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Biomedical subjects

A Fjose

Publications and source records attributed to A Fjose.

At least 19 recordsLinked to original sources
PubMed1998

A zebrafish Six4 homologue with early expression in head mesoderm.

Similar to the Drosophila homeobox gene sine oculis, several of the vertebrate homologues (Six genes) are expressed during eye formation and differentiation. In addition, most of these vertebrate genes show expression in mesodermal derivatives in adults and/or earlier stages of development. We have identified a zebrafish (Danio rerio) gene, six8, which shows the greatest similarity to murine Six4. The deduced proteins of these two genes have an overall sequence identity of 41%, while the homeodomains and Six domains are highly conserved, 90% and 81%, respectively. The spatiotemporal expression pattern of six8 was analyzed by RT-PCR and in situ hybridization. Transcripts were detected in a wide range of embryonic stages and in adults. Notably, the strongest expression was observed in head mesoderm of late gastrula and early neurula stages.

Amino Acid Sequence↗
PubMed1998

Transient expression of a novel Six3-related zebrafish gene during gastrulation and eye formation.

Both the Drosophila homeobox gene sine oculis and its murine homologue Six3 have regulatory functions in eye development. In zebrafish, in addition to two previously reported homologues of murine Six3, we have identified a related gene (six7). Although the deduced Six7 protein shares less than 68% sequence identity with the other known zebrafish Six3-like proteins, the embryonic expression patterns have highly conserved features. The six7 transcripts are first detected in involuting axial mesendoderm and, subsequently, in the overlying neurectoderm from which the forebrain and optic primordia develop. Similar to the two other zebrafish Six3 homologues, the expression boundaries of six7 correspond quite closely with the edges of the optic vesicles. Hence, the partially overlapping expression domains of these three six genes probably contribute to anteroposterior specification and in defining the eye primordia.

Amino Acid Sequence↗
PubMed1998

The zebrafish Pax3 and Pax7 homologues are highly conserved, encode multiple isoforms and show dynamic segment-like expression in the developing brain.

This study describes the isolation and characterization of zebrafish homologues of the mammalian Pax3 and Pax7 genes. The proteins encoded by both zebrafish genes are highly conserved (>83%) relative to the known mammalian sequences. Also the neural expression patterns during embryogenesis are very similar to the murine homologues. However, observed differences in neural crest and mesodermal expression relative to mammals could reflect some functional divergence in the development of these tissues. For the zebrafish Pax7 protein we report the first full-length amino acid sequences in vertebrates and show the existence of three additional isoforms which have truncations in the homeodomain and/or the C-terminal region. These novel variants provide evidence for additional isoform diversity of vertebrate Pax proteins.

Amino Acid Sequence↗
PubMed1998

Expression of two zebrafish homologues of the murine Six3 gene demarcates the initial eye primordia.

The murine homeobox gene Six3 and its Drosophila homologue sine oculis both have regulatory functions in eye development. We report the isolation and characterization of two zebrafish genes, six3 and six6, that are closely related to the murine Six3 gene. Zebrafish six3 may be the structural orthologue, while the six6 gene is more similar with respect to embryonic expression. Transcripts of both zebrafish six genes are first detected in involuting axial mesendoderm and, subsequently, in the overlying anterior neural plate from which the optic vesicles and the forebrain will develop. Direct correspondence between six3/six6 expression boundaries and the optic vesicles indicate essential roles in defining the eye primordia. During later stages only the six6 gene displays similar features of expression in the eyes and rostral brain as reported previously for murine Six3.

Amino Acid Sequence↗
PubMed1997

Solid phase technology improves coupled gel shift/footprinting analysis.

For the analysis of protein-DNA interactions by coupled gel-shift/footprinting, DNA fragments need to be extracted from polyacrylamide gels and subsequently separated on high resolution gels. Due to impurities in the extracted DNA, single nucleotide resolution is frequently not achieved. We now describe an improved experimental strategy that employs transient coupling of DNA fragments to a solid support in order to extract DNA of high purity quantitatively, rapidly and reliably. As an example, we describe the application of our protocol to the 'in-gel footprinting' by copper phenanthroline. The method should also find application to the chemical interference assays.

Bacterial Proteins↗
PubMed1997

A vasa-like gene in zebrafish identifies putative primordial germ cells.

The vasa gene is essential for germline formation in Drosophila. Vasa-related genes have been isolated from several organisms including nematode, frog and mammals. In order to gain insight into the early events in vertebrate germline development, zebrafish was chosen as a model. Two zebrafish vasa-related genes were isolated, pl10a and vlg. The pl10a gene was shown to be widely expressed during embryogenesis. The vlg gene and vasa belong to the same subfamily of RNA helicase encoding genes. Putative maternal vlg transcripts were detected shortly after fertilization and from the blastula stage onwards, expression was restricted to migratory cells most likely to be primordial germ cells.

Amino Acid Sequence↗
PubMed1995

Embryonic expression and DNA-binding properties of zebrafish pax-6.

Zebrafish pax-6 (pax[zf-a]) and its murine homologue are structurally and functionally related to the Drosophila paired box gene eyeless, a master control gene for eye development. This report details the zebrafish pax-6 embryonic expression pattern both at the mRNA and protein level. Transcripts are first detected in the presumptive forebrain and hindbrain regions of the neural plate. After formation of the neural keel, Pax-6 protein accumulates within the same two domains. Expression is also observed in the optic vesicles and lens placodes, confirming that the Pax-6 protein is expressed in those areas of the eye where it is assumed to control differentiation. The relative DNA-binding affinity of the zebrafish Pax-6 protein to different categories of Pax recognition sites is shared with the murine homologue.

Animals↗
PubMed1995

A novel vertebrate svp-related nuclear receptor is expressed as a step gradient in developing rhombomeres and is affected by retinoic acid.

The protein encoded by the zebrafish gene svp[40] belongs to a distinct group within the steroid hormone receptor superfamily that includes Drosophila seven-up and several vertebrate orphan receptors. Svp[40] shares a particularly high degree of amino acid sequence identity (approximately 86%) with the mammalian transcription factors ARP-1 and COUP. The gene is expressed in specific regional and segmental domains within the developing brain. Correspondence between this expression pattern and early sites of neuronal differentiation and axonogenesis in the rostral brain may reflect an involvement in neural patterning. During the early embryonic stages when hindbrain rhombomeres are formed, a segmental expression pattern is established as a step gradient. The single steps of this gradient coincide directly with the four anteriormost segments suggesting a role in controlling rhombomere-specific expression of genes contributing to cell differentiation in the hindbrain. Since COUP/ARP-1 and retinoic acid receptors (RARs/RXRs) are known to have similar DNA-binding specificities, different levels of Svp[40] might modulate retinoid signaling through competition for binding to specific RAREs in the promoters of target genes. Treatment of zebrafish embryos with retinoic acid affects the svp[40] step gradient and causes an elimination of a regional expression domain in the retina. These observations are consistent with svp[40] being an integral part of the retinoid signaling network during hindbrain and eye development.

Amino Acid Sequence↗
PubMed1994

Regulatory gene expression boundaries demarcate sites of neuronal differentiation in the embryonic zebrafish forebrain.

During development of the zebrafish forebrain, a simple scaffold of axon pathways is pioneered by a small number of neurons. We show that boundaries of expression domains of members of the eph, forkhead, pax, and wnt gene families correlate with the positions at which these neurons differentiate and extend axons. Analysis of genetically or experimentally altered forebrains indicates that if a boundary is maintained, there is appropriate neural differentiation with respect to the boundary. Conversely, in the absence of a boundary, there is concomitant disruption of neural patterning. We also show that a strip of cells within the dorsal diencephalon shares features with ventral midline cells. This strip of cells fails to develop in mutant fish in which specification of the ventral CNS is disrupted, suggesting that its development may be regulated by the same inductive pathways that pattern the ventral midline.

Animals↗
PubMed1994

Expression of the zebrafish gene hlx-1 in the prechordal plate and during CNS development.

The zebrafish hlx-1 gene belongs to the H2.0 subfamily of homeobox genes and is closely related to the mouse Dbx gene with respect to both homeodomain homology (96.7%) and neural expression during embryogenesis. Analysis of hlx-1 expression by in situ hybridization reveals several particularly interesting features. In late gastrula embryos, hlx-1 transcripts are detected within a circular area in the region of the presumptive rostral brain. Subsequently, the expression domain becomes restricted to the hypoblast and undergoes dynamic changes involving conversion into a longitudinal stripe which elongates and retracts following a temporal sequence. The site of transient hlx-1 expression along the ventral midline of the rostral neurectoderm, which in part corresponds to the prechordal plate, suggests a role in the determination of head mesoderm as well as in patterning of the rostral brain. As the midline stripe gradually disappears, the hlx-1 gene becomes regionally expressed within the diencephalon and at a specific dorsoventral level along the hindbrain and spinal cord. In the hindbrain, expression is initiated in dorsoventrally restricted transversal stripes which correlate with the segmental pattern of rhombomeres. The stripes fuse into bilateral columns that are later converted to two series of paired transversal stripes at the rhombomere borders. This pattern is consistent with the proposed subdivision of hindbrain segments into rhombomere centers separated by border regions.

Amino Acid Sequence↗
PubMed1993

Zebrafish pou[c]: a divergent POU family gene ubiquitously expressed during embryogenesis.

We report the isolation and characterization of cDNA for a novel zebrafish (Brachyodanio rerio) POU domain gene, pou[c], which is ubiquitously expressed during embryonic development. This gene encodes a 610 amino acids long protein with a 149 amino acid POU domain ending only 8 residues before the C terminus. The 453 amino acids long region N-terminal to the POU domain contains several features typical of transcriptional activation domains such as an acidic region with a putative amphipathic alpha-helix, a glutamine-rich region, and short threonine- and/or serine-rich regions. Comparison of the POU domain of pou[c] to other known POU sequences clearly show that pou[c] has the most divergent POU domain sequence reported to date. Thus, we suggest that pou[c] should be placed as the presently sole member of a new, sixth class of POU proteins. DNA-binding studies revealed that pou[c] is not an octamer-binding transcription factor like the Oct proteins described from mammals, chicken and Xenopus. Rather, pou[c] binds with high affinity to the TAATGARAT motif found in the promoters of the herpes simplex virus immediate early genes and to degenerate octamer-TAATGA motifs. Circular permutation analyses also show that pou[c] induces DNA bending upon sequence-specific binding.

Amino Acid Sequence↗
PubMed1993

Functional conservation of vertebrate seven-up related genes in neurogenesis and eye development.

Several members of the steroid receptor superfamily, including the transcription factor COUP, are closely related to the Drosophila gene seven-up (svp) which is required for the development of the embryonic central nervous system (CNS) and specific photoreceptor cells of the eye. We have identified and characterized two zebrafish (Brachydanio rerio) members of this subfamily of orphan nuclear receptors. While one of them (svp[44]) is the zebrafish cognate of COUP, the second (svp[46]) seems to be a novel member of the COUP/svp group. The proteins encoded by both genes contain highly conserved DNA-binding and putative ligand-binding domains, indicating close similarities in target sequence recognition and ligand binding. Analysis of the spatial distribution of their transcripts in whole-mount embryos revealed that the CNS is a major site of expression for both genes. At early embryonic stages, both genes are expressed in domains corresponding to specific rhombomere primordia in the hindbrain. This suggests an involvement in hindbrain segmentation and/or rhombomere specification. Moreover, transcripts derived from both genes are detected within distinct areas of the eye rudiments, suggesting roles in eye patterning and/or cell differentiation. In the case of the svp[44] gene, expression is also observed within specific parts of the midbrain, diencephalon and telencephalon. These results represent the first evidence that at least some of the nervous system and eye-specific functions of Drosophila svp are conserved in vertebrates.

Amino Acid Sequence↗
PubMed1993

Genomic sequence and embryonic expression of the zebrafish homeobox gene hox-3.4.

We have analyzed the genomic DNA sequence and embryonic expression pattern of the zebrafish hox-3.4 gene. Two exons, encoding a protein with a total size of 232 amino acids, were identified within a 3.5 kbp genomic region. Besides the homeodomain, which is identical to that of the human HOX3D and mouse Hox-3.4 genes, the first 58 residues of the N-terminal domain in the predicted Hox-3.4 protein share 48% sequence identity with the gene product of the human cognate. Some of the N-terminal sequence elements are also conserved relative to the two other members of the Hox-1.3/Hox-2.1/Hox-3.4 paralogy group. In addition, the paralogous genes share a significant degree of sequence identity in non-coding regions. This conservation is particularly evident in the promoter regions of the cognates hox-3.4, Hox-3.4, and HOX3D, where a 180 bp TATA-box-containing element with a 60% identity is located. This is in agreement with the previous finding that the HOX3D promoter region contains response elements for other Hox proteins and retinoids. Also with respect to embryonic expression, the zebrafish hox-3.4 gene is very similar to its mammalian counterparts. Within the central nervous system of 16, 24, and 48 h embryos, hox-3.4 transcripts were detected throughout most of the spinal cord from a boundary at the posterior end of the hindbrain. In 16 h embryos the hox-3.4 gene is also active within a restricted region of the tailbud.

Amino Acid Sequence↗
PubMed1992

The paired domain-containing nuclear factor pax[b] is expressed in specific commissural interneurons in zebrafish embryos.

The zebrafish paired box (Pax) genes are expressed in the early neural tube and are thought to be transcription factors that regulate the differentiation of cells in the central nervous system (CNS). The protein product of one of these Pax genes, pax[b], is detectable as a nuclear antigen in all the regions of the embryo that transcribe the gene including the posterior midbrain, the nephritic primordium, the Wolffian duct, the optic stalk, and, in specific neurons, in the hindbrain and spinal cord. The timing and pattern of axonal outgrowth by the early pax[b]-positive neurons suggest that they are the commissural secondary ascending (CoSA) interneurons in the spinal cord; the primary commissural interneurons (MiD2c and MiD3c) in hindbrain rhombomeres mi2 and mi3; and a previously unclassified set of commissural interneurons that we termed the commissural caudalrhombomere ascending (CoCaA) interneurons in the caudal hindbrain. In contrast, the Mauthner interneurons do not express pax[b] early in development. Shortly after the appearance of the first pax[b]-positive interneurons, additional nuclei adjacent to the first pax[b]-positive interneurons become pax[b] positive. This pattern of expression suggests that the pax[b] protein may be involved in determining the identity of specific commissural interneurons.

3,3'-Diaminobenzidine↗
PubMed1992

Structure and early embryonic expression of the zebrafish engrailed-2 gene.

The Drosophila homeobox gene engrailed (en) is needed for correct embryonic development, and related sequences are active during vertebrate embryogenesis. Here we report the protein coding sequence and embryonic expression pattern of the zebrafish engrailed-2 gene (eng-2) which is directly homologous to En-2 in mice and Xenopus. The predicted zebrafish Eng-2 protein shares 65% overall identity to its Xenopus counterpart. In addition to the highly conserved homeodomain region, sequence conservation is present within three short stretches in the N-terminal region. The embryonic expression of the eng-2 gene was analysed by in situ hybridization to whole-mount embryos and tissue sections. Transcripts are first detected in two lateral bands at the 10-h stage, when epiboly is completed. Within the next 2 h of development, these two bands migrate and fuse at the midline. By the time the neural keel becomes visible (11-12 h), a transverse stripe of eng-2 expressing cells is seen at the presumptive midbrain-hindbrain boundary. Later this stripe becomes significantly compressed along the AP axis, and in 24-h embryos eng-2 transcripts are detected mainly in the posterior midbrain. In the hindbrain, eng-2 expression seems restricted to the primordium of the cerebellum. A second site of activity was observed in each somite where specific myotomal cells, the muscle pioneers, express eng-2. Our observations are discussed in relation to early regionalization of the central nervous system (CNS) and the generation of morphological borders.

Amino Acid Sequence↗
PubMed1992

Expression of four zebrafish wnt-related genes during embryogenesis.

The wnt gene family codes for a group of cysteine-rich, secreted proteins, which are differentially expressed in the developing embryo and are possibly involved in cellular communication. Here, we describe the polymerase chain reaction based cloning and embryonic expression patterns of four zebrafish wnt-related sequences; wnt[a], wnt[b], wnt[c] and wnt[d]. One of these genes, wnt[a], is a potential homologue of murine Wnt-3, while the other three genes most likely represent new members of the vertebrate wnt gene family. In zebrafish embryos, transcripts of wnt[a] are confined to the dorsal diencephalon, the dorsal midbrain, the rhombic lips and the dorsal portions of the spinal cord. wnt[b] is expressed in the tail bud and at considerably lower levels in the mesoderm of the head. wnt[c] transcripts are present within the diencephalon and the posterior midbrain whereas wnt[d] shows a surprisingly similar expression pattern to zebrafish wnt-1. By analogy to wnt-1, it is likely that the members of the zebrafish wnt gene family play an important role in cell-to-cell signalling during pattern formation in the neural tube and the tail bud.

Amino Acid Sequence↗
PubMed1992

The zebrafish homeobox gene hox[zf-114]: primary structure, expression pattern and evolutionary aspects.

It is gradually becoming accepted that vertebrate homeobox genes, like their counterparts in Drosophila, are crucial for normal development of the embryo. Most vertebrate homeoboxes reported so far are related to the Drosophila Antennapedia (Antp) sequence, and here we describe hox[zf-114], a novel Antp-like homeobox gene from the zebrafish. The sequence of the hox[zf-114] homeodomain indicates that this gene could be a member of a subfamily defined by the mouse Hox-1.5/-2.7/-4.1 genes. However, the evolutionary origin of hox[zf-114] is unclear and, based on the putative protein sequence, we conclude that it is not directly homologous to Hox-1.5, Hox-2.7 or Hox-4.1, or to other known mammalian homeobox genes. Nevertheless, as revealed by in situ hybridization, hox[zf-114] exhibits a spatial expression pattern typical for vertebrate Antp-like homeobox genes. Transcripts are detected in the posterior hindbrain, where a sharp anterior border of expression is observed, and throughout the spinal cord. The hox[zf-114] gene is also active in a region that gives rise to the pectoral fins. These findings suggest a role for hox[zf-114] in anteroposterior patterning of the neural tube and in pectoral fin development.

Amino Acid Sequence↗