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At least 253 records · Page 14Linked to original sources
PubMed1999

Tenascin-C expression in the trunk of wild-type, cyclops and floating head zebrafish embryos.

The function and the regulation of the expression of the extracellular matrix molecule tenascin-C during embryonic development are still unclear. In the present study, the expression of tenascin-C was analyzed in the trunk of zebrafish at the end of the first embryonic day. An antiserum raised against a zebrafish tenascin-C (TN-C) fusion protein reacted with 220 (doublet), 200, and 160 KD peptides. In situ hybridization showed that in the zebrafish wild-type embryo, tn-c mRNA was expressed by somites, neural crest cells, roof plate, notochord, hypochord, and tail fin bud. Thus, the expression of tn-c mRNA is an excellent marker for the differentiation of most zebrafish trunk structures. Immunolabelling with the anti-TN-C antibody was detected in the migratory pathway of neural crest cells and in the intersomitic furrows. In situ hybridization analysis of the zebrafish cyclops mutants, lacking the midline floor plate cells, showed normal expression of tn-c mRNA in all trunk structures. Analysis of the floating-head mutant, lacking the notochord, showed that tn-c mRNA expression in neural crest cells, roof plate, and tail fin bud is normal, but it is defective in the somites. By showing that the notochord, but not the floor plate, cells are required for normal tn-c expression in the trunk, this work provides new information on the role played by the embryonic axial structures in the regulation of the expression of tn-c during the development of zebrafish and allows new conclusions about somite patterning in the cyclops and floating-head zebrafish mutants.

Animals↗
PubMed1997

Expression of c-ret in the zebrafish embryo: potential roles in motoneuronal development.

We have isolated and characterized the zebrafish ortholog of c-ret, a gene essential for renal organogenesis and enteric nervous system development in mammals. During zebrafish embryogenesis c-ret transcripts are expressed in a number of tissues including spinal motoneurons, pronephric ducts, cranial ganglia, pharyngeal arches, and the enteric nervous system. We have examined in detail the expression of c-ret during the development of identified spinal primary motoneurons. c-ret expression is regulated in a cell type-specific manner among the three primary motoneurons. c-ret is expressed at its highest levels in caudal primary (CaP) motoneurons and transcripts can be detected shortly before the expression of the CaP-specific gene, islet2. We suggest that c-ret may play a role in specifying CaP cell identity. c-ret is expressed at low levels in the other primary motoneurons and also in a subset of secondary motoneurons, suggesting that it may also play a broader role in motoneuronal survival or maintenance.

Amino Acid Sequence↗
PubMed2001

Dopamine transporter expression distinguishes dopaminergic neurons from other catecholaminergic neurons in the developing zebrafish embryo.

To characterize the formation of the dopaminergic system in the developing zebrafish CNS, we cloned cDNAs encoding tyrosine hydroxylase (th), an enzyme in dopamine synthesis, and the dopamine transporter (dat), a membrane transport protein which terminates dopamine action by re-uptake. Dopaminergic neurons are first detected between 18 and 19 h post-fertilization in a cluster of cells in the ventral diencephalon. Subsequently, th and dat detection identifies dopaminergic neurons in the olfactory bulb, the pretectum, the retina and the locus coeruleus. Neurons expressing th but not dat are adrenergic or noradrenergic, and are found in the locus coeruleus, the medulla, the likely analog of the carotid body, and precursors of the enteric and sympathetic nervous system.

Amino Acid Sequence↗
PubMed1991

Determination of primary motoneuron identity in developing zebrafish embryos.

The developmental determination of primary motoneurons was investigated by transplanting identified motoneurons in embryonic zebrafish to new spinal cord positions. Some cells moved from the new positions in which they were placed back to their original positions, thus it was difficult to evaluate whether they were determined. Among cells that remained in their new positions, those transplanted about 1 hour before axogenesis developed axonal trajectories that were appropriate for their original soma positions, whereas those transplanted 2 to 3 hours before axogenesis developed morphologies appropriate for their new soma positions. These results suggest that motoneuronal identity is determined before axogenesis.

Animals↗
PubMed2004

Fgf signalling controls the dorsoventral patterning of the zebrafish embryo.

The establishment of dorsoventral (DV) patterning in vertebrate embryos depends on the morphogenic activity of a group of Tgfbeta superfamily members, the bone morphogenetic proteins (Bmps) (which specify ventral cell fates), and on their interaction with their dorsally secreted cognate inhibitors chordin and noggin. In the zebrafish, genetic analysis has revealed that Bmp2b and Bmp7, as well as their antagonist chordin, are required for proper DV patterning. The expression of Bmp genes is initially activated in the whole blastula. Well before the beginning of gastrulation, Bmp gene expression progressively disappears from the dorsal side to become restricted to the ventral part of the embryo. We show that this early restriction of Bmp gene expression, which occurs independently of noggin and chordin, is an essential step in the establishment of DV patterning. The progressive ventral restriction of Bmp gene transcripts is coincident with the spreading of Fgf activity from the dorsal side of the embryo, suggesting that Fgf signalling is implicated in dorsal downregulation of Bmp gene expression. In accordance with this, activation of the Fgf/Ras/Mapk-signalling pathway inhibits ventral Bmp gene expression, thereby causing a dorsalisation of the embryo. Conversely, inhibition of Fgf signalling causes Bmp gene expression to expand dorsally, leading to an expansion of ventral cell fates. In accordance with an important role of Fgf signalling in the DV patterning of the zebrafish, we show that loss of Fgf8 function enhances the ventralisation of chordin-deficient embryos. Our results thereby demonstrate that pre-gastrula stage Fgf-signalling is essential to delimit the expression domain of the genes encoding the functional morphogen of the dorsoventral axis of the early zebrafish embryo.

Animals↗
PubMed2006

Microinjecting recombinant rainbow trout Ea4-peptide of pro-IGF-I into zebrafish embryos causes abnormal development in heart, red blood cells, and vasculature.

E-peptides and mature insulin-like growth factors (IGFs) are produced from pre-pro-IGFs during post-translational processing and co-secreted into the circulation. Previously, we reported that introduction of a transgene encoding the secreted form of rainbow trout (rt) Ea4-peptide or human (h) Eb-peptide into newly fertilized eggs of medaka (Oryzias latipes) and zebrafish (Danio rerio) resulted in developmental defects in heart, red blood cells and vasculature. In addition to vasculature and red blood cell developmental defects, multiple phenocopies of heart developmental defects categorized by developmental arrest at cardiomyocyte, heart tube and heart looping stages were also observed. These results raise a question of whether rtEa4- or hEb-peptide exerts pleiotropic inhibitory effects on heart, vasculature and red blood cell development in fish embryos. To answer this question, various amounts of recombinant rtEa4-peptide were microinjected into zebrafish eggs at 1.5, 2.5 and 5.5 h post-fertilization (hpf). Although a dose-dependent developmental defect in heart, vasculature and red blood cells was observed in embryos microinjected with rtEa4-peptide at 1.5 and 2.5 hpf, the heart development in all of the microinjected embryos was arrested at the cardiomyocyte stage. Furthermore, the mRNA levels of Nkx2.5, GATA5, VEGF, GATA1 and GATA2 genes in defective embryos were significantly reduced by rtEa4-peptide. These results confirm our previous findings that rtEa4- or hEb-peptide exhibits pleiotropic effects in inhibiting heart, vasculature and red blood cell development in zebrafish embryos.

Animals↗
PubMed1996

Active complex formation of type I and type II activin and TGF beta receptors in vivo as studied by overexpression in zebrafish embryos.

We have investigated the involvement of activin receptors and TGF beta type I receptor in zebrafish development. Overexpression of either full-length or a truncated form of mouse ActR-IIA interferes with the development. Different splice variants of mouse ActR-IIB have distinct effects; ActR-IIB4 induces abnormal embryos, whereas ActR-IIB2 does not. Activin and TGF beta type I receptors can induce axis duplications. Co-expression of ActR-IA or ActR-IB with the type II activin receptors results in a synergistic increase of the frequency of axis duplication. Moreover, ActR-IIB2 is synergistic with ActR-IA and ActR-IB, demonstrating that ActR-IIB2 can interact with the zebrafish ligand. Overexpression of TGF beta R-I with ActR-IIA or ActR IIB4 results in a synergistic increase in frequency of abnormal embryos, whereas in combination with ActR-IIB2 no such increase occurs.

Activins↗
PubMed1999

Predictability of dorso-ventral asymmetry in the cleavage stage zebrafish embryo: an analysis using lithium sensitivity as a dorso-ventral marker.

The dorso-ventral axis in zebrafish first becomes apparent at gastrulation, when the future ventral side appears thinner than the dorsal side. The exact time of establishment of the dorso-ventral axis is not known. We show here that the dorso-ventral axis is specified as early as the 32 cell stage. Using lithium as a marker for dorso-ventral asymmetry, we show that lithium-sensitivity is a characteristic of future ventral cell, but not future dorsal cells, and that there is an asymmetric lithium-sensitivity along the long axis of the 32 cell stage embryo. Consequently, the dorso-ventral axis corresponds to the long axis of the embryo. Because the effect of lithium treatment is short-lived, the dorso-ventral axis must be specified in zebrafish already at the 32 cell stage.

Animals↗
PubMed1990

Expression of a homeobox gene product in normal and mutant zebrafish embryos: evolution of the tetrapod body plan.

An antibody was used to detect antigens in zebrafish that appear to be homologous to the frog homeodomain-containing protein XlHbox 1. These antigens show a restricted expression in the anteroposterior axis and an anteroposterior gradient in the pectoral fin bud, consistent with the distribution of XlHbox 1 protein in frog and mouse embryos. In the somitic mesoderm, a sharp anterior limit of expression coincides exactly with the boundary between somites 4 and 5, and the protein level fades out posteriorly. A similar, graded expression of the antigen is seen within the series of Rohon-Beard sensory neurons of the CNS. We also immunostained the mutant spt-1 ('spadetail'), in which the trunk mesoderm is greatly depleted and disorganized in the region of XlHbox 1 expression. The defects stem from misdirected cell movements during gastrulation, but nervertheless, newly recruited cells that partially refill the trunk mesoderm express the antigen within the normal span of the anteroposterior axis. This finding suggests that the mutation does not delete positional information required for activation of the XlHbox 1 gene.

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↗
PubMed2005

Efficient RNA interference in zebrafish embryos using siRNA synthesized with SP6 RNA polymerase.

Double-stranded RNA (dsRNA) has been shown to be a useful tool for silencing genes in zebrafish (Danio rerio), while the blocking specificity of dsRNA is still of major concern for application. It was reported that siRNA (small interfering RNA) prepared by endoribonuclease digestion (esiRNA) could efficiently silence endogenous gene expression in mammalian embryos. To test whether esiRNA could work in zebrafish, we utilized Escherichia coli RNaseIII to digest dsRNA of zebrafish no tail (ntl), a mesoderm determinant in zebrafish and found that esi-ntl could lead to developmental defects, however, the effective dose was so close to the toxic dose that esi-ntl often led to non-specific developmental defects. Consequently, we utilized SP6 RNA polymerase to produce si-ntl, siRNA designed against ntl, by in vitro transcription. By injecting in vitro synthesized si-ntl into zebrafish zygotes, we obtained specific phenocopies of reported mutants of ntl. We achieved up to a 59%no tail phenotype when the injection concentration was as high as 4 microg/microL. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization analysis showed that si-ntl could largely and specifically reduce mRNA levels of the ntl gene. As a result, our data indicate that esiRNA is unable to cause specific developmental defects in zebrafish, while siRNA should be an alternative for downregulation of specific gene expression in zebrafish in cases where RNAi techniques are applied to zebrafish reverse genetics.

Animals↗
PubMed2004

E-cadherin regulates cell movements and tissue formation in early zebrafish embryos.

E-cadherin is maternally expressed in most vertebrate species, but its function during early development of the vertebrate embryo proper is unknown. To directly examine E-cadherin gene (cdh1) function in zebrafish, morpholino oligonucleotides (MOs) that inhibit E-cadherin protein (Cdh1) expression were injected into embryos. Cdh1 knockdown reduced embryo survival. In early cdh1 MO-injected embryos, the cleavage plane orientation between blastomeres was irregular and adhesion defects prevented normal compaction. Cdh1 knockdown inhibited epiboly cell movements. Epiboly delay caused yolk cell lysis and produced embryos with a bifurcated embryonic axis. Cdh1 knockdown inhibited gastrulation cell movements, causing defects in convergence and extension. Additionally, prechordal plate derivatives were absent in Cdh1 knockdown embryos even though presumptive prechordal plate markers were induced normally. E-cadherin mRNA coinjection demonstrated the specificity of cdh1 MO-induced defects. Our experiments illustrate the importance of cdh1 in regulating morphogenetic cell movements and tissue formation in the early embryo.

Animals↗
PubMed2006

Scube2 mediates Hedgehog signalling in the zebrafish embryo.

The Hedgehog family of secreted morphogens specifies the fate of a large number of different cell types within invertebrate and vertebrate embryos, including the muscle cell precursors of the embryonic myotome of zebrafish. Formation of Hedgehog-sensitive muscle fates is disrupted within homozygous zebrafish mutants of the "you"-type class, the majority of which disrupt components of the Hedgehog (HH) signal transduction pathway. We have undertaken a phenotypic and molecular characterisation of one of these mutants, you, which we show results from mutations within the zebrafish orthologue of the mammalian gene scube2. This gene encodes a member of the Scube family of proteins, which is characterised by several protein motifs including EGF and CUB domains. Epistatic and molecular analyses position Scube2 function upstream of Smoothened (Smoh), the signalling component of the HH receptor complex, suggesting that Scube2 may act during HH signal transduction prior to, or during, receipt of the HH signal at the plasma membrane. In support of this model we show that scube2 has homology to cubilin, which encodes an endocytic receptor involved in protein trafficking suggesting a possible mode of function for Scube2 during HH signal transduction.

Animals↗
PubMed1994

Structure and distribution of N-cadherin in developing zebrafish embryos: morphogenetic effects of ectopic over-expression.

N-cadherin cDNA was cloned from a zebrafish embryonic cDNA library. Analysis of the deduced amino acid sequence of this molecule (ZN-cadherin) revealed a high degree of homology to N-cadherins of other species, except that its pre-sequence is considerably shorter. Nevertheless, following transfection into chinese hamster ovary (CHO) cells, the expressed protein was functionally active, namely participated in calcium-dependent intercellular interactions. Moreover, ectopic over-expression of ZN-cadherin, following mRNA microinjection into 2-4 cell embryos, caused microaggregation and uneven segregation of deep cells, resulting in distorted embryos. Developmental Northern and Western blot analyses indicated that both the mRNA and the protein first appear at gastrulation. In-situ hybridization showed that ZN-cadherin mRNA was initially present in all deep cells, and later became restricted to various epithelial and neural tissues. Whole-mount immunostaining indicated that while ZN-cadherin was already present at 50% epiboly, it became associated with cell junctions only 4-5 h later. In developing somites ZN-cadherin expression was prominent but transient. High levels of the protein were detected in epithelial somites and its expression was apparently down regulated concomitantly with the onset of myogenesis.

Amino Acid Sequence↗
PubMed2025

H3K4me2 marks the enhancer: Enhancer logic in the zebrafish embryo.

At a key point in development, the embryo activates its genome: a shift that is largely coordinated by maternally derived factors. A new study in PLOS Biology identifies H3K4me2-marked enhancers in zebrafish that function independently and mirror the gamete state.

Animals↗
PubMed1995

Fate maps of the zebrafish embryo.

In the past few years, we have seen a surge of interest in the zebrafish as a model system for the study of embryonic induction and patterning. This review summarizes our current knowledge of the organization of zebrafish fate maps during early development. Recent advances have addressed the relationship between early cleavage planes and the future dorsal axis, the pattern of cell mixing during blastula and gastrula stages, and the morphogenesis of the trunk neural keel. In addition, refined fate maps have become available for the embryonic shield, the central nervous system, and the heart. In combination with recent advances in molecular and genetic manipulations, these fate maps set the stage for new, more incisive, experimental approaches.

Animals↗
PubMed2001

Expression of the anti-dorsalizing morphogenetic protein gene in the zebrafish embryo.

The BMP3 related anti-dorsalizing morphogenetic protein (ADMP) has been proposed to function in the organizer of chick and Xenopus embryos. We report here the cloning and expression pattern of a zebrafish admp gene. The gene is expressed in involuting cells of the embryonic shield, but not in the non-involuting forerunner cells. During gastrulation, admp transcripts are detected in the posterior prechordal plate, in the notochord primordium and in cells of the dorsal blastoderm margin. Expression is also detectable in the neuroectoderm overlying the posterior prechordal plate. Expression persists in the tail bud until the end of somitogenesis while expression in other areas disappears during early somitogenesis stages.

Amino Acid Sequence↗