Histone deacetylase 3 (hdac3) is specifically required for liver development in zebrafish. Dev Biol. 2008;317:336-353. [PMID: 18367159 DOI: 10.1016/j.ydbio.2008.02.034]

GDF11: An emerging therapeutic target for liver diseases and fibrosis

Growth differentiation factor 11 (GDF11), also known as bone morphogenetic protein 11 (BMP11), has been identified as a key player in various biological processes, including embryonic development, aging, metabolic disorders and cancers. GDF11 has also emerged as a critical component in liver development, injury and fibrosis. However, the effects of GDF11 on liver physiology and pathology have been a subject of debate among researchers due to conflicting reported outcomes. While some studies suggest that GDF11 has anti-aging properties, others have documented its senescence-inducing effects. Similarly, while GDF11 has been implicated in exacerbating liver injury, it has also been shown to have the potential to reduce liver fibrosis. In this narrative review, we present a comprehensive report of recent evidence elucidating the diverse roles of GDF11 in liver development, hepatic injury, regeneration and associated diseases such as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), liver fibrosis and hepatocellular carcinoma. We also explore the therapeutic potential of GDF11 in managing various liver pathologies.

Identification of Dhx15 as a Major Regulator of Liver Development, Regeneration, and Tumor Growth in Zebrafish and Mice

RNA helicase DHX15 plays a significant role in vasculature development and lung metastasis in vertebrates. In addition, several studies have demonstrated the overexpression of DHX15 in the context of hepatocellular carcinoma. Therefore, we hypothesized that this helicase may play a significant role in liver regeneration, physiology, and pathology. Dhx15 gene deficiency was generated by CRISPR/Cas9 in zebrafish and by TALEN-RNA in mice. AUM Antisense-Oligonucleotides were used to silence Dhx15 in wild-type mice. The hepatocellular carcinoma tumor induction model was generated by subcutaneous injection of Hepa 1-6 cells. Homozygous Dhx15 gene deficiency was lethal in zebrafish and mouse embryos. Dhx15 gene deficiency impaired liver organogenesis in zebrafish embryos and liver regeneration after partial hepatectomy in mice. Also, heterozygous mice presented decreased number and size of liver metastasis after Hepa 1-6 cells injection compared to wild-type mice. Dhx15 gene silencing with AUM Antisense-Oligonucleotides in wild-type mice resulted in 80% reduced expression in the liver and a significant reduction in other major organs. In addition, Dhx15 gene silencing significantly hindered primary tumor growth in the hepatocellular carcinoma experimental model. Regarding the potential use of DHX15 as a diagnostic marker for liver disease, patients with hepatocellular carcinoma showed increased levels of DHX15 in blood samples compared with subjects without hepatic affectation. In conclusion, Dhx15 is a key regulator of liver physiology and organogenesis, is increased in the blood of cirrhotic and hepatocellular carcinoma patients, and plays a key role in controlling hepatocellular carcinoma tumor growth and expansion in experimental models.

Toxic effects of benfluralin on zebrafish embryogenesis via the accumulation of reactive oxygen species and apoptosis

The dinitroaniline herbicide benfluralin is used weed control in conventional systems and poses a high risk of accumulation in aquatic systems. Previous studies have shown the toxic effects of benfluralin on non-target organisms; however, its developmental toxicity in vertebrates has not yet been reported. This study demonstrated the developmental toxicity of benfluralin and its mechanism of action, using zebrafish as an aquatic vertebrate model. Benfluralin induces morphological and physiological alterations in body length, yolk sac, and heart edema. We also demonstrated a reactive oxygen species (ROS) increase of approximately 325.53 % compared with the control group after 20 μM benfluralin-treatment. In addition, the malformation of the heart and vascular structures was identified using transgenic flk1:eGFP zebrafish models at 20 μM concentration benfluralin exposure. Moreover, benfluralin induced small livers, approximately 59.81 % of normal liver size, via abnormal development of the liver as observed in the transgenic L-fabp:dsRed zebrafish. Benfluralin also inhibits normal growth via abnormal expression of cell cycle regulatory genes and increases oxidative stress, inflammation, and apoptosis. Collectively, we elucidated the mechanisms associated with benfluralin toxicity, which lead to various abnormalities and developmental toxicities in zebrafish. Therefore, this study provides information on the parameters used to assess developmental toxicity in other aquatic organisms, such as herbicides, pesticides, and environmental contaminants.

Zebrafish as a Useful Model System for Human Liver Disease

Liver diseases represent a significant global health challenge, thereby necessitating extensive research to understand their intricate complexities and to develop effective treatments. In this context, zebrafish (Danio rerio) have emerged as a valuable model organism for studying various aspects of liver disease. The zebrafish liver has striking similarities to the human liver in terms of structure, function, and regenerative capacity. Researchers have successfully induced liver damage in zebrafish using chemical toxins, genetic manipulation, and other methods, thereby allowing the study of disease mechanisms and the progression of liver disease. Zebrafish embryos or larvae, with their transparency and rapid development, provide a unique opportunity for high-throughput drug screening and the identification of potential therapeutics. This review highlights how research on zebrafish has provided valuable insights into the pathological mechanisms of human liver disease.

Fluchloralin induces developmental toxicity in heart, liver, and nervous system during early zebrafish embryogenesis

The zebrafish is a prominent vertebrate model popularly used for toxicity testing because of its rapid development and transparent embryos. Fluchloralin, a dinitroaniline herbicide used to control weeds, inhibits microtubule formation and cell division. The structurally homologous substances ethalfluralin and pendimethalin, which belong to the dinitroaniline family, were found to be genotoxic and to exert developmental toxicity via mitochondrial dysfunction in a zebrafish model. To date, developmental toxicity of fluchloralin in zebrafish has not been reported. In the present study, we identified morphological changes in developing zebrafish, including decreased survival rate and body length, and increased yolk sac edema. In dose-dependent response to fluchloralin exposure, inhibition of neurogenesis in the spinal cord and motor neuron defects were observed in transgenic zebrafish models (olig2:dsRed). Zebrafish exposed to fluchloralin also displayed organ dysfunction in the heart, liver, and pancreas in cmlc2:dsRed and lfabp:dsRed;elastase:GFP transgenic models. Fluchloralin increased cell death in the brain by promoting apoptosis, visualized via acridine orange staining, and by activating apoptosis signaling proteins, including cytochrome c1, zBax, and Bcl-XL. This study provides novel evidence supporting the necessity of controlling pollutants in aquatic environments.

Bensulide-induced oxidative stress causes developmental defects of cardiovascular system and liver in zebrafish (Danio rerio)

Bensulide is an organophosphate herbicide commonly used in agricultural crops; however, no studies have reported on its toxic effects in the embryonic development of vertebrates, particularly gene expression level and cellular response. Therefore, to identify developmental toxicity, zebrafish eggs 8 h post-fertilization (hpf) were exposed to bensulide concentrations of up to 3 mg/L. The results indicated that exposure to 3 mg/L bensulide inhibited the hatching of all eggs and decreased the size of the body, eyes, and inner ear. There were demonstrated effects observed in the cardiovascular system and liver caused by bensulide in fli1:eGFP and L-fabp:dsRed transgenic zebrafish models, respectively. Following exposure to 3 mg/L bensulide, normal heart development, including cardiac looping, was disrupted and the heart rate of 96 hpf zebrafish larvae decreased to 16.37%. Development of the liver, the main detoxification organ, was also inhibited by bensulide, and after exposure to 3 mg/L bensulide its size reduced to 41.98%. Additionally, exposure to bensulide resulted in inhibition of antioxidant enzyme expression and an increase in ROS levels by up to 238.29%. Collectively, we identified various biological responses associated with the toxicity of bensulide, which led to various organ malformations and cytotoxic effects in zebrafish.

Developmental toxicity of prometryn induces mitochondrial dysfunction, oxidative stress, and failure of organogenesis in zebrafish (Danio rerio)

Prometryn, 2-methylthio-4,6-bis(isopropylamino)-1,3,5-triazine, is a selective thiomethyl triazine herbicide widely used to control unwanted weeds and harmful insects by inhibiting electron transport in target organisms. Despite having various advantages, herbicides pose as a major threat to the environment and human health due to persistent contamination, bioaccumulation, and damage to non-target organisms. In this study, the developmental toxicity of 5, 10, and 20 mg/L prometryn in zebrafish (Danio rerio) embryos was evaluated and compared to that of the solvent control for 96 h. Several transgenic zebrafish models (fli1a:eGFP, flk1:eGFP, olig2:dsRed and L-fabp:dsRed) were visually assessed to detect fluorescently tagged genes. Results showed that prometryn shortened body length, and induced yolk sac, heart edema, abnormal heart rate, and loss of viability. Fluorescence microscopy revealed that prometryn exposure caused defects in organ development, reactive oxygen species accumulation, and apoptotic cell death. Mitochondrial bioenergetics were also evaluated to determine the effect of prometryn on the electron transport chain activity and metabolic alterations. Prometryn was found to interfere with mitochondrial function, ultimately inhibiting energy metabolism and embryonic development. Collectively, our findings suggest that prometryn is a potential contaminate for non-target sites and organisms, especially aquatic, and emphasize the need to consider the toxic effects of prometryn.

The hepatic effects of GDF11 on health and disease

The growth differentiation factor 11 (GDF11), a member of the superfamily of the transforming growth factor β, has gained relevance in the last few years due to its remarkable effects in cellular biology, particularly in the nervous system, skeletal muscle, the heart, and many epithelial tissues. Some controversies have been raised about this growth factor. Many of them have been related to technical factors but also the nature of the cellular target. In liver biology and pathobiology, the GDF11 has shown to be related in many molecular aspects, with a significant impact on the physiology and the initiation and progression of the natural history of liver diseases. GDF11 has been involved as a critical regulator in lipid homeostasis, which, as it is well known, is the first step in the progression of liver disease. However, also it has been reported that the GDF11 is involved in fibrosis, senescence, and cancer. Although there are some controversies, much of the literature indicates that GDF11 displays effects tending to solve or mitigate pathological states of the liver, with reasonable evidence of correlation with other organs or systems. To a large extent, the controversy, as mentioned, is due to technical problems, such as the specificity of GDF11 antibodies, confusion with its closer family member, myostatin, and the state of differentiation in the tissues. In the present work, we reviewed the specific effects of GDF11 in the biology and pathobiology of the liver as a potential and promising factor for therapeutic intervention shortly.

Potential of the zebrafish (Danio rerio) embryo test to discriminate between chemicals of similar molecular structure-a study with valproic acid and 14 of its analogues

Valproic acid is a frequently used antiepileptic drug and known pediatric hepatotoxic agent. In search of pharmaceuticals with increased effectiveness and reduced toxicity, analogue chemicals came into focus. So far, toxicity and teratogenicity data of drugs and metabolites have usually been collected from mammalian model systems such as mice and rats. However, in an attempt to reduce mammalian testing while maintaining the reliability of toxicity testing of new industrial chemicals and drugs, alternative test methods are being developed. To this end, the potential of the zebrafish (Danio rerio) embryo to discriminate between valproic acid and 14 analogues was investigated by exposing zebrafish embryos for 120 h post fertilization in the extended version of the fish embryo acute toxicity test (FET; OECD TG 236), and analyzing liver histology to evaluate the correlation of liver effects and the molecular structure of each compound. Although histological evaluation of zebrafish liver did not identify steatosis as the prominent adverse effect typical in human and mice, the structure–activity relationship (SAR) derived was comparable not only to human HepG2 cells, but also to available in vivo mouse and rat data. Thus, there is evidence that zebrafish embryos might serve as a tool to bridge the gap between subcellular, cell-based systems and vertebrate models.

Modified Xenopus laevis approach (R-FETAX) as an alternative test for the evaluation of foetal valproate spectrum disorder

In compliance to animal welfare 3Rs principle there is a great demand for refined tests alternative to classical mammal teratogenicity tests. We propose a refined alternative amphibian method (R-FETAX) to evaluate chemical induced embryotoxicity. The human foetal valproate spectrum disorder (FVSD) characteristics are morphological defects (including cranio-facial, neural tube defects) and behavioural alterations due to valproate (VPA) exposure in pregnancy. Vertebrate assays to evaluate FVSD include classical and alternative mammal (implying adult sacrifice), and non-mammal developmental models (zebrafish, amphibians, chick). Among these latter only zebrafish assays report in the same test both morphological and behavioural examinations. Compared to zebrafish, the amphibian Xenopus laevis excels having a more comparable organ development and morphology to mammalian systems. We used X. laevis embryos exposed during developmental specific windows to VPA therapeutic concentrations. Different VPA effects were observed depending on the exposure window: concentration-related embryo-lethal and teratogenic effects (neural tube, facial, tail defects) were observed in groups exposed at the organogenetic phylotypic stages. Neurobehavioral deficits were described using a functional swimming test at the highest VPA concentration exposure during the phylotypic stages and at any concentration during neurocognitive competent stages. Malformations were compared to those obtained in a mammalian assay (the rat post-implantation whole embryo culture method, WEC), that we used in the past to evaluate VPA teratogenicity. R-FETAX and WEC data were modelled and their relative sensitivity was calculated. We suggest the amphibian R-FETAX as a refined windowed alternative test for the evaluation of chemicals inducing both morphological and behavioural anomalies, including VPA.

Heterozygous loss-of-function variants significantly expand the phenotypes associated with loss of GDF11

PURPOSE

Growth differentiation factor 11 (GDF11) is a key signaling protein required for proper development of many organ systems. Only one prior study has associated an inherited GDF11 variant with a dominant human disease in a family with variable craniofacial and vertebral abnormalities. Here, we expand the phenotypic spectrum associated with GDF11 variants and document the nature of the variants.

METHODS

We present a cohort of six probands with de novo and inherited nonsense/frameshift (4/6 patients) and missense (2/6) variants in GDF11. We generated gdf11 mutant zebrafish to model loss of gdf11 phenotypes and used an overexpression screen in Drosophila to test variant functionality.

RESULTS

Patients with variants in GDF11 presented with craniofacial (5/6), vertebral (5/6), neurological (6/6), visual (4/6), cardiac (3/6), auditory (3/6), and connective tissue abnormalities (3/6). gdf11 mutant zebrafish show craniofacial abnormalities and body segmentation defects that match some patient phenotypes. Expression of the patients' variants in the fly showed that one nonsense variant in GDF11 is a severe loss-of-function (LOF) allele whereas the missense variants in our cohort are partial LOF variants.

CONCLUSION

GDF11 is needed for human development, particularly neuronal development, and LOF GDF11 alleles can affect the development of numerous organs and tissues.

Pharmacological inhibition of HDAC1/3-interacting proteins induced morphological changes, and hindered the cell proliferation and migration of hepatocellular carcinoma cells

Liver diseases are particularly severe health problems, but the options available for preventing and treating them remain limited. Accumulating evidence has shown that there is altered expression of individual histone deacetylase (HDAC) family members in hepatocellular carcinoma cells. In a previous study, we have identified a set of proteins which interact with histone deacetylase 1 and 3 (HDAC1/3) in hepatocellular carcinoma cell lines HepG2 by proteomic approach. This study was designed to investigate the therapeutic potential and expression of HDAC1/3-interacting genes in a human hepatocellular carcinoma cell line (HepG2). Pharmacological and transcriptional inhibition of HDAC1/3 resulted in the suppression of cancer cell proliferation, change of cell morphology, and downregulation of HDAC1/3 genes in HepG2 cells. The pharmacological inhibition also resulted in inhibition of liver cancer cell migration by wound scratch assay. Taken together, the results from this study show that the upregulation of HDAC1/3 in hepatocellular carcinoma resulted in the overexpression of CNOT1, PFDN2/6, and HMG20B, and that these genes could serve as novel molecular targets in liver cancer.

Epigenetic biomarkers as tools for chemical hazard assessment: Gene expression profiling using the model Danio rerio

Recent reports raise the concern that exposure to several environmental chemicals may induce persistent changes that go beyond the exposed organisms, being transferred to subsequent generations even in the absence of the original chemical insult. These changes in subsequent non-exposed generations have been related to epigenetic changes. Although highly relevant for hazard and risk assessment, biomarkers of epigenetic modifications that can be associated with adversity, are still not integrated into hazard assessment frameworks. Here, in order to validate new biomarkers of epigenetic modifications in a popular animal model, zebrafish embryos were exposed to different concentrations of Bisphenol A (0.01, 0.1, 1 and 10 mg/L) and Valproic Acid (0.8, 4, 20 and 100 mg/L), two chemicals reported to alter the modulation of the epigenome. Morphological abnormalities and epigenetic changes were assessed at 80 hours-post fertilization, including DNA global methylation and gene expression of both DNA and histone epigenetic modifications. Gene expression changes were detected at concentrations below those inducing morphological abnormalities. These results further support the importance of combining epigenetic biomarkers with apical endpoints to improve guidelines for chemical testing and hazard assessment, and favour the integration of new biomarkers of epigenetic modifications into the standardized OECD test guideline 236 with zebrafish embryos.

Understanding the role of histone deacetylase and their inhibitors in neurodegenerative disorders: Current targets and future perspective

Neurodegenerative diseases are a group of pathological conditions that cause motor inc-ordination (jerking movements), cognitive and memory impairments result from degeneration of neurons in a specific area of the brain. Oxidative stress, mitochondrial dysfunction, excitotoxicity, neuroinflammation, neurochemical imbalance and histone deacetylase enzymes (HDAC) are known to play a crucial role in neurodegeneration. HDAC is classified into four categories (class I, II, III and class IV) depending upon their location and functions. HDAC1 and 2 are involved in neurodegeneration, while HDAC3-11 and class III HDACs are beneficial as neuroprotective. HDACs are localized in different parts of the brain- HDAC1 (hippocampus and cortex), HDAC2 (nucleus), HDAC3, 4, 5, 7 and 9 (nucleus and cytoplasm), HDAC6 & HDAC7 (cytoplasm) and HDAC11 (Nucleus, cornus ammonis 1 and spinal cord). In pathological conditions, HDAC up-regulates glutamate, phosphorylation of tau, and glial fibrillary acidic proteins while down-regulating BDNF, Heat shock protein 70 and Gelsolin. Class III HDACs are divided into seven sub-classes (SIRT1-SIRT7). Sirtuins are localized in the different parts of the brain and neuron -Sirt1 (nucleus), Sirt2 (cortex, striatum, hippocampus and spinal cord), Sirt3 (mitochondria and cytoplasm), Sirt4, Sirt5 & Sirt6 (mitochondria), Sirt7 (nucleus) and Sirt8 (nucleolus). SIRTs (1, 3, 4, and 6) are involved in neuronal survival, proliferation and modulating stress response, and SIRT2 is associated with Parkinsonism, Huntington’s disease and Alzheimer’s disease, whereas SIRT6 is only associated with Alzheimer’s disease. In this critical review, we have discussed the mechanisms and therapeutic targets of HDACs that would be beneficial for the management of neurodegenerative disorders.

DNA methylation and histone modifications are essential for regulation of stem cell formation and differentiation in zebrafish development

The complex processes necessary for embryogenesis require a gene regulatory network that is complex and systematic. Gene expression regulates development and organogenesis, but this process is altered and fine-tuned by epigenetic regulators that facilitate changes in the chromatin landscape. Epigenetic regulation of embryogenesis adjusts the chromatin structure by modifying both DNA through methylation and nucleosomes through posttranslational modifications of histone tails. The zebrafish is a well-characterized model organism that is a quintessential tool for studying developmental biology. With external fertilization, low cost and high fecundity, the zebrafish are an efficient tool for studying early developmental stages. Genetic manipulation can be performed in vivo resulting in quick identification of gene function. Large-scale genome analyses including RNA sequencing, chromatin immunoprecipitation and chromatin structure all are feasible in the zebrafish. In this review, we highlight the key events in zebrafish development where epigenetic regulation plays a critical role from the early stem cell stages through differentiation and organogenesis.

Acoustofluidic rotational tweezing enables high-speed contactless morphological phenotyping of zebrafish larvae

Modern biomedical research and preclinical pharmaceutical development rely heavily on the phenotyping of small vertebrate models for various diseases prior to human testing. In this article, we demonstrate an acoustofluidic rotational tweezing platform that enables contactless, high-speed, 3D multispectral imaging and digital reconstruction of zebrafish larvae for quantitative phenotypic analysis. The acoustic-induced polarized vortex streaming achieves contactless and rapid (~1 s/rotation) rotation of zebrafish larvae. This enables multispectral imaging of the zebrafish body and internal organs from different viewing perspectives. Moreover, we develop a 3D reconstruction pipeline that yields accurate 3D models based on the multi-view images for quantitative evaluation of basic morphological characteristics and advanced combinations of metrics. With its contactless nature and advantages in speed and automation, our acoustofluidic rotational tweezing system has the potential to be a valuable asset in numerous fields, especially for developmental biology, small molecule screening in biochemistry, and pre-clinical drug development in pharmacology.

A zebrafish functional genomics model to investigate the role of human A20 variants in vivo

Germline loss-of-function variation in TNFAIP3, encoding A20, has been implicated in a wide variety of autoinflammatory and autoimmune conditions, with acquired somatic missense mutations linked to cancer progression. Furthermore, human sequence data reveals that the A20 locus contains ~ 400 non-synonymous coding variants, which are largely uncharacterised. The growing number of A20 coding variants with unknown function, but potential clinical impact, poses a challenge to traditional mouse-based approaches. Here we report the development of a novel functional genomics approach that utilizes a new A20-deficient zebrafish (Danio rerio) model to investigate the impact of TNFAIP3 genetic variants in vivo. A20-deficient zebrafish are hyper-responsive to microbial immune activation and exhibit spontaneous early lethality. Ectopic addition of human A20 rescued A20-null zebrafish from lethality, while missense mutations at two conserved A20 residues, S381A and C243Y, reversed this protective effect. Ser381 represents a phosphorylation site important for enhancing A20 activity that is abrogated by its mutation to alanine, or by a causal C243Y mutation that triggers human autoimmune disease. These data reveal an evolutionarily conserved role for TNFAIP3 in limiting inflammation in the vertebrate linage and show how this function is controlled by phosphorylation. They also demonstrate how a zebrafish functional genomics pipeline can be utilized to investigate the in vivo significance of medically relevant human TNFAIP3 gene variants.

Estrogen Acts Through Estrogen Receptor 2b to Regulate Hepatobiliary Fate During Vertebrate Development

BACKGROUND AND AIMS

During liver development, bipotent progenitor cells differentiate into hepatocytes and biliary epithelial cells to ensure a functional liver required to maintain organismal homeostasis. The developmental cues controlling the differentiation of committed progenitors into these cell types, however, are incompletely understood. Here, we discover an essential role for estrogenic regulation in vertebrate liver development to affect hepatobiliary fate decisions.

APPROACH AND RESULTS

Exposure of zebrafish embryos to 17β-estradiol (E2) during liver development significantly decreased hepatocyte-specific gene expression, liver size, and hepatocyte number. In contrast, pharmacological blockade of estrogen synthesis or nuclear estrogen receptor (ESR) signaling enhanced liver size and hepatocyte marker expression. Transgenic reporter fish demonstrated nuclear ESR activity in the developing liver. Chemical inhibition and morpholino knockdown of nuclear estrogen receptor 2b (esr2b) increased hepatocyte gene expression and blocked the effects of E2 exposure. esr2b^-/- mutant zebrafish exhibited significantly increased expression of hepatocyte markers with no impact on liver progenitors, other endodermal lineages, or vasculature. Significantly, E2-stimulated Esr2b activity promoted biliary epithelial differentiation at the expense of hepatocyte fate, whereas loss of esr2b impaired biliary lineage commitment. Chemical and genetic epistasis studies identified bone morphogenetic protein (BMP) signaling as a mediator of the estrogen effects. The divergent impact of estrogen on hepatobiliary fate was confirmed in a human hepatoblast cell line, indicating the relevance of this pathway for human liver development.

CONCLUSIONS

Our studies identify E2, esr2b, and downstream BMP activity as important regulators of hepatobiliary fate decisions during vertebrate liver development. These results have significant clinical implications for liver development in infants exposed to abnormal estrogen levels or estrogenic compounds during pregnancy.

Similar sequences but dissimilar biological functions of GDF11 and myostatin

Growth differentiation factor 11 (GDF11) and myostatin (MSTN) are closely related TGFβ family members that are often believed to serve similar functions due to their high homology. However, genetic studies in animals provide clear evidence that they perform distinct roles. While the loss of Mstn leads to hypermuscularity, the deletion of Gdf11 results in abnormal skeletal patterning and organ development. The perinatal lethality of Gdf11-null mice, which contrasts with the long-term viability of Mstn-null mice, has led most research to focus on utilizing recombinant GDF11 proteins to investigate the postnatal functions of GDF11. However, the reported outcomes of the exogenous application of recombinant GDF11 proteins are controversial partly because of the different sources and qualities of recombinant GDF11 used and because recombinant GDF11 and MSTN proteins are nearly indistinguishable due to their similar structural and biochemical properties. Here, we analyze the similarities and differences between GDF11 and MSTN from an evolutionary point of view and summarize the current understanding of the biological processing, signaling, and physiological functions of GDF11 and MSTN. Finally, we discuss the potential use of recombinant GDF11 as a therapeutic option for a wide range of medical conditions and the possible adverse effects of GDF11 inhibition mediated by MSTN inhibitors.

Histones, Their Variants and Post-translational Modifications in Zebrafish Development

Complex multi-cellular organisms are shaped starting from a single-celled zygote, owing to elaborate developmental programs. These programs involve several layers of regulation to orchestrate the establishment of progressively diverging cell type-specific gene expression patterns. In this scenario, epigenetic modifications of chromatin are central in influencing spatiotemporal patterns of gene transcription. In fact, it is generally recognized that epigenetic changes of chromatin states impact on the accessibility of genomic DNA to regulatory proteins. Several lines of evidence highlighted that zebrafish is an excellent vertebrate model for research purposes in the field of developmental epigenetics. In this review, I focus on the dynamic roles recently emerged for histone post-translational modifications (PTMs), histone modifying enzymes, histone variants and histone themselves in the coordination between the precise execution of transcriptional programs and developmental progression in zebrafish. In particular, I first outline a synopsis of the current state of knowledge in this field during early embryogenesis. Then, I present a survey of histone-based epigenetic mechanisms occurring throughout morphogenesis, with a stronger emphasis on cardiac formation. Undoubtedly, the issues addressed in this review take on particular importance in the emerging field of comparative biology of epigenetics, as well as in translational research.

Unraveling the Epigenetic Basis of Liver Development, Regeneration and Disease

A wealth of studies over several decades has revealed an epigenetic prepattern that determines the competence of cellular differentiation in the developing liver. More recently, studies focused on the impact of epigenetic factors during liver regeneration suggest that an epigenetic code in the quiescent liver may establish its regenerative potential. We review work on the pioneer factors and other chromatin remodelers that impact the gene expression patterns instructing hepatocyte and biliary cell specification and differentiation, along with the requirement of epigenetic regulatory factors for hepatic outgrowth. We then explore recent studies involving the role of epigenetic regulators, Arid1a and Uhrf1, in efficient activation of proregenerative genes during liver regeneration, thus highlighting the epigenetic mechanisms of liver disease and tumor development.

GDF11 Implications in Cancer Biology and Metabolism. Facts and Controversies

Growth Differentiation Factor 11 (GDF11), a member of the super family of the Transforming Growth Factor β, has gained more attention in the last few years due to numerous reports regarding its functions in other systems, which are different to those related to differentiation and embryonic development, such as age-related muscle dysfunction, skin biology, metabolism, and cancer. GDF11 is expressed in many tissues, including skeletal muscle, pancreas, kidney, nervous system, and retina, among others. GDF11 circulating levels and protein content in tissues are quite variable and are affected by pathological conditions or age. Although, GDF11 biology had a lot of controversies, must of them are only misunderstandings regarding the variability of its responses, which are independent of the tissue, grade of cellular differentiation or pathologies. A blunt fact regarding GDF11 biology is that its target cells have stemness feature, a property that could be found in certain adult cells in health and in disease, such as cancer cells. This review is focused to present and analyze the recent findings in the emerging research field of GDF11 function in cancer and metabolism, and discusses the controversies surrounding the biology of this atypical growth factor.

Histone Deacetylase 3 Governs Perinatal Cerebral Development via Neural Stem and Progenitor Cells

We report that cerebrum-specific inactivation of the histone deacetylase 3 (HDAC3) gene causes striking developmental defects in the neocortex, hippocampus, and corpus callosum; post-weaning lethality; and abnormal behaviors, including hyperactivity and anxiety. The defects are due to rapid loss of embryonic neural stem and progenitor cells (NSPCs). Premature neurogenesis and abnormal neuronal migration in the mutant brain alter NSPC homeostasis. Mutant cerebral cortices also display augmented DNA damage responses, apoptosis, and histone hyperacetylation. Moreover, mutant NSPCs are impaired in forming neurospheres in vitro, and treatment with the HDAC3-specific inhibitor RGFP966 abolishes neurosphere formation. Transcriptomic analyses of neonatal cerebral cortices and cultured neurospheres support that HDAC3 regulates transcriptional programs through interaction with different transcription factors, including NFIB. These findings establish HDAC3 as a major deacetylase critical for perinatal development of the mouse cerebrum and NSPCs, thereby suggesting a direct link of this enzymatic epigenetic regulator to human cerebral and intellectual development.

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HDAC3 inactivation causes developmental defects in the neocortex and hippocampus

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HDAC3 loss leads to depletion of embryonic neural stem and progenitor cells

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HDAC3 inhibition abolishes neurosphere formation in vitro

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HDAC3 interacts with NFIB and other transcription factors in cerebral development

Investigation mechanisms between normal, developing and regenerating livers for regenerative liver drug design

Aim: A systematic multimolecule drug design procedure is proposed for promoting hepatogenesis and liver regeneration. Materials & methods: Genome-wide microarray data including three hepatic conditions are obtained from the GEO database (GSE15238). System modeling and big data mining methods are used to construct real genome-wide genetic-and-epigenetic networks (GWGENs). Then, we extracted the core GWGENs by applying principal network projection on real GWGENs of normal, developing and regenerating livers, respectively. After that, we investigated the significant signal pathways and epigenetic modifications in the core GWGENs to identify potential biomarkers as drug targets. Result & conclusion: A multimolecule drug consisting of sulmazole, clofibrate, colchicine, furazolidone, nadolol, eticlopride and felbinac is proposed to target on novel biomarkers for promoting hepatogenesis and liver regeneration.

Comparative transcriptome analysis reveals potential evolutionary differences in adaptation of temperature and body shape among four Percidae species

Considering the divergent temperature habitats and morphological traits of four Percidae species: yellow perch (Perca flavescens), Eurasian perch (Perca fluviatilis), pike perch (Sander lucioperca), and ruffe (Gymnocephalus cernua), we stepped into the transcriptome level to discover genes and mechanisms that drive adaptation to different temperature environments and evolution in body shape. Based on 93,566 to 181,246 annotated unigenes of the four species, we identified 1,117 one-to-one orthologous genes and subsequently constructed the phylogenetic trees that are consistent with previous studies. Together with the tree, the ratios of nonsynonymous to synonymous substitutions presented decreased evolutionary rates from the D. rerio branch to the sub-branch clustered by P. flavescens and P. fluviatilis. The specific 93 fast-evolving genes and 57 positively selected genes in P. flavescens, compared with 22 shared fast-evolving genes among P. fluviatilis, G. cernua, and S. lucioperca, showed an intrinsic foundation that ensure its adaptation to the warmer Great Lakes and farther south, especially in functional terms like “Cul4-RING E3 ubiquitin ligase complex.” Meanwhile, the specific 78 fast-evolving genes and 41 positively selected genes in S. lucioperca drew a clear picture of how it evolved to a large and elongated body with camera-type eyes and muscle strength so that it could occupy the highest position in the food web. Overall, our results uncover genetic basis that support evolutionary adaptation of temperature and body shape in four Percid species, and could furthermore assist studies on environmental adaptation in fishes.

Inhibitory effects of growth differentiation factor 11 on autophagy deficiency-induced dedifferentiation of arterial smooth muscle cells

Growth differentiation factor (GDF)11 has been reported to reverse age-related cardiac hypertrophy in mice and cause youthful regeneration of cardiomyocytes. The present study attempted to test a hypothesis that GDF11 counteracts the pathologic dedifferentiation of mouse carotid arterial smooth muscle cells (CASMCs) due to deficient autophagy. By real-time RT-PCR and Western blot analysis, exogenously administrated GDF11 was found to promote CASMC differentiation with increased expression of various differentiation markers (α-smooth muscle actin, myogenin, myogenic differentiation, and myosin heavy chain) as well as decreased expression of dedifferentiation markers (vimentin and proliferating cell nuclear antigen). Upregulation of the GDF11 gene by trichostatin A (TSA) or CRISPR-cas9 activating plasmids also stimulated the differentiation of CASMCs. Either GDF11 or TSA treatment blocked 7-ketocholesterol-induced CASMC dedifferentiation and autophagosome accumulation as well as lysosome inhibitor bafilomycin-induced dedifferentiation and autophagosome accumulation. Moreover, in CASMCs from mice lacking the CD38 gene, an autophagy deficiency model in CASMCs, GDF11 also inhibited its phenotypic transition to dedifferentiation status. Correspondingly, TSA treatment was shown to decrease GDF11 expression and reverse CASMC dedifferentiation in the partial ligated carotid artery of mice. The inhibitory effects of TSA on dedifferentiation of CASMCs were accompanied by reduced autophagosome accumulation in the arterial wall, which was accompanied by attenuated neointima formation in partial ligated carotid arteries. We concluded that GDF11 promotes CASMC differentiation and prevents the phenotypic transition of these cells induced by autophagosome accumulation during different pathological stimulations, such as Western diet, lysosome function deficiency, and inflammation. NEW & NOTEWORTHY The present study demonstrates that growth differentiation factor (GDF)11 promotes autophagy and subsequent differentiation in carotid arterial smooth muscle cells. Upregulation of GDF11 counteracts dedifferentiation under different pathological conditions. These findings provide novel insights into the regulatory role of GDF11 in the counteracting of sclerotic arterial diseases and also suggest that activation or induction of GDF11 may be a new therapeutic strategy for the treatment or prevention of these diseases.

Histone deacetylase 3 promotes liver regeneration and liver cancer cells proliferation through signal transducer and activator of transcription 3 signaling pathway

Histone deacetylase 3 (HDAC3) plays pivotal roles in cell cycle regulation and is often aberrantly expressed in various cancers including hepatocellular carcinoma (HCC), but little is known about its role in liver regeneration and liver cancer cells proliferation. Using an inducible hepatocyte-selective HDAC3 knockout mouse, we find that lack of HDAC3 dramatically impaired liver regeneration and blocked hepatocyte proliferation in the G1 phase entry. HDAC3 inactivation robustly disrupted the signal transducer and activator of transcription 3 (STAT3) cascade. HDAC3 silencing impaired the ac-STAT3-to-p-STAT3 transition in the cytoplasm, leading to the subsequent breakdown of STAT3 signaling. Furthermore, overexpressed HDAC3 was further associated with increased tumor growth and a poor prognosis in HCC patients. Inhibition of HDAC3 expression reduced liver cancer cells growth and inhibited xenograft tumor growth. Our results suggest that HDAC3 is an important regulator of STAT3-dependent cell proliferation in liver regeneration and cancer. These findings provide novel insights into the HDAC3-STAT3 pathway in liver pathophysiological processes.

GDF11/BMP11 as a novel tumor marker for liver cancer

Growth differentiation factor 11 (GDF11), also known as bone morphogenetic protein 11, a member of the transforming growth factor-β superfamily, has been reported to be involved in colorectal cancer. However, the roles of GDF11 in Chinese patients with liver cancer and the underlying mechanisms have remained elusive. The present study assessed the expression of GDF11 in 10 paired samples of cancerous and normal tissues from Chinese liver cancer patients. The results indicated that the expression of GDF11 was significantly lower in cancerous tissues than in normal tissues. In vitro, the expression of GDF11 was reduced in a panel of liver cancer cell lines compared with that in a normal liver cell line at the mRNA and protein level. Treatment with GDF11 reduced the viability of HepG2 for up to 72 h and GDF11 treatment reduced the viability of SMMC-7721 after 48 and 72 h. Furthermore, GDF11 activated Smad2/3 signaling in HepG2 cells. In conclusion, GDF11 has a tumor suppressor role in liver cancer, exerts its effects through Smad2/3 signaling and may serve as a novel tumor marker in liver cancer diagnosis.

Epigenetics in teleost fish: From molecular mechanisms to physiological phenotypes

While the field of epigenetics is increasingly recognized to contribute to the emergence of phenotypes in mammalian research models across different developmental and generational timescales, the comparative biology of epigenetics in the large and physiologically diverse vertebrate infraclass of teleost fish remains comparatively understudied. The cypriniform zebrafish and the salmoniform rainbow trout and Atlantic salmon represent two especially important teleost orders, because they offer the unique possibility to comparatively investigate the role of epigenetic regulation in 3R and 4R duplicated genomes. In addition to their sequenced genomes, these teleost species are well-characterized model species for development and physiology, and therefore allow for an investigation of the role of epigenetic modifications in the emergence of physiological phenotypes during an organism's lifespan and in subsequent generations. This review aims firstly to describe the evolution of the repertoire of genes involved in key molecular epigenetic pathways including histone modifications, DNA methylation and microRNAs in zebrafish, rainbow trout, and Atlantic salmon, and secondly, to discuss recent advances in research highlighting a role for molecular epigenetics in shaping physiological phenotypes in these and other teleost models. Finally, by discussing themes and current limitations of the emerging field of teleost epigenetics from both theoretical and technical points of view, we will highlight future research needs and discuss how epigenetics will not only help address basic research questions in comparative teleost physiology, but also inform translational research including aquaculture, aquatic toxicology, and human disease.

Systematic analysis of the regulatory roles of microRNAs in postnatal maturation and metergasis of liver of breeder cocks

The liver function of chickens is intensively remodeled from birth to adult, which was validated by metabolomics research in the present study. In order to understand the roles of microRNAs (miRNA) in liver maturation and metergasis, miRNA expression profiles in livers of 20 male chicks aged one day and five adult cocks aged 35 weeks were determined. A total of 191 differentially expressed miRNAs with the criteria of P < 0.05 and fold changes either >1.5 or <0.67 and 32 differentially expressed miRNAs with the criteria of false discovery value (FDR) < 0.05 and fold changes either >1.5 or <0.67 were detected. Subsequently, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of the targets revealed that candidate miRNAs may involve in the regulation of hepatic metabolism and immune functions, and some pathways including cell cycle which were implicated in postnatal liver development. Furthermore, 1211 differentially expressed mRNAs (messenger RNA) in livers between the postnatal and matured chickens were used to define the roles of differentially expressed miRNAs in regulating the expression of target genes. Our results revealed the first miRNA profile related to the adaption of mature liver functions after birth in breeder cock.

Synthesis of Novel Class of N-Alkyl-isatin-3-iminobenzoic Acid Derivatives and Their Biological Activity in Zebrafish Embryos and Human Cancer Cell Lines

Isatin (1H-indole-2,3-dione) and many of its derivatives are reported to have pharmacological properties. In this study, we report the synthesis and biological activity of a new class of N-alkyl-isatin-3-iminobenzoic acid derivatives prepared via the condensation of N-alkyl isatin with 4-aminobenzoic acid by conventional, microwave, and ultrasonic methods. Microwave irradiation yielded the products in a shorter reaction time with higher yields and purities. The compounds were screened in zebrafish embryos, and also in three human cancer cell lines (MCF7, HepG2, and Jurkat) and one normal human cell line i.e., human foreskin cell line (HFF-1). Two compounds (3c, 3f) were found to be highly effective against hematopoiesis in live zebrafish embryo at 10 µM concentration. The developmental stage-dependent treatment indicated that these compounds interfered with the differentiation of hemangioblasts to hematopoietic cells in zebrafish embryos. The comparative screening of semaxanib (SU5416) (a known isatin derivatives), to compounds synthesized in this study, revealed the contrasting effects of these two classes of isatin derivatives on zebrafish hematopoiesis. Most of the N-alkyl-isatin-3-iminobenzoic acid derivatives were toxic on cancer and non-cancer tested human cells lines, however, the compounds 3c and 3f specifically affected the cell viability of Jurkat cells (human hematological cell line) with least IC₅₀ values of 16.5 and 7.8 µM. The structure-activity relationship (SAR) analysis indicated that the substitution pattern of the isatin at the 5-position was vital for activity. The in vivo and in vitro biological activities of these compounds suggested their potential use as pharmaceutical compounds for human leukemia treatment.

Epigenetic regulation of left-right asymmetry by DNA methylation

DNA methylation is a major epigenetic modification; however, the precise role of DNA methylation in vertebrate development is still not fully understood. Here, we show that DNA methylation is essential for the establishment of the left-right (LR) asymmetric body plan during vertebrate embryogenesis. Perturbation of DNA methylation by depletion of DNA methyltransferase 1 (dnmt1) or dnmt3bb.1 in zebrafish embryos leads to defects in dorsal forerunner cell (DFC) specification or collective migration, laterality organ malformation, and disruption of LR patterning. Knockdown of dnmt1 in Xenopus embryos also causes similar defects. Mechanistically, loss of dnmt1 function induces hypomethylation of the lefty2 gene enhancer and promotes lefty2 expression, which consequently represses Nodal signaling in zebrafish embryos. We also show that Dnmt3bb.1 regulates collective DFC migration through cadherin 1 (Cdh1). Taken together, our data uncover dynamic DNA methylation as an epigenetic mechanism to control LR determination during early embryogenesis in vertebrates.

Role of growth differentiation factor 11 in development, physiology and disease

Growth differentiation factor (GDF11) is a member of TGF-β/BMP superfamily that activates Smad and non-Smad signaling pathways and regulates expression of its target nuclear genes. Since its discovery in 1999, studies have shown the involvement of GDF11 in normal physiological processes, such as embryonic development and erythropoiesis, as well as in the pathophysiology of aging, cardiovascular disease, diabetes mellitus, and cancer. In addition, there are contradictory reports regarding the role of GDF11 in aging, cardiovascular disease, diabetes mellitus, osteogenesis, skeletal muscle development, and neurogenesis. In this review, we describe the GDF11 signaling pathway and its potential role in development, physiology and disease.

Clinical significance of expression of histone deacetylase 3 in hepatocellular carcinoma

AIM

To detect the expression of histone deacetylase 3 (HDAC3) in hepatocellular carcinoma (HCC) and analyze its clinicopathological significance.

METHODS

Immunohistochemistry was performed in 60 pairs of HCC tissues and tumor-adjacent normal tissues. The relationship of HDAC3 expression with clinical and pathological features and overall survival was analyzed statistically.

RESULTS

HDAC3 expression was significantly up-regulated in the HCC specimens compared to corresponding normal tissues (P < 0.05). The expression of HDAC3 in HCC had no significant correlation with gender, age, history of hepatitis B virus infection, TNM stage, pathological classification, α-fetoprotein level, liver cirrhosis, tumor size, or tumor number (P > 0.05). There was a positive correlation between HDAC3 and p-STAT3 expression in HCC tissues (r² = 0.622, P < 0.001). However, HDAC3 expression had a significant correlation with tumor recurrence (P < 0.05). The overall survival of postoperative HCC patients in the HDAC3 positive group was obviously poorer than that of patients in the HDAC3 negative group (P < 0.05), suggesting that high HDAC3 expression is associated with a poor prognosis in HCC patients.

CONCLUSION

The up-regulated expression of HDAC3 may be closely related with the occurrence and development of HCC.

Making It New Again: Insight Into Liver Development, Regeneration, and Disease From Zebrafish Research

The adult liver of most vertebrates is predominantly comprised of hepatocytes. However, these cells must work in concert with biliary, stellate, vascular, and immune cells to accomplish the vast array of hepatic functions required for physiological homeostasis. Our understanding of liver development was accelerated as zebrafish emerged as an ideal vertebrate system to study embryogenesis. Through work in zebrafish and other models, it is now clear that the cells in the liver develop in a coordinated fashion during embryogenesis through a complex yet incompletely understood set of molecular guidelines. Zebrafish research has uncovered many key players that govern the acquisition of hepatic potential, cell fate, and plasticity. Although rare, some hepatobiliary diseases-especially biliary atresia-are caused by developmental defects; we discuss how research using zebrafish to study liver development has informed our understanding of and approaches to liver disease. The liver can be injured in response to an array of stressors including viral, mechanical/surgical, toxin-induced, immune-mediated, or inborn defects in metabolism. The liver has thus evolved the capacity to efficiently repair and regenerate. We discuss the emerging field of using zebrafish to study liver regeneration and highlight recent advances where zebrafish genetics and imaging approaches have provided novel insights into how cell plasticity contributes to liver regeneration.

Zebrafish Pancreas Development and Regeneration: Fishing for Diabetes Therapies

The zebrafish pancreas shares its basic organization and cell types with the mammalian pancreas. In addition, the developmental pathways that lead to the establishment of the pancreatic islets of Langherhans are generally conserved from fish to mammals. Zebrafish provides a powerful tool to probe the mechanisms controlling establishment of the pancreatic endocrine cell types from early embryonic progenitor cells, as well as the regeneration of endocrine cells after damage. This knowledge is, in turn, applicable to refining protocols to generate renewable sources of human pancreatic islet cells that are critical for regulation of blood sugar levels. Here, we review how previous and ongoing studies in zebrafish and beyond are influencing the understanding of molecular mechanisms underlying various forms of diabetes and efforts to develop cell-based approaches to cure this increasingly widespread disease.

Selenoprotein H is an essential regulator of redox homeostasis that cooperates with p53 in development and tumorigenesis

Selenium, an essential micronutrient known for its cancer prevention properties, is incorporated into a class of selenocysteine-containing proteins (selenoproteins). Selenoprotein H (SepH) is a recently identified nucleolar oxidoreductase whose function is not well understood. Here we report that seph is an essential gene regulating organ development in zebrafish. Metabolite profiling by targeted LC-MS/MS demonstrated that SepH deficiency impairs redox balance by reducing the levels of ascorbate and methionine, while increasing methionine sulfoxide. Transcriptome analysis revealed that SepH deficiency induces an inflammatory response and activates the p53 pathway. Consequently, loss of seph renders larvae susceptible to oxidative stress and DNA damage. Finally, we demonstrate that seph interacts with p53 deficiency in adulthood to accelerate gastrointestinal tumor development. Overall, our findings establish that seph regulates redox homeostasis and suppresses DNA damage. We hypothesize that SepH deficiency may contribute to the increased cancer risk observed in cohorts with low selenium levels.

Endoderm specification and liver development

The endoderm is the innermost embryonic germ layer, and in zebrafish, it gives rise to the lining of the gut, the gills, liver, pancreas, gallbladder, and derivatives of the pharyngeal pouch. These organs form the gastrointestinal tract and are involved with the absorption, delivery, and metabolism of nutrients. The liver has a central role in regulating these processes because it controls carbohydrate and lipid metabolism, protein synthesis, and breakdown of endogenous and xenobiotic products. Liver dysfunction frequently leads to significant morbidity and mortality; however, in most settings of organ injury, the liver exhibits remarkable regenerative capacity. In this chapter, we review the principal mechanisms of endoderm and liver formation and provide protocols to assess liver formation and liver regeneration.

Epigenetic targets in hepatocellular carcinoma cells: identification of chaperone protein complexes with histone deacetylases

AIMS

The study was designed to find out the protein complex(s) associated with HDAC3 in liver cancer using a modified form of affinity purification coupled with a mass spectrometry technique in HepG2 cells. The organ-specific requirement for HDAC1 and HDAC3 during liver formation in zebrafish and their altered expression in liver cancer tissues indicates they are indispensible for hepato-organogenesis and hepatocarcinogenesis. However, how they exert their function is unknown.

MATERIAL & METHODS

HepG2 cells were transfected with either mock or construct-containing HDAC3 using a C-terminal strepIII-HA tag as bait. The bait proteins were purified by double affinity columns and were analyzed on a Thermo LTQ Orbitrap™ (Thermo Scientific, MA, USA) chromatography system.

RESULTS

Affinity purification coupled with mass spectrometry resulted in the identification of 24 putative binders of HDAC3 in HepG2 cells. The majority (83%) of these are novel interactions are reported for the first time in this study.

CONCLUSION

This is the first study reporting the affinity purification and identification of protein complexes with two closely related proteins in one cell line. The novel HDAC1 and HDAC3 complexes identified in HepG2 cells could serve as a platform for the design of future therapeutic medicine for the treatment of liver cancer.

In Vivo Screening Using Transgenic Zebrafish Embryos Reveals New Effects of HDAC Inhibitors Trichostatin A and Valproic Acid on Organogenesis

The effects of endocrine disrupting chemicals (EDCs) on reproduction are well known, whereas their developmental effects are much less characterized. However, exposure to endocrine disruptors during organogenesis may lead to deleterious and permanent problems later in life. Zebrafish (Danio rerio) transgenic lines expressing the green fluorescent protein (GFP) in specific organs and tissues are powerful tools to uncover developmental defects elicited by EDCs. Here, we used seven transgenic lines to visualize in vivo whether a series of EDCs and other pharmaceutical compounds can alter organogenesis in zebrafish. We used transgenic lines expressing GFP in pancreas, liver, blood vessels, inner ear, nervous system, pharyngeal tooth and pectoral fins. This screen revealed that four of the tested chemicals have detectable effects on different organs, which shows that the range of effects elicited by EDCs is wider than anticipated. The endocrine disruptor tetrabromobisphenol-A (TBBPA), as well as the three drugs diclofenac, trichostatin A (TSA) and valproic acid (VPA) induced abnormalities in the embryonic vascular system of zebrafish. Moreover, TSA and VPA induced specific alterations during the development of pancreas, an observation that was confirmed by in situ hybridization with specific markers. Developmental delays were also induced by TSA and VPA in the liver and in pharyngeal teeth, resulting in smaller organ size. Our results show that EDCs can induce a large range of developmental alterations during embryogenesis of zebrafish and establish GFP transgenic lines as powerful tools to screen for EDCs effects in vivo.

Four and a Half LIM Domains 1b (Fhl1b) Is Essential for Regulating the Liver versus Pancreas Fate Decision and for β-Cell Regeneration

The liver and pancreas originate from overlapping embryonic regions, and single-cell lineage tracing in zebrafish has shown that Bone morphogenetic protein 2b (Bmp2b) signaling is essential for determining the fate of bipotential hepatopancreatic progenitors towards the liver or pancreas. Despite its pivotal role, the gene regulatory networks functioning downstream of Bmp2b signaling in this process are poorly understood. We have identified four and a half LIM domains 1b (fhl1b), which is primarily expressed in the prospective liver anlage, as a novel target of Bmp2b signaling. fhl1b depletion compromised liver specification and enhanced induction of pancreatic cells from endodermal progenitors. Conversely, overexpression of fhl1b favored liver specification and inhibited induction of pancreatic cells. By single-cell lineage tracing, we showed that fhl1b depletion led lateral endodermal cells, destined to become liver cells, to become pancreatic cells. Reversely, when fhl1b was overexpressed, medially located endodermal cells, fated to differentiate into pancreatic and intestinal cells, contributed to the liver by directly or indirectly modulating the discrete levels of pdx1 expression in endodermal progenitors. Moreover, loss of fhl1b increased the regenerative capacity of β-cells by increasing pdx1 and neurod expression in the hepatopancreatic ductal system. Altogether, these data reveal novel and critical functions of Fhl1b in the hepatic versus pancreatic fate decision and in β-cell regeneration.

Lineage-specific multipotent progenitors play crucial roles in embryonic development, regeneration in adult tissues, and diseases such as cancer. Bone morphogenetic protein (Bmp) signaling is critical for regulating the cell fate choice of liver versus pancreas, two essential organs of body metabolism. Through transcriptome profiling of endodermal tissues exposed to increased or decreased Bmp2b signaling, we have discovered the zebrafish gene four and a half LIM domains 1b (fhl1b) as a novel target of Bmp2b signaling. fhl1b is primarily expressed in the prospective liver anlage. Loss- and gain-of-function analyses indicate that Fhl1b suppresses specification of the pancreas and induces the liver. By single-cell lineage tracing, we showed that depletion of fhl1b caused a liver-to-pancreas fate switch, while fhl1b overexpression redirected pancreatic progenitors to become liver cells. At later stages, Fhl1b regulates regeneration of insulin-secreting β-cells by directly or indirectly modulating pdx1 and neurod expression in the hepatopancreatic ductal system. Therefore, our work provides a novel paradigm of how Bmp signaling regulates the hepatic versus pancreatic fate decision and β-cell regeneration through its novel target Fhl1b.

Histone deacetylase 1 is required for the development of the zebrafish inner ear

Histone deacetylase 1 (HDAC1) has been reported to be important for multiple aspects of normal embryonic development, but little is known about its function in the development of mechanosensory organs. Here, we first confirmed that HDAC1 is expressed in the developing otic vesicles of zebrafish by whole-mount in situ hybridization. Knockdown of HDAC1 using antisense morpholino oligonucleotides in zebrafish embryos induced smaller otic vesicles, abnormal otoliths, malformed or absent semicircular canals, and fewer sensory hair cells. HDAC1 loss of function also caused attenuated expression of a subset of key genes required for otic vesicle formation during development. Morpholino-mediated knockdown of HDAC1 resulted in decreased expression of members of the Fgf family in the otic vesicles, suggesting that HDAC1 is involved in the development of the inner ear through regulation of Fgf signaling pathways. Taken together, our results indicate that HDAC1 plays an important role in otic vesicle formation.

Zebrafish Discoveries in Cancer Epigenetics

The cancer epigenome is fundamentally different than that of normal cells. How these differences arise in and contribute to carcinogenesis is not known, and studies using model organisms such as zebrafish provide an opportunity to address these important questions. Modifications of histones and DNA comprise the complex epigenome, and these influence chromatin structure, genome stability and gene expression, all of which are fundamental to the cellular changes that cause cancer. The cancer genome atlas covers the wide spectrum of genetic changes associated with nearly every cancer type, however, this catalog is currently uni-dimensional. As the pattern of epigenetic marks and chromatin structure in cancer cells is described and overlaid on the mutational landscape, the map of the cancer genome becomes multi-dimensional and highly complex. Two major questions remain in the field: (1) how the epigenome becomes repatterned in cancer and (2) which of these changes are cancer-causing. Zebrafish provide a tractable in vivo system to monitor the epigenome during transformation and to identify epigenetic drivers of cancer. In this chapter, we review principles of cancer epigenetics and discuss recent work using zebrafish whereby epigenetic modifiers were established as cancer driver genes, thus providing novel insights into the mechanisms of epigenetic reprogramming in cancer.

Zebrafish as a disease model for studying human hepatocellular carcinoma

Liver cancer is one of the world’s most common cancers and the second leading cause of cancer deaths. Hepatocellular carcinoma (HCC), a primary hepatic cancer, accounts for 90%-95% of liver cancer cases. The pathogenesis of HCC consists of a stepwise process of liver damage that extends over decades, due to hepatitis, fatty liver, fibrosis, and cirrhosis before developing fully into HCC. Multiple risk factors are highly correlated with HCC, including infection with the hepatitis B or C viruses, alcohol abuse, aflatoxin exposure, and metabolic diseases. Over the last decade, genetic alterations, which include the regulation of multiple oncogenes or tumor suppressor genes and the activation of tumorigenesis-related pathways, have also been identified as important factors in HCC. Recently, zebrafish have become an important living vertebrate model organism, especially for translational medical research. In studies focusing on the biology of cancer, carcinogen induced tumors in zebrafish were found to have many similarities to human tumors. Several zebrafish models have therefore been developed to provide insight into the pathogenesis of liver cancer and the related drug discovery and toxicology, and to enable the evaluation of novel small-molecule inhibitors. This review will focus on illustrative examples involving the application of zebrafish models to the study of human liver disease and HCC, through transgenesis, genome editing technology, xenografts, drug discovery, and drug-induced toxic liver injury.

HDAC3 Is Required for Posterior Lateral Line Development in Zebrafish

Histone deacetylases (HDACs) are involved in multiple developmental processes, but their functions in the development of mechanosensory organs are largely unknown. In the present study, we report the presence of HDAC3 in the zebrafish posterior lateral line primordium and newly deposited neuromasts. We used morpholinos to show that HDAC3 knockdown severely disrupts the development of the posterior lateral line and reduces the numbers of neuromasts and sensory hair cells within these organs. In HDAC3 morphants, we also observed decreased cell proliferation and increased apoptosis, which might lead to these defects. Finally, we show that HDAC3 deficiency results in attenuated Fgf signaling in the migrating primordium. In situ hybridizations indicate aberrant expression patterns of Notch signaling pathway genes in HDAC3 morphants. In addition, inhibition of HDAC3 function diminishes cxcr7b and alters cxcl12a expression in the migrating primordium. Our results indicate that HDAC3 plays a crucial role in regulating posterior lateral line (PLL) formation and provide evidence for epigenetic regulation in auditory organ development.

Acinar cell reprogramming: a clinically important target in pancreatic disease

Acinar cells of the pancreas produce the majority of enzymes required for digestion and make up >90% of the cells within the pancreas. Due to a common developmental origin and the plastic nature of the acinar cell phenotype, these cells have been identified as a possible source of β cells as a therapeutic option for Type I diabetes. However, recent evidence indicates that acinar cells are the main source of pancreatic intraepithelial neoplasias (PanINs), the predecessor of pancreatic ductal adenocarcinoma (PDAC). The conversion of acinar cells to either β cells or precursors to PDAC is dependent on reprogramming of the cells to a more primitive, progenitor-like phenotype, which involves changes in transcription factor expression and activity, and changes in their epigenetic program. This review will focus on the mechanisms that promote acinar cell reprogramming, as well as the factors that may affect these mechanisms.

Synthesis, Characterization, and Anti-Cancer Activity of Some New N'-(2-Oxoindolin-3-ylidene)-2-propylpentane hydrazide-hydrazones Derivatives

Eight novel N'-(2-oxoindolin-3-ylidene)-2-propylpentane hydrazide-hydrazone derivatives 4a-h were synthesized and fully characterized by IR, NMR ((1)H-NMR and (13)C-NMR), elemental analysis, and X-ray crystallography. The cyto-toxicity and in vitro anti-cancer evaluation of the prepared compounds have been assessed against two different human tumour cell lines including human liver (HepG2) and leukaemia (Jurkat), as well as in normal cell lines derived from human embryonic kidney (HEK293) using MTT assay. The compounds 3e, 3f, 4a, 4c, and 4e revealed promising anti-cancer activities in tested human tumour cells lines (IC50 values between 3 and 7 μM) as compared to the known anti-cancer drug 5-Fluorouracil (IC50 32-50 μM). Among the tested compounds, 4a showed specificity against leukaemia (Jurkat) cells, with an IC50 value of 3.14 μM, but this compound was inactive in liver cancer and normal cell lines.

Biological screening of novel derivatives of valproic acid for anticancer and antiangiogenic properties

BACKGROUND

Valproic acid (VPA) is a potent anticancer and antiangiogenic agent. However, design and synthesis of chemical derivatives with improved antiangiogenic and anticancer activities are still necessary. In this study a library of novel derivatives of VPA was synthesized and tested.

METHODS

A human liver cancer cell line (HepG2) and a human normal embryonic kidney cell line (HEK 293) were exposed to various concentrations of VPA derivatives for 24 hours and cell viability was checked by MTT colorimetric assay. Anti-angiogenic properties were evaluated in transgenic zebrafish embryos.

RESULTS

N-valproylglycine derivatives suppressed survival almost 70% (p value 0.001) in HepG2 cells but only 10-12% in HEK 293 cells (p value 0.133). They also suppressed angiogenic blood vessel formation by 80% when used between 2-20 μM in zebrafish embryos. Valproic acid hydrazides showed moderate level of anticancer activity by affecting 30-50% (p value 0.001) of cell viability in HepG2 cells and 8-10% in HEK293 cells (p value 0.034).

CONCLUSION

The majority of compounds in this study showed potent and stronger antiangiogenic and anticancer activity than VPA. They proved selectively toxic to cancer cells and safer for normal cells. Moreover, these compounds inhibited developmental angiogenesis in zebrafish embryos. Based on the fact that liver is a highly vascularized organ, in case of liver carcinoma these compounds have the potential to target the pathological angiogenesis and could be an effective strategy to treat hepatocellular carcinoma.