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Joachim Wittbrodt

Publications and source records attributed to Joachim Wittbrodt.

At least 19 recordsLinked to original sources
PubMed2025

Measurement and classification of bold-shy behaviours in medaka fish.

MOTIVATION: Boldness-shyness is considered a fundamental axis of behavioural variation in humans and other species, with obvious adaptive causes and evolutionary implications. Besides an individual's own genetics, this phenotype is also affected by the genetic make-up of peers in the individual's social environment. To identify genetic determinants of variation along the bold-shy behavioural axis, a reliable experimental and analytical set-up able to highlight direct and indirect genetic effects is needed. RESULTS: We describe a custom assay designed to detect bold-shy behaviours in medaka fish, combining an open-field and novel-object component. We use this assay to explore direct and social genetic effects on the behaviours of 307 pairs of fish from five inbred medaka strains. Applying a hidden Markov model (HMM) to classify behavioural modes, we find that direct genetic effects influence the proportions of time the five strains spent in slow-moving states, explaining up to 29.7% of the variance in time spent in those states. We also found that an individual's behaviour is influenced by the genetics of its tank partner, explaining up to 8.64% of the variance in the time spent in slow-moving states. Our behavioural assay in combination with the HMM analysis is applicable to follow-up genetic linkage studies of genetic variants involved in direct behavioural effects and indirect social genetic effects. A suitable genetic resource for such studies, the Medaka Inbred Kiyosu-Karlsruhe (MIKK) panel has recently been established. AVAILABILITY AND IMPLEMENTATION: The code associated with this work is available on GitHub (https://github.com/birneylab/medaka_behaviour_pilot) and Software Heritage (swh: 1: dir: c9abec1c5d62d22e43c9e97d995c56261784d9ab). Experimental data have been uploaded to the EBI Bioimage Archive (https://doi.org/10.6019/S-BIAD1421).

Animals↗
PubMed2007

Birth and life of tissue macrophages and their migration in embryogenesis and inflammation in medaka.

Macrophages detecting and migrating toward sites of injury and infection represent one of the first steps in an immune response. Here we directly image macrophage birth and migration in vivo in transgenic medaka fish. Macrophages are born as frequently dividing, immotile cells with spherical morphology that differentiate into flat, highly motile cells. They retain mitotic activity while spreading over the entire body. Cells follow restricted paths not only in directed migration, but also during patrolling. Along those paths the macrophages rapidly patrol the tissue and respond to wounding and bacterial infection from long distances. Upon injury they increase their speed and migratory persistence. Specifically targeting PI3-kinase isoforms efficiently blocks the wounding response and results in a distinct inhibition of cell motility and chemotaxis. Our study provides in situ insights into the properties of immature and migratory macrophages and presents a unique model to further test modulating compounds in vivo.

Animals↗
PubMed2006

Individual cell migration serves as the driving force for optic vesicle evagination.

The cellular mechanisms underlying organ formation are largely unknown. We visualized early vertebrate eye morphogenesis at single-cell resolution by in vivo imaging in medaka (Oryzias latipes). Before optic vesicle evagination, retinal progenitor cells (RPCs) modulate their convergence in a fate-specific manner. Presumptive forebrain cells converge toward the midline, whereas medial RPCs remain stationary, predetermining the site of evagination. Subsequent optic vesicle evagination is driven by the active migration of individual RPCs. The analysis of mutants demonstrated that the retina-specific transcription factor rx3 determines the convergence and migration behaviors of RPCs. Hence, the migration of individual cells mediates essential steps of organ morphogenesis.

Animals↗
PubMed2006

Identification and lineage tracing of two populations of somatic gonadal precursors in medaka embryos.

The gonad contains two major cell lineages, germline and somatic cells. Little is known, however, about the somatic gonadal cell lineage in vertebrates. Using fate mapping studies and ablation experiments in medaka fish (Oryzias latipes), we determined that somatic gonadal precursors arise from the most posterior part of the sdf-1a expression domain in the lateral plate mesoderm at the early segmentation stage; this region has the properties of a gonadal field. Somatic gonadal precursors in this field, which continuously express sdf-1a, move anteriorly and medially to the prospective gonadal area by convergent movement. By the stage at which these somatic gonadal precursors have become located adjacent to the embryonic body, the precursors no longer replace the surrounding lateral plate mesoderm, becoming spatially organized into two distinct populations. We further show that, prior to reaching the prospective gonadal area, these populations can be distinguished by expression of either ftz-f1 or sox9b. These results clearly indicate that different populations of gonadal precursors are present before the formation of a single gonadal primordium, shedding new light on the developmental processes of somatic gonadal cell and subsequent sex differentiation.

Animals↗
PubMed2006

Rx-Cre, a tool for inactivation of gene expression in the developing retina.

Rx is a homeobox-containing gene that is critical for vertebrate eye development. Its expression domain delineates a field of cells from which the retina and the ventral hypothalamus develop. The 5' upstream regulatory sequences of the medaka fish Rx gene are functionally conserved during evolution to a degree that they direct gene expression into the Rx-expressing field of cells in mice. Using these sequences, we made a Cre line that can be used for inactivation of gene expression in the developing retina.

Alleles↗
PubMed2005

MEPD: a resource for medaka gene expression patterns.

The Medaka Expression Pattern Database (MEPD) is a database for gene expression patterns determined by in situ hybridization in the small freshwater fish medaka (Oryzias latipes). Data have been collected from various research groups and MEPD is developing into a central expression pattern depository within the medaka community. Gene expression patterns are described by images and terms of a detailed medaka anatomy ontology of over 4000 terms, which we have developed for this purpose and submitted to Open Biological Ontologies. Sequences have been annotated via BLAST match results and using Gene Ontology terms. These new features will facilitate data analyses using bioinformatics approaches and allow cross-species comparisons of gene expression patterns. Presently, MEPD has 19,757 entries, for 1024 of them the expression pattern has been determined.

Animals↗
PubMed2005

Medial floor plate formation in zebrafish consists of two phases and requires trunk-derived Midkine-a.

The medial floor plate (MFP) organizes the specification of neurons and outgrowth of axons in the ventral spinal cord of vertebrates. We show that the growth factor Midkine-a, expressed in the paraxial mesoderm, is required for formation of the MFP in zebrafish. Our epistatic analyses demonstrate that development of MFP comprises two independent sequential phases. Following initial MFP induction in the gastrula organizer, Midkine-a regulates allocation of MFP cells during subsequent development. Thus in zebrafish, trunk-derived signals are required for complete MFP formation from a common pool of organizer-derived midline precursor cells.

Animals↗
PubMed2005

Differentiation of the vertebrate retina is coordinated by an FGF signaling center.

In vertebrates, midline-derived sonic hedgehog and nodal are crucial for the initial proximal-distal patterning of the eye. The establishment of the distal optic stalk is in turn a prerequisite to initiate retinogenesis. However, the signal that activates this process is unknown. Here, we demonstrate that in both chick and fish, the initiation of retinal differentiation is triggered by a species-specific localized Fgf signaling center that acts as mediator of the midline signals. The concerted activity of Fgf8 and Fgf3 is both necessary and sufficient to coordinate retinal differentiation independent of the connecting optic stalk.

Animals↗
PubMed2005

Cell cycle control by homeobox genes in development and disease.

Homeobox-containing transcription factors are among the most studied players during normal embryonic development. In the last few years, they have also been shown to act as modulators of cell proliferation. In the present review, we highlight recent studies that demonstrated the influences of homeobox genes on crucial components of the cell cycle machinery. Homeobox genes may have direct or indirect influence on their transcription levels but can also interact with those components via protein-protein interaction. In many cases, these studies were done in the context of pathological states like cancer as well as during vertebrate development.

Cell Cycle↗
PubMed2004

Ciliary photoreceptors with a vertebrate-type opsin in an invertebrate brain.

For vision, insect and vertebrate eyes use rhabdomeric and ciliary photoreceptor cells, respectively. These cells show distinct architecture and transduce the light signal by different phototransductory cascades. In the marine rag-worm Platynereis, we find both cell types: rhabdomeric photoreceptor cells in the eyes and ciliary photoreceptor cells in the brain. The latter use a photopigment closely related to vertebrate rod and cone opsins. Comparative analysis indicates that both types of photoreceptors, with distinct opsins, coexisted in Urbilateria, the last common ancestor of insects and vertebrates, and sheds new light on vertebrate eye evolution.

Amino Acid Sequence↗
PubMed2004

Efficient activation of gene expression using a heat-shock inducible Gal4/Vp16-UAS system in medaka.

BACKGROUND: Genetic interference by DNA, mRNA or morpholino injection is a widely used approach to study gene function in developmental biology. However, the lack of temporal control over the activity of interfering molecules often hampers investigation of gene function required during later stages of embryogenesis. To elucidate the roles of genes during embryogenesis a precise temporal control of transgene expression levels in the developing organism is on demand. RESULTS: We have generated a transgenic Gal4/Vp16 activator line that is heat-shock inducible, thereby providing a tool to drive the expression of specific effector genes via Gal4/Vp16. Merging the Gal4/Vp16-UAS system with the I-SceI meganuclease and the Sleeping Beauty transposon system allows inducible gene expression in an entirely uniform manner without the need to generate transgenic effector lines. Combination of this system with fluorescent protein reporters furthermore facilitates the direct visualization of transgene expressing cells in live embryos. CONCLUSION: The combinatorial properties of this expression system provide a powerful tool for the analysis of gene function during embryonic and larval development in fish by ectopic expression of gene products.

Animals↗
PubMed2004

Optical sectioning deep inside live embryos by selective plane illumination microscopy.

Large, living biological specimens present challenges to existing optical imaging techniques because of their absorptive and scattering properties. We developed selective plane illumination microscopy (SPIM) to generate multidimensional images of samples up to a few millimeters in size. The system combines two-dimensional illumination with orthogonal camera-based detection to achieve high-resolution, optically sectioned imaging throughout the sample, with minimal photodamage and at speeds capable of capturing transient biological phenomena. We used SPIM to visualize all muscles in vivo in the transgenic Medaka line Arnie, which expresses green fluorescent protein in muscle tissue. We also demonstrate that SPIM can be applied to visualize the embryogenesis of the relatively opaque Drosophila melanogaster in vivo.

Anatomy, Cross-Sectional↗
PubMed2004

The homeobox gene Xbh1 cooperates with proneural genes to specify ganglion cell fate within the Xenopus neural retina.

Recent studies on vertebrate eye development have focused on the molecular mechanisms of specification of different retinal cell types during development. Only a limited number of genes involved in this process has been identified. In Drosophila, BarH genes are necessary for the correct specification of R1/R6 eye photoreceptors. Vertebrate Bar homologues have been identified and are expressed in vertebrate retinal ganglion cells during differentiation; however, their retinal function has not yet been addressed. In this study, we report on the role of the Xenopus Bar homologue Xbh1 in retinal ganglion cell development and its interaction with the proneural genes Xath5 and Xath3, whose ability to promote ganglion cell fate has been demonstrated. We show that XHB1 plays a crucial role in retinal cell determination, acting as a switch towards ganglion cell fate. Detailed expression analysis, animal cap assays and in vivo lipofection assays, indicate that Xbh1 acts as a late transcriptional repressor downstream of the atonal genes Xath3 and Xath5. However, the action of Xbh1 on ganglion cell development is different and more specific than that of the Xath genes, and accounts for only a part of their activities during retinogenesis.

Animals↗
PubMed2004

Rapid chromosomal assignment of medaka mutants by bulked segregant analysis.

Genetic screens in medaka are leading to the identification of an increasing number of unique mutant phenotypes. However, so far only a few genes responsible for these phenotypes have been characterized. Furthermore, no protocols using a systematic positional cloning strategy have been developed to determine the implicated genes. The PCR-based bulked segregant analysis is a fast and reliable tool to accomplish the initial steps of the positional cloning of a mutation. Here we describe the selection of a panel of genetic markers that, evenly distributed over the 24 chromosomes of medaka, provide a full coverage of the compact medaka genome (800 Mb) when used in bulked segregant analysis. The reference panel, which consists of 48 EST-derived markers, is anchored to a collection of more than 2000 polymorphic markers, thus facilitating a rapid transition from chromosomal assignment to fine mapping of the mutants. More importantly, since most of the genetic screens have been performed in the inbred Cab strain (derived from the Southern population), the selection of markers included in this panel was intended to optimize the recognition of polymorphisms between Cab and the polymorphic inbred mapping strain Kaga. Here we present a reliable mapping panel, confirmed both by the assignment of the locus responsible for the medaka mutation eyeless/Rx3 to chromosome 12, and by the analysis of its resolution power using representative markers.

Animals↗
PubMed2004

Direct interaction of geminin and Six3 in eye development.

Organogenesis in vertebrates requires the tight control of cell proliferation and differentiation. The homeobox-containing transcription factor Six3 plays a pivotal role in the proliferation of retinal precursor cells. In a yeast two-hybrid screen, we identified the DNA replication-inhibitor geminin as a partner of Six3. Geminin inhibits cell-cycle progression by sequestering Cdt1 (refs 4, 5), the key component for the assembly of the pre-replication complex. Here, we show that Six3 efficiently competes with Cdt1 directly to bind to geminin, which reveals how Six3 can promote cell proliferation without transcription. In common with Six3 inactivation, overexpression of the geminin gene (Gem; also known as Gmn) in medaka (Oryzias latipes) induces specific forebrain and eye defects that are rescued by Six3. Conversely, loss of Gem (in common with gain of Six3 (ref. 1)) promotes retinal precursor-cell proliferation and results in expanded optic vesicles, markedly potentiating Six3 gain-of-function phenotypes. Our data indicate that the transcription factor Six3 and the replication-initiation inhibitor geminin act antagonistically to control the balance between proliferation and differentiation during early vertebrate eye development.

Animals↗
PubMed2004

GSD: a genetic screen database.

The systematic assignment of gene function to a sequenced genome is one of the outstanding challenges in the post-genomic era. Large-scale systematic mutagenesis screens are important tools for reaching this goal. Here we describe GSD, a software package that allows storage and integration of data from genetic screens. GSD was initially developed for a large-scale F3 mutagenesis screen for developmental mutants of medaka (Oryzias latipes). The version presented here supports a wide range of different screens (mutagenesis, RNAi, morpholinos, transgenesis and others) using different organisms. Data are stored in a relational database and can be made accessible through web interfaces. Researchers can enter data describing their screened embryos: They can track statistics, submit images and describe the resulting phenotypes using a phenotype classification ontology. We developed a fish phenotype classification ontology of medaka and zebrafish for this software package and made it available to the public. In addition, a list of genetic lines resulting from each screen can be generated. These lines (mutant alleles, transgenic lines) can be described and categorized in the same ways as the screened individuals. Raw data from the screen can be integrated to describe these lines. A query module that searches this list can be used to publish the screen results on the Internet. A test version is available at and the software can be downloaded from this site.

Animals↗
PubMed2004

Mutations affecting retina development in Medaka.

In a large scale mutagenesis screen of Medaka we identified 60 recessive zygotic mutations that affect retina development. Based on the onset and type of phenotypic abnormalities, the mutants were grouped into five categories: the first includes 11 mutants that are affected in neural plate and optic vesicle formation. The second group comprises 15 mutants that are impaired in optic vesicle growth. The third group includes 18 mutants that are affected in optic cup development. The fourth group contains 13 mutants with defects in retinal differentiation. 12 of these have smaller eyes, whereas one mutation results in enlarged eyes. The fifth group consists of three mutants with defects in retinal pigmentation. The collection of mutants will be used to address the molecular genetic mechanisms underlying vertebrate eye formation.

Animals↗