From embryogenesis to adulthood: Critical role for GATA factors in heart development and function

RNA binding proteins in cardiovascular development and disease

Congenital heart disease (CHD) is the most common birth defect affecting>1.35 million newborn babies worldwide. CHD can lead to prenatal, neonatal, postnatal lethality or life-long cardiac complications. RNA binding protein (RBP) mutations or variants are emerging as contributors to CHDs. RBPs are wizards of gene regulation and are major contributors to mRNA and protein landscape. However, not much is known about RBPs in the developing heart and their contributions to CHD. In this chapter, we will discuss our current knowledge about specific RBPs implicated in CHDs. We are in an exciting era to study RBPs using the currently available and highly successful RNA-based therapies and methodologies. Understanding how RBPs shape the developing heart will unveil their contributions to CHD. Identifying their target RNAs in the embryonic heart will ultimately lead to RNA-based treatments for congenital heart disease.

Genetics of congenital heart disease

During embryonic development, the cardiovascular system and the central nervous system exhibit a coordinated developmental process through intricate interactions. Congenital heart disease (CHD) refers to structural or functional abnormalities that occur during embryonic or prenatal heart development and is the most common congenital disorder. One of the most common complications in CHD patients is neurodevelopmental disorders (NDD). However, the specific mechanisms, connections, and precise ways in which CHD co-occurs with NDD remain unclear. According to relevant research, both genetic and non-genetic factors are significant contributors to the co-occurrence of sporadic CHD and NDD. Genetic variations, such as chromosomal abnormalities and gene mutations, play a role in the susceptibility to both CHD and NDD. Further research should aim to identify common molecular mechanisms that underlie the co-occurrence of CHD and NDD, possibly originating from shared genetic mutations or shared gene regulation. Therefore, this review article summarizes the current advances in the genetics of CHD co-occurring with NDD, elucidating the application of relevant gene detection techniques. This is done with the aim of exploring the genetic regulatory mechanisms of CHD co-occurring with NDD at the gene level and promoting research and treatment of developmental disorders related to the cardiovascular and central nervous systems.

GATA binding protein 6 regulates apoptosis in silkworms through interaction with poly (ADP-ribose) polymerase

The GATA family of genes plays various roles in crucial biological processes, such as development, cell differentiation, and disease progression. However, the roles of GATA in insects have not been thoroughly explored. In this study, a genome-wide characterization of the GATA gene family in the silkworm, Bombyx mori, was conducted, revealing lineage-specific expression profiles. Notably, GATA6 is ubiquitously expressed across various developmental stages and tissues, with predominant expression in the midgut, ovaries, and Malpighian tubules. Overexpression of GATA6 inhibits cell growth and promotes apoptosis, whereas, in contrast, knockdown of PARP mitigates the apoptotic effects driven by GATA6 overexpression. Co-immunoprecipitation (co-IP) has demonstrated that GATA6 can interact with Poly (ADP-ribose) polymerase (PARP), suggesting that GATA6 may induce cell apoptosis by activating the enzyme's activity. These findings reveal a dynamic and regulatory relationship between GATA6 and PARP, suggesting a potential role for GATA6 as a key regulator in apoptosis through its interaction with PARP. This research deepens the understanding of the diverse roles of the GATA family in insects, shedding light on new avenues for studies in sericulture and pest management.

Polymorphism within the GATA binding protein 4 gene is significantly associated with goat litter size

GATA binding protein 4 (GATA4) is a typical transcription binding factor, and its main functions include regulating the proliferation, differentiation and apoptosis of ovarian granulosa cells, promoting spermatogenesis and sex differentiation, implying that this gene have possibly roles in animal reproduction. This study aims to detect five potential insertion/deletions (indels) of the GATA4 gene in 606 healthy unrelated Shaanbei white cashmere (SBWC) goats and analyze its association with the litter size. The electrophoresis and DNA sequencing identified two polymorphic indels (e.g., P4-Del-8bp and P5-Ins-9bp indel). Then T-test analysis showed that P4-Del-8bp was significantly correlated with litter size (p = 0.022) because of two different genotypes detected, e.g., insertion-deletion (ID) and deletion-deletion (DD), and the average litter size of individuals with DD genotype goats was higher than that of others. However, there was no correlation between P5-Ins-9bp and lambing of goats. Chi-square (X2) test found that the distribution of and P4-Del-8bp genotypes (X2 = 6.475, p = 0.011) was significantly different between single and multiple-lamb groups, while P5-Ins-9bp (X2 = 0.030, p = 0.862) was not. Therefore, these findings revealed that P4-Del-8bp polymorphism of goat GATA4 gene was a potential molecular marker significantly associated with litter size, which can be used for the marker-assisted selection (MAS) breeding to improve goat industry.

Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Translation of upstream open reading frames (uORFs) typically abrogates translation of main (m)ORFs. The molecular mechanism of uORF regulation in cells is not well understood. Here, we data-mined human and mouse heart ribosome profiling analyses and identified a double-stranded RNA (dsRNA) structure within the GATA4 uORF that cooperates with the start codon to augment uORF translation and inhibits mORF translation. A trans-acting RNA helicase DDX3X inhibits the GATA4 uORF-dsRNA activity and modulates the translational balance of uORF and mORF. Antisense oligonucleotides (ASOs) that disrupt this dsRNA structure promote mORF translation, while ASOs that base-pair immediately downstream (i.e., forming a bimolecular double-stranded region) of either the uORF or mORF start codon enhance uORF or mORF translation, respectively. Human cardiomyocytes and mice treated with a uORF-enhancing ASO showed reduced cardiac GATA4 protein levels and increased resistance to cardiomyocyte hypertrophy. We further show the broad utility of uORF-dsRNA- or mORF-targeting ASO to regulate mORF translation for other mRNAs. This work demonstrates that the uORF-dsRNA element regulates the translation of multiple mRNAs as a generalizable translational control mechanism. Moreover, we develop a valuable strategy to alter protein expression and cellular phenotypes by targeting or generating dsRNA downstream of a uORF or mORF start codon.

Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Translation of upstream open reading frames (uORFs) typically abrogates translation of main (m)ORFs. The molecular mechanism of uORF regulation in cells is not well understood. Here, we identified a double-stranded RNA (dsRNA) structure residing within the GATA4 uORF that augments uORF translation and inhibits mORF translation. Antisense oligonucleotides (ASOs) that disrupt this dsRNA structure promote mORF translation, while ASOs that base-pair immediately downstream (i.e., forming a bimolecular double-stranded region) of either the uORF or mORF start codon enhance uORF or mORF translation, respectively. Human cardiomyocytes and mice treated with a uORF-enhancing ASO showed reduced cardiac GATA4 protein levels and increased resistance to cardiomyocyte hypertrophy. We further show the general utility of uORF-dsRNA- or mORF- targeting ASO to regulate mORF translation for other mRNAs. Our work demonstrates a regulatory paradigm that controls translational efficiency and a useful strategy to alter protein expression and cellular phenotypes by targeting or generating dsRNA downstream of a uORF or mORF start codon.

Bullet points for discoveries

dsRNA within GATA4 uORF activates uORF translation and inhibits mORF translation. ASOs that target the dsRNA can either inhibit or enhance GATA4 mORF translation. ASOs can be used to impede hypertrophy in human cardiomyocytes and mouse hearts.uORF- and mORF-targeting ASOs can be used to control translation of multiple mRNAs.

Deciphering the Cardiovascular Potential of Human CD34+ Stem Cells

Ex vivo monitored human CD34⁺ stem cells (SCs) injected into myocardium scar tissue have shown real benefits for the recovery of patients with myocardial infarctions. They have been used previously in clinical trials with hopeful results and are expected to be promising for cardiac regenerative medicine following severe acute myocardial infarctions. However, some debates on their potential efficacy in cardiac regenerative therapies remain to be clarified. To elucidate the levels of CD34⁺ SC implication and contribution in cardiac regeneration, better identification of the main regulators, pathways, and genes involved in their potential cardiovascular differentiation and paracrine secretion needs to be determined. We first developed a protocol thought to commit human CD34⁺ SCs purified from cord blood toward an early cardiovascular lineage. Then, by using a microarray-based approach, we followed their gene expression during differentiation. We compared the transcriptome of undifferentiated CD34⁺ cells to those induced at two stages of differentiation (i.e., day three and day fourteen), with human cardiomyocyte progenitor cells (CMPCs), as well as cardiomyocytes as controls. Interestingly, in the treated cells, we observed an increase in the expressions of the main regulators usually present in cardiovascular cells. We identified cell surface markers of the cardiac mesoderm, such as kinase insert domain receptor (KDR) and the cardiogenic surface receptor Frizzled 4 (FZD4), induced in the differentiated cells in comparison to undifferentiated CD34⁺ cells. The Wnt and TGF-β pathways appeared to be involved in this activation. This study underlined the real capacity of effectively stimulated CD34⁺ SCs to express cardiac markers and, once induced, allowed the identification of markers that are known to be involved in vascular and early cardiogenesis, demonstrating their potential priming towards cardiovascular cells. These findings could complement their paracrine positive effects known in cell therapy for heart disease and may help improve the efficacy and safety of using ex vivo expanded CD34⁺ SCs.

Impact of polyphenols on heart failure and cardiac hypertrophy: clinical effects and molecular mechanisms

Polyphenols are abundant in regular diets and possess antioxidant, anti-inflammatory, anti-cancer, neuroprotective, and cardioprotective effects. Regarding the inadequacy of the current treatments in preventing cardiac remodeling following cardiovascular diseases, attention has been focused on improving cardiac function with potential alternatives such as polyphenols. The following online databases were searched for relevant orginial published from 2000 to 2023: EMBASE, MEDLINE, and Web of Science databases. The search strategy aimed to assess the effects of polyphenols on heart failure and keywords were "heart failure" and "polyphenols" and "cardiac hypertrophy" and "molecular mechanisms". Our results indicated polyphenols are repeatedly indicated to regulate various heart failure-related vital molecules and signaling pathways, such as inactivating fibrotic and hypertrophic factors, preventing mitochondrial dysfunction and free radical production, the underlying causes of apoptosis, and also improving lipid profile and cellular metabolism. In the current study, we aimed to review the most recent literature and investigations on the underlying mechanism of actions of different polyphenols subclasses in cardiac hypertrophy and heart failure to provide deep insight into novel mechanistic treatments and direct future studies in this context. Moreover, due to polyphenols' low bioavailability from conventional oral and intravenous administration routes, in this study, we have also investigated the currently accessible nano-drug delivery methods to optimize the treatment outcomes by providing sufficient drug delivery, targeted therapy, and less off-target effects, as desired by precision medicine standards.

Genetic Alterations of Transcription Factors and Signaling Molecules Involved in the Development of Congenital Heart Defects-A Narrative Review

Congenital heart defects (CHD) are the most common congenital abnormality, with an overall global birth prevalence of 9.41 per 1000 live births. The etiology of CHDs is complex and still poorly understood. Environmental factors account for about 10% of all cases, while the rest are likely explained by a genetic component that is still under intense research. Transcription factors and signaling molecules are promising candidates for studies regarding the genetic burden of CHDs. The present narrative review provides an overview of the current knowledge regarding some of the genetic mechanisms involved in the embryological development of the cardiovascular system. In addition, we reviewed the association between the genetic variation in transcription factors and signaling molecules involved in heart development, including TBX5, GATA4, NKX2-5 and CRELD1, and congenital heart defects, providing insight into the complex pathogenesis of this heterogeneous group of diseases. Further research is needed in order to uncover their downstream targets and the complex network of interactions with non-genetic risk factors for a better molecular-phenotype correlation.

KLF13 overexpression protects sepsis-induced myocardial injury and LPS-induced inflammation and apoptosis

Sepsis remains a worldwide public health problem. This study aims to explore the role and mechanism of transcriptional factors (TFs) in sepsis-induced myocardial injury. Firstly, TF KLF13 was selected to explore its role in sepsis-induced myocardial injury. The caecal ligation and puncture (CLP) -induced sepsis mouse model was established and the septic mice were examined using standard histopathological methods. KLF13 expression was detected in the septic mouse heart and was also seen in a lipoploysaccharide (LPS) -induced cellular inflammation model. To explore this further both pro-apoptotic cleaved-caspase3/caspase3 and Bax levels and anti-apoptotic Bcl2 levels were examined, also in both models, In addition inflammatory cytokine (IL-1β, TNF-α, IL-8 and MCP-1) production and IκB-α protein level and p65 phosphorylation were examined in both septic mice and LPS-induced cells. Thus three parameters - cardiomyocyte apoptosis, inflammatory response and NF-κB pathway activation were evaluated under similar conditions. The septic mice showed significant oedema, disordered myofilament arrangement and degradation and necrosis to varying degrees in the myocardial cells. KLF13 was downregulated in both the septic mouse heart and the LPS-induced cellular inflammation model. Furthermore, both models showed abnormally increased cardiomyocyte apoptosis (increased cleaved-caspase3/caspase and Bax protein levels and decreased Bcl2 level), elevated inflammation (increased production of inflammatory cytokines) and the activated NF-κB pathway (increased p65 phosphorylation and decreased IκB-α protein level). KLF13 overexpression notably ameliorated sepsis-induced myocardial injury in vivo and in vitro. KLF13 overexpression protected against sepsis-induced myocardial injury and LPS-induced cellular inflammation and apoptosis via inhibiting the inflammatory pathways (especially NF-κB signalling) and cardiomyocyte apoptosis.

Functional characterization of GATA6 genetic variants associated with mild congenital heart defects

Damaging GATA6 variants can cause moderate congenital heart defects. With the application of next-generation sequencing approaches, various novel GATA6 variants with unknown significance have been identified from a broad spectrum of congenital heart defects. However, functional assessment for distinct GATA6 variants from different severity of congenital heart defects, especially from mild defects, is lacking, which hinders our understanding of the genotype-phenotype correlations and underlying mechanisms. Here, we assessed the functional consequences of nine rare GATA6 variants, which had been implicated as the most significant variants associated with mild congenital heart defects using the largest case and control cohort. We examined the effects of these variants on subcellular localization, transcriptional activity, and protein interactions in 293T or AC16 cells and their ability to rescue heart malformation in gata6 zebrafish mutant. We found that two of these nine variants, Q120X and S424I, significantly decreased transcriptional activity. Additionally, Q120X altered subcellular localization. Consistent with the in vitro results, the in vivo results showed that Q120X and S424I lost their potency to rescue ventricular malformation in gata6 -/- embryos. The results indicated that Q120X and S424I are pathogenic in mild congenital heart defects. Further, the inconsistence of severely impaired Q120X function and mild CHDs phenotype suggested the complexity of the genotype-phenotype correlation between the GATA6 variant and heart phenotype, which may help to inform prenatal genetic counseling and pre-implantation genotyping for congenital heart defects.

A GRIP-1-EZH2 switch binding to GATA-4 is linked to the genesis of rhabdomyosarcoma through miR-29a

Terminal differentiation failure is an important cause of rhabdomyosarcoma genesis, however, little is known about the epigenetic regulation of aberrant myogenic differentiation. Here, we show that GATA-4 recruits polycomb group proteins such as EZH2 to negatively regulate miR-29a in undifferentiated C2C12 myoblast cells, whereas recruitment of GRIP-1 to GATA-4 proteins displaces EZH2, resulting in the activation of miR-29a during myogenic differentiation of C2C12 cells. Moreover, in poorly differentiated rhabdomyosarcoma cells, EZH2 still binds to the miR-29a promoter with GATA-4 to mediate transcriptional repression of miR-29a. Interestingly, once re-differentiation of rhabdomyosarcoma cells toward skeletal muscle, EZH2 was dispelled from miR-29a promoter which is similar to that in myogenic differentiation of C2C12 cells. Eventually, this expression of miR-29a results in limited rhabdomyosarcoma cell proliferation and promotes myogenic differentiation. We thus establish that GATA-4 can function as a molecular switch in the up- and downregulation of miR-29a expression. We also demonstrate that GATA-4 acts as a tumor suppressor in rhabdomyosarcoma partly via miR-29a, which thus provides a potential therapeutic target for rhabdomyosarcoma.

Transcription Factor GATA4 Regulates Cell Type-Specific Splicing Through Direct Interaction With RNA in Human Induced Pluripotent Stem Cell-Derived Cardiac Progenitors

BACKGROUND

GATA4 (GATA-binding protein 4), a zinc finger-containing, DNA-binding transcription factor, is essential for normal cardiac development and homeostasis in mice and humans, and mutations in this gene have been reported in human heart defects. Defects in alternative splicing are associated with many heart diseases, yet relatively little is known about how cell type- or cell state-specific alternative splicing is achieved in the heart. Here, we show that GATA4 regulates cell type-specific splicing through direct interaction with RNA and the spliceosome in human induced pluripotent stem cell-derived cardiac progenitors.

METHODS

We leveraged a combination of unbiased approaches including affinity purification of GATA4 and mass spectrometry, enhanced cross-linking with immunoprecipitation, electrophoretic mobility shift assays, in vitro splicing assays, and unbiased transcriptomic analysis to uncover GATA4's novel function as a splicing regulator in human induced pluripotent stem cell-derived cardiac progenitors.

RESULTS

We found that GATA4 interacts with many members of the spliceosome complex in human induced pluripotent stem cell-derived cardiac progenitors. Enhanced cross-linking with immunoprecipitation demonstrated that GATA4 also directly binds to a large number of mRNAs through defined RNA motifs in a sequence-specific manner. In vitro splicing assays indicated that GATA4 regulates alternative splicing through direct RNA binding, resulting in functionally distinct protein products. Correspondingly, knockdown of GATA4 in human induced pluripotent stem cell-derived cardiac progenitors resulted in differential alternative splicing of genes involved in cytoskeleton organization and calcium ion import, with functional consequences associated with the protein isoforms.

CONCLUSIONS

This study shows that in addition to its well described transcriptional function, GATA4 interacts with members of the spliceosome complex and regulates cell type-specific alternative splicing via sequence-specific interactions with RNA. Several genes that have splicing regulated by GATA4 have functional consequences and many are associated with dilated cardiomyopathy, suggesting a novel role for GATA4 in achieving the necessary cardiac proteome in normal and stress-responsive conditions.

A novel causative functional mutation in GATA6 gene is responsible for familial dilated cardiomyopathy as supported by in silico functional analysis

Dilated cardiomyopathy (DCM), one of the most common types of cardiomyopathies has a heterogeneous nature and can be seen in Mendelian forms. Next Generation Sequencing is a powerful tool for identifying novel variants in monogenic disorders. We used whole-exome sequencing (WES) and Sanger sequencing techniques to identify the causative mutation of DCM in an Iranian pedigree. We found a novel variant in the GATA6 gene, leading to substituting Histidine by Tyrosine at position 329, observed in all affected family members in the pedigree, whereas it was not established in any of the unaffected ones. We hypothesized that the H329Y mutation may be causative for the familial pattern of DCM in this family. The predicted models of GATA6 and H329Y showed the high quality according to PROCHECK and ERRAT. Nonetheless, simulation results revealed that the protein stability decreased after mutation, while the flexibility may have been increased. Hence, the mutation led to the increased compactness of GATA6. Overall, these data indicated that the mutation could affect the protein structure, which may be related to the functional impairment of GATA6 upon H329Y mutation, likewise their involvement in pathologies. Further functional investigations would help elucidating the exact mechanism.

DEC1 represses cardiomyocyte hypertrophy by recruiting PRP19 as an E3 ligase to promote ubiquitination-proteasome-mediated degradation of GATA4

Although the pro-hypertrophic role of GATA binding protein 4 (GATA4) during cardiac hypertrophy has been well established, the negative regulatory mechanism to counteract its hyperactivation remains elusive. We hypothesized that the hyperactivation of GATA4 could be a result of loss of interaction between GATA4 with specific suppressors. Using high throughput mass spectrometry technology, we carried out a proteomic screen for endogenous suppressor of GATA4, which disassociated with GATA4 during the hypertrophic response in a cultured cardiac myoblast cell line (H9C2 cells). We identified differentiated embryo chondrocyte 1 (DEC1) negatively regulated the function of GATA4 through physical interaction and negatively regulated cardiac hypertrophy both in vivo and in vitro. Particularly, DEC1 promoted the ubiquitination and proteasome-mediated degradation of GATA4, but did not function as an E3 ligase. Again, using mass spectrometry technology, we systematically identified pre-mRNA processing factor 19 (PRP19) as a newfound E3 ligase, which promoted the K6-linked ubiquitination of GATA4 at its lysine 256. Functional experiments performed in cultured neonatal rat ventricular myocytes and H9C2 cells demonstrated that both DEC1 and PRP19 negatively regulated agonist-induced cardiomyocyte hypertrophic responses. Furthermore, rescue experiments performed in these cells revealed that DEC1 and PRP19 suppressed cardiomyocyte hypertrophy by inhibiting the function of GATA4. Our study thus defined the novel DEC1-PRP19-GATA4 axis to be a previously unknown mechanism in regulating cardiomyocyte hypertrophy. Although GATA4 is indispensable for normal cardiac function, harnessing DEC1- or PRP19-mediated negative regulation to counteract the hyperactivation of GATA4 might serve as a novel therapeutic strategy for pathological cardiac hypertrophy.

Towards Understanding the Gene-Specific Roles of GATA Factors in Heart Development: Does GATA4 Lead the Way?

Transcription factors play crucial roles in the regulation of heart induction, formation, growth and morphogenesis. Zinc finger GATA transcription factors are among the critical regulators of these processes. GATA4, 5 and 6 genes are expressed in a partially overlapping manner in developing hearts, and GATA4 and 6 continue their expression in adult cardiac myocytes. Using different experimental models, GATA4, 5 and 6 were shown to work together not only to ensure specification of cardiac cells but also during subsequent heart development. The complex involvement of these related gene family members in those processes is demonstrated through the redundancy among them and crossregulation of each other. Our recent identification at the genome-wide level of genes specifically regulated by each of the three family members and our earlier discovery that gata4 and gata6 function upstream, while gata5 functions downstream of noncanonical Wnt signalling during cardiac differentiation, clearly demonstrate the functional differences among the cardiogenic GATA factors. Such suspected functional differences are worth exploring more widely. It appears that in the past few years, significant advances have indeed been made in providing a deeper understanding of the mechanisms by which each of these molecules function during heart development. In this review, I will therefore discuss current evidence of the role of individual cardiogenic GATA factors in the process of heart development and emphasize the emerging central role of GATA4.

Two Isoforms of serpent Containing Either One or Two GATA Zinc Fingers Provide Functional Diversity During Drosophila Development

GATA transcription factors play crucial roles in various developmental processes in organisms ranging from flies to humans. In mammals, GATA factors are characterized by the presence of two highly conserved domains, the N-terminal (N-ZnF) and the C-terminal (C-ZnF) zinc fingers. The Drosophila GATA factor Serpent (Srp) is produced in different isoforms that contains either both N-ZnF and C-ZnF (SrpNC) or only the C-ZnF (SrpC). Here, we investigated the functional roles ensured by each of these isoforms during Drosophila development. Using the CRISPR/Cas9 technique, we generated new mutant fly lines deleted for one (ΔsrpNC) or the other (ΔsrpC) encoded isoform, and a third one with a single point mutation in the N-ZnF that alters its interaction with its cofactor, the Drosophila FOG homolog U-shaped (Ush). Analysis of these mutants revealed that the Srp zinc fingers are differentially required for Srp to fulfill its functions. While SrpC is essential for embryo to adult viability, SrpNC, which is the closest conserved isoform to that of vertebrates, is not. However, to ensure its specific functions in larval hematopoiesis and fertility, Srp requires the presence of both N- and C-ZnF (SrpNC) and interaction with its cofactor Ush. Our results also reveal that in vivo the presence of N-ZnF restricts rather than extends the ability of GATA factors to regulate the repertoire of C-ZnF bound target genes.

Transcription Factors Involved in the Development and Prognosis of Cardiac Remodeling

To compensate increasing workload, heart must work harder with structural changes, indicated by increasing size and changing shape, causing cardiac remodeling. However, pathological and unlimited compensated cardiac remodeling will ultimately lead to decompensation and heart failure. In the past decade, numerous studies have explored many signaling pathways involved in cardiac remodeling, but the complete mechanism of cardiac remodeling is still unrecognized, which hinders effective treatment and drug development. As gene transcriptional regulators, transcription factors control multiple cellular activities and play a critical role in cardiac remodeling. This review summarizes the regulation of fetal gene reprogramming, energy metabolism, apoptosis, autophagy in cardiomyocytes and myofibroblast activation of cardiac fibroblasts by transcription factors, with an emphasis on their potential roles in the development and prognosis of cardiac remodeling.

Environmental level of bisphenol F induced reproductive toxicity toward zebrafish

Bisphenol F (BPF), as an important bisphenol A substitute, is being increasingly used for industrial production. Here we performed large scale fecundity test for zebrafish that are continuous exposed to environmental levels of BPF (0.5, 5 and 50 μg/L) from embryonic stage, and identified suppressed spawning capacity of females and reduced fertility rate of males in adulthood. Although pathological change is only observed in female gonads, the transcriptional change in the hypothalamic-pituitary-gonad axis genes occurred in the gonads of both female and male fish at 150 days post-exposure. F1 generation embryos showed abnormal developmental outcomes including decreased heart rate, reduced body length, and inhibition of spontaneous movement after parental exposure to BPF. RNA-sequencing showed that the genes involved in skeletal/cardiac muscle development were significantly altered in F1 embryos spawned by BPF-treated zebrafish. The advanced pathway analysis showed that cancer and tumour formation were the most enriched pathways in the offspring of 0.5 and 5.0 μg/L groups; organismal development and cardiovascular system development were mainly affected after parental exposure to 50 μg/L of BPF; these changes were mediated by several involved regulators such as GATA4, MYF6, and MEF2C. These findings confirmed that long-term exposure to BPF at environment relevant concentration would result in reproductive toxicity among zebrafish indicating the urgent demand for the control of BPA substitutes.

Targeted Genetic Reduction of Mutant Huntingtin Lessens Cardiac Pathology in the BACHD Mouse Model of Huntington's Disease

Individuals affected by Huntington's disease (HD) present with progressive degeneration that results in a wide range of symptoms, including cardiovascular (CV) dysfunction. The huntingtin gene (HTT) and its product are ubiquitously expressed, hence, the cardiomyopathy could also be driven by defects caused by its mutated form (mHTT) in the cardiomyocytes themselves. In the present study, we sought to determine the contribution of the mHTT expressed in the cardiomyocytes to CV symptoms. We utilized the BACHD mouse model, which exhibits many of the HD core symptoms, including CV dysfunction. This model allows the targeted genetic reduction of mHTT expression in the cardiomyocytes while maintaining the expression of the mHTT in the rest of the body. The BACHD line was crossed with a line of mice in which the expression of Cre recombinase is driven by the cardiac-specific alpha myosin-heavy chain (Myh6) promoter. The offspring of this cross (BMYO mice) exhibited a dramatic reduction in mHTT in the heart but not in the striatum. The BMYO mice were evaluated at 6 months old, as at this age, the BACHD line displays a strong CV phenotype. Echocardiogram measurements found improvement in the ejection fraction in the BMYO line compared to the BACHD, while hypertrophy was observed in both mutant lines. Next, we examined the expression of genes known to be upregulated during pathological cardiac hypertrophy. As measured by qPCR, the BMYO hearts exhibited significantly less expression of collagen1a as well as Gata4, and brain natriuretic peptide compared to the BACHD. Fibrosis in the hearts assessed by Masson's trichrome stain and the protein levels of fibronectin were reduced in the BMYO hearts compared to BACHD. Finally, we examined the performance of the mice on CV-sensitive motor tasks. Both the overall activity levels and grip strength were improved in the BMYO mice. Therefore, we conclude that the reduction of mHtt expression in the heart benefits CV function in the BACHD model, and suggest that cardiomyopathy should be considered in the treatment strategies for HD.

Insights Into the Roles of GATA Factors in Mammalian Testis Development and the Control of Fetal Testis Gene Expression

Defining how genes get turned on and off in a correct spatiotemporal manner is integral to our understanding of the development, differentiation, and function of different cell types in both health and disease. Testis development and subsequent male sex differentiation of the XY fetus are well-orchestrated processes that require an intricate network of cell-cell communication and hormonal signals that must be properly interpreted at the genomic level. Transcription factors are at the forefront for translating these signals into a coordinated genomic response. The GATA family of transcriptional regulators were first described as essential regulators of hematopoietic cell differentiation and heart morphogenesis but are now known to impact the development and function of a multitude of tissues and cell types. The mammalian testis is no exception where GATA factors play essential roles in directing the expression of genes crucial not only for testis differentiation but also testis function in the developing male fetus and later in adulthood. This minireview provides an overview of the current state of knowledge of GATA factors in the male gonad with a particular emphasis on their mechanisms of action in the control of testis development, gene expression in the fetal testis, testicular disease, and XY sex differentiation in humans.

Activated Protein C Ameliorates Diabetic Cardiomyopathy via Modulating OTUB1/YB-1/MEF2B Axis

Aims: The pathogenesis of diabetic cardiomyopathy (DCM) is complex and the detailed mechanism remains unclear. Coagulation protease activated Protein C (aPC) has been reported to have a protective effect in diabetic microvascular disease. Here, we investigated whether aPC could play a protective role in the occurrence and development of major diabetic complication DCM, and its underlying molecular mechanism.

Methods and Results: In a mouse model of streptozotocin (STZ) induced DCM, endogenous aPC levels were reduced. Restoring aPC levels by exogenous administration of zymogen protein C (PC) improved cardiac function of diabetic mice measured by echocardiography and invasive hemodynamics. The cytoprotective effect of aPC in DCM is mediated by transcription factor Y-box binding protein-1 (YB-1). Mechanistically, MEF2B lies downstream of YB-1 and YB-1/MEF2B interaction restrains deleterious MEF2B promoter activity in DCM. The regulation of YB-1 on MEF2B transcription was analyzed by dual-luciferase and chromatin immunoprecipitation assays. In diabetic mice, aPC ameliorated YB-1 degradation via reducing its K48 ubiquitination through deubiquitinating enzyme otubain-1 (OTUB1) and improving the interaction between YB-1 and OTUB1. Using specific agonists and blocking antibodies, PAR1 and EPCR were identified as crucial receptors for aPC's dependent cytoprotective signaling.

Conclusion: These data identify that the cytoprotective aPC signaling via PAR1/EPCR maintains YB-1 levels by preventing the ubiquitination and subsequent proteasomal degradation of YB-1 via OTUB1. By suppressing MEF2B transcription, YB-1 can protect against DCM. Collectively, the current study uncovered the important role of OTUB1/YB-1/MEF2B axis in DCM and targeting this pathway might offer a new therapeutic strategy for DCM.

Translational Perspective: DCM is emerging at epidemic rate recently and the underlying mechanism remains unclear. This study explored the protective cell signaling mechanisms of aPC in mouse models of DCM. As a former FDA approved anti-sepsis drug, aPC along with its derivatives can be applied from bench to bed and can be explored as a new strategy for personalized treatment for DCM. Mechanistically, OTUB1/YB-1/MEF2B axis plays a critical role in the occurrence and development of DCM and offers a potential avenue for therapeutic targeting of DCM.

Cardiomyocyte-specific Srsf3 deletion reveals a mitochondrial regulatory role

Serine-rich splicing factor 3 (SRSF3) was recently reported as being necessary to preserve RNA stability via an mTOR mechanism in a cardiac mouse model in adulthood. Here, we demonstrate the link between Srsf3 and mitochondrial integrity in an embryonic cardiomyocyte-specific Srsf3 conditional knockout (cKO) mouse model. Fifteen-day-old Srsf3 cKO mice showed dramatically reduced (below 50%) survival and reduced the left ventricular systolic performance, and histological analysis of these hearts revealed a significant increase in cardiomyocyte size, confirming the severe remodeling induced by Srsf3 deletion. RNA-seq analysis of the hearts of 5-day-old Srsf3 cKO mice revealed early changes in expression levels and alternative splicing of several transcripts related to mitochondrial integrity and oxidative phosphorylation. Likewise, the levels of several protein complexes of the electron transport chain decreased, and mitochondrial complex I-driven respiration of permeabilized cardiac muscle fibers from the left ventricle was impaired. Furthermore, transmission electron microscopy analysis showed disordered mitochondrial length and cristae structure. Together with its indispensable role in the physiological maintenance of mouse hearts, these results highlight the previously unrecognized function of Srsf3 in regulating the mitochondrial integrity.

Ambient air PM2.5 exposure induces heart injury and cardiac hypertrophy in rats through regulation of miR-208a/b, α/β-MHC, and GATA4

Ambient air fine particulate matter (PM2.5) may increase cardiovascular disease risks. In this study, we investigated the miR-208/GATA4/myosin heavy chain (MHC) regulation mechanisms on cardiac injury in rats after PM2.5 exposure via an animal inhalation device. The results showed that PM2.5 exposure for 2 months caused pathological heart injury, reduced nucleus-cytoplasm ratio, and increased the levels of CK-MB and cTnI, showing cardiac hypertrophy. Oxidative stress and inflammatory responses were also observed in rats' hearts exposed to PM2.5. Of note, PM2.5 exposure for 2-month significantly elevated GATA4 and β-MHC mRNA and protein expression compared with the corresponding controls, along with the high-expression of miR-208b. The ratios of β-MHC/α-MHC expression induced by PM2.5 were remarkably raised in comparison to their controls. It suggested that the up-regulation of miR-208b/β-MHC and GATA4 and the conversion from α-MHC to β-MHC may be the important causes of cardiac hypertrophy in rats incurred by PM2.5.

Update in Biomolecular and Genetic Bases of Bicuspid Aortopathy

Bicuspid aortic valve (BAV) associated with aortopathy is the most common congenital heart disease in the general population. Far from being a simple harmless valve malformation, it can be a complex and heterogeneous disease and a source of chronic and acute pathology (early valvular disease, aneurysm, dissection). In the previous years, intense research has been carried out to find out and understand its mechanisms, but the pathophysiology of the disease is still not fully understood and many questions remain open. Recent studies have discovered several genetic mutations involved in the development of valvular and aortic malformations, but still cannot explain more than 5–10% of cases. Other studies have also focused on molecular alterations and cellular processes (TGF-β pathway, microRNAs, degradation of the extracellular matrix, metalloproteinases, etc.), being a field in constant search and development, looking for a therapeutic target to prevent the development of the disease. Increased knowledge about this multifaceted disorder, derived from both basic and clinical research, may influence the diagnosis, follow-up, prognosis, and therapies of affected patients in the near future. This review focuses on the latest and outstanding developments on the molecular and genetic investigations of the bicuspid aortopathy.

Long-term prognostic value of myocardin expression levels in non-ischemic dilated cardiomyopathy

The mortality of patients with non-ischemic dilated cardiomyopathy (NIDCM) remains substantial. We evaluated gene expression levels of myocardin, an early cardiac gene, in the peripheral blood cells of NIDCM patients as a prognostic biomarker in their long-term outcome and mortality from congestive HF (CHF). We retrospectively analyzed 101 consecutives optimally treated NIDCM patients of Cretan origin who were enrolled from the HF clinic of our hospital from November 2005 to December 2008. Our patient data were either taken from their medical files or recorded during visits to the HF unit or hospitalizations. Follow-up was carried out by telephone interview and by accessing information from general practitioners and cardiologists in private practice. The median follow-up period was 8 years (mean follow-up 7 ± 3.4 years). The overall mortality during follow-up was 61.4%, while mortality due to congestive heart failure (CHF) was 49.5%. Higher CHF and all-cause mortality were observed in patients with myocardin levels < 14.26 (p < 0.001 for both CHF and all-cause mortality). A multivariate Cox regression analysis showed that myocardin level of expression had independent significant prognostic value for the risk of death from CHF (HR 14.5, 95% confidence interval (CI) 5.3-39) in those patients. Peripheral blood cells gene expression of myocardin, an early myocardial marker, may serve as prognostic biomarkers of the long-term outcome of patients with NIDCM. Our findings open new prospects in the risk stratification of these patients.

Epigenomic and Transcriptomic Dynamics During Human Heart Organogenesis

RATIONALE

There is growing evidence that common variants and rare sequence alterations in regulatory sequences can result in birth defects or predisposition to disease. Congenital heart defects are the most common birth defect and have a clear genetic component, yet only a third of cases can be attributed to structural variation in the genome or a mutation in a gene. The remaining unknown cases could be caused by alterations in regulatory sequences.

OBJECTIVE

Identify regulatory sequences and gene expression networks that are active during organogenesis of the human heart. Determine whether these sites and networks are enriched for disease-relevant genes and associated genetic variation.

METHODS AND RESULTS

We characterized ChromHMM (chromatin state) and gene expression dynamics during human heart organogenesis. We profiled 7 histone modifications in embryonic hearts from each of 9 distinct Carnegie stages (13-14, 16-21, and 23), annotated chromatin states, and compared these maps to over 100 human tissues and cell types. We also generated RNA-sequencing data, performed differential expression, and constructed weighted gene coexpression networks. We identified 177 412 heart enhancers; 12 395 had not been previously annotated as strong enhancers. We identified 92% of all functionally validated heart-positive enhancers (n=281; 7.5× enrichment; P<2.2×10-16). Integration of these data demonstrated novel heart enhancers are enriched near genes expressed more strongly in cardiac tissue and are enriched for variants associated with ECG measures and atrial fibrillation. Our gene expression network analysis identified gene modules strongly enriched for heart-related functions, regulatory control by heart-specific enhancers, and putative disease genes.

CONCLUSIONS

Well-connected hub genes with heart-specific expression targeted by embryonic heart-specific enhancers are likely disease candidates. Our functional annotations will allow for better interpretation of whole genome sequencing data in the large number of patients affected by congenital heart defects.

Cardiovascular Changes Associated with Hypertensive Heart Disease and Aging

Cardiovascular diseases are the leading cause of mortality and morbidity worldwide and account for more than 17.9 million deaths (World Health Organization report). Hypertension and aging are two major risk factors for the development of cardiac structural and functional abnormalities. Hypertension, or elevated blood pressure, if left untreated can result in myocardial hypertrophy leading to heart failure (HF). Left ventricular hypertrophy consequent to pressure overload is recognized as the most important predictor of congestive HF and sudden death. The pathological changes occurring during hypertensive heart disease are very complex and involve many cellular and molecular alterations. In contrast, the cardiac changes that occur with aging are a slow but life-long process and involve all of the structural components in the heart and vasculature. However, these structural changes in the cardiovascular system lead to alterations in overall cardiac physiology and function. The pace at which these pathophysiological changes occur varies between individuals owing to many genetic and environmental risk factors. This review highlights the molecular mechanisms of cardiac structural and functional alterations associated with hypertension and aging.