sox9b is required in cardiomyocytes for cardiac morphogenesis and function.

The high mobility group transcription factor SOX9 is expressed in stem cells, progenitor cells, and differentiated cell-types in developing and mature organs. Exposure to a variety of toxicants including dioxin, di(2-ethylhexyl) phthalate, 6:2 chlorinated polyfluorinated ether sulfonate, and chlorpyrifos results in the downregulation of tetrapod Sox9 and/or zebrafish sox9b. Disruption of Sox9/sox9b function through environmental exposures or genetic mutations produce a wide range of phenotypes and adversely affect organ development and health.

Analysis of the zebrafish sox9b promoter: Identification of elements that recapitulate organ-specific expression of sox9b.

The SRY-related high-mobility box 9 (SOX9) gene is expressed in many different tissues. To better understand the DNA elements that control tissue-specific expression, we cloned and sequenced a 2.5 kb fragment lying 5' to the zebrafish sox9b gene transcriptional start site.

A co-culture assay of embryonic zebrafish hearts to assess migration of epicardial cells in vitro.

Background: The vertebrate heart consists of three cell layers: the innermost endothelium, the contractile myocardium and the outermost epicardium. The epicardium is vital for heart development and function, and forms from epicardial progenitor cells (EPCs), which migrate to the myocardium during early development. Disruptions in EPC migration and epicardium formation result in a number of cardiac malformations, many of which resemble congenital heart diseases in humans.

Dioxin disrupts cranial cartilage and dermal bone development in zebrafish larvae.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin) disrupts craniofacial development in zebrafish larvae. However, the cellular changes responsible for the decreased jaw size remain poorly understood. We show that smaller jaw size is due to a decrease in both the size and number of chondrocytes in the developing craniofacial cartilages.

Dioxin inhibition of swim bladder development in zebrafish: is it secondary to heart failure?

The swim bladder is a gas-filled organ that is used for regulating buoyancy and is essential for survival in most teleost species. In zebrafish, swim bladder development begins during embryogenesis and inflation occurs within 5 days post fertilization (dpf). Embryos exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) before 96 h post fertilization (hpf) developed swim bladders normally until the growth/elongation phase, at which point growth was arrested.

Dioxin induction of transgenerational inheritance of disease in zebrafish.

Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD) is an aryl hydrocarbon receptor (AHR) agonist, an endocrine disruptor, and a potent global pollutant. TCDD exposure is associated with diseases of almost every organ system, and its toxicity is highly conserved across vertebrates. While the acute developmental effects of dioxin exposure have been extensively studied, the ability of early sublethal exposure to produce toxicity in adulthood or subsequent generations is poorly understood.

Cardiac myocyte-specific AHR activation phenocopies TCDD-induced toxicity in zebrafish.

Exposure of zebrafish embryos to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) activates the zebrafish aryl hydrocarbon receptor 2 (AHR) to produce developmental and cardiovascular toxicity. AHR is found in the heart; however, AHR activation by TCDD is not confined to the heart and occurs throughout the organism. In order to understand the cause of cardiotoxicity, we constructed a constitutively active AHR (caAHR) based on the zebrafish AHR2 and expressed it specifically in cardiomyocytes.

Multiple modes of proepicardial cell migration require heartbeat.

Background: The outermost layer of the vertebrate heart, the epicardium, forms from a cluster of progenitor cells termed the proepicardium (PE). PE cells migrate onto the myocardium to give rise to the epicardium. Impaired epicardial development has been associated with defects in valve development, cardiomyocyte proliferation and alignment, cardiac conduction system maturation and adult heart regeneration.

Using zebrafish as a model system for studying the transgenerational effects of dioxin.

2,3,7,8 Tetrachlorodibenzo-p-dioxin (TCDD) has been associated with many disease states in humans. A rising concern is that exposure early in life can lead to adult toxicity and toxicity in subsequent generations. Juvenile zebrafish exposed to TCDD (50 pg/ml in water; 1 h exposure) at 3 and 7 weeks post fertilization showed toxicity only later in adulthood.

Adverse effects in adulthood resulting from low-level dioxin exposure in juvenile zebrafish.

There is strong evidence indicating that disease in adult humans stems from a combination of genetic and environmental factors. A problem in identifying environmental factors is that subacute exposures during early life are often unnoticed, or exposures are variable among a diverse population. This leads to a confusing pattern in adulthood.

Construction and characterization of a sox9b transgenic reporter line.

The transcription factor SOX9 is a member of the SRY-related high-mobility-group box (SOX) superfamily of genes. In mammals, Sox9 plays important roles in many developmental processes including craniofacial, skeletal and heart morphogenesis, retinal and brain development, and gonad differentiation. Human mutations in SOX9 or the SOX9 promoter result in campomelic dysplasia, a severe genetic disorder, which disrupts skeletal, craniofacial, cardiac, neural and reproductive development.

Epicardium Formation as a Sensor in Toxicology.

Zebrafish ( rerio) are an excellent vertebrate model for studying heart development, regeneration and cardiotoxicity. Zebrafish embryos exposed during the temporal window of epicardium development to the aryl hydrocarbon receptor (AHR) agonist 2,3,7,8-tetrachlorodibenzo--dioxin (TCDD) exhibit severe heart malformations. TCDD exposure prevents both proepicardial organ (PE) and epicardium development.

Toxicity of oxidatively degraded quantum dots to developing zebrafish (Danio rerio).

Once released into the environment, engineered nanoparticles (eNPs) are subjected to processes that may alter their physical or chemical properties, potentially altering their toxicity vis-à-vis the as-synthesized materials. We examined the toxicity to zebrafish ( Danio rerio ) embryos of CdSecore/ZnSshell quantum dots (QDs) before and after exposure to an in vitro chemical model designed to simulate oxidative weathering in soil environments based on a reductant-driven Fenton's reaction. Exposure to these oxidative conditions resulted in severe degradation of the QDs: the Zn shell eroded, Cd(2+) and selenium were released, and amorphous Se-containing aggregates were formed.

Early dioxin exposure causes toxic effects in adult zebrafish.

The acute effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure have been well documented in many vertebrate species. However, less is known about the consequences in adulthood from sublethal exposure during development. To address this, we exposed zebrafish to sublethal levels of TCDD (1h; 50 pg/ml), either in early embryogenesis (day 0) or during sexual determination (3 and 7 weeks), and assessed the effects later in adulthood.

Sox9b is required for epicardium formation and plays a role in TCDD-induced heart malformation in zebrafish.

Activation of the transcription factor aryl hydrocarbon receptor by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) prevents the formation of the epicardium and leads to severe heart malformations in developing zebrafish (Danio rerio). The downstream genes that cause heart malformation are not known. Because TCDD causes craniofacial malformations in zebrafish by downregulating the sox9b gene, we hypothesized that cardiotoxicity might also result from sox9b downregulation.

Statistically enhanced spectral counting approach to TCDD cardiac toxicity in the adult zebrafish heart.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental pollutant and teratogen that produces cardiac toxicity in the developing zebrafish. Here we adopted a label free quantitative proteomic approach based on normalized spectral abundance factor (NSAF) to investigate the disturbance of the cardiac proteome induced by TCDD in the adult zebrafish heart. The protein expression level changes between heart samples from TCDD-treated and control zebrafish were systematically evaluated by a large scale MudPIT analysis, which incorporated triplicate analyses for both control and TCDD-exposed heart proteomic samples to overcome the data-dependent variation in shotgun proteomic experiments and obtain a statistically significant protein data set with improved quantification confidence.

Characterization of zebrafish cardiac proteome using online pH gradient SCX-RP HPLC-MS/MS platform.

Two-dimensional HPLC coupled with tandem MS (MS/MS) has become a mainstream technique in the shotgun proteomics for large-scale identification of proteins from biological samples. This powerful technology provides speed, sensitivity, and dynamic range which are essential to probe complex peptide mixtures from proteomic samples. Herein we present a pH gradient SCX-RP 2D HPLC-MS/MS method designed to improve the peptide resolution and protein identification from complex proteomic samples.

TiO2 nanoparticle exposure and illumination during zebrafish development: mortality at parts per billion concentrations.

Photoactivation of titanium dioxide nanoparticles (TiO2NPs) can produce reactive oxygen species (ROS). Over time, this has the potential to produce cumulative cellular damage. To test this, we exposed zebrafish (Danio rerio) to two commercial TiO2NP preparations at concentrations ranging from 0.

Influence of humic acid on titanium dioxide nanoparticle toxicity to developing zebrafish.

Titanium dioxide nanoparticle (TiO2NP) suspension stability can be altered by adsorption of dissolved organic matter (DOM). This is expected to impact their environmental fate and bioavailability. To date, the influence of DOM on the toxicity of TiO2NPs to aquatic vertebrates has not been reported.

TCDD inhibits heart regeneration in adult zebrafish.

Normal adult zebrafish can completely regenerate lost myocardium following partial amputation of the ventricle apex. We report that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) significantly impairs this regeneration. Adult male zebrafish were injected with vehicle (control) or TCDD (70ng/g, ip) 1 day prior to partial amputation of the ventricle apex.

Dioxin inhibits zebrafish epicardium and proepicardium development.

Embryonic exposure to the environmental contaminant and aryl hydrocarbon receptor agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin), disrupts cardiac development and function in fish, birds, and mammals. In zebrafish, the temporal window of sensitivity to the cardiotoxic effects of TCDD coincides with epicardium formation. We hypothesized that this TCDD-induced heart failure results from disruption of epicardial development.

Glucose, nitrogen, and phosphate repletion in Saccharomyces cerevisiae: common transcriptional responses to different nutrient signals.

Saccharomyces cerevisiae are able to control growth in response to changes in nutrient availability. The limitation for single macronutrients, including nitrogen (N) and phosphate (P), produces stable arrest in G1/G0. Restoration of the limiting nutrient quickly restores growth.

Sensitivity to dioxin decreases as zebrafish mature.

The embryos of teleost fish are exquisitely sensitive to the toxic effects of exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, several lines of evidence suggest that adults are less sensitive to TCDD. To better understand and characterize this difference between early life stage and adults, we exposed zebrafish (Danio rerio) to graded TCDD concentrations at different ages.

A dominant negative zebrafish Ahr2 partially protects developing zebrafish from dioxin toxicity.

The toxicity by 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) is thought to be caused by activation of the aryl hydrocarbon receptor (AHR). However, our understanding of how AHR activation by TCDD leads to toxic effects is poor. Ideally we would like to manipulate AHR activity in specific tissues and at specific times.

Reproductive and developmental toxicity of dioxin in fish.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin) is a global environmental contaminant and the prototypical ligand for investigating aryl hydrocarbon receptor (AHR)-mediated toxicity. Environmental exposure to TCDD results in developmental and reproductive toxicity in fish, birds and mammals. To resolve the ecotoxicological relevance and human health risks posed by exposure to dioxin-like AHR agonists, a vertebrate model is needed that allows for toxicity studies at various levels of biological organization, assesses adverse reproductive and developmental effects and establishes appropriate integrative correlations between different levels of effects.