD support, to elucidate their potential functions (Gene Ontology), and to predict their target genes (miRWalk database).

Results

We identified two upregulated miRNAs (miR-29b-1-5p, miR-338-3p) and four downregulated miRNAs (miR-199a-5p, miR-199b-5p, miR-19a-3p, miR-1246) after VAD support. Gene enrichment analysis identified heart development/function, apoptosis and metabolism as main process modulated by the selected miRNAs (Fig A). Moreover, twenty genes were selected as putative miRNA targets involved in the pathophysiology of HF (Fig B).

Conclusion

In summary, the results of the present study suggest that modification of six miRNAs in cardiac tissue from HF children after VAD support may be involved in the regulation of several pathophysiological mechanisms underlying HF, thus providing novel perspectives for future researches.

alpha-Amanitin resistance is developmentally regulated in carrot

Carrot cells are capable of inactivating alpha-amanitin only in embryogenic conditions (regenerating cells and embryoids). Instead, the mutant line a3 is capable of inactivating the drug also in nonembryogenic conditions (vegetative growth). The mutation is dominant in somatic hybrids and is pleiotropic, allowing expression during vegetative growth of other embryonal functions. The inactivation of alpha-amanitin is due to the oxidative activity of tyrosinase.

Proliferation-dependent pattern of expression of a dihydrofolate reductase-thymidylate synthase gene from Daucus carota

The pattern of expression of a carrot dhfr-ts gene was evaluated in different plant organs, in somatic embryos, and in hypocotyl explants induced to dedifferentiate in vitro by the addition of the synthetic auxin 2,4 dichorophenoxyacetic acid. The promoter of this gene was also placed upstream of a uidA (GUS) reporter gene and, using biolistic and protoplasts transient expression assays, was shown to drive a particularly high level of expression in actively growing suspension cells. The results from these expression analyses combined with the presence of putative cell cycle-related cis-acting elements in the dhfr-ts promoter, strongly point to a cell division-dependent expression of this gene.

The antifungal Dm-AMP1 protein from Dahlia merckii expressed in Solanum melongena is released in root exudates and differentially affects pathogenic fungi and mycorrhizal symbiosis

•  Transformed aubergine plants constitutively expressing the Dm-AMP1 antimicrobial defensin (from Dahlia merckii) were generated and characterized. •  Transgenic plants were selected on kanamycin and screened by polymerase chain reaction analysis. The expression of Dm-AMP1 in plant tissues and its release in root exudates were detected by Western blot analyses. Dm-AMP1 localization was performed by immunohistochemical experiments. •  Dm-AMP1 expression ranged from 0.2% to 0.48% of total soluble proteins in primary transformants and from 0.16% to 0.66% in F₂ plants. Transformed clones showed resistance to the pathogenic fungus Botrytis cinerea, whose development on leaves was reduced by 36-100%, with respect to controls. The protein was released in root exudates of the transformed plants and was active in reducing the growth of the co-cultured pathogenic fungus Verticillium albo-atrum, whereas it did not interfere with recognition responses and symbiosis establishment by the arbuscular mycorrhizal fungus Glomus mosseae. •  Dm-AMP1 transformants may represent a useful model to study the interactions between genetically modified plants and pathogenic fungi or beneficial nontarget microorganisms.

Spatial expression of DNA topoisomerase I genes during cell proliferation in Daucus carota

The spatial expression of carrot (Daucus carota L.) top1 genes encoding the two isoforms of the enzyme DNA topoisomerase I (EC 5.99.1.2) was investigated. In situ hybridization analysis performed with a probe recognizing both top1 transcripts provided evidence that in explanted hypocotyls induced to proliferate in vitro by the addition of the growth regulator 2,4-dichlorophenoxyacetic acid (2,4-D), the mRNA accumulation parallels the proliferation of provascular cells of the stelar cylinder. During somatic embryogenesis, the histological distribution of top1 transcripts was strongly evident at the stage of torpedo-shaped embryos, but gene expression was not only restricted to meristematic regions. When the spatial localization was extended to carrot vegetative apices and the investigation was carried out with specific probes for top1alpha and top1beta, both transcripts preferentially accumulated in tissues having mitotic activity.

Floral genes expressed in tomato hypocotyl explants in liquid culture

This paper confirms, at molecular level, previous data showing that small explants of many plants do form a floral meristem and express specific floral genes after only few days in culture. After 15-20 days of culture, small tomato hypocotyl explants develop differentiated structures often resembling primitive ancestral reproductive organs. Other specific reproductive functions such as chromosomal segregation (somatic meiosis) were also present and demonstrated by means of a cytological and histological analysis. By reverse transcriptase-PCR and in situ hybridization it was found that these structures are indeed able to express flower-specific genes. The TM8 gene, a tomato gene that is expressed very early during floral development, is detectable on the proliferating hypocotyl explants during the first week of culture. The MON9612 gene, which in vivo is expressed only by tomato pistils and ovules, is detectable on the ovulelike structures developed after 20 days of culture. The construction of transgenic tomato plants expressing the GUS gene under the control of the MON9612 promoter allowed us to follow the induction and the expression of this gene during explant proliferation and development of the flowerlike structures. These data confirm the hypothesis that a floral reprogramming can be induced in plant explants as a consequence of wounding and growth factors action. It appears to be an effort to survive stress by means of an unscheduled reproductive program.

Characterization of carrot nuclear proteins that exhibit specific binding affinity towards conventional and non-conventional DNA methylation

DNA methylation is associated with transcriptional silencing in vertebrates and plants. In mammals, the effects of methylation are mediated by a family of methyl-CpG-binding proteins. In plants the mechanisms by which methylation represses transcription are still not clear. In this paper we describe protein factors in carrot nuclear extracts exhibiting specific affinities for conventional or non-conventional methylation acceptor sites. We characterized two classes of proteins: the first, dcMBPI (Daucus carota methylated DNA-binding protein 1), shows high affinity for sequences containing 5-methylcytosine; the second, dcMBP2 (Daucus carota methylated DNA-binding protein 2), efficiently complexes sequences containing 5-methylcytosine in both CpXpX and CpXpG trinucleotides and shows much lower affinity for 5-methyl CpG dinucleotides. Both dcMBP1 and dcMBP2 are abundant proteins differing in molecular weight and binding features. Their activities are modulated during carrot vegetative cell growth and somatic embryo development. This is the first time that, in either plants or mammals, proteins exhibiting specific binding affinities for conventional or non-conventional DNA methylation have been shown. Based on these results, the possibility that both the extent and the context of the methylation might contribute to modulate gene expression is discussed.

DcE2F, a functional plant E2F-like transcriptional activator from Daucus carota

In animal cells the progression of the cell cycle through G(1)/S transition and S phase is under the control of the pRB/E2F regulatory pathway. The E2F transcription factors are key activators of genes coding for several regulatory proteins and for enzymes involved in nucleotide and DNA synthesis. In this report we have detected the presence of E2F-like DNA binding activities in carrot nuclear extracts, and we have isolated a carrot cDNA (DcE2F) encoding a plant E2F homologue. The DcE2F gene is expressed in proliferating cells and is induced during the G(1)/S transition of the cell cycle. Supershift experiments using anti-DcE2F antiserum have confirmed that the DcE2F protein is a component of the carrot E2F-like nuclear activities. DNA binding assays have demonstrated that the DcE2F protein can recognize a canonical E2F cis-element in association with a mammalian DP protein. Furthermore, transactivation assays have revealed that DcE2F is a functional transcription factor that can transactivate, together with a DP partner, an E2F-responsive reporter gene in both plant and mammalian cells.

Carrot DNA-methyltransferase is encoded by two classes of genes with differing patterns of expression

In the present study, the isolation and characterization of two distinct cDNAs that code for carrot DNA (cytosine-5)-methyltransferase (DNA-METase) are reported. The screening of a cDNA library with a carrot genomic DNA fragment, previously obtained by PCR using degenerate primers, has led to the isolation of clones that belong to two distinct classes of genes (Met1 and Met2) which differ in sequence and size. Met1-5 and Met2-21 derived amino acid sequences are more than 85% identical for most of the polypeptide and completely diverge at the N-terminus. The larger size of the Met2-21 cDNA is due to the presence of nearly perfect fivefold repeat of a 171 bp sequence present only once in the Met1-5 cDNA. Northern and in situ hybridization analyses with young carrot plants and somatic embryos indicate that both genes are maximally expressed in proliferating cells (suspension cells, meristems and leaf primordia), but differ quantitatively and spatially in their mode of expression. Polyclonal antibodies were raised in rabbit using fusion proteins corresponding to the regulatory and catalytic regions of the most highly expressed gene (Met1-5). In nuclear carrot extracts, both antibodies were found to recognize a band of about 200 kDa along with some additional bands of lower size. These results provide the first direct demonstration that DNA-METases of a higher eukaryote are encoded by a gene family.

Translational control during recovery from heat shock in the absence of heat shock proteins

Heat shock results in a reduction in translational efficiency and an increase in mRNA stability in plants that is proportional to the severity of the stress. To determine whether the absence of heat shock proteins may affect the observed changes during translation or mRNA turnover, the effect that inhibiting transcription during a heat shock has on the subsequent translation of a reporter mRNA was examined. The presence of actinomycin D repressed heat shock protein synthesis in response to the application of a heat shock by more than 80%. The translational efficiency of the reporter mRNA was subject to a greater degree of repression following a heat shock when transcription was inhibited than it was in heat-shocked cells in which transcription was not inhibited. In contrast, inhibiting transcription during a heat shock did not prevent the heat-mediated increase in mRNA stability. These data suggest that ongoing transcription is needed during a heat shock to support a basal level of translational activity in the subsequent recovery from the stress but does not appear to be required for the heat-mediated increase in mRNA stability.

Regulation of a carotenoid biosynthesis gene promoter during plant development

Carotenoids are terpenoid pigments which are accumulated in the chloroplasts of leaves and in the chromoplasts of many flowers and fruits. Phytoene desaturase (Pds), the second dedicated enzyme in carotenoid biosynthesis, is encoded in tomato by a single copy gene. A 2 kb fragment from the tomato Pds gene, comprising 1.5 kb from the promoter and 0.5 kb from the 5' non-translated region, is able to drive developmentally regulated expression of the GUS reporter gene in transgenic tomato and tobacco plants. In tomato, high levels of Pds/GUS expression are found in organs and at stages of development where chromoplasts are formed: petals, anthers and ripening fruits. Tobacco petals and fruits, which do not contain chromoplasts, show instead low levels of Pds/GUS expression. Transgenic tobacco seedlings were subjected to treatment with a range of inhibitors of carotenoid and chlorophyll biosynthesis. The results indicate that, in green tissues, carotenoid and chlorophyll levels are tightly co-regulated and that a chemically induced arrest in pigment biosynthesis results in activation of the Pds promoter. The promoter is also induced in etiolated seedlings, which contain much lower carotenoid levels than light-grown seedlings. These data suggest that in green tissues Pds gene transcription may respond to end-product regulation.

Heat Shock Disrupts Cap and Poly(A) Tail Function during Translation and Increases mRNA Stability of Introduced Reporter mRNA

The effect of heat shock on translational efficiency and message stability of a reporter mRNA was examined in carrot (Daucus carota). Heat shock of short duration resulted in an increase in protein yield, whereas repression was observed following extended exposure to the stress. Regardless of the duration of the heat shock, a loss in the function of the 5[prime] cap [m7G(5[prime])ppp(5[prime])N, where N represents any nucleotide] and the 3[prime] poly(A) tail, two regulatory elements that work in concert to establish an efficient level of translation, was observed. This apparent paradox was resolved upon examination of the mRNA half-life following thermal stress, in which increases up to 10-fold were observed. Message stability increased as a function of the severity of the heat shock so that following a mild to moderate stress the increase in message stability more than compensated for the reduction in cap and poly(A) tail function. Following a severe heat shock, the increased mRNA half-life was not sufficient to overcome the virtual loss in cap and poly(A) tail function. No stimulation of protein synthesis was observed following a heat shock in Chinese hamster ovary cells, data suggesting that the heat-induced increases in mRNA stability may be unique to the heat-shock response in plants.

Role of the Leader Sequence during Thermal Repression of Translation in Maize, Tobacco, and Carrot Protoplasts

The 5'-untranslated leader of maize (Zea mays) heat-shock protein (hsp) 70 mRNA is required for translational competence during heat shock in protoplasts. When the beta-glucuronidase gene was used as a reporter mRNA, expression at elevated temperatures increased more than 10-fold when the hsp70 leader constituted the 5'-untranslated region. The hsp70 leader did not affect the physical half-life of the mRNA and, therefore, does not function at the level of transcript stability. The maize hsp70 leader was required to escape thermal repression in both maize and tobacco (Nicotiana tabacum) but was less effective in carrot. In addition, mRNAs containing the tobacco mosaic virus untranslated leader (omega) were also efficiently translated during heat shock, data suggesting that the presence of the omega sequence enables the transcript to escape the translational repression that occurs during thermal stress.

A carrot cell variant temperature sensitive for somatic embryogenesis reveals a defect in the glycosylation of extracellular proteins

The temperature-sensitive carrot cell variant ts11c, arrested in somatic embryogenesis after the globular stage, was characterized. The sensitivity to a shift from 24 degrees C (permissive temperature) to 32 degrees C (non-permissive temperature) is greatest at the globular stage of embryogenesis, while cells proliferating in unorganized fashion and plantlets are not affected. Embryogenesis in ts11c is also arrested at the permissive temperature by replacement of conditioned culture medium with fresh medium. The timing of sensitivity of ts11c to medium replacement coincides with the sensitivity to temperature shift. Both sensitivities are recessive in somatic hybrids between ts11c and wild-type cells. Extracellular glycoproteins synthesized by ts11c at the non-permissive temperature contain much less fucose than those synthesized by the wild type. The glycoproteins synthesized by the variant under non-permissive conditions do not accumulate at the periphery of the embryo, as their wild-type counterparts do, but instead show a diffuse distribution throughout the embryo. The defect in ts11c can be fully complemented by the addition of extracellular wild-type proteins. A revertant of ts11c was isolated that simultaneously reacquired temperature insensitivity and normal glycosylation ability. Collectively, these observations indicate that ts11c is not able to perform proper glycosylation at the non-permissive temperature and suggest that the activity of certain extracellular proteins, essential for the transition of globular to heart stage somatic embryos, depends on the correct modification of their oligosaccharide side-chains.

Reversible variations in the methylation pattern of carrot DNA during somatic embryogenesis

Twenty five clones from a carrot genomic library were used as probes to detect variations in the 5-methyl-cytosine pattern during somatic embryogenesis. The majority of them evidenced an invariant pattern. With two clones however, differences were found between the adulttype DNA pattern and the embryonic one. The level of transcription of the relevant DNA fragments during embryogenesis was investigated by Northern blotting. One of the two probes did not show signals in any of the developmental stages whereas the other showed developmentally regulated expression. This fact suggests a novel strategy for cloning developmentally expressed functions.

DNA methylation of embryogenic carrot cell cultures and its variations as caused by mutation, differentiation, hormones and hypomethylating drugs

The level of auxin - both natural and synthetic - in the medium has a strong effect on the level of 5-methyl-cytosine in the DNA of carrot cells in culture. This level may vary from approximately 15% to 70% of total cytosine without apparent effects on growth rate and cell morphology. No effect was seen with cytokinin. During somatic embryogenesis, in the absence of hormones, variations were seen in the level of methylation according to a characteristic pattern. If hypomethylation is induced with drugs such as azacytidine, ethionine or ethoxy-carbonyl-pyrimidine, embryogenesis is immediately blocked. A mutant was isolated which is resistant to the action of hypomethylating drugs. It shows variations in the methylation pattern and variations in indole-acetic acid metabolism. In addition its regeneration is often associated with the production of tumors.

Analysis of the heat-shock protein pattern during somatic embryogenesis of carrot

The pattern of proteins synthesized by carrot cells after heat-shock was analyzed by SDS-polyacrylamide gel electrophoresis. A study was made of the time of appearance and disappearance of the heat-shock bands and a comparison was made of the heat-shock proteins present in cell extracts obtained from cell suspensions, callus, protoplasts and the different stages of somatic embryogenesis.From this comparison a number of differences and hence of stage-specific markers could be seen. This type of analysis was also carried out in the presence of α-amanitin in order to get information on the type of control of heat-shock protein synthesis. It turned out that in all stages after the initial globular stage, α-amanitin does not alter the heat-shock protein pattern suggesting pre-existence of the relative mRNA's.