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  • 1
    Electronic Resource
    Electronic Resource
    Mutations of early neurogenesis inDrosophila (1981)
    Springer
    Development genes and evolution 190 (1981), S. 226-229 
    Details
    ISSN: 1432-041X
    Keywords: Early neurogenesis ; Mutants ; Drosophila melanogaster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Embryonic lethal mutations at the Notch locus are known to produce a conspicuous central nervous system hypertrophy accompanied by a hypotrophy of the epidermal sheath. We have studied several zygotic mutants belonging to four different autosomal complementation groups which produce the same phenotype. The embryonic development of the new mutants, as well as that of Notch, consists of an initial enlargement of the neurogenic region at the expenses of epidermal cell precursors. The possibility is discussed that these five loci are involved in the determination of neural and epidermal cell precursors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848307
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  • 2
    Electronic Resource
    Electronic Resource
    A cell arrangement specific to thoracic ganglia in the central nervous system of theDrosophila embryo: Its behaviour in homoeotic mutants (1981)
    Springer
    Development genes and evolution 190 (1981), S. 370-373 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Homoeotic mutants ; Ventral cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe a set of cells in the central nervous system of theDrosophila embryo which are restricted to the thoracic ganglia in the wildtype. Taking these cells as indication of thoracic identity, we find that the ventral cord of embryos homozygous mutant for different bithorax functions and for Polycomb undergoes homoeotic transformations equivalent to those observed in the larval cuticle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863276
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  • 3
    Electronic Resource
    Electronic Resource
    Cell clones and pattern formation: Developmental restrictions in the compound eye ofDrosophila (1978)
    Springer
    Development genes and evolution 184 (1978), S. 155-170 
    Details
    ISSN: 1432-041X
    Keywords: Developmental restrictions ; Compound eye ; Pattern formation ; Genetic mosaics ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five regions of the compound eye have been found to be preferential boundaries for clones of labelledMinute + cells, and to act restrictively on the growth of cell clones after a given developmental stage. One of these regions is topographically related to the line of pattern inversion existing at the level of the equator. The results of experiments showing independency of origin of restriction lines and line of pattern inversion are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848224
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  • 4
    Electronic Resource
    Electronic Resource
    Cell clones and pattern formation: Genetic eye mosaics inDrosophila melanogaster (1976)
    Springer
    Development genes and evolution 179 (1976), S. 275-289 
    Details
    ISSN: 1432-041X
    Keywords: Compound eye Development Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Genetic eye mosaics ofDrosophila melanogaster have been studied by means of anatomical techniques. Using different cell markers it was found that the ommatidia at the boundaries between phenotypes are composed of cells belonging to different clones. Therefore, the formation of an individual ommatidium does not obey a mechanism based on a common clonal origin of its constituent elements. A statistical analysis of mosaic ommatidia shows that there is a significant tendency for the receptor cellsR2-R5 on the one hand and the receptor cellsR1, R6 andR7 on the other to belong to the same cell clone. The implications of these findings are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848237
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  • 5
    Electronic Resource
    Electronic Resource
    The development of ommatidial patterning in metamorphosed eye imaginal discs implants ofDrosophila melanogaster (1976)
    Springer
    Development genes and evolution 179 (1976), S. 373-392 
    Details
    ISSN: 1432-041X
    Keywords: Compound Eye ; Development ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of the rhabdomeric pattern in the compound eye ofDrosophila has been studied using combined transplantation and electron microscope techniques. In a first series of experiments eye imaginal discs of increasing age were implanted into larvae ready to pupate, thus losing variable amounts of the normal time for development. A sequence of differentiative abilities was found in the metamorphosed test pieces. As far as the photoreceptor cells are concerned, the most prominent steps of this sequence are: ability to form groups with other similar elements, anatomical polarization of microvilli, establishment of the rhabdomeric pattern and formation of an equator line. The stability of determination of the equator line was tested in a second experimental series. Fragment of different topographical origin within the mature eye anlage were brought to metamorphosis by implantation into larvae ready to pupate. It was found that an equator line differentiates only in those pieces which according to the published anlage maps contain the prospective equator region prior to metamorphosis. The mitotic abilities of implanted eye imaginal discs were investigated by means of “in vitro”3H-thymidine pulse-labelling and light microscope autoradiography of the differentiated test pieces. During the third larval stage the eye anlage is traversed by two consecutive mitotic waves, each one of them producing different categories of receptor cells. The first, anterior wave predominantly produces cells oriented toward the poles of the eye within the ommatidia, while the second, posterior wave gives rise to elements exclusively in an equatorial position. The dynamics of this proliferation are discussed in relation to the findings in the implantation experiments. Silver-grain counts support the possibility that at least two successive cell divisions occur in the eye anlage between labeling with tritiated thymidine and beginning of morphological differentiation. The relevance of this finding for the understanding of the concept of acquisition of competence is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848244
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  • 6
    Electronic Resource
    Electronic Resource
    Cell clones and pattern formation: On the lineage of photoreceptor cells in the compound eye ofDrosophila (1977)
    Springer
    Development genes and evolution 181 (1977), S. 227-245 
    Details
    ISSN: 1432-041X
    Keywords: Compound eye ; Development ; Cell lineages ; Genetic mosaics ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The generalogical relationships of photoreceptor cells within the compound eye ofDrosophila have been studied using cell labelling, with either3H-thymidine or recessive mutations, during the third larval stage. It has been found that photoreceptor and secondary pigment cells arise from different precursor cells. Under the present experimental conditions, precursors of receptor cells give rise to about 8 elements which differentiate as R cells of two different groups. One of the cells differentiates as R7 and the remaining as any one of the R1 to R6. The last cells behave initially as equivalent, and can differentiate within the same or within different, but neighbouring, ommatidia. The class of R1 to R6 cell in which each one of these elements differentiates, seems to depend on the time of its origin. The implications of these findings for the formation of the ommatidial pattern are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848423
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of temperature onshibire ts cell clones in the compound eye ofDrosophila melanogaster (1980)
    Springer
    Development genes and evolution 188 (1980), S. 55-63 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Compound eye ; shibire ts ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analysed the effect of temperature on both developing and adult eye cell clones homozygous forshi ST139, a temperature-sensitive mutant ofDrosophila melanogaster. The mutant gene, autonomous in its cellular expression, causes structural modifications of ommatidial cells when adult clones of cells are exposed to the restrictive temperature (29°C) for several days. However, the mutant phenotype reverses to normal within 4 days at the permissive temperature (20°C). The results of pulse, shift-up and shift-down experiments show that the temperaturesensitive period for developing compound eye cells is from the late second instar up to the early pupa. Cytodifferentiation of compound eye cells is blocked by restrictive temperature treatment during this period, whereas cell proliferation does not seem to be directly affected. These results are discussed with regard to the other known aspects of the phenotype observed in mutant individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848610
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  • 8
    Electronic Resource
    Electronic Resource
    cell clones and pattern formation: Studies onsevenless, a mutant ofDrosophila melanogaster (1979)
    Springer
    Development genes and evolution 186 (1979), S. 27-50 
    Details
    ISSN: 1432-041X
    Keywords: Compound eye ; Development ; Determination of R7 cells ; sevenless mutant analysis ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary sev LY3,the only existing allele at thesev locus (1–33,2±0,2), behaves as strongly hypomorph or even as amorph. Ommatidia in asev compound eye have only seven receptor cells, the position of the R7 pattern element being vacant. Various criteria showing that the missing cell is R7 have been verified. These include (i) anatomical characteristics ofsev ommatidia; (ii) behaviour of central R cells insev rdgB double mutants; (iii) medullary projection of central R cell axons; and (iv) mitotic pattern ofsev imaginal discs. The analysis of morphogeneticsev-sev + mosaics has shown thatsev is expressed autonomously by R7 cells, indicating that thesev phenotype is not due to asev genotype of ommatidial pattern elements other than R7. The study of third instarsev imaginal discs has not brought any direct evidence for death of clustered presumptive R7 cells; however, clonal analysis of the developingsev compound eye has given evidence of developmental parameters comparable to those ofsev +, therefore favouring the hypothesis that R7 cells die insev mutants. On the other hand,sev + seems to be required for the determination of the R7 cells, since thesev phenotype cannot be uncovered during the last mitoses of heterozygous mutant cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848106
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  • 9
    Electronic Resource
    Electronic Resource
    Maternal effects of zygotic mutants affecting early neurogenesis inDrosophila (1982)
    Springer
    Development genes and evolution 191 (1982), S. 191-201 
    Details
    ISSN: 1432-041X
    Keywords: Neurogenic mutants ; Maternal effects ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The size of the neurogenic region ofDrosophila melanogaster is under the control of several genes of zygotic expression. Lack of function from any of those genes produces an increase of the size of the neurogenic region at the expense of the epidermal anlage. However, differences exist in the extent of neuralisation achieved by each of the genetic loci upon mutation. The present results show that in the case ofN andmam phenotype differences are due to different contributions of maternal gene expression. This could be shown by studying the phenotype which appeared in mutant embryos when the oocytes developed from homozygous mutant precursor cells. Clones of mutant cells were induced in the germ line of females heterozygous for the neurogenic mutationin trans over germ line dependent, dominant female sterile mutations. After removing maternal information the phenotype ofN andmam mutants became identical in both cases. Furthermore maternal information fromN + was found to be necessary for viability of the wildtype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848335
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  • 10
    Electronic Resource
    Electronic Resource
    Topological specificity of phenotype expression of neurogenic mutations inDrosophila (1983)
    Springer
    Development genes and evolution 192 (1983), S. 317-326 
    Details
    ISSN: 1432-041X
    Keywords: Neurogenic mutations ; Topological specificity ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Neurogenic mutations have been found to cause the neuralization of certain regions of the ectoderm and yet to permit normal development of the remaining embryonic cells. Thus, it seems that the activity of the wild-type alleles of these genes is dispensable in a considerable fraction of the embryo during wild-type development. This effect might be a consequence of the cells' position within the embryo; alternatively, it might be independent of the position but be due rather to the genetic activity experienced by the cells previous to their commitment. The results described in this paper indicate that genes controlling patterning along the embryonic dorso-ventral perimeter (dorsal and Toll) are epistatic to genes controlling neurogenesis, their activity deciding which ectodermal cells are susceptible to neurogenesis. Using alleles with low expressivity, evidence was obtained showing that the tracheal placodes define the boundary of the territory which has neurogenic abilities at thoracic and abdominal levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848811
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