SEARCH · PubMed Health

Results for “Zebrafish development”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources

PubMed1998

Efficient mutagenesis of zebrafish by a DNA cross-linking agent.

We developed a novel procedure for efficient mutagenesis of zebrafish using a DNA cross-linking agent 4,5',8-trimethylpsoralen (TMP), which is known to frequently induce small deletions in Escherichia coli and Caenorhabditis elegans. A specific-locus test and pilot screenings indicated that the TMP mutagenesis procedure was efficient. To confirm the successful mutagenesis by TMP, we characterized mutants with selective impairments in the nervous system. The no tectal neuron mutation hindered the development of the tectal neurons, while the edawakare mutation resulted in the enhancement of the extension and branching of the peripheral axons of trigeminal ganglion and Rohon-Beard sensory neurons. These results suggest that the TMP mutagenesis will provide an efficient method to isolate and characterize zebrafish mutants at molecular level.

Animals↗

PubMed2000

Development of the hypochord and dorsal aorta in the zebrafish embryo (Danio rerio).

The hypochord of the zebrafish embryo (Danio rerio) emerges at the 9-somite stage as a single row of cells in the dorsomedial endoderm immediately ventral to the notochord. It is recognizable from the 2(nd) or 3(rd) somite and extends along the trunk to the same extent as the somites. A basal lamina surrounds the hypochord and its cells are slightly larger than the nearby endoderm cells. TEM studies have shown that the hypochord cells contain, in addition to mitochondria, well-developed rough endoplasmic reticula and Golgi networks, indicating synthetic activity. Once formed, the hypochord will stay in close association with the notochord, and this axial complex gradually moves dorsally, separating the hypochord from the endoderm as a one-cell-wide, rod-like structure that is bean-shaped in transverse section. This is the situation in the 15-somite embryo, at the level of the 4-5(th) somites. In the gap between the hypochord and the endoderm, angioblast cells aggregate and start to form the dorsal aorta, which becomes intimately associated with the hypochord. In the 17-somite embryo the aortic rudiment is established just ventral to the hypochord as a tube with a lumen. As development proceeds, the size of the hypochord decreases. In the pec fin embryo the hypochord is still recognizable in the posterior trunk, but has apparently vanished in anterior regions. The temporal correlation between the appearance of the hypochord and the formation of the dorsal aorta, coupled with the intimate relationship between these structures, suggest that the hypochord may play a role in the positioning of the dorsal aorta.

Animals↗

PubMed2005

Scl is required for dorsal aorta as well as blood formation in zebrafish embryos.

Blood and endothelial cells arise in close association in developing embryos, possibly from a shared precursor, the hemangioblast, or as hemogenic endothelium. The transcription factor, Scl/Tal1 (stem cell leukemia protein), is essential for hematopoiesis but thought to be required only for remodeling of endothelium in mouse embryos. By contrast, it has been implicated in hemangioblast formation in embryoid bodies. To resolve the role of scl in endothelial development, we knocked down its synthesis in zebrafish embryos where early precursors and later phenotypes can be more easily monitored. With respect to blood, the zebrafish morphants phenocopied the mouse knockout and positioned scl in the genetic hierarchy. Importantly, endothelial development was also clearly disrupted. Dorsal aorta formation was substantially compromised and gene expression in the posterior cardinal vein was abnormal. We conclude that scl is especially critical for the development of arteries where adult hematopoietic stem cells emerge, implicating scl in the formation of hemogenic endothelium.

Animals↗

PubMed2002

Applications of molecular genetics to the understanding of congenital ocular motility disorders.

The congenital fibrosis syndromes (CFS), including congenital fibrosis of the extraocular muscles (CFEOM) and Duane syndrome (DS), are rare congenital strabismus syndromes that present with nonprogressive restrictive ophthalmoplegia with or without ptosis. Although historically believed to result from primary extraocular muscle (EOM) fibrosis, our laboratory's work is based on the hypothesis that these disorders result from distinct, but analogous, developmental defects of the oculomotor (nIII), trochlear (nIV), and abducens (nVI) nuclei. We have defined three inherited CFEOM phenotypes (CFEOM1-3) and have mapped each phenotype to a distinct genetic locus (FEOM1-3). Individuals with CFEOM1 are born with bilateral ptosis and both eyes fixed in a downward position with absent upgaze and aberrant horizontal gaze. This disorder maps to the FEOM1 locus on chromosome 12cen.(1,2) Neuropathology studies of CFEOM1 reveal the absence of the superior division of oculomotor nerve and its corresponding alpha motor neurons in the midbrain, with abnormalities of target EOMs.(3) These neuropathology findings parallel those previously identified in Duane syndrome, in which there is an absence of nVI and the abducens nerve.(4,5) Individuals with CFEOM2 are born with bilateral ptosis and exotropia. This atypical form of CFEOM maps to the FEOM2 locus on chromosome 11q13 and results from mutations in ARIX (PHOX2A).(6,7) ARIX encodes a homeodomain transcription factor protein previously shown to be required for nIII/nIV development in mouse and zebrafish.(8,9) Together, these findings support the hypothesis that the congenital fibrosis syndromes result from parallel defects in nIII, nIV, and nVI nuclear development. Functional studies of the CFEOM genes should provide additional insight into the unique features of the extraocular lower motor neuron axis in health and disease. (For full (refs. 1-9), see reference list of the main paper.)

Chromosome Mapping↗

PubMed1988

Segmental pattern of development of the hindbrain and spinal cord of the zebrafish embryo.

In the ventral hindbrain and spinal cord of zebrafish embryos, the first neurones that can be identified appear as single cells or small clusters of cells, distributed periodically at intervals equal to the length of a somite. In the hindbrain, a series of neuromeres of corresponding length is present, and the earliest neurones are located in the centres of each neuromere. Young neurones within both the hindbrain and spinal cord were identified in live embryos using Nomarski optics, and histochemically by labelling for acetylcholinesterase activity and expression of an antigen recognized by the monoclonal antibody zn-1. Among them are individually identified hindbrain reticulospinal neurones and spinal motoneurones. These observations suggest that early development in these regions of the CNS reflects a common segmental pattern. Subsequently, as more neurones differentiate, the initially similar patterning of the cells in these two regions diverges. A continuous longitudinal column of developing neurones appears in the spinal cord, whereas an alternating series of large and small clusters of neurones is present in the hindbrain.

Acetylcholinesterase↗

PubMed2005

Histone deacetylase 1 is essential for oligodendrocyte specification in the zebrafish CNS.

Histone deacetylases are critical components of transcriptional silencing mechanisms that regulate embryonic development. Recent work has shown that histone deacetylase 1 (hdac1) is required for neuronal specification during zebrafish CNS development. We show here that specification of oligodendrocytes, the myelinating cells of the CNS, also fails to occur in the hdac1 mutant hindbrain, but persistence of neural progenitors in the hindbrain ventricular zone, which express pax6a and sox2, is independent of hdac1 activity. Commitment of ventral neural progenitors to the oligodendrocyte fate is thought to require co-ordinate, hedgehog-dependent expression of olig2 and nkx2.2a in these cells, leading to expression of sox10 and subsequent differentiation of oligodendrocytes. Remarkably, transcription of olig2 is extinguished in ventral neural progenitors of the hdac1 mutant hindbrain, whereas expression of nkx2.2a is up-regulated in these cells, and sox10 expression is suppressed. Our results identify hdac1 as a novel, essential component of the mechanism that allocates neural progenitors to the oligodendrocyte fate, by attenuating expression of a subset of neural progenitor genes and rendering olig2 expression responsive to Hedgehog signalling.

Animals↗

PubMed1998

beta-lactamase as a marker for gene expression in live zebrafish embryos.

In this report we describe the development of a sensitive assay for gene expression in zebrafish embryos using beta-lactamase as a reporter gene. We show that injection of a green fluorescent substrate for beta-lactamase allows the detection of reporter gene expression in live embryos. The beta-lactamase enzyme catalyzes the hydrolysis of the substrate, thereby disrupting fluorescence resonance energy transfer from the donor to the acceptor dye in the molecule. As a result, a blue fluorescent product is produced and retained specifically in cells within which the enzyme is expressed. beta-Lactamase is therefore suitable for monitoring spatially restricted patterns of gene expression in the early embryo. We suggest that this new reporter system provides a major advancement in sensitivity over the existing methods for monitoring gene expression in vivo during early embryogenesis.

Animals↗

PubMed2004

Mosaic eyes, genomic instability mutants, and cancer susceptibility.

We now know that genomic instability contributes to cancer. The zebrafish mosaic eye assay developed by George Streisinger takes advantage of the organism's transparency to provide an excellent assay for detecting somatic mutation. This assay allowed us to identify zebrafish mutants with increased frequencies of somatic mutation and spontaneous cancer. Here, we have described details of mutagenesis, the basis and practical use of the mosaic eye assay, and the histological methods used to study genomic instability mutants and cancer susceptibility. These techniques should prove useful to other zebrafish researchers, as they are broadly applicable to many other biological investigations of embryos, larvae, and adult zebrafish.

Animals↗

PubMed2003

Zebrafish atonal homologue zath3 is expressed during neurogenesis in embryonic development.

Basic helix-loop-helix (bHLH) transcriptional activators function in development of various cell lineages, including the central nervous system. One of the bHLH proteins, Math3/Xath3/NeuroM, was suggested to act as a late proneural gene in the mouse, Xenopus, and chick. Here, we isolated a zebrafish homologue, named zath3, and analyzed its expression pattern in zebrafish embryos. In the neural plate, zath3 is expressed first in the primordia of the tegmentum and trigeminal ganglia and three classes of primary neurons: sensory neurons, interneurons, and motor neurons. During later development, zath3 transcripts were localized along the boundaries of the optic tectum in the midbrain and rhombomeres of the hindbrain. Analyses of zath3 expression in three mid-hindbrain boundary mutants, acerebellar, no isthmus, and spiel-ohne-grensen, indicated that distribution of zath3 mRNAs in the midbrain and hindbrain was dramatically disturbed. In addition, these mutants also affect expression of zath3 in the neuroretina.

Amino Acid Sequence↗

PubMed2005

Xenopus aristaless-related homeobox (xARX) gene product functions as both a transcriptional activator and repressor in forebrain development.

Mutations in the aristaless-related homeobox (ARX) gene have been found in patients with a variety of X-linked mental retardation syndromes with forebrain abnormalities, including lissencephaly. Arx is expressed in the developing mouse, Xenopus, and zebrafish forebrain. We have used whole-mount in situ hybridization, overexpression, and loss-of-function studies to investigate the involvement of xArx in Xenopus brain development. We verified that xArx is expressed in the prospective diencephalon, as the forebrain is patterned and specified during neural plate stages. Expression spreads into the ventral and medial telencephalon as development proceeds through neural tube and tadpole stages. Overexpression of xArx resulted in morphological abnormalities in forebrain development, including loss of rostral midline structures, syn- or anophthalmia, dorsal displacement of the nasal organ, and ventral neural tube hyperplasia. Additionally, there is a delay in expression of many molecular markers of brain and retinal development. However, expression of some markers, dlx5 and wnt8b, was enhanced in xArx-injected embryos. Loss-of-function experiments indicated that xArx was necessary for normal forebrain development. Expansion of wnt8b expression depended on xArx function as a transcriptional repressor, whereas ectopic expression of dlx5, accompanied by development of ectopic otic structures, depended on function of Arx as a transcriptional activator. These results suggest that Arx acts as a bifunctional transcriptional regulator in brain development.

Animals↗

PubMed2002

Thyroid hormones are important for embryonic to larval transitory phase in zebrafish.

In zebrafish, like many other teleost species, the development and differentiation of many major organs continue unabated into the yolk-sac larval stage before culminating in a free-swimming larva capable of exogenous feeding. We investigated the role of thyroid hormone (TH) in this important embryonic to larval transitory phase. Thyroid hormone receptor (TR) alpha and beta mRNAs are expressed during the early stages of zebrafish embryonic development. Beginning from the midblastula stage, the level of TR beta mRNAs increases dramatically and is maintained until the end of the transitory phase. Excessive exogenous thyroxine (T4; 30 nM) is toxic and causes severe developmental defects. Cotreatment of embryos with amiodarone, an antagonist of TR, and goitrogen methimazole (MMI) lead to severe retardation in the maturation of the gastrointestinal system, swim bladder, and the lower jaw cartilages and the resorption of the yolk sac. The developmental arrest is lethal, and treated larvae do not survive beyond 7 day postfertilization (dpf), but can be completely rescued by the presence of 10 nM T4. We propose that the embryonic to larval transitory phase in many teleost species is characterized by its dependency on the timely synthesis of TH and the concomitant autoinductive increase in TR beta mRNA levels.

Air Sacs↗

PubMed2005

HSPG synthesis by zebrafish Ext2 and Extl3 is required for Fgf10 signalling during limb development.

Heparan sulphate proteoglycans (HSPGs) are known to be crucial for signalling by the secreted Wnt, Hedgehog, Bmp and Fgf proteins during invertebrate development. However, relatively little is known about their effect on developmental signalling in vertebrates. Here, we report the analysis of daedalus, a novel zebrafish pectoral fin mutant. Positional cloning identified fgf10 as the gene disrupted in daedalus. We find that fgf10 mutants strongly resemble zebrafish ext2 and extl3 mutants, which encode glycosyltransferases required for heparan sulphate biosynthesis. This suggests that HSPGs are crucial for Fgf10 signalling during limb development. Consistent with this proposal, we observe a strong genetic interaction between fgf10 and extl3 mutants. Furthermore, application of Fgf10 protein can rescue target gene activation in fgf10, but not in ext2 or extl3 mutants. By contrast, application of Fgf4 protein can activate target genes in both ext2 and extl3 mutants, indicating that ext2 and extl3 are differentially required for Fgf10, but not Fgf4, signalling during limb development. This reveals an unexpected specificity of HSPGs in regulating distinct vertebrate Fgfs.

Animals↗

PubMed2006

Cyclin-dependent kinase 5 influences Rohon-Beard neuron survival in zebrafish.

Cyclin-dependent kinase 5 (cdk5), a member of the cyclin-dependent kinase family, is expressed predominantly in post-mitotic cell populations. Unlike the other cdks, cdk5 is abundant and most active in differentiated neurons. Here, we describe the function of a cdk5 ortholog in zebrafish. Cdk5 catalytic activity is meager but present in early stages of development. However, at 24 h post-fertilization (hpf), the activity is remarkably higher and continues to be high through 48 and 72 hpf. Knocking down cdk5 by micro-injection of a specific siRNA resulted in decreased cdk5 protein level accompanied by reduced kinase activity. In the cdk5 siRNA-injected embryos, the number of primary sensory Rohon-Beard (RB) neurons was significantly reduced and there were more apoptotic cells in the brain. These phenotypes were rescued by co-injection of cdk5 mRNA. Within the first two days of development, RB neurons undergo apoptosis in zebrafish. To examine whether cdk5 has a role in RB neuron survival, cdk5 mRNA was injected into the one- to two-cell embryos. In these embryos, RB neuron apoptosis was inhibited compared with the uninjected control embryos. These results suggest that in zebrafish, cdk5 influences RB neuron survival and potentially regulates early neuronal development.

Animals↗

PubMed2006

The zebrafish orphan nuclear receptor genes nr2e1 and nr2e3 are expressed in developing eye and forebrain.

Mammalian Nr2e1 (Tailless, Mtll or Tlx) and Nr2e3 (photoreceptor-specific nuclear receptor, Pnr) are highly related orphan nuclear receptors, that are expressed in eye and forebrain-derived structures. In this study, we analyzed the developmental expression patterns of zebrafish nr2e1 and nr2e3. RT-PCR analysis showed that nr2e1 and nr2e3 are both expressed during embryonic and post-embryonic development. To examine the spatial distribution of nr2e1 and nr2e3 during development whole-mount in situ hybridization was performed. At tailbud stage, initial nr2e1 expression was localized to the rostral brain rudiment anterior to pax2.1 and eng2 expression at the prospective midbrain-hindbrain boundary. During subsequent stages, nr2e1 became widely expressed in fore- and midbrain primordia, eye and olfactory placodes. At 24hpf, strong nr2e1 expression was detected in telencephalon, hypothalamus, dorsal thalamus, pretectum, midbrain tectum, and retina. At 2dpf, the initially widespread nr2e1 expression became more restricted to distinct regions within the fore- and midbrain and to the retinal ciliary margin, the germinal zone which gives rise to retina and presumptive iris. Expression of nr2e3 was exclusively found in the developing retina and epiphysis. In both structures, nr2e3 expression was found in photoreceptor cells. The developmental expression profile of zebrafish nr2e1 and nr2e3 is consistent with evolutionary conserved functions in eye and rostral brain structures.

Amino Acid Sequence↗

PubMed2004

Zebrafish beta tubulin 1 expression is limited to the nervous system throughout development, and in the adult brain is restricted to a subset of proliferative regions.

Tubulin, the building block of microtubules, consists of an alpha and beta subunit, each in itself a family of several highly homologous isotypes. Abundance, tissue specificity, developmental regulation, and possibly function vary between isotypes. Six isotypes of beta tubulin (class I to class VI) have been cloned from several vertebrate species. Class I beta tubulin is believed to be widely expressed, but has not been studied by in situ hybridization in any vertebrate species so far. We have cloned a beta tubulin from zebrafish that appears most similar to other vertebrate class I tubulins and name it zbeta1 tubulin, accordingly. We report a distinct expression pattern of zbeta1 tubulin in the zebrafish embryo in restricted regions of the peripheral and central nervous system that comprise early-differentiating neurons. The expression pattern changes during development and in the adult zebrafish expression mostly is confined to a subset of proliferative zones that include the subependymal zone around the telencephalic ventricle, zones in the preoptic and hypothalamic area and in the olfactory epithelium. Thus, zbeta1 tubulin is expressed with remarkable selectivity during neuronal differentiation and neurogenesis in the embryonic and adult nervous system, respectively.

Animals↗

PubMed2006

SMC3 knockdown triggers genomic instability and p53-dependent apoptosis in human and zebrafish cells.

BACKGROUND: The structural maintenance of chromosome 3 (SMC3) protein is a constituent of a number of nuclear multimeric protein complexes that are involved in DNA recombination and repair in addition to chromosomal segregation. Overexpression of SMC3 activates a tumorigenic cascade through which mammalian cells acquire a transformed phenotype. This has led us to examine in depth how SMC3 level affects cell growth and genomic stability. In this paper the effect of SMC3 knockdown has been investigated. RESULTS: Mammalian cells that are SMC3 deficient fail to expand in a clonal population. In order to shed light on the underlying mechanism, experiments were conducted in zebrafish embryos in which cell competence to undergo apoptosis is acquired at specific stages of development and affects tissue morphogenesis. Zebrafish Smc3 is 95% identical to the human protein, is maternally contributed, and is expressed ubiquitously at all developmental stages. Antisense-mediated loss of Smc3 function leads to increased apoptosis in Smc3 expressing cells of the developing tail and notocord causing morphological malformations. The apoptosis and the ensuing phenotype can be suppressed by injection of a p53-specific MO that blocks the generation of endogenous p53 protein. Results in human cells constitutively lacking p53 or BAX, confirmed that a p53-dependent pathway mediates apoptosis in SMC3-deficient cells. A population of aneuploid cells accumulated in zebrafish embryos following Smc3-knockdown whereas in human cells the transient downregulation of SMC3 level lead to the generation of cells with amplified centrosome number. CONCLUSION: Smc3 is required for normal embryonic development. Its deficiency affects the morphogenesis of tissues with high mitotic index by triggering an apoptotic cascade involving p53 and the downstream p53 target gene bax. Cells with low SMC3 level display centrosome abnormalities that can lead to or are the consequence of dysfunctional mitosis and/or aneuploidy. Collectively the data support the view that SMC3 deficiency affects chromosomal stability leading to the activation of p53-dependent mitotic checkpoint.

Amino Acid Sequence↗

PubMed2002

Identification of a second presenilin gene in zebrafish with similarity to the human Alzheimer's disease gene presenilin2.

Presenilins play prominent roles in the molecular pathogenesis of Alzheimer's disease and during embryo development. We have isolated a zebrafish presenilin orthologue (pre2), which shows a high degree of sequence identity to the human PS2 protein. Zebrafish pre2 is maternally and ubiquitously expressed during early embryo development, whereas Pre2 protein expression is initiated between 6 and 12 hours post fertilisation (hpf), suggesting strict regulation of pre2 translation. pre2 expression is especially high in neural-crest-derived melanocytes.

Alzheimer Disease↗

PubMed1991

Stereotyped pathway selection by growth cones of early epiphysial neurons in the embryonic zebrafish.

In this report we have examined the development of one of the earliest projections in the embryonic zebrafish brain, that from the epiphysis. Epiphysial axons and growth cones were labelled anterogradely in whole-mounted brains, using either the carbocyanine dye, diI, or horseradish peroxidase (HRP). Some embryos were also either stained with anti-acetylated tubulin or HNK-1 antibodies to reveal other axons in the brain, or were secondarily sectioned for light and electron microscopy. The epiphysial axons have a very specific projection pattern and virtually all axons grow precisely to their target regions without error. The first epiphysial growth cone extends ventrally from the epiphysis into the dorsoventral diencephalic tract at 19-20 h post-fertilisation (h PF). Several hours later, it turns rostrally to grow alongside axons in the tract of the postoptic commissure. The morphology of the leading growth cone changes in predictable ways at different locations along its pathway and these changes correlate with differences in the local environment that it encounters. In contrast to other published descriptions of other developing systems, the epiphysial growth cone is no more complex either when pioneering a pathway, or when encountering divergent axonal pathways. Indeed, it is most complex (i.e. has the greatest number of processes) when it first starts to follow the tract of the postoptic commissure. The presence and selective retention of filopodia within other axonal pathways suggests that growth cones have access to these pathways but do not select them. These observations support the notion that local guidance cues exist within the early scaffold of brain tracts. Subsequent epiphysial axons form a tight fascicle within the dorsoventral diencephalic tract, but abruptly defasciculate from each other upon turning rostrally into the tract of the postoptic commissure. Epiphysial growth cones that enter this tract at abnormal locations still turn in the appropriate direction. Therefore, guidance cues are not restricted solely to the normal intersections but may be distributed along the length of the tracts. The epiphysial growth cones and axons have very characteristic spatial relations to other axons in the tracts of the developing brain. They are restricted to the dorsal region of the tract of the postoptic commissure and the rostral region of the postoptic commissure. At early developmental stages, the epiphysial axons are the only axons within the dorsoventral diencephalic tract and they are located very superficially within the neuroepithelium. At later stages, they are displaced to deeper regions of the neuropil by non-epiphysial axons.

Animals↗