Modulation of PPAR signaling disrupts pancreas development in the zebrafish, Danio rerio.

Peroxisome Proliferator Activated Receptors (PPARs) are transcription factors that regulate processes such as lipid and glucose metabolism. Synthetic PPAR ligands, designed as therapeutics for metabolic disease, provide a tool to assess the relationship between PPAR activity and pancreas development in vivo, an area that remains poorly characterized. Here, we aim to assess the effects of PPAR agonists and antagonists on gene expression, embryonic morphology and pancreas development in transgenic zebrafish embryos. To evaluate developmental perturbations, we assessed gross body and pancreas morphology at 4 days post fertilization (dpf) in response to developmental exposures with PPARα, PPARγ, and PPARß/δ agonists and antagonists at 0, 0.01, 0.1, 1, and 10 µM concentrations. All ligand exposures, with the exception of the PPARα agonist, resulted in significantly altered fish length and yolk sac area. PPARγ agonist and antagonist had higher incidence of darkened yolk sac and craniofacial deformities, whereas PPARα antagonist had higher incidence of pericardial edema and death. Significantly reduced endocrine pancreas area was observed in both PPARγ ligands and PPARα agonist exposed embryos, some of which also exhibited aberrant endocrine pancreas morphology. Both PPARß/δ ligands caused reduced exocrine pancreas length and novel aberrant phenotype, and disrupted gene expression of pancreatic targets pdx1, gcga, and try. Lipid staining was performed at 8 dpf and revealed altered lipid accumulation consistent with isoform function. These data indicate chronic exposure to synthetic ligands may induce morphological and pancreatic defects in zebrafish embryos.

L-Carnitine ameliorates congenital myopathy in a tropomyosin 3 de novo mutation transgenic zebrafish.

BACKGROUND: Congenital myopathy (CM) is a group of clinically and genetically heterogeneous muscle disorders, characterized by muscle weakness and hypotonia from birth. Currently, no definite treatment exists for CM. A de novo mutation in Tropomyosin 3-TPM3(E151G) was identified from a boy diagnosed with CM, previously TPM3(E151A) was reported to cause CM. However, the role of TPM3(E151G) in CM is unknown. METHODS: Histopathological, swimming behavior, and muscle endurance were monitored in TPM3 wild-type and mutant transgenic fish, modelling CM. Gene expression profiling of muscle of the transgenic fish were studied through RNAseq, and mitochondria respiration was investigated. RESULTS: While TPM3(WT) and TPM3(E151A) fish show normal appearance, amazingly a few TPM3(E151G) fish display either no tail, a crooked body in both F0 and F1 adults. Using histochemical staining for the muscle biopsy, we found TPM3(E151G) displays congenital fiber type disproportion and TPM3(E151A) resembles nemaline myopathy. TPM3(E151G) transgenic fish dramatically swimming slower than those in TPM3(WT) and TPM3(E151A) fish measured by DanioVision and T-maze, and exhibit weaker muscle endurance by swimming tunnel instrument. Interestingly, L-carnitine treatment on TPM3(E151G) transgenic larvae significantly improves the muscle endurance by restoring the basal respiration and ATP levels in mitochondria. With RNAseq transcriptomic analysis of the expression profiling from the muscle specimens, it surprisingly discloses large downregulation of genes involved in pathways of sodium, potassium, and calcium channels, which can be rescued by L-carnitine treatment, fatty acid metabolism was differentially dysregulated in TPM3(E151G) fish and rescued by L-carnitine treatment. CONCLUSIONS: These results demonstrate that TPM3(E151G) and TPM3(E151A) exhibit different pathogenicity, also have distinct gene regulatory profiles but the ion channels were downregulated in both mutants, and provides a potential mechanism of action of TPM3 pathophysiology. Our results shed a new light in the future development of potential treatment for TPM3-related CM.

Biallelic mutations in nucleoporin NUP88 cause lethal fetal akinesia deformation sequence.

Nucleoporins build the nuclear pore complex (NPC), which, as sole gate for nuclear-cytoplasmic exchange, is of outmost importance for normal cell function. Defects in the process of nucleocytoplasmic transport or in its machinery have been frequently described in human diseases, such as cancer and neurodegenerative disorders, but only in a few cases of developmental disorders. Here we report biallelic mutations in the nucleoporin NUP88 as a novel cause of lethal fetal akinesia deformation sequence (FADS) in two families. FADS comprises a spectrum of clinically and genetically heterogeneous disorders with congenital malformations related to impaired fetal movement. We show that genetic disruption of nup88 in zebrafish results in pleiotropic developmental defects reminiscent of those seen in affected human fetuses, including locomotor defects as well as defects at neuromuscular junctions. Phenotypic alterations become visible at distinct developmental stages, both in affected human fetuses and in zebrafish, whereas early stages of development are apparently normal. The zebrafish phenotypes caused by nup88 deficiency are rescued by expressing wild-type Nup88 but not the disease-linked mutant forms of Nup88. Furthermore, using human and mouse cell lines as well as immunohistochemistry on fetal muscle tissue, we demonstrate that NUP88 depletion affects rapsyn, a key regulator of the muscle nicotinic acetylcholine receptor at the neuromuscular junction. Together, our studies provide the first characterization of NUP88 in vertebrate development, expand our understanding of the molecular events causing FADS, and suggest that variants in NUP88 should be investigated in cases of FADS.

Radioprotective Effects of Kelulut Honey in Zebrafish Model.

Large doses of ionizing radiation can damage human tissues. Therefore, there is a need to investigate the radiation effects as well as identify effective and non-toxic radioprotectors. This study evaluated the radioprotective effects of Kelulut honey (KH) from stingless bee (Trigona sp.) on zebrafish (Danio rerio) embryos. Viable zebrafish embryos at 24 hpf were dechorionated and divided into four groups, namely untreated and non-irradiated, untreated and irradiated, KH pre-treatment and amifostine pre-treatment. The embryos were first treated with KH (8 mg/mL) or amifostine (4 mM) before irradiation at doses of 11 Gy to 20 Gy using gamma ray source, caesium-137 (137Cs). Lethality and abnormality analysis were performed on all of the embryos in the study. Immunohistochemistry assay was also performed using selected proteins, namely γ-H2AX and caspase-3, to investigate DNA damages and incidences of apoptosis. KH was found to reduce coagulation effects at up to 20 Gy in the lethality analysis. The embryos developed combinations of abnormality, namely microphthalmia (M), body curvature and microphthalmia (BM), body curvature with microphthalmia and microcephaly (BMC), microphthalmia and pericardial oedema (MO), pericardial oedema (O), microphthalmia with microcephaly and pericardial oedema (MCO) and all of the abnormalities (AA). There were more abnormalities developed from 24 to 72 h (h) post-irradiation in all groups. At 96 h post-irradiation, KH was identified to reduce body curvature effect in the irradiated embryos (up to 16 Gy). γ-H2AX and caspase-3 intensities in the embryos pre-treated with KH were also found to be lower than the untreated group at gamma irradiation doses of 11 Gy to 20 Gy and 11 Gy to 19 Gy, respectively. KH was proven to increase the survival rate of zebrafish embryos and exhibited protection against organ-specific abnormality. KH was also found to possess cellular protective mechanism by reducing DNA damage and apoptosis proteins expression.

Involvement of the centrosomal protein 55 (cep55) gene in zebrafish head formation.

Mammalian CEP55 (centrosomal protein 55 kDa) is a coiled-coil protein localized to the centrosome in interphase cells and is required for cytokinesis. A homozygous non-sense mutation in human CEP55 has been recently identified in perinatal lethal MARCH (multinucleated neurons, anhydramnios, renal dysplasia, cerebellar hypoplasia and hydranencephaly) syndrome. We have isolated zebrafish cep55 mutants defective in head morphology. The zebrafish cep55 gene was expressed in the head including the retina and the pectoral fin at 1 day post-fertilization (dpf), and extensive cell death was widely observed in the head and tail of the cep55 mutant. In the cep55 mutant, the anterior-posterior distance of the ventral pharyngeal arches was short, and retinal lamination was disorganized. Neural cells, such as islet1-positive cells and pax2-positive cells, and fli1b-positive vascular cells were reduced in the head of the cep55 mutant. Thus, we propose that the zebrafish cep55 mutant is a model organism for human MARCH syndrome.

Multifactorial Genetic and Environmental Hedgehog Pathway Disruption Sensitizes Embryos to Alcohol-Induced Craniofacial Defects.

BACKGROUND: Prenatal alcohol exposure (PAE) is perhaps the most common environmental cause of human birth defects. These exposures cause a range of structural and neurological defects, including facial dysmorphologies, collectively known as fetal alcohol spectrum disorders (FASD). While PAE causes FASD, phenotypic outcomes vary widely. It is thought that multifactorial genetic and environmental interactions modify the effects of PAE. However, little is known of the nature of these modifiers. Disruption of the Hedgehog (Hh) signaling pathway has been suggested as a modifier of ethanol teratogenicity. In addition to regulating the morphogenesis of craniofacial tissues commonly disrupted in FASD, a core member of the Hh pathway, Smoothened, is susceptible to modulation by structurally diverse chemicals. These include environmentally prevalent teratogens like piperonyl butoxide (PBO), a synergist found in thousands of pesticide formulations. METHODS: Here, we characterize multifactorial genetic and environmental interactions using a zebrafish model of craniofacial development. RESULTS: We show that loss of a single allele of shha sensitized embryos to both alcohol- and PBO-induced facial defects. Co-exposure of PBO and alcohol synergized to cause more frequent and severe defects. The effects of this co-exposure were even more profound in the genetically susceptible shha heterozygotes. CONCLUSIONS: Together, these findings shed light on the multifactorial basis of alcohol-induced craniofacial defects. In addition to further implicating genetic disruption of the Hh pathway in alcohol teratogenicity, our findings suggest that co-exposure to environmental chemicals that perturb Hh signaling may be important variables in FASD and related craniofacial disorders.

De Novo Mutations in SON Disrupt RNA Splicing of Genes Essential for Brain Development and Metabolism, Causing an Intellectual-Disability Syndrome.

The overall understanding of the molecular etiologies of intellectual disability (ID) and developmental delay (DD) is increasing as next-generation sequencing technologies identify genetic variants in individuals with such disorders. However, detailed analyses conclusively confirming these variants, as well as the underlying molecular mechanisms explaining the diseases, are often lacking. Here, we report on an ID syndrome caused by de novo heterozygous loss-of-function (LoF) mutations in SON. The syndrome is characterized by ID and/or DD, malformations of the cerebral cortex, epilepsy, vision problems, musculoskeletal abnormalities, and congenital malformations. Knockdown of son in zebrafish resulted in severe malformation of the spine, brain, and eyes. Importantly, analyses of RNA from affected individuals revealed that genes critical for neuronal migration and cortex organization (TUBG1, FLNA, PNKP, WDR62, PSMD3, and HDAC6) and metabolism (PCK2, PFKL, IDH2, ACY1, and ADA) are significantly downregulated because of the accumulation of mis-spliced transcripts resulting from erroneous SON-mediated RNA splicing. Our data highlight SON as a master regulator governing neurodevelopment and demonstrate the importance of SON-mediated RNA splicing in human development.

Di-butyl phthalate (DBP) induces craniofacial defects during embryonic development in zebrafish.

Di-butyl phthalate (DBP) is commonly added to make plastics softer and more pliable and is found in a variety of consumer and industrial products. Alarmingly high levels of DBP have been detected in water and sediment as DBP leaches from products. These levels are concerning and have led the Environmental Protection Agency to label DBP as a priority environmental pollutant and the European Commission to label DBP as a priority substance. Given the ubiquitous presence of DBP globally and continuous exposure to DBP, studies on the developmental toxicity of DBP are needed. The endocrine disrupting effects of DBP are well documented, but developmental toxicity of DBP during critical developmental time windows is understudied. Here, we investigate the developmental effects of DBP exposure during early development. We find defects in craniofacial development including a decrease in overall cranial size in DBP treated embryos, but the intraocular distance was increased compared to controls. Further investigation of jawbone development demonstrated loss of and disorganization of cartilage development. Defects in vascular innervation and neuronal patterning were also noted. Here we conclude that exposure to DBP during crucial time windows of embryonic development is toxic to craniofacial development.

Zebrafish embryos exposed to deltamethrin exhibit abnormalities despite induced expression of related genes ( you, you-too, momo and u-boot).

Evaluation of the toxic effects of a widely used synthetic pyrethroid, deltamethrin (DM), was carried out in this study. This pesticide is preferred for pest control because of its low environmental persistence and toxicity. We investigated the expression pattern of four genes, namely, you ( you), yot ( you-too), momo ( mom) and ubo ( u-boot) during early development of zebrafish, that is, from 12 hpf to 48 hpf stages. These stages are selected as most of the important developmental aspects take place during this period. All four genes are known to play a vital role in development of notochord and somites. To understand the effect of DM on development, embryos of 4 hpf stage were exposed to two concentrations (100 and 200 µg/L) of DM, and observations were made at 12, 24 and 48 hpf stages. Our earlier studies have shown phenotypic abnormalities such as notochord bending, tail deformation, yolk sac and pericardial edema, lightening of body and eye pigmentation and interfered in somite patterning, during these stages of development. Understanding the relationship of phenotypic abnormalities with these four genes has been our primary objective. These four genes were analyzed by Reverse transcription (RT)-polymerase chain reaction and intensity of the bands has shown induction in their expression after exposure to the toxicant. In spite of the expression of genes, it was noticed that DM caused abnormalities. It can be said from the results that translational pathway could have been affected.

KCTD13 is a major driver of mirrored neuroanatomical phenotypes of the 16p11.2 copy number variant.

Copy number variants (CNVs) are major contributors to genetic disorders. We have dissected a region of the 16p11.2 chromosome--which encompasses 29 genes--that confers susceptibility to neurocognitive defects when deleted or duplicated. Overexpression of each human transcript in zebrafish embryos identified KCTD13 as the sole message capable of inducing the microcephaly phenotype associated with the 16p11.2 duplication, whereas suppression of the same locus yielded the macrocephalic phenotype associated with the 16p11.2 deletion, capturing the mirror phenotypes of humans. Analyses of zebrafish and mouse embryos suggest that microcephaly is caused by decreased proliferation of neuronal progenitors with concomitant increase in apoptosis in the developing brain, whereas macrocephaly arises by increased proliferation and no changes in apoptosis. A role for KCTD13 dosage changes is consistent with autism in both a recently reported family with a reduced 16p11.2 deletion and a subject reported here with a complex 16p11.2 rearrangement involving de novo structural alteration of KCTD13. Our data suggest that KCTD13 is a major driver for the neurodevelopmental phenotypes associated with the 16p11.2 CNV, reinforce the idea that one or a small number of transcripts within a CNV can underpin clinical phenotypes, and offer an efficient route to identifying dosage-sensitive loci.

Characterization of the effects of trace concentrations of graphene oxide on zebrafish larvae through proteomic and standard methods.

The effects of graphene oxide (GO) carbon nanomaterials on ecosystems have been well characterized, but the toxicity of GO at predicted environmental concentrations to living organisms at the protein level remain largely unknown. In the present work, the adverse effects and mechanisms of GO at predicted environmental concentrations were evaluated by integrating proteomics and standard analyses for the first time. The abundances of 243 proteins, including proteins involved in endocytosis (e.g., cltcb, arf6, capzb and dnm1a), oxidative stress (e.g., gpx4b, sod2, and prdx1), cytoskeleton assembly (e.g., krt8, krt94, lmna and vim), mitochondrial function (e.g., ndufa10, ndufa8, cox5aa, and cox6b1), Ca2+ handling (e.g., atp1b2a, atp1b1a, atp6v0a1b and ncx4a) and cardiac function (e.g., tpm4a, tpm2, tnni2a.1 and tnnt3b), were found to be notably altered in response to exposure 100 µg/L GO. The results revealed that GO caused malformation and mortality, likely through the downregulation of proteins related to actin filaments and formation of the cytoskeleton, and induced oxidative stress and mitochondrial disorders by altering the levels of antioxidant enzymes and proteins associated with the mitochondrial membrane respiratory chain. Exposure to GO also increased the heart rate of zebrafish larvae and induced pericardial edema, likely by changing the expression of proteins related to Ca2+ balance and cardiac function. This study provides new proteomic-level insights into GO toxicity against aquatic organisms, which will greatly benefit our understanding of the bio-safety of GO and its toxicity at predicted environmental concentrations.

Silver nanoparticles affect lens rather than retina development in zebrafish embryos.

Silver nanoparticles (AgNPs) have been reported to inhibit specification and differentiation of erythroid cells, chromatophores, and myofibrils during zebrafish embryogenesis. However, the knowledge of biological effects of AgNPs on eye development, especially on lens development is scarce. In this study, embryos were exposed to or injected with 0.4 mg/L AgNPs, and the results indicate that no obvious morphological changes in eye formation were observed in the stressed embryos compared to the controls. However, clefts and vacuoles were observed in lens of embryos from AgNPs stressed group. Additionally, the down-regulated expressions of different lens crystallin isoform genes and the normal expression of retinal genes were observed in AgNPs stressed embryos, suggesting AgNPs might inhibit the development of lens rather than the development of retina in zebrafish embryos. Moreover, no obvious cell apoptosis was observed, but normal nuclear DNA and RNA export was observed in lens cells. Together, the data in this study reveal that AgNPs damage the development of lens rather than retina resulting in eye abnormalities via some unknown mechanisms rather than via triggering cells apoptosis or blocking nuclear DNA or RNA export.

Zebrafish sin3b mutants are viable but have size, skeletal, and locomotor defects.

BACKGROUND: The transcriptional co-repressor Sin3 is highly conserved from yeast to vertebrates and has multiple roles controlling cell fate, cell cycle progression, and senescence programming. Sin3 proteins recruit histone deacetylases and other chromatin modifying factors to specific loci through interactions with transcription factors including Myc, Rest, p53 and E2F. Most vertebrates have two Sin3 family members (sin3a and sin3b), but zebrafish have a second sin3a paralogue. In mice, sin3a and sin3b are essential for embryonic development. Sin3b knockout mice show defects in growth as well as bone and blood differentiation. RESULTS: To study the requirement for Sin3b during development, we disrupted zebrafish sin3b using CRISPR-Cas9, and studied the effects on early development and locomotor behavior. CONCLUSIONS: Surprisingly, Sin3b is not essential in zebrafish. sin3b mutants show a decrease in fitness, small size, changes to locomotor behavior, and delayed bone development. We did not detect a role for Sin3b in cell proliferation. Our analysis of the sin3b mutant revealed a more nuanced requirement for zebrafish Sin3b than would be predicted from analysis of mutants in other species. Developmental Dynamics 246:946-955, 2017. © 2017 Wiley Periodicals, Inc.

Recurrent CNVs and SNVs at the NPHP1 locus contribute pathogenic alleles to Bardet-Biedl syndrome.

Homozygosity for a recurrent 290 kb deletion of NPHP1 is the most frequent cause of isolated nephronophthisis (NPHP) in humans. A deletion of the same genomic interval has also been detected in individuals with Joubert syndrome (JBTS), and in the mouse, Nphp1 interacts genetically with Ahi1, a known JBTS locus. Given these observations, we investigated the contribution of NPHP1 in Bardet-Biedl syndrome (BBS), a ciliopathy of intermediate severity. By using a combination of array-comparative genomic hybridization, TaqMan copy number assays, and sequencing, we studied 200 families affected by BBS. We report a homozygous NPHP1 deletion CNV in a family with classical BBS that is transmitted with autosomal-recessive inheritance. Further, we identified heterozygous NPHP1 deletions in two more unrelated persons with BBS who bear primary mutations at another BBS locus. In parallel, we identified five families harboring an SNV in NPHP1 resulting in a conserved missense change, c.14G>T (p.Arg5Leu), that is enriched in our Hispanic pedigrees; in each case, affected individuals carried additional bona fide pathogenic alleles in another BBS gene. In vivo functional modeling in zebrafish embryos demonstrated that c.14G>T is a loss-of-function variant, and suppression of nphp1 in concert with each of the primary BBS loci found in our NPHP1-positive pedigrees exacerbated the severity of the phenotype. These results suggest that NPHP1 mutations are probably rare primary causes of BBS that contribute to the mutational burden of the disorder.

A noncoding expansion in EIF4A3 causes Richieri-Costa-Pereira syndrome, a craniofacial disorder associated with limb defects.

Richieri-Costa-Pereira syndrome is an autosomal-recessive acrofacial dysostosis characterized by mandibular median cleft associated with other craniofacial anomalies and severe limb defects. Learning and language disabilities are also prevalent. We mapped the mutated gene to a 122 kb region at 17q25.3 through identity-by-descent analysis in 17 genealogies. Sequencing strategies identified an expansion of a region with several repeats of 18- or 20-nucleotide motifs in the 5' untranslated region (5' UTR) of EIF4A3, which contained from 14 to 16 repeats in the affected individuals and from 3 to 12 repeats in 520 healthy individuals. A missense substitution of a highly conserved residue likely to affect the interaction of eIF4AIII with the UPF3B subunit of the exon junction complex in trans with an expanded allele was found in an unrelated individual with an atypical presentation, thus expanding mutational mechanisms and phenotypic diversity of RCPS. EIF4A3 transcript abundance was reduced in both white blood cells and mesenchymal cells of RCPS-affected individuals as compared to controls. Notably, targeting the orthologous eif4a3 in zebrafish led to underdevelopment of several craniofacial cartilage and bone structures, in agreement with the craniofacial alterations seen in RCPS. Our data thus suggest that RCPS is caused by mutations in EIF4A3 and show that EIF4A3, a gene involved in RNA metabolism, plays a role in mandible, laryngeal, and limb morphogenesis.

Nanotoxicological and teratogenic effects: A linkage between dendrimer surface charge and zebrafish developmental stages.

This article reports novel results about nanotoxicological and teratogenic effects of the PAMAM dendrimers DG4 and DG4.5 in zebrafish (Danio rerio). Zebrafish embryos and larvae were used as a rapid, high-throughput, cost-effective whole-animal model. The objective was to provide a more comprehensive and predictive developmental toxicity screening of DG4 and DG4.5 and test the influence of their surface charge. Nanotoxicological and teratogenic effects were assessed at developmental, morphological, cardiac, neurological and hepatic level. The effect of surface charge was determined in both larvae and embryos. DG4 with positive surface charge was more toxic than DG4.5 with negative surface charge. DG4 and DG4.5 induced teratogenic effects in larvae, whereas DG4 also induced lethal effects in both zebrafish embryos and larvae. However, larvae were less sensitive than embryos to the lethal effects of DG4. The platform of assays proposed and data obtained may contribute to the characterization of hazards and differential effects of these nanoparticles.

Developmental toxicity and induction of vitellogenin in embryo-larval stages of zebrafish (Danio rerio) exposed to methyl Paraben.

MethylParaben (MP), a methyl ester of p-hydroxybenzoic acid, is used as an anti-microbial preservative in foods, drugs and cosmetics for decades. It enters the aquatic environment, and can have toxic effects on aquatic organisms. Little is known on the developmental toxicity of MP exposure to zebrafish during early life stages. In this study, the developmental effects of MP were evaluated in embryo-larval zebrafish (at concentrations ranging from 100µM, 200µM, 400µM, 800µM and 1000µM for 96h post fertilization (hpf). The survival, hatching, heart beat rate and developmental abnormalities were observed in the embryos exposed to MP. MP exposure resulted in decreased heart rate and hatching rate. Defects including pericardial edema blood cell accumulation and bent spine were observed in all the treated concentration, except at 100µM. With increasing concentrations, the frequency of these defects increased. The 96 hpf LC50 of MP was calculated to be 428µM (0.065mg/L). Furthermore, RT-PCR result showed that in larval zebrafish exposed to 100µM (0.015mg/L) of MP till 96 hpf, expression of vitellogenin I (Vtg -I) was significantly upregulated compared to the control group. This data suggest that even though lower concentrations of MP do not cause phenotypic malformations, it leads to dysregulated expression of estrogenic biomarker gene Vtg-I.

Pdgfra protects against ethanol-induced craniofacial defects in a zebrafish model of FASD.

Human birth defects are highly variable and this phenotypic variability can be influenced by both the environment and genetics. However, the synergistic interactions between these two variables are not well understood. Fetal alcohol spectrum disorders (FASD) is the umbrella term used to describe the wide range of deleterious outcomes following prenatal alcohol exposure. Although FASD are caused by prenatal ethanol exposure, FASD are thought to be genetically modulated, although the genes regulating sensitivity to ethanol teratogenesis are largely unknown. To identify potential ethanol-sensitive genes, we tested five known craniofacial mutants for ethanol sensitivity: cyp26b1, gata3, pdgfra, smad5 and smoothened. We found that only platelet-derived growth factor receptor alpha (pdgfra) interacted with ethanol during zebrafish craniofacial development. Analysis of the PDGF family in a human FASD genome-wide dataset links PDGFRA to craniofacial phenotypes in FASD, prompting a mechanistic understanding of this interaction. In zebrafish, untreated pdgfra mutants have cleft palate due to defective neural crest cell migration, whereas pdgfra heterozygotes develop normally. Ethanol-exposed pdgfra mutants have profound craniofacial defects that include the loss of the palatal skeleton and hypoplasia of the pharyngeal skeleton. Furthermore, ethanol treatment revealed latent haploinsufficiency, causing palatal defects in ∼62% of pdgfra heterozygotes. Neural crest apoptosis partially underlies these ethanol-induced defects in pdgfra mutants, demonstrating a protective role for Pdgfra. This protective role is mediated by the PI3K/mTOR pathway. Collectively, our results suggest a model where combined genetic and environmental inhibition of PI3K/mTOR signaling leads to variability within FASD.

High-throughput characterization of chemical-associated embryonic behavioral changes predicts teratogenic outcomes.

New strategies are needed to address the data gap between the bioactivity of chemicals in the environment versus existing hazard information. We address whether a high-throughput screening (HTS) system using a vertebrate organism (embryonic zebrafish) can characterize chemical-elicited behavioral responses at an early, 24 hours post-fertilization (hpf) stage that predict teratogenic consequences at a later developmental stage. The system was used to generate full concentration-response behavioral profiles at 24 hpf across 1060 ToxCast™ chemicals. Detailed, morphological evaluation of all individuals was performed as experimental follow-up at 5 days post-fertilization (dpf). Chemicals eliciting behavioral responses were also mapped against external HTS in vitro results to identify specific molecular targets and neurosignalling pathways. We found that, as an integrative measure of normal development, significant alterations in movement highlighted active chemicals representing several modes of action. These early behavioral responses were predictive for 17 specific developmental abnormalities and mortality measured at 5 dpf, often at lower (i.e., more potent) concentrations than those at which morphological effects were observed. Therefore, this system can provide rapid characterization of chemical-elicited behavioral responses at an early developmental stage that are predictive of observable adverse effects later in life.

Transcriptional and morphological effects of tamoxifen on the early development of zebrafish (Danio rerio).

Tamoxifen is a widely used anticancer drug with both an estrogen agonist and antagonist effect. This study focused on its endocrine disrupting effect, and overall environmental significance. Zebrafish embryos were exposed to different concentrations (0.5, 5, 50 and 500 µg l(-1) ) of tamoxifen for 96 h. The results showed a complex effect of tamoxifen on zebrafish embryo development. For the 500 µg l(-1) exposure group, the heart rate was decreased by 20% and mild defects in caudal fin and skin were observed. Expressions of a series of genes related to endocrine and morphological changes were subsequently tested through quantitative real-time polymerase chain reaction. Bisphenol A as a known estrogen was also tested as an endocrine-related comparison. Among the expression of endocrine-related genes, esr1, ar, cyp19a1b, hsd3b1 and ugt1a1 were all increased by tamoxifen exposure, similar to bisphenol A. The cyp19a1b is a key gene that controls estrogen synthesis. Exposure to 0.5, 5, 50 and 500 µg l(-1) of tamoxifen caused upregulation of cyp19a1b expression to 152%, 568%, 953% and 2024% compared to controls, higher than the effects from the same concentrations of bisphenol A treatment, yet vtg1 was suppressed by 24% from exposure to 500 µg l(-1) tamoxifen. The expression of metabolic-related genes such as cyp1a, cyp1c2, cyp3a65, gpx1a, gstp1, gsr and genes related to observed morphological changes such as krt17 were also found to be upregulated by high concentrations of tamoxifen. These findings indicated the potential environmental effect of tamoxifen on teleost early development. Copyright © 2015 John Wiley & Sons, Ltd.