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  • 1
    Electronic Resource
    Electronic Resource
    On the phenotype and development of mutants of early neurogenesis inDrosophila melanogaster (1983)
    Springer
    Development genes and evolution 192 (1983), S. 62-74 
    Details
    ISSN: 1432-041X
    Keywords: Early neurogenesis ; Neurogenic mutants ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The central nervous system (CNS) ofDrosophila develops from precursor cells called neuroblasts. Neuroblasts segregate in early embryogenesis from an apparantly undifferentiated ectoderm and move into the embryo, whereas most of the remaining ectodermal cells continue development as epidermal cell precursors. Segregation of neuroblasts occurs within a region called the neurogenic field. We are interested in understanding how the genome ofDrosophila controls the parcelling of the ectoderm into epidermal and neural territories. We describe here mutations belonging to seven complementation groups which effect an abnormal neurogenesis. The phenotypes produced by these mutations are similar. Essential features of these phenotypes are a conspicuous hypertrophy of the CNS accompanied by epidermal defects; the remaining organs and tissues of the mutants are apparently unaffected. The study of mutant phenotype development strongly suggests this phenotype to be due to misrouting into the neural pathway of development of ectodermal cells which in the wildtype would have given rise to epidermal cells, i.e. to an initial enlargement of the neurogenic region at the expense of the epidermogenic region. These observations indicate that the seven genetic loci revealed by the mutations described in this study contribute to control the neurogenic field. The present results suggest that in wildtype development neurogenic genes are supressed within all derivatives of the mesoderm and endoderm and some derivatives of the ectoderm, and conditionally expressed in the remaining ectoderm. The organisation of the neurogenic field in the wildtype is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848482
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  • 2
    Electronic Resource
    Electronic Resource
    Early neurogenesis in wild-typeDrosophila melanogaster (1984)
    Springer
    Development genes and evolution 193 (1984), S. 308-325 
    Details
    ISSN: 1432-041X
    Keywords: Neurogenesis ; Pattern of neuroblasts ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper deals with morphological aspects of early neurogenesis inDrosophila, in particular with the segregation of neuroblasts from the neurogenic region of the ectoderm and the pattern formed by those wells within both the germ band and the procephalic lobe. The neurogenic ectoderm was found to contain neural precursors intermingled with epidermal precursors, extending from the midline up to the primordia of the tracheal tree along the germ band and laterodorsally in the procephalic lobe. Germ band neuroblasts segregate from the neurogenic ectoderm during a period of several hours according to characteristic spatial and temporal patterns. During the first half of the segregation process the pattern of germ band neuroblasts was found to be the same in different animals in both spatial arrangement and number of cells; this permitted the identification of individual neuroblasts from different embryos. Later in development several difficulties were encountered which precluded an exact description of the neuroblast pattern. The constitution of the neurogenic region is discussed in relation to the phenotype of mutants affecting neurogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848159
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  • 3
    Electronic Resource
    Electronic Resource
    A functional analysis of the genes Enhancer of split and HLH-m5 during early neurogenesis in Drosophila melanogaster (1993)
    Springer
    Development genes and evolution 203 (1993), S. 10-17 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila neurogenesis ; Helix-loop-helix protein ; Enhancer of split
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To assess the functional domains of the proteins encoded by E(spl) and HLH-m5, two genes of the Enhancer of split complex [E(SPL)-C] of Drosophila melanogaster, a number of variants have been made by in vitro mutagenesis, transformed into the germ line of the wild-type, and genetically combined with a chromosomal deletion lacking four of the genes of the E(SPL)-C. All constructs used attenuated the neurogenic phenotype associated with this deletion. However, constructs encoding proteins with truncated carboxy-termini exibited in all cases a higher activity than constructs encoding the full length version of the protein. Neutralization of the basic domain severely reduced, but did not completely abolish the rescuing activity of E(spl), while proteins in which a proline residue within the basic domain had been changed to either threonine or asparagine were slightly less efficient in their rescuing activity than the corresponding wild-type versions. We discuss the possible significance of these results for the function of the protein domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539885
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  • 4
    Electronic Resource
    Electronic Resource
    Two groups of interrelated genes regulate early neurogenesis in Drosophila melanogaster (1988)
    Springer
    Development genes and evolution 197 (1988), S. 457-470 
    Details
    ISSN: 1432-041X
    Keywords: Neurogenesis ; Neurogenic genes ; Achaetescute complex ; Daughterless ; Genetic interactions ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Drosophila melanogaster the neuroblasts separate from epidermoblasts to give rise to the neural primordium. This process is under the control of several genes. The group of the so-called neurogenic genes is required for epidermal development; other genes, comprising those of the achaete-scute complex and daughterless, are required for neural development. We have studied the relationships between both groups of genes in two different ways. We have analyzed the phenotype of double-mutant embryos and our results show that the neural hyperplasia caused by neurogenic mutations can be partially prevented if a mutation in one of the other genes is present in the same genome. Only the neural cells that do not require the function of a particular gene of the achaete-scute complex in the wild-type seem to develop to a neural fate in the double mutant embryos. At least some of the genetic interactions affect the transcriptional level, as shown by in situ hybridization, since the territories of transcription of the achaetescute genes are expanded in neurogenic mutants. All cells of the neurogenic region of the double mutants apparently initiate neural development. However, during later development some of these cells switch their fate either to epidermogenesis or to cell death and this leads to the final phenotype of the double mutants. We discuss these results with respect to the events of early neurogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385679
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  • 5
    Electronic Resource
    Electronic Resource
    Transcription of a zebrafish gene of the hairy-Enhancer of split family delineates the midbrain anlage in the neural plate (1996)
    Springer
    Development genes and evolution 206 (1996), S. 153-160 
    Details
    ISSN: 1432-041X
    Keywords: Key words hairy-E(spl) homologues ; Zebrafish ; Midbrain primordium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  her5 encodes a basic helix-loop-helix (bHLH) protein with all features characteristic of the Drosophila hairy-E(spl) family. her5 is expressed in a band of cells within the neural anlage from about 90% epiboly on to at least 36 h postfertilization (hpf). After completion of brain morphogenesis, her5-expressing cells are located in the caudal region of the midbrain, at the boundary with the rhombencephalon. Labelling of cells within the her5 expression domain in the neural plate by injection of fluorescein-dextran allows their labelled progeny to be localized in the 36-hpf-old embryo using an anti-fluorescein antibody. This shows that the her5 expression domain corresponds to the midbrain primordium, including both the tectum and the tegmentum, in the neural plate. A possible function for her5 in regionalization of the brain and/or control of the midbrain-hindbrain boundary is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050041
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  • 6
    Electronic Resource
    Electronic Resource
    Dorso-ventral polarity of the zebrafish embryo is distinguishable prior to the onset of gastrulation (1994)
    Springer
    Development genes and evolution 203 (1994), S. 374-380 
    Details
    ISSN: 1432-041X
    Keywords: Zebrafish ; Gastrulation ; Dye applications ; Dorso-ventral polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe a set of observations on developing zebrafish embryos and discuss the main conclusions they allow:(1) the embryonic dorso-ventral polarity axis is morphologically distinguishable prior to the onset of gastrulation; and (2) the involution of deep layer cells starts on the prospective dorsal side of the embryo. An asymmetry can be distinguished in the organization of the blastomeres in the zebrafish blastula at the 30% epiboly stage, in that one sector of the blastoderm is thicker than the other. Dye-labelling experiments with DiI and DiO and histological analysis allow us to conclude that the embryonic shield will form on the thinner side of the blastoderm. Therefore, this side corresponds to the prospective dorsal side of the embryo. Simultaneous injections of dyes on the thinner side of the blastoderm and on the opposite side show that involution of deep layer cells during gastrulation starts at the site at which the embryonic shield will form and extends from here to the prospective ventral regions of the germ ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188685
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  • 7
    Electronic Resource
    Electronic Resource
    A new β-globin gene from the zebrafish, β E1 , and its pattern of transcription during embryogenesis (1999)
    Springer
    Development genes and evolution 209 (1999), S. 126-131 
    Details
    ISSN: 1432-041X
    Keywords: Key words Globin genes ; Transcription pattern ; Erythropoiesis ; Zebrafish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In a search for novel, developmentally regulated genes we screened randomly picked cDNA clones, obtained from zebrafish mRNA, by in situ hybridization with digoxigenin-labelled riboprobes. Out of 150 clones tested, 1 codes for a new β-globin gene and is expressed during embryogenesis. Here we describe its pattern of expression and its use as a marker for early zebrafish erythropoiesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050235
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  • 8
    Electronic Resource
    Electronic Resource
    Region-specific cell clones in the developing spinal cord of the zebrafish (1999)
    Springer
    Development genes and evolution 209 (1999), S. 135-144 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To analyse the proliferative abilities of cells within particular regions of the zebrafish neural plate, injections of fluorescein-dextran were made into single cells at either medial or intermediary positions in the neural plate region of two-somite stage embryos. The resulting cell clones were analysed in 3.5-day-old embryos. Clones with similar compositions were found among those derived from injections in both regions, and these were grouped into classes. 78 clones 29 obtained following injections in the medial region, and 22 of 59 cell clones derived from injections in the intermediary region, were classifiable into 9 and 10 different classes, respectively, each comprising a variable number of clones. Several identified cell types, as well as each of the clone classes themselves, were specific for the regions of the neural plate from which they derived, i.e. they were not represented among the clones derived from the other region. These results suggest that the composition of the lineages derived from particular cells is constant in different animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050237
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  • 9
    Electronic Resource
    Electronic Resource
    Lineage analysis of transplanted individual cells in embryos of Drosophila melanogaster (1986)
    Springer
    Development genes and evolution 195 (1986), S. 489-498 
    Details
    ISSN: 1432-041X
    Keywords: Pole cells and midgut progenitors ; Cell lineages ; Embryogenesis ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In this paper experiments concerning some aspects of the development of pole cells and midgut progenitors in Drosophila are reported. Cells were labelled by injecting horseradish-peroxidase (HRP) in embryos before pole bud formation and transplanted at different stages into unlabelled embryos, where the transplanted cells developed together with the unlabelled cells of the host. The hosts were then fixed and stained at different ages in order to demonstrate the presence of HRP in the progenies of transplanted cells. The main conlusions of the study are as follows. The gonads are the only organ to the formation of which pole cells normally contribute; those pole cells which do not participate in the formation of the gonads are finally eliminated or degenerate. Since the number of primordial germ cells in the gonads is the same irrespective of the number of pole cells present in the embryo, an (unknown) mechanism must exist regulating the final number of pole cells in each of the gonads. After their formation and before reaching the gonads, pole cells have been found to divide only up to two times. With respect to the midgut progenitors, the cells of both anlagen have been found to be committed to develop into midgut, although they behave as equivalent in that they do not apparently distinguish between the anterior and posterior anlage. Midgut progenitors have been found to divide a maximum of three times and to produce two different types of cells, epithelial cells of the midgut wall and spindle-like cells located internally in the gut.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375889
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  • 10
    Electronic Resource
    Electronic Resource
    Regulatory signals and signal molecules in early neurogenesis of Drosophila melanogaster (1992)
    Springer
    Development genes and evolution 201 (1992), S. 1-11 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Neurogenesis ; Signals ; Delta ; Notch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ectodermal germ layer of Drosophila melanogaster gives rise to two major cell lineages, the neural and the epidermal. Progenitor cells for each of these lineages arise from groups of cells, whose elements must decide between taking on either fate. Commitment of the progenitor cells to one of the developmental fates implies two factors. One is intrinsic to the ectodermal cells and determines a propensity to take on neural fate; this factor is probably represented by the products of the so-called proneural genes, which are differentially distributed throughout the ectoderm. The other factor in the cells' decision to adopt one of the two alternative fates is intercellular communication, which is mediated by the products of the so-called neurogenic genes. Two types of interactions, one inhibiting and the other stimulating neural development, have been inferred. We discuss here the assumed role of various neurogenic genes, in particular Notch and Delta, in these processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188770
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