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Results for “Zebrafish development”

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At least 451 records · Page 25Linked to original sources

PubMed2004

The deafness gene dfna5 is crucial for ugdh expression and HA production in the developing ear in zebrafish.

Over 30 genes responsible for human hereditary hearing loss have been identified during the last 10 years. The proteins encoded by these genes play roles in a diverse set of cellular functions ranging from transcriptional regulation to K(+) recycling. In a few cases, the genes are novel and do not give much insight into the cellular or molecular cause for the hearing loss. Among these poorly understood deafness genes is DFNA5. How the truncation of the encoded protein DFNA5 leads to an autosomal dominant form of hearing loss is not clear. In order to understand the biological role of Dfna5, we took a reversegenetic approach in zebrafish. Here we show that morpholino antisense nucleotide knock-down of dfna5 function in zebrafish leads to disorganization of the developing semicircular canals and reduction of pharyngeal cartilage. This phenotype closely resembles previously isolated zebrafish craniofacial mutants including the mutant jekyll. jekyll encodes Ugdh [uridine 5'-diphosphate (UDP)-glucose dehydrogenase], an enzyme that is crucial for production of the extracellular matrix component hyaluronic acid (HA). In dfna5 morphants, expression of ugdh is absent in the developing ear and pharyngeal arches, and HA levels are strongly reduced in the outgrowing protrusions of the developing semicircular canals. Previous studies suggest that HA is essential for differentiating cartilage and directed outgrowth of the epithelial protrusions in the developing ear. We hypothesize that the reduction of HA production leads to uncoordinated outgrowth of the canal columns and impaired facial cartilage differentiation.

Amino Acid Sequence↗

PubMed2005

Rbm19 is a nucleolar protein expressed in crypt/progenitor cells of the intestinal epithelium.

Intestinal development and homeostasis rely on the coordination of proliferation and differentiation of the epithelium. To better understand this process, we are studying Rbm19, a gene expressed in the gut epithelium that is essential for intestinal morphogenesis and differentiation in the zebrafish (Development 130, 3917). Here we analyzed the expression of Rbm19 in several biological contexts that feature proliferation/differentiation cell fate decisions. In the undifferentiated embryonic gut tube, Rbm19 is expressed throughout the epithelium, but then becomes localized to the crypts of Lieberkühn of the adult intestine. Consistent with its expression in adult crypt/progenitor cells, expression is widespread in human colorectal carcinomas and dividing Caco-2 cells. Its expression in Caco-2 cells recapitulates the in vivo pattern, declining when the cells undergo confluence-induced arrest and differentiation. Rbm19 protein localizes to the nucleolus during interphase and to the perichromosomal sheath during mitosis, in accordance with the pattern described for other nucleolar proteins implicated in ribosome biogenesis. Interestingly, the loss of nucleolar rbm19, nucleolin/C23, and nucleophosmin/B23 in confluent Caco-2 cells did not signify loss of nucleoli as detected by electron microscopy. Taken together, these data point to the nucleolus as a possible locus for regulating the proliferation/differentiation cell fate decision in the intestinal epithelium.

Animals↗

PubMed2004

Reiterated Wnt signaling during zebrafish neural crest development.

While Wnt/beta-catenin signaling is known to be involved in the development of neural crest cells in zebrafish, it is unclear which Wnts are involved, and when they are required. To address these issues we employed a zebrafish line that was transgenic for an inducible inhibitor of Wnt/beta-catenin signaling, and inhibited endogenous Wnt/beta-catenin signaling at discrete times in development. Using this approach, we defined a critical period for Wnt signaling in the initial induction of neural crest, which is distinct from the later period of development when pigment cells are specified from neural crest. Blocking Wnt signaling during this early period interfered with neural crest formation without blocking development of dorsal spinal neurons. Transplantation experiments suggest that neural crest precursors must directly transduce a Wnt signal. With regard to identifying which endogenous Wnt is responsible for this initial critical period, we established that wnt8 is expressed in the appropriate time and place to participate in this process. Supporting a role for Wnt8, blocking its function with antisense morpholino oligonucleotides eliminates initial expression of neural crest markers. Taken together, these results demonstrate that Wnt signals are critical for the initial induction of zebrafish neural crest and suggest that this signaling pathway plays reiterated roles in its development.

Animals↗

PubMed1997

The development of the posterior body in zebrafish.

In order to understand the developmental mechanisms of posterior body formation in the zebrafish, a fate map of the zebrafish tailbud was generated along with a detailed analysis of tailbud cell movements. The fate map of the zebrafish tailbud shows that it contains tissue-restricted domains and is not a homogeneous blastema. Furthermore, time-lapse analysis shows that some cell movements and behaviors in the tailbud are similar to those seen during gastrulation, while others are unique to the posterior body. The extension of axial mesoderm and the continuation of ingression throughout zebrafish tail development suggests the continuation of processes initiated during gastrulation. Unique properties of zebrafish posterior body development include the bilateral distribution of tailbud cell progeny and the exhibition of different forms of ingression within specific tailbud domains. The ingression of cells in the anterior tailbud only gives rise to paraxial mesoderm, at the exclusion of axial mesoderm. Cells of the posterior tailbud undergo subduction, a novel form of ingression resulting in the restriction of this tailbud domain to paraxial mesodermal fates. The intermixing of spinal cord and muscle precursor cells, as well as evidence for pluripotent cells within the tailbud, suggest that complex inductive mechanisms accompany these cell movements throughout tail elongation. Rates of cell proliferation in the tailbud were examined and found to be relatively low at the tip of the tail indicating that tail elongation is not due to growth at its posterior end. However, higher rates of cell proliferation in the dorsomedial region of the tail may contribute to the preferential posterior movement of cells in this tailbud region and to the general extension of the tail. Understanding the cellular movements, cell fates and gene expression patterns in the tailbud will help to determine the nature of this important aspect of vertebrate development.

Animals↗

PubMed1998

Isolation and functional analysis of the histone H3 promoter from atlantic salmon (Salmo salar L.).

The histone H3 (sH3) promoter of Atlantic salmon (Salmo salar) was cloned via polymerase chain reaction using primers designed from the rainbow trout (Oncorhynchus mykiss) promoter sequence. A comparison of the nucleotide sequence with the equivalent sequences from rainbow trout and sockeye salmon (Oncorhynchus nerka) revealed a high degree of conservation. In vivo expression analysis of the sH3 promoter was carried out in both rainbow trout and zebrafish (Danio rerio) embryos. A direct comparison of the sH3 promoter with the viral RSV promoter in rainbow trout resulted in stronger expression of the sH3 promoter. Furthermore, lacZ expression directed by the sH3 promoter was ubiquitous in several different cell types in developing zebrafish embryos. These results suggest that the sH3 promoter will be useful in transgenic studies in Atlantic salmon.

Animals↗

PubMed2025

Toxicological Assessment of Melamine-Functionalized Graphene Oxide and Carbon Nanotubes Using Zebrafish Models.

Graphene oxide (GO) and carbon nanotube (CNT)-based nanomaterials have attracted significant interest in various industrial and biomedical applications due to their unique physicochemical properties; however, concerns about their potential toxicity, especially when modified with additives like melamine (M), remain largely unresolved. This study investigates the toxicological effects and underlying mechanisms of graphene oxide-melamine (GO-M) and carbon nanotube-melamine (CNT-M) nanoparticles in zebrafish (Danio rerio) embryos and larvae. To this end, developmental toxicity, phenotypic and behavioral changes, as well as histopathological and immunofluorescence alterations, were evaluated following acute exposure to GO-M and CNT-M nanoparticles at concentrations of 5, 10, and 20 mg/L. Results showed that both nanoparticles delayed larval hatching, particularly at higher concentrations (10 and 20 mg/L). Malformations were observed at 20 mg/L in the GO-M group and at 10 and 20 mg/L in the CNT-M group. Additionally, significant changes in larval length and eye area were observed at all concentrations for both nanoparticles. Behavioral assessments revealed that CNT-M exposure at 10 and 20 mg/L significantly impaired head sensorimotor reflexes, while all concentrations affected tail reflexes. In contrast, GO-M exposure did not significantly alter sensorimotor responses. These findings suggest differential toxic mechanisms and neurobehavioral effects of GO-M and CNT-M nanoparticles during early zebrafish development.

Animals↗

PubMed2000

Too much interference: injection of double-stranded RNA has nonspecific effects in the zebrafish embryo.

We have investigated the ability of double-stranded RNA (dsRNA) to inhibit gene expression in a vertebrate, the zebrafish, Danio rerio. Injection of dsRNA corresponding to the T-box gene tbx16/spadetail (spt) into early wild-type embryos caused a rapid and dramatic loss of tbx16/spt mRNA in the blastula. mRNAs from the papc, tbx6, and gata1 genes, which depend on tbx16/spt function for their expression, were reduced, apparently mimicking the spt mutant phenotype. However, mRNAs from a number of genes that are unaffected by the spt mutation, such as beta catenin, stat3, and no tail, were also lost, indicating that the "interference" effect of tbx16/spt dsRNA was not restricted to the endogenous tbx16/spt mRNA. We compared the effects of injecting dsRNA from the zebrafish tbx16/spadetail, nieuwkoid/bozozok, and Brachyury/no tail genes with dsRNA from the bacterial lacZ gene. In each case the embryos displayed a variable syndrome of abnormalities at 12 and 24 h postfertilization. In blind studies, we could not distinguish between the effects of the various dsRNAs. Consistent with a common effect of dsRNA, regardless of sequence, injection of dsRNA from the lacZ gene was likewise effective in strongly reducing tbx16/spt and beta catenin mRNA in the blastula. These findings indicate that, despite published reports, the current methodology of double-stranded RNA interference is not a practical technique for investigating zygotic gene function during early zebrafish development.

Animals↗

PubMed2001

Expression of receptor protein-tyrosine phosphatase alpha, sigma and LAR during development of the zebrafish embryo.

Receptor protein-tyrosine phosphatases (RPTPs) are key players in Drosophila development. To study the role of RPTPs in vertebrate development, we have cloned zebrafish (zf) RPTPs, including RPTP alpha (RPTPalpha), RPTP sigma (RPTPsigma) and LAR. These three RPTPs are broadly transcribed in early development. At 24h post fertilisation (hpf), all three genes are expressed in the nervous system in partially overlapping patterns. At 3 days post fertilisation zf-RPTPalpha and zf-LAR show similar expression patterns in the central nervous system (CNS), the pharyngeal arches, the pectoral fins and the spinal cord. Interestingly, zf-LAR is uniquely expressed in the neuromast cells, whereas zf-RPTPsigma expression is confined to the central nervous system.

Animals↗

PubMed2006

Zebrafish G protein gamma2 is required for VEGF signaling during angiogenesis.

Vascular endothelial growth factor (VEGF) is a major mediator of pathologic angiogenesis, a process necessary for the formation of new blood vessels to support tumor growth. Historically, VEGF has been thought to signal via receptor tyrosine kinases, which are not typically considered to be G protein dependent. Here, we show that targeted knockdown of the G protein gng2 gene (Ggamma2) blocks the normal angiogenic process in developing zebrafish embryos. Moreover, loss of gng2 function inhibits the ability of VEGF to promote the angiogenic sprouting of blood vessels by attenuating VEGF induced phosphorylation of phospholipase C-gamma1 (PLCgamma1) and serine/threonine kinase (AKT). Collectively, these results demonstrate a novel interaction between Ggamma2- and VEGF-dependent pathways to regulate the angiogenic process in a whole-animal model. Blocking VEGF function using a humanized anti-VEGF antibody has emerged as a promising treatment for colorectal, non-small lung cell, and breast cancers. However, this treatment may cause considerable side effects. Our findings provide a new opportunity for cotargeting G protein- and VEGF-dependent pathways to synergistically block pathologic angiogenesis, which may lead to a safer and more efficacious therapeutic regimen to fight cancer.

Animals↗

PubMed2004

ARNT2 is not required for TCDD developmental toxicity in zebrafish.

ZfAHR2 has been identified as the receptor that is essential for mediating the developmental toxicity caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in zebrafish. One form of zfARNT2, zfARNT2b, forms a functional heterodimer with zfAHR2 that specifically recognizes XREs in gel shift experiments and induces XRE-driven transcription in COS-7 cells treated with TCDD. However, it has not been demonstrated that zfARNT2b acts as the physiological dimerization partner for zfAHR2 to mediate TCDD toxicity in developing zebrafish. An antisense morpholino targeted against zfARNT2 (zfarnt2-MO) along with a line of mutant zebrafish lacking expression of the zfarnt2 gene have been used to test the hypothesis that zfARNT2 mediates the developmental toxicity of TCDD. Injection of the zfarnt2-MO decreased expression of the zfARNT2 protein but did not provide any protection against the formation of pericardial edema at 72 hpf. In addition, in TCDD dose response studies the zfarnt2(-/-) embryos showed no protection against three endpoints of TCDD toxicity observed at 96 hpf: pericardial edema, reduced trunk blood flow, and shortened lower jaw. Finally, immunostaining results at 96 hpf demonstrate that the zfarnt2(-/-) embryos show a similar pattern of TCDD-induced zfCYP1A expression as WT embryos. These results demonstrate that zfARNT2 is not essential for mediating TCDD developmental toxicity in zebrafish and suggest that alternate dimerization partner(s) exist for zfAHR2 in vivo.

Abnormalities, Drug-Induced↗

PubMed2002

Removal of dystroglycan causes severe muscular dystrophy in zebrafish embryos.

Muscular dystrophy is frequently caused by disruption of the dystrophin-glycoprotein complex (DGC), which links muscle cells to the extracellular matrix. Dystroglycan, a central component of the DGC, serves as a laminin receptor via its extracellular alpha subunit, and interacts with dystrophin (and thus the actin cytoskeleton) through its integral membrane beta subunit. We have removed the function of dystroglycan in zebrafish embryos. In contrast to mouse, where dystroglycan mutations lead to peri-implantation lethality, dystroglycan is dispensable for basement membrane formation during early zebrafish development. At later stages, however, loss of dystroglycan leads to a disruption of the DGC, concurrent with loss of muscle integrity and necrosis. In addition, we find that loss of the DGC leads to loss of sarcomere and sarcoplasmic reticulum organisation. The DGC is required for long-term survival of muscle cells in zebrafish, but is dispensable for muscle formation. Dystroglycan or the DGC is also required for normal sarcomere and sarcoplasmic reticulum organisation. Because zebrafish embryos lacking dystroglycan share several characteristics with human muscular dystrophy, they should serve as a useful model for the disease. In addition, knowing the dystroglycan null phenotype in zebrafish will facilitate the isolation of other molecules involved in muscular dystrophy pathogenesis.

Animals↗

PubMed1999

A second CYP26 P450 in humans and zebrafish: CYP26B1.

A new P450 gene has been found in humans. It has 44% sequence identity to CYP26A1 from human and mouse, which places it in a new subfamily, CYP26B. There is only one human EST from a retinal library (AA012833) that matches the coding region. No homologous ESTs are found in mouse. A zebrafish EST AI721901 shows 68% identity to the human protein. This zebrafish EST is only 41% identical to the zebrafish CYP26A1 protein sequence, so it represents the homolog of the human CYP26B1 sequence. It is not known if this gene product will act on all-trans-retinoic acid like the CYP26A1 protein or if it might hydroxylate the 9-cis- or 13-cis-retinoic acid isoforms not recognized by CYP26A1. The importance of the CYP26A1 P450 in mouse and zebrafish development flags the CYP26B1 gene as a potential developmental gene.

Amino Acid Sequence↗

PubMed2002

Structure and spatio temporal expression of the full length DNA complementary to RNA coding for alpha2 type I collagen of zebrafish.

Twenty distinct genetic types of collagen have been identified up to now. Their structure and function are not completely elucidated. We have chosen zebrafish as a model to bring information about the role of collagen during embryogenesis. In the present study, we isolated four overlapping DNA complementary to RNA clones covering the 4879 nucleotides of a zebrafish messenger RNA (mRNA) encoding a fibrillar procollagen chain. The comparison of its primary structure with known other vertebrate collagens allowed to conclude that it encodes collagen pro-alpha2(I) chain. The 5' untranslated region showed a typical stem-loop structure with three ATG codons which is found in mammals types I and III collagen chains (but not in type II), which are expressed in the same tissues. This suggests that the supposed regulatory role of the stem loop structure could be tissue specific. The comparison of the Gly-Gly doublets found along the helical domain of several species allowed to speculate that the Gly-Gly repeats could be a poikilotherm feature. Expression of pro-alpha2(I) was examined during zebrafish development by reverse transcriptase-polymerase chain reaction and in situ hybridization on whole embryo and tissue section. Col1a2 was expressed as early as stage10 h post fertilization (hpf) and two peaks of expression were observed at 20 and 48 hpf. alpha2 mRNAs, whose presence suggests a collagen synthesis, were detected principally in the superficial cell layers surrounding 20-72 hpf embryos which are characterized by an acellular collagen stratum. At 26-30 days, fibroblasts invade the dermis and take over from the epithelial cells to synthesize collagen. This suggests a fine regulation of collagen synthesis in these cells that remains to be elucidated. alpha2 mRNA were also detected in other tissues such as the tail fin primordium and the notochord primordium suggesting a participation of type I collagen in a pathway for notochord and tail formation.

5' Untranslated Regions↗

PubMed2006

Identification and isolation of a BTB-POZ-containing gene expressed in oocytes and early embryos of the zebrafish Danio rerio.

In this report, we describe the cloning of a cDNA from the zebrafish Danio rerio encoding a protein containing a BTB-POZ domain closely resembling the BTBD1 and BTBD2 proteins previously identified in mammals. However, unlike other BTB-POZ-containing genes, expression of this gene in adults is most abundant in oocytes, where the RNA can be detected at all stages of oogenesis examined. The presence of the RNA persists through early cleavage, but is decreased significantly by gastrulation. Although the function of this gene has yet to be determined, its resemblance to the BTB-POZ family of genes coupled with its expression pattern suggests that it may have an important function in oogenesis and (or) early zebrafish development.

Amino Acid Sequence↗

PubMed2000

Studying vascular development in the zebrafish.

The zebrafish, a genetically accessible vertebrate with an externally developing, optically clear embryo, is ideally suited for in vivo functional dissection of the embryonic development of the circulatory system. Here, we review the advantages of the zebrafish as a model system for studying vascular development, and describe genetic and experimental tools, methods and resources that have been developed to exploit these advantages. We also discuss briefly how some of these tools and methods can be brought to bear on problems of relevance to human health.

Animals↗

PubMed2006

Pituitary-interrenal interaction in zebrafish interrenal organ development.

To further elucidate pituitary adrenal interactions during development, we studied the organogenesis of the interrenal organ, the teleost homolog of the mammalian adrenal gland, in zebrafish. To this end we compared wild-type zebrafish interrenal development with that of mutants lacking pituitary cell types including corticotrophs. In addition, we studied the effects of ACTH receptor (Mc2r) knockdown and dexamethasone (dex) on interrenal development and pituitary feedback. Until 2 d post fertilization (2 dpf) interrenal development assessed by transcripts of key steroidogenic genes (cyp11a1, mc2r, star) is independent of proopiomelanocortin (Pomc) as demonstrated in aal/eya1and lia/fgf3 mutants. However, at 5 dpf lack of pituitary cells leads to reduced expression of steroidogenic genes at both the transcriptional and the protein level. Pituitary control of interrenal development resides in corticotrophs, because pit1 mutants lacking pituitary cells except corticotrophs have a phenotype similar to that of wild-type controls. Furthermore, development in mc2r knockdown morphants does not differ from aal/eya1 and lia/fgf3 mutants. Inhibition of steroidogenesis by mc2r knockdown induces up-regulation of pomc expression in the anterior domain of pituitary corticotrophs. Accordingly, dex suppresses pomc in the anterior domain only, leading to impaired expression of steroidogenic genes commencing at 3 dpf and interrenal hypoplasia via reduced interrenal proliferation. In contrast, negative feedback on pituitary corticotrophs by dex is evident at 2 dpf and precedes effects of Pomc on the interrenal primordium. These data demonstrate a gradual transition from early pituitary-independent interrenal organogenesis to developmental control by the anterior domain of pituitary corticotrophs acting via Mc2 receptors.

Animals↗

PubMed1996

Inhibitory interactions controlling organizer activity in fish.

An experimental system allowing the observation of 2 active organizing centers during zebrafish development is described. It was achieved by injection into a single marginal cell at the 16-cell stage of TARAM-A-D mRNA. TARAM-A-D was previously described as the mutated constitutive form of a type I receptor for transforming growth factor beta. In 80% of the injected embryos, 2 distinct organizers were observed at the onset of gastrulation. At the end of gastrulation, these embryos showed duplicated axial structures. Nevertheless, only 25% of the injected embryos displayed a recognizable axis duplication after 1 day of development. This paradox is taken as an evidence for suppressive effects exerted in a reciprocal manner when more than 1 organizing center is present.

Animals↗

PubMed1997

Notochord alters the permissiveness of myotome for pathfinding by an identified motoneuron in embryonic zebrafish.

During zebrafish development, identified motoneurons innervate cell-specific regions of each trunk myotome. One motoneuron, CaP, extends an axon along the medial surface of the ventral myotome. To learn how this pathway is established during development, the CaP axon was used as an assay to ask whether other regions of the myotome were permissive for normal CaP pathfinding. Native myotomes were replaced with donor myotomes in normal or reversed dorsoventral orientations and CaP pathfinding was assayed. Ventral myotomes were permissive for CaP axons, even when they were taken from older embryos, suggesting that the CaP pathway remained present on ventral myotome throughout development. Dorsal myotomes from young embryos were also permissive for CaP axons, however, older dorsal myotomes were non-permissive, showing that permissiveness of dorsal myotome for normal CaP pathfinding diminished over time. This process appears to depend on signals from the embryo, since dorsal myotomes matured in vitro remained permissive for CaP axons. Genetic mosaics between wild-type and floating head mutant embryos revealed notochord involvement in dorsal myotome change of permissiveness. Dorsal and ventral myotomes from both younger and older floating head mutant embryos were permissive for CaP axons. These data suggest that initially both dorsal and ventral myotomes are permissive for CaP axons but as development proceeds, there is a notochord-dependent decrease in permissiveness of dorsal myotome for CaP axonal outgrowth. This change participates in restricting the CaP pathway to the ventral myotome and thus to neuromuscular specificity.

Animals↗