MicroRNA 218 mediates the effects of Tbx5a over-expression on zebrafish heart development

Environmentally Relevant Concentrations of Triphenyl Phosphate (TPhP) Impact Development in Zebrafish

A common flame-retardant and plasticizer, triphenyl phosphate (TPhP) is an aryl phosphate ester found in many aquatic environments at nM concentrations. Yet, most studies interrogating its toxicity have used µM concentrations. In this study, we used the model organism zebrafish (Danio rerio) to uncover the developmental impact of nM exposures to TPhP at the phenotypic and molecular levels. At concentrations of 1.5-15 nM (0.5 µg/L-5 µg/L), chronically dosed 5dpf larvae were shorter in length and had pericardial edema phenotypes that had been previously reported for exposures in the µM range. Cardiotoxicity was observed but did not present as cardiac looping defects as previously reported for µM concentrations. The RXR pathway does not seem to be involved at nM concentrations, but the tbx5a transcription factor cascade including natriuretic peptides (nppa and nppb) and bone morphogenetic protein 4 (bmp4) were dysregulated and could be contributing to the cardiac phenotypes. We also demonstrate that TPhP is a weak pro-oxidant, as it increases the oxidative stress response within hours of exposure. Overall, our data indicate that TPhP can affect animal development at environmentally relevant concentrations and its mode of action involves multiple pathways.

Hexafluoropropylene oxide trimer acid, a perfluorooctanoic acid alternative, induces cardiovascular toxicity in zebrafish embryos

As an increasingly used alternative to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been widely detected in global water environments. However, little is known regarding its toxic effects on cardiovascular development. Here, zebrafish embryos were treated with egg water containing 0, 60, 120, or 240 mg/L HFPO-TA. Results showed that HFPO-TA treatment led to a significant reduction in both larval survival percentage and heart rate. Furthermore, HFPO-TA exposure caused severe pericardial edema and elongation of the sinus venous to bulbus arteriosus distance (SV-BA) in Tg (myl7: GFP) transgenic larvae, disrupting the expression of genes involved in heart development and thus causing abnormal heart looping. Obvious sprouting angiogenesis was observed in the 120 and 240 mg/L exposed Tg (fli: GFP) transgenic larvae. HFPO-TA treatment also impacted the mRNA levels of genes involved in the vascular endothelial growth factor (VEGF) pathway and embryonic vascular development. HFPO-TA exposure significantly decreased erythrocyte number in Tg (gata1: DsRed) transgenic embryos and influenced gene expression associated with the heme metabolism pathway. HFPO-TA also induced oxidative stress and altered the transcriptional levels of genes related to cell cycle and apoptosis, inhibiting cell proliferation while promoting apoptosis. Therefore, HFPO-TA exposure may induce abnormal development of the cardiovascular and hematopoietic systems in zebrafish embryos, suggesting it may not be a suitable or safe alternative for PFOA.

Regulatory Mechanisms That Guide the Fetal to Postnatal Transition of Cardiomyocytes

Heart disease remains a global leading cause of death and disability, necessitating a comprehensive understanding of the heart's development, repair, and dysfunction. This review surveys recent discoveries that explore the developmental transition of proliferative fetal cardiomyocytes into hypertrophic postnatal cardiomyocytes, a process yet to be well-defined. This transition is key to the heart's growth and has promising therapeutic potential, particularly for congenital or acquired heart damage, such as myocardial infarctions. Although significant progress has been made, much work is needed to unravel the complex interplay of signaling pathways that regulate cardiomyocyte proliferation and hypertrophy. This review provides a detailed perspective for future research directions aimed at the potential therapeutic harnessing of the perinatal heart transitions.

Exosomes mediated fibrogenesis in dilated cardiomyopathy through a MicroRNA pathway

Cardiac fibrosis is a hallmark in late-stage familial dilated cardiomyopathy (DCM) patients, although the underlying mechanism remains elusive. Cardiac exosomes (Exos) have been reported relating to fibrosis in ischemic cardiomyopathy. Thus, we investigated whether Exos secreted from the familial DCM cardiomyocytes could promote fibrogenesis. Using human iPSCs differentiated cardiomyocytes we isolated Exos of angiotensin II stimulation conditioned media from either DCM or control (CTL) cardiomyocytes. Of interest, cultured cardiac fibroblasts had increased fibrogenesis following exposure to DCM-Exos rather than CTL-Exos. Meanwhile, injecting DCM-Exos into mouse hearts enhanced cardiac fibrosis and impaired cardiac function. Mechanistically, we identified the upregulation of miRNA-218-5p in the DCM-Exos as a critical contributor to fibrogenesis. MiRNA-218-5p activated TGF-β signaling via suppression of TNFAIP3, a master inflammation inhibitor. In conclusion, our results illustrate a profibrotic effect of cardiomyocytes-derived Exos that highlights an additional pathogenesis pathway for cardiac fibrosis in DCM.

Screening and identification of miRNAs regulating Tbx4/5 genes of Pampus argenteus

Background

Silver pomfret (Pampus argenteus) is one of the most widely distributed and economically important pelagic fish species. However, an unique morphological feature of P. argenteus is the loss of pelvic fins, which can increase the energy requirement during food capture to some extent and is therefore not conducive to artificial culture. Tbx4/5 genes are highly conserved regulatory factors that regulate limb development in vertebrates and are in turn regulated by microRNAs (miRNAs). However, the miRNAs that directly regulate the Tbx4/5 genes in P. argenteus remain to be elucidated.

Methods

The Tbx4/5 genes of P. argenteus were first cloned, and the small RNA transcriptomes were sequenced by high-throughput sequencing during the critical period of the fin development at days 1, 7, and 13 of hatching. The miRNAs regulating the Tbx4/5 genes of P. argenteus were subsequently predicted by bioinformatics analysis, and the related miRNAs were verified in vitro using a dual fluorescence reporter system.

Results

A total of 662 miRNAs were identified, of which 257 were known miRNAs and 405 were novel miRNAs were identified. Compared to day 1, 182 miRNAs were differentially expressed (DE) on day 7, of which 77 and 105 miRNAs were downregulated and upregulated, respectively, while 278 miRNAs were DE on day 13, of which 136 and 142 miRNAs were downregulated and upregulated, respectively. Compared to day 13, four miRNAs were DE on day 7, of which three miRNAs were downregulated and one miRNA was upregulated. The results of hierarchical clustering of the miRNAs revealed that the DE genes were inversely expressed between days 1 and 7, and between days 1 and 13 of larval development, indicating that the larvae were in the peak stage of differentiation. However, the number of DE genes between days 7 and 13 of larval development was relatively small, suggesting the initiation of development. The potential target genes of the DE miRNAs were subsequently predicted, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of target genes were performed. The results suggested that the DE miRNAs were involved in growth, development, and signal transduction pathways, of which the Wnt and Fgfs signaling pathways are known to play important roles in the growth and development of fins. The results of dual fluorescence reporter assays demonstrated that miR-102, miR-301c, and miR-589 had a significant negative regulatory effect on the 3'-UTR of the Tbx4 gene, while miR-187, miR-201, miR-219, and miR-460 had a significant negative regulatory effect on the 3'-UTR of the Tbx5 gene. Altogether, the findings indicated that miRNAs play an important role in regulating the growth and development of pelvic fins in P. argenteus. This study provides a reference for elucidating the interactions between the miRNAs and target genes of P. argenteus in future studies.

Effect of hyperglycemia on tbx5a and nppa gene expression and its correlation to structural and functional changes in developing zebrafish heart

The objective of the current study is to analyze the effects of gestational diabetes on structural and functional changes in correlation with these two essential regulators of developing hearts in vivo using zebrafish embryos. We employed fertilized zebrafish embryos exposed to a hyperglycemic condition of 25 mM glucose for 96 h postfertilization. The embryos were subjected to various structural and functional analyses in a time-course manner. The data showed that exposure to high glucose significantly affected the embryo's size, heart length, heart rate, and looping of the heart compared to the control. Further, we observed an increased incidence of ventricular standstill and valvular regurgitation with a marked reduction of peripheral blood flow in the high glucose-exposed group compared to the control. In addition, the histological data showed that the high-glucose exposure markedly reduced the thickness of the wall and the number of cardiomyocytes in both atrium and ventricles. We also observed striking alterations in the pericardium like edema, increase in diameter with thinning of the wall compared to the control group. Interestingly, the expression of tbx5a and nppa was increased in the early development and found to be repressed in the later stage of development in the hyperglycemic group compared to the control. In conclusion, the developing heart is more susceptible to hyperglycemia in the womb, thereby showing various developmental defects possibly by altering the expression of crucial gene regulators such as tbx5a and nppa.

Post-Transcriptional Regulation of Molecular Determinants during Cardiogenesis

Cardiovascular development is initiated soon after gastrulation as bilateral precardiac mesoderm is progressively symmetrically determined at both sides of the developing embryo. The precardiac mesoderm subsequently fused at the embryonic midline constituting an embryonic linear heart tube. As development progress, the embryonic heart displays the first sign of left-right asymmetric morphology by the invariably rightward looping of the initial heart tube and prospective embryonic ventricular and atrial chambers emerged. As cardiac development progresses, the atrial and ventricular chambers enlarged and distinct left and right compartments emerge as consequence of the formation of the interatrial and interventricular septa, respectively. The last steps of cardiac morphogenesis are represented by the completion of atrial and ventricular septation, resulting in the configuration of a double circuitry with distinct systemic and pulmonary chambers, each of them with distinct inlets and outlets connections. Over the last decade, our understanding of the contribution of multiple growth factor signaling cascades such as Tgf-beta, Bmp and Wnt signaling as well as of transcriptional regulators to cardiac morphogenesis have greatly enlarged. Recently, a novel layer of complexity has emerged with the discovery of non-coding RNAs, particularly microRNAs and lncRNAs. Herein, we provide a state-of-the-art review of the contribution of non-coding RNAs during cardiac development. microRNAs and lncRNAs have been reported to functional modulate all stages of cardiac morphogenesis, spanning from lateral plate mesoderm formation to outflow tract septation, by modulating major growth factor signaling pathways as well as those transcriptional regulators involved in cardiac development.

Identification of a novel TBX5 c.755 + 1 G > A variant and related pathogenesis in a family with Holt-Oram syndrome

The proband with congenital heart disease and abnormal thumb was clinically diagnosed as Holt-Oram syndrome (HOS). A novel variant, T-box transcription factor 5 (TBX5) c.755 + 1 G > A, was identified in the proband via whole exome sequencing and validated using Sanger sequencing. Pedigree analysis and clinical examinations revealed three/seven individuals over three generations within the family, with features suggestive of HOS. Deep amplicon sequencing confirmed that the allele frequencies of the novel variant in the proband (III-1), her brother (III-2), and her mother (II-2) were 50%, 48.3%, and 38.1%, respectively, indicating that III-1 and III-2 harbored heterozygous variants, while II-2 harbored mosaic heterozygous variants. The minigene splicing assay showed that the novel variant affected the normal splicing of exon 7, resulting in the production of abnormal TBX5 transcripts. Reverse transcription-quantitative polymerase chain reaction and western blot analyses revealed that the novel variant upregulated TBX5 expression at the transcriptional and translational levels. Nuclear localization assay demonstrated impaired nuclear localization of the mutant TBX5. Cell viability assay revealed the inhibition of cell activity by the mutant TBX5. Our findings indicate that the novel variant was potentially induced HOS, probably by causing aberrant splicing, reducing the enrichment of nuclear TBX5 protein, and inhibiting cellular proliferation.

A Novel Circular RNA circITSN2 Targets the miR-218-5p/LMO7 Axis to Promote Chicken Embryonic Myoblast Proliferation and Differentiation

Circular RNA (circRNA) is a class of endogenous non-coding RNAs without 5′ and 3′ ends; an increasing number of studies show that circRNA is involved in skeletal muscle development. From our previous sequencing data, the circRNAome in breast muscle of two chicken lines with a distinct rate of muscle development, which included a fast muscle growing broiler (FMGB) and a slow muscle growing layer (SMGL), we found a novel differentially expressed circRNA generated by intersectin 2 (ITSN2) gene (named circITSN2). We verified that circITSN2 is a skeletal muscle-enriched circRNA that promotes chicken primary myoblast (CPM) proliferation and differentiation. Further molecular mechanism analysis of circITSN2 in chicken myogenesis was performed, and we found circITSN2 directly targeting miR-218-5p. Besides, miR-218-5p inhibits CPM proliferation and differentiation, which is contrary to circITSN2. Commonly, circRNAs act as a miRNA sponge to alleviate the inhibition of miRNAs on mRNAs. Thus, we also identified that a downstream gene LIM domain 7 (LMO7) was inhibited by miR-218-5p, while circITSN2 could block the inhibitory effect of miR-218-5p by targeting it. Functional analysis revealed that LMO7 also accelerates CPM proliferation and differentiation, which was similar to circITSN2 but contrary to miR-218-5p. Taken together, these results suggested that circITSN2 promotes chicken embryonic skeletal muscle development via relieving the inhibition of miR-218-5p on LMO7. Our findings revealed a novel circITSN2/miR-218-5p/LMO7 axis in chicken embryonic skeletal muscle development, which expands our understanding of the complex muscle development regulatory network.

Pyridaben induced cardiotoxicity during the looping stages of zebrafish (Danio rerio) embryos

Pyridaben is a widely used acaricide in agriculture and reaches a high concentration (97 μg/L) in paddy water for a short time when pyridaben was applied to rice. However, its toxicity to aquatic organisms is still poorly understood. Therefore, we assessed the pyridaben cardiotoxicity to aquatic organisms using the zebrafish (Danio rerio) model. We found that pyridaben is highly toxic to aquatic organisms, and LC₅₀ of pyridaben for zebrafish at 72 hpf was 100.6 μg/L. Pyridaben caused severe cardiac malformations and functional abnormalities. Morphologic abnormity included severe pericardial edema, cardiomegaly, decreased cardiomyocytes, thinning of the myocardial layer, linear heart, and increased the distance between sinus venous and bulbus arteriosus (SV-BA). Functional failure included arrhythmia, heart failure, and reduced pumping efficiency. The genes involved in heart development, WNT signaling, BMP signaling, ATPase, and cardiac troponin C were abnormally expressed in the pyridaben treatment group. Exposure to pyridaben increased oxidative stress and induced cell apoptosis. The above causes may lead to cardiac toxicity. The results suggest that pyridaben exposure induced elevated oxidative stress through the WNT signaling pathway, which in turn led to apoptosis in the heart and cardiotoxicity. Besides, pyridaben exposure at the critical stage of cardiac looping (24-36 hpf) resulted in the greatest cardiotoxicity. The chorion reduced the entry of pyridaben and protected zebrafish embryos, resulting in cardiotoxicity second only to the stage of cardiac looping. The study should provide valuable information that pyridaben exposure causes cardiotoxicity in zebrafish embryos and have potential health risks for other aquatic organisms and humans.

miRNA in cardiac development and regeneration

Ischemic heart disease is one of the main causes of morbidity and mortality in the world. In adult mammalian hearts, most cardiomyocytes are terminally differentiated and have extremely limited capacity of proliferation, making it impossible to regenerate the heart after injuries such as myocardial infarction. MicroRNAs (miRNAs), a class of non-coding single-stranded RNA, which are involved in mRNA silencing and the regulation of post-transcriptional gene expression, have been shown to play a crucial role in cardiac development and cardiomyocyte proliferation. Muscle specific miRNAs such as miR-1 are key regulators of cardiomyocyte maturation and growth, while miR-199-3p and other miRNAs display potent activity to induce proliferation of cardiomyocytes. Given their small size and relative pleiotropic effects, miRNAs have gained significant attraction as promising therapeutic targets or tools in cardiac regeneration. Increasing number of studies demonstrated that overexpression or inhibition of specific miRNAs could induce cardiomyocyte proliferation and cardiac regeneration. Some common targets of pro-proliferation miRNAs, such as the Hippo-Yap signaling pathway, were identified in multiple species, highlighting the power of miRNAs as probes to dissect core regulators of biological processes. A number of miRNAs have been shown to improve heart function after myocardial infarction in mice, and one trial in swine also demonstrated promising outcomes. However, technical difficulties, especially in delivery methods, and adverse effects, such as uncontrolled proliferation, remain. In this review, we summarize the recent progress in miRNA research in cardiac development and regeneration, examine the mechanisms of miRNA regulating cardiomyocyte proliferation, and discuss its potential as a new strategy for cardiac regeneration therapy.

MicroRNAs: roles in cardiovascular development and disease

Cardiovascular diseases (CVDs) comprise a group of disorders ranging from peripheral artery, coronary artery, cardiac valve, cardiac muscle, and congenital heart diseases to arrhythmias and ultimately, heart failure. For all the advances in therapeutics, CVDs are still the leading cause of mortality the world over, hence the significance of a thorough understanding of CVDs at the molecular level. Disparities in the expressions of genes and microRNAs (miRNAs) play a crucial role in the determination of the fate of cellular pathways, which ultimately affect an organism's physiology. Indeed, miRNAs serve as the regulators of gene expressions in that they perform key functions both in several important cellular pathways and in the regulation of the onset of various diseases such as CVDs. Many miRNAs are expressed in embryonic, postnatal, and adult hearts; their aberrant expression or genetic deletion is associated with abnormal cardiac cell differentiation, disruption in heart development, and cardiac dysfunction. A substantial body of evidence implicates miRNAs in CVD development and suggests them as diagnostic biomarkers and intriguing therapeutic tools. The present review provides an overview of the history, biogenesis, and processing of miRNAs, as well as their function in the development, remodeling, and diseases of the heart.

MicroRNAs As Master Regulators of Atherosclerosis: From Pathogenesis to Novel Therapeutic Options

Significance: Cardiovascular disease (CVD) remains the major cause of morbidity and mortality worldwide. Accumulating evidence indicates that atherosclerosis and its sequelae, coronary artery disease, contribute to the majority of cardiovascular deaths. Atherosclerosis is a chronic inflammatory disease of the arteries in which atherosclerotic plaques form within the vessel wall. Epidemiological studies have identified various risk factors for atherosclerosis, such as diabetes, hyperlipidemia, smoking, genetic predisposition, and sedentary lifestyle. Recent Advances: Through the advancement of genetic manipulation techniques and their use in cardiovascular biology, it was shown that small RNAs, especially microRNAs (miRNAs), are dynamic regulators of disease pathogenesis. They are considered to be central during the regulation of gene expression through numerous mechanisms and provide a means to develop biomarkers and therapeutic tools for the diagnosis and therapy of atherosclerosis. Circulating miRNAs encapsulated within membrane-surrounded vesicles, which originate from diverse subcellular compartments, are now emerging as novel regulators of intercellular communication. The miRNAs, in both freely circulating and vesicle-bound forms, represent a valuable tool for diagnosing and monitoring CVD, recently termed as "liquid biopsy." Critical Issues: However, despite the recent advancements in miRNA-based diagnostics and therapeutics, understanding how miRNAs can regulate atherosclerosis is still crucial to achieving an effective intervention and reducing the disease burden. Future Directions: We provide a landscape of the current developmental progression of RNA therapeutics as a holistic approach for treating CVD in different animal models and clinical trials. Future interrogations are warranted for the development of miRNA-based therapeutics to overcome challenges for the treatment of the disease.

miR-182-5p is an evolutionarily conserved Tbx5 effector that impacts cardiac development and electrical activity in zebrafish

To dissect the TBX5 regulatory circuit, we focused on microRNAs (miRNAs) that collectively contribute to make TBX5 a pivotal cardiac regulator. We profiled miRNAs in hearts isolated from wild-type, CRE, Tbx5lox/+and Tbx5del/+ mice using a Next Generation Sequencing (NGS) approach. TBX5 deficiency in cardiomyocytes increased the expression of the miR-183 cluster family that is controlled by Kruppel-like factor 4, a transcription factor repressed by TBX5. MiR-182-5p, the most highly expressed miRNA of this family, was functionally analyzed in zebrafish. Transient overexpression of miR-182-5p affected heart morphology, calcium handling and the onset of arrhythmias as detected by ECG tracings. Accordingly, several calcium channel proteins identified as putative miR-182-5p targets were downregulated in miR-182-5p overexpressing hearts. In stable zebrafish transgenic lines, we demonstrated that selective miRNA-182-5p upregulation contributes to arrhythmias. Moreover, cardiac-specific down-regulation of miR-182-5p rescued cardiac defects in a zebrafish model of Holt-Oram syndrome. In conclusion, miR-182-5p exerts an evolutionarily conserved role as a TBX5 effector in the onset of cardiac propensity for arrhythmia, and constitutes a relevant target for mediating the relationship between TBX5, arrhythmia and heart development.

Combining Nanomaterials and Developmental Pathways to Design New Treatments for Cardiac Regeneration: The Pulsing Heart of Advanced Therapies

The research for heart therapies is challenged by the limited intrinsic regenerative capacity of the adult heart. Moreover, it has been hampered by the poor results obtained by tissue engineering and regenerative medicine attempts at generating functional beating constructs able to integrate with the host tissue. For this reason, organ transplantation remains the elective treatment for end-stage heart failure, while novel strategies aiming to promote cardiac regeneration or repair lag behind. The recent discovery that adult cardiomyocytes can be ectopically induced to enter the cell cycle and proliferate by a combination of microRNAs and cardioprotective drugs, like anti-oxidant, anti-inflammatory, anti-coagulants and anti-platelets agents, fueled the quest for new strategies suited to foster cardiac repair. While proposing a revolutionary approach for heart regeneration, these studies raised serious issues regarding the efficient controlled delivery of the therapeutic cargo, as well as its timely removal or metabolic inactivation from the site of action. Especially, there is need for innovative treatment because of evidence of severe side effects caused by pleiotropic drugs. Biocompatible nanoparticles possess unique physico-chemical properties that have been extensively exploited for overcoming the limitations of standard medical therapies. Researchers have put great efforts into the optimization of the nanoparticles synthesis and functionalization, to control their interactions with the biological milieu and use as a viable alternative to traditional approaches. Nanoparticles can be used for diagnosis and deliver therapies in a personalized and targeted fashion. Regarding the treatment of cardiovascular diseases, nanoparticles-based strategies have provided very promising outcomes, in preclinical studies, during the last years. Efficient encapsulation of a large variety of cargos, specific release at the desired site and improvement of cardiac function are some of the main achievements reached so far by nanoparticle-based treatments in animal models. This work offers an overview on the recent nanomedical applications for cardiac regeneration and highlights how the versatility of nanomaterials can be combined with the newest molecular biology discoveries to advance cardiac regeneration therapies.

APRISMA-compliant systematic review and meta-analysis determining the association of miRNA polymorphisms and risk of congenital heart disease

PURPOSE

Recent genetic association studies showed conflicting results on the relationship of miRNA single-nucleotide polymorphisms (SNPs) and congenital heart disease (CHD) risk. The purpose of the present systematic review was to collect the current available evidences to evaluate the association between miRNA polymorphisms and CHD risk.

METHODS

Four electronic databases including PubMed, EMBASE, ISI Web of Science, and CENTRAL were extensively searched for relevant studies published before February, 2019. Observational studies determining the association between miRNA polymorphisms and risk of CHD were included. Risk of bias was evaluated using the Newcastle-Ottawa Scale by 2 independent researchers. Major characteristics of each study and estimation of effect size of individual locus polymorphism were summarized. In addition, meta-analysis was performed to quantify the associations between miRNA polymorphisms and CHD risk.

RESULTS

Nine studies containing 6502 CHD patients and 6969 healthy controls were included in this systematic review. Ten loci in 9 miRNAs were reported. Only rs11614913 in miR-196a2 was determined to have significant associations with CHD susceptibility, which was supported by meta-analysis (CC vs CT+TT: odds ratio 1.54, 95% confidence interval 1.30, 1.82; P < .00001). A strong evidence indicated lack of association between rs2910164 in miR-146a and CHD. Limited or conflicting evidences were found for the associations of the other variants (rs11134527, rs139365823, rs76987351, rs3746444, rs4938723, rs2292832, rs41291957, rs895819) and risk of CHD.

CONCLUSIONS

Locus polymorphisms in miRNAs are not generally associated with CHD. Only rs11614913 was found to have significant associations with CHD. Further studies will be needed, using larger populations of different ethnicities, to obtain a better understanding of these associations.

Upregulation of microRNA-218 reduces cardiac microvascular endothelial cells injury induced by coronary artery disease through the inhibition of HMGB1

This study is performed to examine the impacts of microRNA-218 (miR-218) on cardiac microvascular endothelial cells (CMECs) injury induced by coronary artery disease (CAD). Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) was applied for detecting miR-218 expression in serum of patients with CAD and healthy controls, and the correlation between miR-218 expression and the clinical indexes such as creatine kinase, creatine kinase-myocardial band, cardiac troponin I, and coronary Gensini score was analyzed. CMECs were coincubated with homocysteine for 24 hr for CMECs injury, and the cells were transfected with miR-218 mimics or miR-218 inhibitors. Besides, we used oxidized low density lipoprotein as an inducer to incubate with CMECs for 24 hr, and the model of CMECs injury was established to be transfected with miR-218 mimics. RT-qPCR and western blot analysis were used to detect miR-218 and HMGB1 expression in CMECs. A series of experiments were used to determine cell proliferation, apoptosis, migration, and angiogenesis ability of CMECs. Vascular endothelial growth factor expression and inflammatory factor contents were measured. The obtained results suggested that miR-218 expression in peripheral blood of patients with CAD descended substantially versus that of healthy controls. Low miR-218 expression was found in CAD-induced CMECs injury. Overexpressed miR-218 promoted the proliferation, migration, angiogenesis ability, induced apoptosis, and alleviated the inflammatory injury of CAD-induced CMECs. miR-218 may negatively regulate the expression of HMGB1 in CAD. This study demonstrates that upregulation of miR-218 reduces CMECs injury induced by CAD through the inhibition of HMGB1.

High-throughput sequencing reveals biofluid exosomal miRNAs associated with immunity in pigs

Large numbers of miRNAs are found in biofluid exosomes. We isolated ~50-200 nm diameter exosomes from four types of porcine biofluid (urine, plasma, semen, and bile) using serial centrifugation and ultracentrifugation procedures. A total of 42.15 M raw data were generated from four small RNA libraries. This produced 40.17 M map-able sequences, of which we identified 204 conserved miRNAs, and 190 novel candidate miRNAs. Furthermore, we identified 34 miRNAs specifically expressed in only one library, all with well-characterized immune-related functions. A set of five universally abundant miRNAs (miR-148a-3p, miR-21-5p, let-7f-5p, let-7i-5p, and miR-99a-5p) across all four biofluids was also found. Function enrichment analysis revealed that the target genes of the five ubiquitous miRNAs are primarily involved in immune and RNA metabolic processes. In summary, our findings suggest that porcine biofluid exosomes contain a large number of miRNAs, many of which may be crucial regulators of the immune system.

Downregulation of microRNA-218 is cardioprotective against cardiac fibrosis and cardiac function impairment in myocardial infarction by binding to MITF

OBJECTIVE

This study is intended to figure out the function of microRNA-218 (miR-218) together with microphthalmia-associated transcription factor (MITF) on the cardiac fibrosis and cardiac function impairment in rat models of myocardial infarction (MI).

RESULTS

The rats with MI exhibited cardiac function impairment, cardiac fibrosis, oxidative stress, cardiomyocyte apoptosis, as well as inflammatory injury. Additionally, upregulated miR-218 and downregulated MITF were detected in cardiac tissues of MI rats. MI rats injected with miR-218 inhibitors or overexpressed MITF exhibited elevated MITF expression, improved cardiac function, and diminished pathological damages, infarct size, cardiomyocyte apoptosis, cardiac fibrosis, oxidative stress as well as inflammatory injury in cardiac tissues. Furthermore, downregulated miR-218 and MITF aggravated the conditions than downregulation of miR-218 alone in MI rats.

METHODS

MI models were performed in rats, and then the rats were injected with miR-218 inhibitors and/or MITF overexpression plasmid to elucidate the role of miR-218 and/or MITF on the cardiac function, pathological damage, cardiac fibrosis, angiogenesis, oxidative stress and inflammatory injury of cardiac tissues in MI rats by performing a series of assays.

CONCLUSION

Collectively, we found that the suppression of miR-218 alleviates cardiac fibrosis and cardiac function impairment, and stimulates angiogenesis in MI rats through inhibiting MITF.

The role of microRNAs in congenital heart disease

Congenital heart diseases (CHDs) are the leading inherited cause of perinatal and infant mortality. CHD refers to structural anomalies of the heart and blood vessels that arise during cardiac development and represents a broad spectrum of malformations, including septal and valve defects, lesions affecting the outflow tract and ventricules. Advanced treatment strategies have greatly improved life expectancy and led to expanded population of adult patients with CHD. Thus, a better understanding of the pathogenesis and molecular mechanisms underlying CHDs is essential to improve the diagnosis and prognosis of patients. The etiology of CHD is largely unknown, genetic and environmental factors may contribute to the disease. In addition to the mutations affecting genomic DNA, epigenetic changes are being increasingly acknowledged as key factors in the development and progression of CHDs. The posttranscriptional regulation of gene expression by microRNAs (miRs) controls the highly complex multi-cell lineage process of cardiac tissue formation. In recent years, multiplex experimental models have provided evidence that changes in expression levels of miRs are associated with human cardiovascular disease, including CHD. The newly described correlations between miRs and heart development suggest the potential importance of miRs as diagnostic markers in human cardiovascular diseases. In the future, more intensive research is likely to be carried out to clarify their contribution to personalized management and treatment of CHD patients. In this paper, we discuss the current knowledge on the causative role of miRs in cardiac development and CHDs.

Epigenetic Regulation of Organ Regeneration in Zebrafish

The zebrafish is broadly used for investigating de novo organ regeneration, because of its strong regenerative potential. Over the past two decades of intense study, significant advances have been made in identifying both the regenerative cell sources and molecular signaling pathways in a variety of organs in adult zebrafish. Epigenetic regulation has gradually moved into the center-stage of this research area, aided by comprehensive work demonstrating that DNA methylation, histone modifications, chromatin remodeling complexes, and microRNAs are essential for organ regeneration. Here, we present a brief review of how these epigenetic components are induced upon injury, and how they are involved in sophisticated organ regeneration. In addition, we highlight several prospective research directions and their potential implications for regenerative medicine.

MiR-218 regulated cardiomyocyte differentiation and migration in mouse embryonic stem cells by targeting PDGFRα

MicroRNAs (miRNAs) have been identified as key players in cardiogenesis and heart pathophysiological processes. However, many miRNAs are still not recognized for their roles in cardiomyocytes differentiation. In this study, we evaluated the effects of microRNA-218 (miR-218) in cardiomyocyte differentiation of the mouse embryonic stem cells (ESCs) in vitro. The percentage of the beating embryoid bodies (EBs) in miR-218 mimic-treated cells was reduced to 32% compared with miR-218 mimic negative control (56%) on day 5 + 3. The amplitude of the intracellular Ca²⁺ transients in the cardiomyocytes derived from ESCs was reduced upon miR-218 overexpression, followed by the decreased calcium-related proteins and cell junction proteins expressions. Besides, miR-218 expression in ESCs was related to the directional spreading ability of EBs during differentiation. The increased expression of miR-218 could promote the migration of ESCs in vitro, while the decreased expression of miR-218 could inhibit the migration by the transwell experiment. Meanwhile, miR-218 could regulate cell migration-related proteins Cdc42 and Rac1. Platelet-derived growth factor receptor α (PDGFRα) was further confirmed to be a direct target of miR-218 both physically and functionally by dual-luciferase reporter assay. Our data further described that overexpression of PDGFRα rescued the miR-218-mediated inhibition of cardiomyocyte differentiation and restored the miR-218-mediated promotion of cell migration. In conclusion, miR-218 was demonstrated to exert an inhibitory function and promoted cell migration via targeting PDGFRα during cardiomyocyte differentiation from ESCs. The current study revealed the role of miR-218 and may provide an important hint for cardiomyocyte differentiation of ESCs and induced pluripotent stem cells.

MicroRNA-218-5p Promotes Endovascular Trophoblast Differentiation and Spiral Artery Remodeling

Preeclampsia (PE) is the leading cause of maternal and neonatal morbidity and mortality. Defects in trophoblast invasion, differentiation of endovascular extravillous trophoblasts (enEVTs), and spiral artery remodeling are key factors in PE development. There are no markers clinically available to predict PE, leaving expedited delivery as the only effective therapy. Dysregulation of miRNA in clinical tissues and maternal circulation have opened a new avenue for biomarker discovery. In this study, we investigated the role of miR-218-5p in PE development. miR-218-5p was highly expressed in EVTs and significantly downregulated in PE placentas. Using first-trimester trophoblast cell lines and human placental explants, we found that miR-218-5p overexpression promoted, whereas anti-miR-218-5p suppressed, trophoblast invasion, EVT outgrowth, and enEVT differentiation. Furthermore, miR-218-5p accelerated spiral artery remodeling in a decidua-placenta co-culture. The effect of miR-218-5p was mediated by the suppression of transforming growth factor (TGF)-β2 signaling. Silencing of TGFB2 mimicked, whereas treatment with TGF-β2 partially reversed, the effects of miR-218-5p. Taken together, these findings demonstrate that miR-218-5p promotes trophoblast invasion and enEVT differentiation through a novel miR-218-5p-TGF-β2 pathway. This study elucidates the role of an miRNA in enEVT differentiation and spiral artery remodeling and suggests that downregulation of miR-218-5p contributes to PE development.

Hyperglycaemia-induced epigenetic changes drive persistent cardiac dysfunction via the adaptor p66Shc

AIMS

Hyperglycaemia-induced reactive oxygen species (ROS) are key mediators of cardiac dysfunction. Intensive glycaemic control (IGC) has failed to reduce risk of heart failure in patients with diabetes but the underlying mechanisms remain to be elucidated. The present study investigates whether epigenetic regulation of the pro-oxidant adaptor p66^Shc contributes to persistent myocardial dysfunction despite IGC.

METHODS AND RESULTS

p66^Shc expression was increased in the heart of diabetic mice, and 3-week IGC by slow-release insulin implants did not revert this phenomenon. Sustained p66^Shc upregulation was associated with oxidative stress, myocardial inflammation and left ventricular dysfunction, as assessed by conventional and 2D speckle-tracking echocardiography. In vivo gene silencing of p66^Shc, performed during IGC, inhibited ROS production and restored cardiac function. Furthermore, we show that dysregulation of methyltransferase DNMT3b and deacetylase SIRT1 causes CpG demethylation and histone 3 acetylation on p66^Shc promoter, leading to persistent transcription of the adaptor. Altered DNMT3b/SIRT1 axis in the diabetic heart was explained by upregulation of miR-218 and miR-34a. Indeed, in human cardiomyocytes exposed to high glucose, inhibition of these miRNAs restored the expression of DNMT3b and SIRT1 and erased the adverse epigenetic signatures on p66^Shc promoter. Consistently, reprogramming miR-218 and miR-34a attenuated persistent p66^Shc expression and ROS generation.

CONCLUSIONS

In diabetic left ventricular dysfunction, a complex epigenetic mechanism linking miRNAs and chromatin modifying enzymes drives persistent p66^Shc transcription and ROS generation. Our results set the stage for pharmacological targeting of epigenetic networks to alleviate the clinical burden of diabetic cardiomyopathy.

Post-transcriptional Modulation of Sphingosine-1-Phosphate Receptor 1 by miR-19a Affects Cardiovascular Development in Zebrafish

Sphingosine-1-phosphate is a bioactive lipid and a signaling molecule integrated into many physiological systems such as differentiation, proliferation and migration. In mammals S1P acts through binding to a family of five trans-membrane, G-protein coupled receptors (S1PRs) whose complex role has not been completely elucidated. In this study we use zebrafish, in which seven s1prs have been identified, to investigate the role of s1pr1. In mammals S1PR1 is the most highly expressed S1P receptor in the developing heart and regulates vascular development, but in zebrafish the data concerning its role are contradictory. Here we show that overexpression of zebrafish s1pr1 affects both vascular and cardiac development. Moreover we demonstrate that s1pr1 expression is strongly repressed by miR-19a during the early phases of zebrafish development. In line with this observation and with a recent study showing that miR-19a is downregulated in a zebrafish Holt-Oram model, we now demonstrate that s1pr1 is upregulated in heartstring hearts. Next we investigated whether defects induced by s1pr1 upregulation might contribute to the morphological alterations caused by Tbx5 depletion. We show that downregulation of s1pr1 is able to partially rescue cardiac and fin defects induced by Tbx5 depletion. Taken together, these data support a role for s1pr1 in zebrafish cardiovascular development, suggest the involvement of this receptor in the Tbx5 regulatory circuitry, and further support the crucial role of microRNAs in early phase of zebrafish development.

Lack of association between miR-218 rs11134527 A>G and Kawasaki disease susceptibility

Kawasaki disease (KD) is a type of disease that includes the development of a fever that lasts at least 5 days and involves the clinical manifestation of multicellular vasculitis. KD has become one of the most common pediatric cardiovascular diseases. Previous studies have reported that miR-218 rs11134527 A>G is associated with susceptibility to various cancer risks. However, there is a lack of evidence regarding the relationship between this polymorphism and KD risk. The present study explored the correlation between the miR-218 rs11134527 A>G polymorphism and the risk of KD. We recruited 532 patients with KD and 623 controls to genotype the miR-218 rs11134527 A>G polymorphism with a TaqMan allelic discrimination assay. Our results illustrated that the miR-218 rs11134527 A>G polymorphism was not associated with KD risk. In an analysis stratified by age, sex, and coronary artery lesions, we found only that the risk of KD was significantly decreased for children older than 5 years (GG vs. AA/AG: adjusted OR = 0.26, 95% CI = 0.07–0.94, P=0.041). The present study demonstrated that the miR-218 rs1113452 A>G polymorphism may have an age-related relationship with KD susceptibility that has not previously been revealed.

Continuous addition of progenitors forms the cardiac ventricle in zebrafish

The vertebrate heart develops from several progenitor lineages. After early-differentiating first heart field (FHF) progenitors form the linear heart tube, late-differentiating second heart field (SHF) progenitors extend the atrium and ventricle, and form inflow and outflow tracts (IFT/OFT). However, the position and migration of late-differentiating progenitors during heart formation remains unclear. Here, we track zebrafish heart development using transgenics based on the cardiopharyngeal gene tbx1. Live imaging uncovers a tbx1 reporter-expressing cell sheath that continuously disseminates from the lateral plate mesoderm towards the forming heart tube. High-speed imaging and optogenetic lineage tracing corroborates that the zebrafish ventricle forms through continuous addition from the undifferentiated progenitor sheath followed by late-phase accrual of the bulbus arteriosus (BA). FGF inhibition during sheath migration reduces ventricle size and abolishes BA formation, refining the window of FGF action during OFT formation. Our findings consolidate previous end-point analyses and establish zebrafish ventricle formation as a continuous process.

Late-differentiating second heart field progenitors contribute to atrium, ventricle, and outflow tract in the zebrafish heart but how remains unclear. Here, the authors image heart formation in transgenics based on the cardiopharyngeal gene tbx1 and show that progenitors are continuously added.

Slit-Robo signalling in heart development

The Slit ligands and their Robo receptors are well-known for their roles during axon guidance in the central nervous system but are still relatively unknown in the cardiac field. However, data from different animal models suggest a broad involvement of the pathway in many aspects of heart development, from cardiac cell migration and alignment, lumen formation, chamber formation, to the formation of the ventricular septum, semilunar and atrioventricular valves, caval veins, and pericardium. Absence of one or more of the genes in the pathway results in defects ranging from bicuspid aortic valves to ventricular septal defects and abnormal venous connections to the heart. Congenital heart defects are the most common congenital malformations found in life new-born babies and progress in methods for large scale human genetic testing has significantly enhanced the identification of new causative genes involved in human congenital heart disease. Recently, loss of function variants in ROBO1 have also been linked to ventricular septal defects and tetralogy of Fallot in patients. Here, we will give an overview of the role of the Slit-Robo signalling pathway in Drosophila, zebrafish, and mouse heart development. The extent of these data warrant further attention on the SLIT-ROBO signalling pathway as a candidate for an array of human congenital heart defects.

Gene locations may contribute to predicting gene regulatory relationships

We propose that locations of genes on chromosomes can contribute to the prediction of gene regulatory relationships. We constructed a time-based gene regulatory network of zebrafish cardiogenesis on the basis of a spatio-temporal neighborhood method. Through the network, specific regulatory pathways and order of gene expression during zebrafish cardiogenesis were obtained. By comparing the order with locations of these genes on chromosomes, we discovered that there exists a reversal phenomenon between the order and order of gene locations. The discovery provides an inherent rule to instruct exploration of gene regulatory relationships. Specifically, the discovery can help to predict if regulatory relationships between genes exist and contribute to evaluating the correctness of discovered gene regulatory relationships.

A TBX5 3'UTR variant increases the risk of congenital heart disease in the Han Chinese population

TBX5 is a vital transcription factor involved in cardiac development in a dosage-dependent manner. But little is known about the potential association of TBX5 3′ untranslated region (UTR) variations with congenital cardiac malformations. This study aimed to investigate the relationship between TBX5 3′UTR variants and risk for congenital heart disease (CHD) susceptibility in two Han Chinese populations, and to reveal its molecular mechanism. The relationship between TBX5 3′UTR variants and CHD susceptibility was examined in 1 177 CHD patients and 990 healthy controls in two independent case–control studies. Variant rs6489956 C>T was found to be associated with increased CHD susceptibility in both cohorts. The combined CHD risk for the CT and TT genotype carriers was 1.83 times higher than that of CC genotype, while the risk for CT or TT genotype was 1.94 times and 2.31 times higher than that of CC carriers, respectively. Quantitative real-time PCR and western blot analysis showed that T allele carriers exhibited reduced TBX5 mRNA and protein levels in CHDs tissues. Compared with C allele, T allele showed increased binding affinity to miR-9 and miR-30a in both luciferase assays and surface plasmon resonance analysis. Functional analysis confirmed that miR-9 and miR-30a downregulated TBX5 expression at the transcriptional and translational levels, respectively. The assays in zebrafish model were in support of the interaction of miR-9/30a and TBX5 3′UTR (C and T allele). We concluded that TBX5 3′UTR variant rs6489956 increased susceptibility of CHD in the Han Chinese population because it changes the binding affinity of two target miRNAs that specifically mediate TBX5 expression.

Sexual dimorphisms of mRNA and miRNA in human/murine heart disease

BACKGROUND

Sexual dimorphisms are well recognized in various cardiac diseases such as ischemic cardiomyopathy (ICM), hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Thorough understanding of the underlying genetic programs is crucial to optimize treatment strategies specified for each gender. By performing meta-analysis and microarray analysis, we sought to comprehensively characterize the sexual dimorphisms in the healthy and diseased heart at the level of both mRNA and miRNA transcriptome.

RESULTS

Existing mRNA microarray data of both mouse and human heart were integrated, identifying dozens/ hundreds of sexually dimorphic genes in healthy heart, ICM, HCM, and DCM. These sexually dimorphic genes overrepresented gene ontologies (GOs) important for cardiac homeostasis. Further, microarray of miRNA, isolated from mouse sham left ventricle (LV) (n = 6 & n = 5 for male & female) and chronic MI LV (n = 19 & n = 19) and from human normal LV (n = 6 & n = 6) and ICM LV (n = 4 & n = 5), was conducted. This revealed that 13 mouse miRNAs are sexually dimorphic in MI and 6 in normal heart. In human, 3 miRNAs were sexually dimorphic in ICM and 15 in normal heart. These data revealed miRNA-mRNA networks that operate in a sexually-biased fashion.

CONCLUSIONS

mRNA and miRNA transcriptome of normal and disease heart show significant sex differences, which might impact the cardiac homeostasis. Together this study provides the first comprehensive picture of the genome-wide program underlying the heart sexual dimorphisms, laying the foundation for gender specific treatment strategies.

Interactions between microRNAs and long non-coding RNAs in cardiac development and repair

Non-coding RNAs (ncRNAs) are emerging players in muscle regulation. Based on their length and differences in molecular structure, ncRNAs are subdivided into several categories including small interfering RNAs, stable non-coding RNAs, microRNAs (miRs), long non-coding RNAs (lncRNAs), and circular RNAs. miRs and lncRNAs are able to post-transcriptionally regulate many genes and bring into play several traits simultaneously due to a myriad of different targets. Recent studies have emphasized their importance in cardiac regeneration and repair. As their altered expression affects cardiac function, miRs and lncRNAs could be potential targets for therapeutic intervention. In this context, miR- and lncRNA-based gene therapies are an interesting field for harnessing the complexity of ncRNA-based therapeutic approaches in cardiac diseases. In this review we will focus on lncRNA- and miR-driven regulations of cardiac development and repair. Finally, we will summarize miRs and lncRNAs as promising candidates for the treatment of heart diseases.

miR-873 suppresses H9C2 cardiomyocyte proliferation by targeting GLI1

MicroRNAs (miRNAs) are a class of endogenous, non-coding small RNAs that regulate the expression of target genes. Previous studies have suggested that miRNAs are key regulators in cardiovascular systems. This study investigated the role of miR-873 in H9C2 cardiomyocytes by targeting glioma-associated oncogene 1 (GLI1). miR-873 was significantly up-regulated in serum samples from congenital heart disease (CHD) patients compared with those from normal individuals. Furthermore, miR-873 over-expression suppressed H9C2 proliferation and induced cell cycle arrest. Bioinformatic algorithms revealed a predicted target site for miR-873 in the 3'-untranslated region (3'UTR) of GLI1, which was verified using a dual-luciferase reporter assay. qPCR and western blot analysis also showed that miR-873 negatively regulated GLI1 mRNA and protein expression in H9C2 cells. Conversely, GLI1 over-expression partially reversed the growth-inhibitory effect of miR-873. To summarize, our data suggest that miR-873 is a novel miRNA that regulates H9C2 cell proliferation via targeting GLI1, and miR-873 may serve as a new potential biomarker diagnosis in CHD in the future.

MicroRNAs: pleiotropic players in congenital heart disease and regeneration

Congenital heart disease (CHD) is the leading cause of infant death, affecting approximately 4-14 live births per 1,000. Although surgical techniques and interventions have improved significantly, a large number of infants still face poor clinical outcomes. MicroRNAs (miRs) are known to coordinately regulate cardiac development and stimulate pathological processes in the heart, including fibrosis or hypertrophy and impair angiogenesis. Dysregulation of these regulators could therefore contribute (I) to the initial development of CHD and (II) at least partially to the observed clinical outcomes of many CHD patients by stimulating the aforementioned pathways. Thus, miRs may exhibit great potential as therapeutic targets in regenerative medicine. In this review we provide an overview of miR function and elucidate their role in selected CHDs, including hypoplastic left heart syndrome (HLHS), tetralogy of Fallot (TOF), ventricular septal defects (VSDs) and Holt-Oram syndrome (HOS). We then bridge this knowledge to the potential usefulness of miRs and/or their targets in therapeutic strategies for regenerative purposes in CHDs.

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.

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.

Maximizing mutagenesis with solubilized CRISPR-Cas9 ribonucleoprotein complexes

CRISPR-Cas9 enables efficient sequence-specific mutagenesis for creating somatic or germline mutants of model organisms. Key constraints in vivo remain the expression and delivery of active Cas9-sgRNA ribonucleoprotein complexes (RNPs) with minimal toxicity, variable mutagenesis efficiencies depending on targeting sequence, and high mutation mosaicism. Here, we apply in vitro assembled, fluorescent Cas9-sgRNA RNPs in solubilizing salt solution to achieve maximal mutagenesis efficiency in zebrafish embryos. MiSeq-based sequence analysis of targeted loci in individual embryos using CrispRVariants, a customized software tool for mutagenesis quantification and visualization, reveals efficient bi-allelic mutagenesis that reaches saturation at several tested gene loci. Such virtually complete mutagenesis exposes loss-of-function phenotypes for candidate genes in somatic mutant embryos for subsequent generation of stable germline mutants. We further show that targeting of non-coding elements in gene regulatory regions using saturating mutagenesis uncovers functional control elements in transgenic reporters and endogenous genes in injected embryos. Our results establish that optimally solubilized, in vitro assembled fluorescent Cas9-sgRNA RNPs provide a reproducible reagent for direct and scalable loss-of-function studies and applications beyond zebrafish experiments that require maximal DNA cutting efficiency in vivo.

Genome-wide association study of periweaning failure-to-thrive syndrome (PFTS) in pigs

Porcine periweaning-failure-to-thrive syndrome (PFTS) is a condition that affects newly weaned piglets. It is characterised by a progressive debilitation leading to death, in the absence of infectious, nutritional, management or environmental factors. In this study, we present the first report of PFTS in South America and the results of a genome-wide association study to identify the genetic markers associated with the appearance of this condition in a crossbred swine population. Four chromosomal regions were associated with PFTS predisposition, one located on SSCX, one on SSC8, and the two other regions on SSC14. Regions on SSC8 and SSC14 harbour important functional candidate genes involved in human depression and might have an important role in PFTS. Our findings contribute to the increasing knowledge about this syndrome, which has been investigated since 2007, and to the identification of the aetiology of this disease.

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.

MicroRNA 19a replacement partially rescues fin and cardiac defects in zebrafish model of Holt Oram syndrome

Holt-Oram Syndrome (HOS) is an autosomal dominant heart-hand syndrome caused by mutations in the TBX5 gene, a transcription factor capable of regulating hundreds of cardiac-specific genes through complex transcriptional networks. Here we show that, in zebrafish, modulation of a single miRNA is sufficient to rescue the morphogenetic defects generated by HOS. The analysis of miRNA-seq profiling revealed a decreased expression of miR-19a in Tbx5-depleted zebrafish embryos compared to the wild type. We revealed that the transcription of the miR-17-92 cluster, which harbors miR-19a, is induced by Tbx5 and that a defined dosage of miR-19a is essential for the correct development of the heart. Importantly, we highlighted that miR-19a replacement is able to rescue cardiac and pectoral fin defects and to increase the viability of HOS zebrafish embryos. We further observed that miR-19a replacement shifts the global gene expression profile of HOS-like zebrafish embryos towards the wild type condition, confirming the ability of miR-19a to rescue the Tbx5 phenotype. In conclusion our data demonstrate the importance of Tbx5/miR-19a regulatory circuit in heart development and provide a proof of principle that morphogenetic defects associated with HOS can be rescued by transient miRNA modulation.

Unique patterns of transcript and miRNA expression in the South American strong voltage electric eel (Electrophorus electricus)

Background

With its unique ability to produce high-voltage electric discharges in excess of 600 volts, the South American strong voltage electric eel (Electrophorus electricus) has played an important role in the history of science. Remarkably little is understood about the molecular nature of its electric organs.

Results

We present an in-depth analysis of the genome of E. electricus, including the transcriptomes of eight mature tissues: brain, spinal cord, kidney, heart, skeletal muscle, Sachs’ electric organ, main electric organ, and Hunter’s electric organ. A gene set enrichment analysis based on gene ontology reveals enriched functions in all three electric organs related to transmembrane transport, androgen binding, and signaling. This study also represents the first analysis of miRNA in electric fish. It identified a number of miRNAs displaying electric organ-specific expression patterns, including one novel miRNA highly over-expressed in all three electric organs of E. electricus. All three electric organ tissues also express three conserved miRNAs that have been reported to inhibit muscle development in mammals, suggesting that miRNA-dependent regulation of gene expression might play an important role in specifying an electric organ identity from its muscle precursor. These miRNA data were supported using another complete miRNA profile from muscle and electric organ tissues of a second gymnotiform species.

Conclusions

Our work on the E. electricus genome and eight tissue-specific gene expression profiles will greatly facilitate future research on determining the coding and regulatory sequences that specify the function, development, and evolution of electric organs. Moreover, these data and future studies will be informed by the first comprehensive analysis of miRNA expression in an electric fish presented here.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1288-8) contains supplementary material, which is available to authorized users.

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.

Barley beta-glucan promotes MnSOD expression and enhances angiogenesis under oxidative microenvironment

Manganese superoxide dismutase (MnSOD), a foremost antioxidant enzyme, plays a key role in angiogenesis. Barley-derived (1.3) β-d-glucan (β-d-glucan) is a natural water-soluble polysaccharide with antioxidant properties. To explore the effects of β-d-glucan on MnSOD-related angiogenesis under oxidative stress, we tested epigenetic mechanisms underlying modulation of MnSOD level in human umbilical vein endothelial cells (HUVECs) and angiogenesis in vitro and in vivo. Long-term treatment of HUVECs with 3% w/v β-d-glucan significantly increased the level of MnSOD by 200% ± 2% compared to control and by 50% ± 4% compared to untreated H₂O₂-stressed cells. β-d-glucan-treated HUVECs displayed greater angiogenic ability. In vivo, 24 hrs-treatment with 3% w/v β-d-glucan rescued vasculogenesis in Tg (kdrl: EGFP) s843Tg zebrafish embryos exposed to oxidative microenvironment. HUVECs overexpressing MnSOD demonstrated an increased activity of endothelial nitric oxide synthase (eNOS), reduced load of superoxide anion (O₂⁻) and an increased survival under oxidative stress. In addition, β-d-glucan prevented the rise of hypoxia inducible factor (HIF)1-α under oxidative stress. The level of histone H4 acetylation was significantly increased by β-d-glucan. Increasing histone acetylation by sodium butyrate, an inhibitor of class I histone deacetylases (HDACs I), did not activate MnSOD-related angiogenesis and did not impair β-d-glucan effects. In conclusion, 3% w/v β-d-glucan activates endothelial expression of MnSOD independent of histone acetylation level, thereby leading to adequate removal of O₂⁻, cell survival and angiogenic response to oxidative stress. The identification of dietary β-d-glucan as activator of MnSOD-related angiogenesis might lead to the development of nutritional approaches for the prevention of ischemic remodelling and heart failure.

microRNAs and Cardiac Cell Fate

The role of small, non-coding microRNAs (miRNAs) has recently emerged as fundamental in the regulation of the physiology of the cardiovascular system. Several specific miRNAs were found to be expressed in embryonic, postnatal, and adult cardiac tissues. In the present review, we will provide an overview about their role in controlling the different pathways regulating cell identity and fate determination. In particular, we will focus on the involvement of miRNAs in pluripotency determination and reprogramming, and specifically on cardiac lineage commitment and cell direct transdifferentiation into cardiomyocytes. The identification of cardiac-specific miRNAs and their targets provide new promising insights into the mechanisms that regulate cardiac development, function and dysfunction. Furthermore, due to their contribution in reprogramming, they could offer new opportunities for developing safe and efficient cell-based therapies for cardiovascular disorders.

miR-10a and miR-10b target the 3'-untranslated region of TBX5 to repress its expression

As a well-known transcription factor, TBX5 is involved in embryonic cardiac development. Although TBX5 functions in a dose-dependent manner, the posttranscriptional regulation of human TBX5 is poorly understood. Thus, this study aimed to identify microRNAs that modulate TBX5 expression. Luciferase assays were used to screen miRNAs predicted to modulate TBX5 expression. Using quantitative reverse transcriptase-polymerase chain reaction and Western blot analysis, the authors found that miR-10a and miR-10b significantly repressed TBX5 expression and decreased TBX5 protein levels by targeting the TBX5 3'-untranslated region. In addition, miR-10a and miR-10b expression levels were respectively 2.77 and 3.51 times higher in the heart tissues of congenital heart disease patients than in healthy control subjects, suggesting that they are potential diagnostic biomarkers. In conclusion, the study results indicate that miR-10a and miR-10b inhibit TBX5 expression at the level of translation. Higher levels of miR-10a and miR-10b expression are associated with a higher risk of congenital heart defects.

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.