Characterization of zebrafish mutants with defects in bone calcification during development

CHD7 regulates craniofacial cartilage development via controlling HTR2B expression

Mutations in the Chromodomain helicase DNA-binding protein 7 - coding gene (CHD7) cause CHARGE syndrome (CS). Although craniofacial and skeletal abnormalities are major features of CS patients, the role of CHD7 in bone and cartilage development remain largely unexplored. Here, using a zebrafish (Danio rerio) CS model, we show that chd7-/- larvae display abnormal craniofacial cartilage development and spinal deformities. The craniofacial and spine defects are accompanied by a marked reduction of bone mineralization. At the molecular level, we show that these phenotypes are associated with significant reduction in the expression levels of osteoblast differentiation markers. Additionally, we detected a marked depletion of collagen 2α1 in the cartilage of craniofacial regions and vertebrae, along with significantly reduced number of chondrocytes. Chondrogenesis defects are at least in part due to downregulation of htr2b, which we found to be also dysregulated in human cells derived from an individual with CHD7 mutation-positive CS. Overall, this study thus unveils an essential role for CHD7 in cartilage and bone development, with potential clinical relevance for the craniofacial defects associated with CS.

Aspartame Causes Developmental Defects and Teratogenicity in Zebra Fish Embryo: Role of Impaired SIRT1/FOXO3a Axis in Neuron Cells

Aspartame, a widely used artificial sweetener, is present in many food products and beverages worldwide. It has been linked to potential neurotoxicity and developmental defects. However, its teratogenic effect on embryonic development and the underlying potential mechanisms need to be elucidated. We investigated the concentration- and time-dependent effects of aspartame on zebrafish development and teratogenicity. We focused on the role of sirtuin 1 (SIRT1) and Forkhead-box transcription factor (FOXO), two proteins that play key roles in neurodevelopment. It was found that aspartame exposure reduced the formation of larvae and the development of cartilage in zebrafish. It also delayed post-fertilization development by altering the head length and locomotor behavior of zebrafish. RNA-sequencing-based DEG analysis showed that SIRT1 and FOXO3a are involved in neurodevelopment. In silico and in vitro analyses showed that aspartame could target and reduce the expression of SIRT1 and FOXO3a proteins in neuron cells. Additionally, aspartame triggered the reduction of autophagy flux by inhibiting the nuclear translocation of SIRT1 in neuronal cells. The findings suggest that aspartame can cause developmental defects and teratogenicity in zebrafish embryos and reduce autophagy by impairing the SIRT1/FOXO3a axis in neuron cells.

Avermectin induces cardiac toxicity in early embryonic stage of zebrafish

Avermectin is a widely used insecticide, and it is mainly effective against animal parasites and insects. Given its extensive use in agriculture, a large amount of avermectin is accumulated in natural waters. Avermectin is a neurotoxin that affects the autonomous behavior of zebrafish and inhibits neurological responses in invertebrates via GABA-chloride channels. In this study, we used zebrafish as a model organism to explore the lethal teratogenic effects of different avermectin concentrations. We found that 50-μg/L avermectin could cause significant malformation abnormalities during the development of zebrafish heart, changes in heart rate, and significant reduction in hatching rate and body length. Transcriptome data revealed that 499 genes were upregulated and 877 genes were downregulated at 72 h post-fertilization (hpf), whereas 1805 genes were upregulated and 836 genes were downregulated at 120 hpf. According to gene ontology (GO) enrichment analysis, avermectin affected cardiac circulation and myocardial fiber development. KEGG analysis revealed that avermectin treatment significantly altered the activity of signal pathways associated with cardiac rhythm and vascular smooth muscle contraction. The main target of avermectin was identified as the heart, as it affected heart development and function by altering cardiac-related gene expression that led to a heart defect phenotype. Our findings indicate that developing zebrafish are sensitive to avermectin, which targets the heart.

Zebrafish as an Emerging Model for Osteoporosis: A Primary Testing Platform for Screening New Osteo-Active Compounds

Osteoporosis is metabolic bone disease caused by an altered balance between bone anabolism and catabolism. This dysregulated balance is responsible for fragile bones that fracture easily after minor falls. With an aging population, the incidence is rising and as yet pharmaceutical options to restore this imbalance is limited, especially stimulating osteoblast bone-building activity. Excitingly, output from large genetic studies on people with high bone mass (HBM) cases and genome wide association studies (GWAS) on the population, yielded new insights into pathways containing osteo-anabolic players that have potential for drug target development. However, a bottleneck in development of new treatments targeting these putative osteo-anabolic genes is the lack of animal models for rapid and affordable testing to generate functional data and that simultaneously can be used as a compound testing platform. Zebrafish, a small teleost fish, are increasingly used in functional genomics and drug screening assays which resulted in new treatments in the clinic for other diseases. In this review we outline the zebrafish as a powerful model for osteoporosis research to validate potential therapeutic candidates, describe the tools and assays that can be used to study bone homeostasis, and affordable (semi-)high-throughput compound testing.

Atrazine affects craniofacial chondrogenesis and axial skeleton mineralization in zebrafish (Danio rerio)

Atrazine is a commonly used herbicide that has previously been implicated as an endocrine-disrupting compound. Previous studies have shown that estrogenic endocrine-disrupting compounds affect the development of the heart, cartilage, and bone in zebrafish ( Danio rerio). To determine whether atrazine has effects similar to other endocrine disruptors, zebrafish embryos were treated with a range of atrazine concentrations. Atrazine treatment at a low concentration of 0.1 µM resulted in significant differences in craniofacial cartilage elements, while concentrations ≥1 µM led to decreased survival and increased heart rates. Fish treated with ≥1 µM atrazine also developed with delayed vertebrae mineralization. Higher concentrations of atrazine caused gross craniofacial defects and decreased hatching rates. Further studies into the molecular pathways disrupted in these developmental processes could shed light on a link between endocrine-disrupting compounds and developmental abnormalities.

Synthesis of multi-functional green fluorescence carbon dots and their applications as a fluorescent probe for Hg2+ detection and zebrafish imaging

Green fluorescence carbon dots for mercury detection and zebrafish imaging.

Zebrafish Collagen Type I: Molecular and Biochemical Characterization of the Major Structural Protein in Bone and Skin

Over the last years the zebrafish imposed itself as a powerful model to study skeletal diseases, but a limit to its use is the poor characterization of collagen type I, the most abundant protein in bone and skin. In tetrapods collagen type I is a trimer mainly composed of two α1 chains and one α2 chain, encoded by COL1A1 and COL1A2 genes, respectively. In contrast, in zebrafish three type I collagen genes exist, col1a1a, col1a1b and col1a2 coding for α1(I), α3(I) and α2(I) chains. During embryonic and larval development the three collagen type I genes showed a similar spatio-temporal expression pattern, indicating their co-regulation and interdependence at these stages. In both embryonic and adult tissues, the presence of the three α(I) chains was demonstrated, although in embryos α1(I) was present in two distinct glycosylated states, suggesting a developmental-specific collagen composition. Even though in adult bone, skin and scales equal amounts of α1(I), α3(I) and α2(I) chains are present, the presented data suggest a tissue-specific stoichiometry and/or post-translational modification status for collagen type I. In conclusion, this data will be useful to properly interpret results and insights gained from zebrafish models of skeletal diseases.

Danio rerio: the Janus of the bone from embryo to scale

Danio rerio (zebrafish), like the Roman god Janus, is an old animal model which is recently emerged and looks to the future with an increasing scientific success. Unlike other traditional animal models, zebrafish represents a versatile way to approach the study of the skeleton. Transparency of the larval stage, genetic manipulability and unique anatomical structures (scales) makes zebrafish a powerful and versatile instrument to investigate the bone tissue in terms of structure and function. Like Janus, zebrafish offers two different faces, or better, two models in one animal: larval and adult stage. The embryo can be used to isolate new genes involved in osteogenesis by large-scale mutagenesis screenings. The behavior of bone cells and genes in osteogenesis can be investigate by using transgenic lines, vital dyes, mutants and traditional molecular biology techniques. The adult zebrafish represents an important resource to study the pathways related to the bone metabolism and turnover. In particular, the properties of the caudal fin allow to study mechanisms of bone regeneration and reparation whereas the elasmoid scale represents an unique tool to investigate the bone metabolism under physiological or pathological conditions.

Role of Cbl-PI3K Interaction during Skeletal Remodeling in a Murine Model of Bone Repair

Mice in which Cbl is unable to bind PI3K (YF mice) display increased bone volume due to enhanced bone formation and repressed bone resorption during normal bone homeostasis. We investigated the effects of disrupted Cbl-PI3K interaction on fracture healing to determine whether this interaction has an effect on bone repair. Mid-diaphyseal femoral fractures induced in wild type (WT) and YF mice were temporally evaluated via micro-computed tomography scans, biomechanical testing, histological and histomorphometric analyses. Imaging analyses revealed no change in soft callus formation, increased bony callus formation, and delayed callus remodeling in YF mice compared to WT mice. Histomorphometric analyses showed significantly increased osteoblast surface per bone surface and osteoclast numbers in the calluses of YF fractured mice, as well as increased incorporation of dynamic bone labels. Furthermore, using laser capture micro-dissection of the fracture callus we found that cells lacking Cbl-PI3K interaction have higher expression of Osterix, TRAP, and Cathepsin K. We also found increased expression of genes involved in propagating PI3K signaling in cells isolated from the YF fracture callus, suggesting that the lack of Cbl-PI3K interaction perhaps results in enhanced PI3K signaling, leading to increased bone formation, but delayed remodeling in the healing femora.

Carbon Quantum Dots for Zebrafish Fluorescence Imaging

Carbon quantum dots (C-QDs) are becoming a desirable alternative to metal-based QDs and dye probes owing to their high biocompatibility, low toxicity, ease of preparation, and unique photophysical properties. Herein, we describe fluorescence bioimaging of zebrafish using C-QDs as probe in terms of the preparation of C-QDs, zebrafish husbandry, embryo harvesting, and introduction of C-QDs into embryos and larvae by soaking and microinjection. The multicolor of C-QDs was validated with their imaging for zebrafish embryo. The distribution of C-QDs in zebrafish embryos and larvae were successfully observed from their fluorescence emission. the bio-toxicity of C-QDs was tested with zebrafish as model and C-QDs do not interfere to the development of zebrafish embryo. All of the results confirmed the high biocompatibility and low toxicity of C-QDs as imaging probe. The absorption, distribution, metabolism and excretion route (ADME) of C-QDs in zebrafish was revealed by their distribution. Our work provides the useful information for the researchers interested in studying with zebrafish as a model and the applications of C-QDs. The operations related zebrafish are suitable for the study of the toxicity, adverse effects, transport, and biocompatibility of nanomaterials as well as for drug screening with zebrafish as model.