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C Nüsslein-Volhard

Publications and source records attributed to C Nüsslein-Volhard.

At least 55 records · Page 3Linked to original sources
PubMed1996

Jaw and branchial arch mutants in zebrafish II: anterior arches and cartilage differentiation.

In a large scale screen for mutants that affect the early development of the zebrafish, 109 mutants were found that cause defects in the formation of the jaw and the more posterior pharyngeal arches. Here we present the phenotypic description and results of the complementation analysis of mutants belonging to two major classes: (1) mutants with defects in the mandibular and hyoid arches and (2) mutants with defects in cartilage differentiation and growth in all arches. Mutations in four of the genes identified during the screen show specific defects in the first two arches and leave the more posterior pharyngeal arches largely unaffected (schmerle, sucker, hoover and sturgeon). In these mutants ventral components of the mandibular and hyoid arches are reduced (Meckel's cartilage and ceratohyal cartilage) whereas dorsal structures (palatoquadrate and hyosymplectic cartilages) are of normal size or enlarged. Thus, mutations in single genes cause defects in the formation of first and second arch structures but also differentially affect development of the dorsal and ventral structures within one arch. In 27 mutants that define at least 8 genes, the differentiation of cartilage and growth is affected. In hammerhead mutants particularly the mesodermally derived cartilages are reduced, whereas jellyfish mutant larvae are characterized by a severe reduction of all cartilaginous elements, leaving only two pieces in the position of the ceratohyal cartilages. In all other mutant larvae all skeletal elements are present, but consist of smaller and disorganized chondrocytes. These mutants also exhibit shortened heads and reduced pectoral fins. In homozygous knorrig embryos, tumor-like outgrowths of chondrocytes occur along the edges of all cartilaginous elements. The mutants presented here may be valuable tools for elucidating the genetic mechanisms that underlie the development of the mandibular and the hyoid arches, as well as the process of cartilage differentiation.

Animals↗
PubMed1996

Zebrafish pigmentation mutations and the processes of neural crest development.

Neural crest development involves cell-fate specification, proliferation, patterned cell migration, survival and differentiation. Zebrafish neural crest derivatives include three distinct chromatophores, which are well-suited to genetic analysis of their development. As part of a large-scale mutagenesis screen for embryonic/early larval mutations, we have isolated 285 mutations affecting all aspects of zebrafish larval pigmentation. By complementation analysis, we define 94 genes. We show here that comparison of their phenotypes permits classification of these mutations according to the types of defects they cause, and these suggest which process of neural crest development is probably affected. Mutations in eight genes affect the number of chromatophores: these include strong candidates for genes necessary for the processes of pigment cell specification and proliferation. Mutations in five genes remove part of the wild-type pigment pattern, and suggest a role in larval pigment pattern formation. Mutations in five genes show ectopic chromatophores in distinct sites, and may have implications for chromatophore patterning and proliferation. 76 genes affect pigment or morphology of one or more chromatophore types: these mutations include strong candidates for genes important in various aspects of chromatophore differentiation and survival. In combination with the embryological advantages of zebrafish, these mutations should permit cellular and molecular dissection of many aspects of neural crest development.

Adaptation, Physiological↗
PubMed1996

Mutations affecting xanthophore pigmentation in the zebrafish, Danio rerio.

In a large-scale screen for mutants with defects in embryonic development we identified 17 genes (65 mutants) specifically required for the development of xanthophores. We provide evidence that these genes are required for three different aspects of xanthophore development. (1) Pigment cell formation and migration (pfeffer and salz); (2) pigment synthesis (edison, yobo, yocca and brie) and (3) pigment translocation (esrom, tilsit and tofu). The number of xanthophore cells that appear in the body is reduced in embryos with mutations in the two genes, salz and pfeffer. In heterozygous and homozygous salz and pfeffer adults, the melanophore stripes are interrupted, indicating that xanthophore cells have an important function in adult melanophore pattern formation. Most other genes affect only larval pigmentation. In embryos mutant for edison, yobo, yocca and brie, differences in pteridine synthesis can be observed under UV light and by thin-layer chromatography. Homozygous mutant females of yobo show a recessive maternal effect. Embryonic development is slowed down and embryos display head and tail truncations. Xanthophores in larvae mutant in the three genes esrom, tilsit and tofu appear less spread out. In addition, these mutants display a defect in retinotectal axon pathfinding. These mutations may affect xanthophore pigment distribution within the cells or xanthophore cell shape. Mutations in seven genes affecting xanthophore pigmentation remain unclassified.

Animals↗
PubMed1996

Genes controlling and mediating locomotion behavior of the zebrafish embryo and larva.

Zebrafish embryos and larvae have stage-specific patterns of motility or locomotion. Two embryonic structures accomplish this behavior: the central nervous system (CNS) and skeletal muscles. To identify genes that are functionally involved in mediating and controlling different patterns of embryonic and larval motility, we included a simple touch response test in our zebrafish large-scale genetic screen. In total we identified 166 mutants with specific defects in embryonic motility. These mutants fall into 14 phenotypically distinct groups comprising at least 48 genes. Here we describe the various phenotypic groups including mutants with no or reduced motility, mechanosensory defective mutants, 'spastic' mutants, circling mutants and motor circuit defective mutants. In 63 mutants, defining 18 genes, striation of somitic muscles is reduced. Phenotypic analysis provides evidence that these 18 genes have distinct and consecutive functions during somitic muscle development. The genes sloth (slo) and frozen (fro) already act during myoblast differentiation, while 13 genes appear to function later, in the formation of myofibers and the organization of sarcomeres. Mutations in four other genes result in muscle-specific degeneration. 103 mutations, defining at least 30 genes, cause no obvious defects in muscle formation and may instead affect neuronal development. Analysis of the behavioral defects suggests that these genes participate in the diverse locomotion patterns observed, such as touch response, rhythmic tail movements, equilibrium control, or that they simply confer general motility to the animal. In some of these mutants specific defects in the developing nervous system are detected. Mutations in two genes, nevermind (nev) and macho (mao), affect axonal projection in the optic tectum, whereas axon formation and elongation of motorneurons are disrupted by mutations in the diwanka (diw) and the unplugged (unp) genes.

Animals↗
PubMed1996

Genetic dissection of the retinotectal projection.

A systematic search for mutations affecting the retinotectal projection in zebrafish larvae was performed, as part of the large-scale Tubingen screen for homozygous diploid mutants in embryonic development. 2,746 inbred lines (F2 families) from males mutagenized with ethylnitroso urea were screened. In wild-type larvae, developing retinal axons travel along a stereotyped route to the contralateral optic tectum. Here, their terminals form a highly ordered retinotopic map. To detect deviations from this pattern, an axon tracing assay was developed that permits screening of large numbers of mutagenized fish. Two fluorescent tracer dyes (DiI and DiO) were injected at opposite poles of the eyes of day-5 aldehyde-fixed larvae. 12 hours later, retinal axons were labelled over their entire length, and could be observed through the intact skin. The assay procedure (aldehyde fixation, mounting, injection of dyes, microscopic analysis) took about 1 minute per fish. In total, 125,000 individual fish larvae were processed. During the screen, 114 mutations in approx. 35 genes were discovered. For the mutants subjected to complementation testing, the number of alleles per locus ranges from 1 to 15. The mutations affect distinct steps in the retinotectal pathway, from pathfinding between eye and tectum to map formation along the dorsal-ventral and the anterior-posterior axis of the tectum. Mutations that disturb axon pathfinding to the tectum for the most part do not disrupt retinotopic mapping, and vice versa. The majority of the mutants display associated defects in other tissues and die before day 10. These mutants provide new tools for studying the formation of neuronal maps. The results of this screen show that a large-scale genetic approach can be applied to relatively late and circumscribed developmental processes in the vertebrate brain.

Animals↗
PubMed1996

Zebrafish mutations affecting retinotectal axon pathfinding.

We have isolated mutants in the zebrafish Danio rerio that have defects in axonal connectivity between the retina and tectum. 5-day-old fish larvae were screened by labeling retinal ganglion cells with DiI and DiO and observing their axonal projections to and on the tectum. 82 mutations, representing 13 complementation groups and 6 single allele loci, were found that have defects in retinal ganglion cell axon pathfinding to the tectum. These pathfinding genes fall into five classes, based on the location of pathfinding errors between eye and tectum. In Class I mutant larvae (belladonna, detour, you-too, iguana, umleitung, blowout) axons grow directly to the ipsilateral tectal lobe after leaving the eye. Class II mutant larvae (chameleon, bashful) have ipsilaterally projecting axons and, in addition, pathfinding mistakes are seen within the eye. In Class III mutant larvae (esrom, tilsit, tofu) fewer axons than normal cross the midline, but some axons do reach the contralateral tectal lobe. Class IV mutant larvae (boxer, dackel, pinscher) have defects in axon sorting after the midline and retinal axons occasionally make further pathfinding errors upon reaching the contralateral tectal lobe. Finally, Class V mutant larvae (bashful, grumpy, sleepy, cyclops, astray) have anterior-posterior axon trajectory defects at or after the midline. The analysis of these mutants supports several conclusions about the mechanisms of retinal axon pathfinding from eye to tectum. A series of sequential cues seems to guide retinal axons to the contralateral tectal lobe. Pre-existing axon tracts seem not to be necessary to guide axons across the midline. The midline itself seems to play a central role in guiding retinal axons. Axons in nearby regions of the brain seem to use different cues to cross the ventral midline. Mutant effects are not all-or-none, as misrouted axons may reach their target, and if they do, they project normally on the tectum. The retinotectal pathfinding mutants reveal important choice points encountered by neuronal growth cones as they navigate between eye and tectum.

Animals↗
PubMed1996

Mutations disrupting the ordering and topographic mapping of axons in the retinotectal projection of the zebrafish, Danio rerio.

Retinal ganglion cells connect to their target organ, the rectum, in a highly ordered fashion. We performed a large-scale screen for mutations affecting the retinotectal projection of the zebrafish, which resulted in the identification of 114 mutations. 44 of these mutations disturb either the order of RGC axons in the optic nerve and tract, the establishment of a topographic map on the tectum, or the formation of proper termination fields. Mutations in three genes, boxer, dackel and pinscher, disrupt the sorting of axons in the optic tract but do not affect mapping on the tectum. In these mutants, axons from the dorsal retina grow along both the ventral and the dorsal branch of the optic tract. Mutations in two genes, nevermind and who-cares, affect the dorsoventral patterning of the projection. In embryos homozygous for either of these mutations, axons from dorsal retinal ganglion cells terminate ventrally and dorsally in the tectum. In nevermind, the retinotopic order of axons along the optic nerve and tract is changed in a characteristic way as well, while it appears to be unaffected in who-cares. Two mutations in two complementation groups, gnarled and macho, affect the anteroposterior patterning of the projection. In these mutants, nasodorsal axons branch and terminate too soon in the anterior tectum. In 27 mutants belonging to six complementation groups, retinal axons do not form normal termination fields. Some implications for models concerning the formation of topographic projections are discussed.

Animals↗
PubMed1996

The zebrafish epiboly mutants.

Epiboly, the enveloping of the yolk cell by the blastoderm, is the first zebrafish morphogenetic movement. We isolated four mutations that affect epiboly: half baked, avalanche, lawine and weg. Homozygous mutant embryos arrest the vegetal progress of the deep cells of the blastoderm; only the yolk syncytial layer of the yolk cell and the enveloping layer of the blastoderm reach the vegetal pole of the embryo. The mutations half baked, avalanche and lawine produce a novel dominant effect, termed a zygotic-maternal dominant effect: heterozygous embryos produced from heterozygous females slow down epiboly and accumulate detached cells over the neural tube; a small fraction of these mutant individuals are viable. Heterozygous embryos produced from heterozygous males crossed to homozygous wild-type females complete epiboly normally and are completely viable. Additionally, embryos heterozygous for half baked have an enlarged hatching gland, a partial dominant phenotype. The phenotypes of these mutants demonstrate that, for the spreading of cells during epiboly, the movement of the deep cells of the blastoderm require the function of genes that are not necessary for the movement of the enveloping layer or the yolk cell. Furthermore, the dominant zygotic-maternal effect phenotypes illustrate the maternal and zygotic interplay of genes that orchestrate the early cell movements of the zebrafish.

Animals↗
PubMed1996

The zebrafish early arrest mutants.

This report describes mutants of the zebrafish having phenotypes causing a general arrest in early morphogenesis. These mutants identify a group of loci making up about 20% of the loci identified by mutants with visible morphological phenotypes within the first day of development. There are 12 Class I mutants, which fall into 5 complementation groups and have cells that lyse before morphological defects are observed. Mutants at three loci, speed bump, ogre and zombie, display abnormal nuclei. The 8 Class II mutants, which fall into 6 complementation groups, arrest development before cell lysis is observed. These mutants seemingly stop development in the late segmentation stages, and maintain a body shape similar to a 20 hour embryo. Mutations in speed bump, ogre, zombie, specter, poltergeist and troll were tested for cell lethality by transplanting mutant cells into wild-type hosts. With poltergeist, transplanted mutant cells all survive. The remainder of the mutants tested were autonomously but conditionally lethal: mutant cells, most of which lyse, sometimes survive to become notochord, muscles, or, in rare cases, large neurons, all cell types which become postmitotic in the gastrula. Some of the genes of the early arrest group may be necessary for progression though the cell cycle; if so, the survival of early differentiating cells may be based on having their terminal mitosis before the zygotic requirement for these genes.

Animals↗
PubMed1996

Genes establishing dorsoventral pattern formation in the zebrafish embryo: the ventral specifying genes.

We identified 6 genes that are essential for specifying ventral regions of the early zebrafish embryo. Mutations in these genes cause an expansion of structures normally derived from dorsal-lateral regions of the blastula at the expense of ventrally derived structures. A series of phenotypes of varied strengths is observed with different alleles of these mutants. The weakest phenotype is a reduction in the ventral tail fin, observed as a dominant phenotype of swirl, piggytail, and somitabun and a recessive phenotype of mini fin, lost-a-fin and some piggytail alleles. With increasing phenotypic strength, the blood and pronephric anlagen are also reduced or absent, while the paraxial mesoderm and anterior neuroectoderm is progressively expanded. In the strong phenotypes, displayed hy homozygous embryos of snailhouse, swirl and somitabun, the somites circle around the embryo and the midbrain region is expanded laterally. Several mutations in this group of genes are semidominant as well as recessive indicating a strong dosage sensitivity of the processes involved. Mutations in the piggytail gene display an unusual dominance that depends on both a maternal and zygotic heterozygous genotype, while somitabun is a fully penetrant dominant maternal-effect mutation. The similar and overlapping phenotypes of mutants of the 6 genes identified suggest that they function in a common pathway, which begins in oogenesis, but also depends on factors provided after the onset of zygotic transcription, presumably during blastula stages. This pathway provides ventral positional information, counteracting the dorsalizing instructions of the organizer, which is localized in the dorsal shield.

Animals↗
PubMed1996

dino and mercedes, two genes regulating dorsal development in the zebrafish embryo.

We describe two genes, dino and mercedes, which are required for the organization of the zebrafish body plan. In dino mutant embryos, the tail is enlarged at the expense of the head and the anterior region of the trunk. The altered expression patterns of various marker genes reveal that, with the exception of the dorsal most marginal zone, all regions of the early dino mutant embryo acquire more ventral fates. These alterations are already apparent before the onset of gastrulation. mercedes mutant embryos show a similar but weaker phenotype, suggesting a role in the same patterning processes. The phenotypes suggests that dino and mercedes are required for the establishment of dorsal fates in both the marginal and the animal zone of the early gastrula embryo. Their function in the patterning of the ventrolateral mesoderm and the induction of the neuroectoderm is similar to the function of the Spemann organizer in the amphibian embryo.

Animals↗
PubMed1996

Large scale genetics in a small vertebrate, the zebrafish.

The systematic isolation and characterization of mutants in Drosophila has enormously facilitated the analysis of molecular mechanisms underlying developmental pathways in the embryo. A similar approach is presently being used to study embryonic development of the zebrafish, which is becoming a mainstream model organism for vertebrate development. With its genetic versatility and sophisticated embryology, zebrafish offers the possibility to rapidly increase our knowledge of vertebrate development and add to what we have learned from other vertebrate model organisms.

Animals↗
PubMed1994

Staufen protein associates with the 3'UTR of bicoid mRNA to form particles that move in a microtubule-dependent manner.

Staufen protein is required in order to anchor bicoid (bcd) mRNA at the anterior pole of the Drosophila egg. Here we show that staufen protein colocalizes with bcd mRNA at the anterior, and that this localization depends upon its association with the mRNA. Upon injection into the embryo, bcd transcripts specifically interact with staufen, and we have mapped the sequences required to three regions of the 3'UTR, each of which is predicted to form a long stem-loop. The resulting staufen-bcd 3'UTR complexes form particles that show a microtubule-dependent localization. Since staufen is also transported with oskar (osk) mRNA during oogenesis, staufen associates specifically with both osk and bcd mRNAs to mediate their localizations, but at two distinct stages of development.

Animals↗
PubMed1994

Activation of the kinase Pelle by Tube in the dorsoventral signal transduction pathway of Drosophila embryo.

The concentration of Dorsal protein in the nucleus determines cell fate along the dorsoventral axis of the Drosophila embryo. The dorsal-group genes and the cactus gene are required for production and transmission of a localized signal on the ventral side of the embryo which determines the position of the highest nuclear concentration of Dorsal protein. The ventralizing signal produced in somatic cells is transmitted through the perivitelline space to the integral membrane protein Toll. Inside the embryo it leads to dissociation of the cytoplasmic Dorsal-Cactus complex and subsequent nuclear localization of Dorsal protein. Two components are known to mediate the signal transduction between Toll and Dorsal-Cactus: Pelle, a serine/threonine protein kinase, and Tube, a protein with an unknown biochemical activity. Here we construct gain-of-function alleles of pelle and tube and show that pelle functions downstream of tube. In addition, Pelle and Tube interact directly with one another. We propose that Tube is a direct activator of the protein kinase Pelle.

Alleles↗
PubMed1994

Disulfide cross-linking in crude embryonic lysates reveals three complexes of the Drosophila morphogen dorsal and its inhibitor cactus.

In Drosophila embryos dorsoventral polarity is determined by a concentration gradient of dorsal (dl) protein in the nuclei formed by the differential regulation of nuclear localization of dl protein. cactus (cact) represses the nuclear localization of dl protein. By introducing intermolecular disulfide bonds in homogenates of embryos, we detected three complexes of dl and/or cact proteins. Complex 1 (190 kDa) is a dl protein homodimer (dl2). Complex 2 (270 kDa) consists of one complex 1 and one cact molecule (dl2cact). Complex 3 (200 kDa) is a cact protein complex that does not contain dl protein. In wild-type embryos dl2cact was detected as the major form of dl protein, and dl2 was minor. With this assay virtually no dl monomer is detected. Analysis of the dl protein complexes in ventralized and dorsalized mutant embryos indicates that dl2cact is a cytoplasmic form, whereas dl2 is localized mainly in the nuclei. It seems that a small amount of dl2 is also present in the cytoplasm.

Animals↗
PubMed1994

Large-scale mutagenesis in the zebrafish: in search of genes controlling development in a vertebrate.

BACKGROUND: In Drosophila melanogaster and Caenorhabditis elegans, the elucidation of developmental mechanisms has relied primarily on the systematic induction and isolation of mutations in genes with specific functions in development. Such an approach has not yet been possible in a vertebrate species, owing to the difficulty of analyzing and keeping a sufficiently high number of mutagenized lines of animals. RESULTS: We have developed the methods necessary to perform large-scale saturation screens for mutations affecting embryogenesis in the zebrafish, Danio (Brachydanio) rerio. Firstly, a new aquarium system was developed to raise and keep large numbers of strains of genetically different fish safely and with little maintenance care. Secondly, by placing adult male fish in water containing the chemical mutagen, ethylnitrosourea, we induced point mutations in premeiotic germ cells with a rate of one to three mutations per locus per 1,000 mutagenized haploid genomes. This rate, which is similar to the mutagenesis rates produced by ethylmethanesulfonate in Drosophila, was determined for alleles at four different pigmentation genes. Finally, in a pilot screen in which mutagenized fish were inbred for two generations and scored for embryonic mutants, we isolated 100 recessive mutations with phenotypes visible in the homozygous embryos. CONCLUSION: The high rate of induction and recovery of point mutations, in addition to an efficient aquarium system to house large numbers of mutagenized lines, means that it is now possible to perform saturation mutagenesis screens in a vertebrate, similar to those done in invertebrates.

Animal Husbandry↗
PubMed1994

no tail (ntl) is the zebrafish homologue of the mouse T (Brachyury) gene.

The mouse T (Brachyury) gene is required for normal mesoderm development and the extension of the body axis. Recently, two mutant alleles of a zebrafish gene, no tail (ntl), have been isolated (Halpern, M. E., Ho., R. K., Walker, C. and Kimmel, C. B. (1993) Cell 75, 99-111). ntl mutant embryos resemble mouse T/T mutant embryos in that they lack a differentiated notochord and the caudal region of their bodies. We report here that this phenotype is caused by mutation of the zebrafish homologue of the T gene. While ntl embryos express mutant mRNA, they show no nuclear protein product. Later, expression of mRNA in mutants, but not in wild types, is greatly reduced along the dorsal midline where the notochord normally forms. This suggests that the protein is required for maintaining transcription of its own gene.

Amino Acid Sequence↗