Specification of cell fate in the developing eye ofDrosophila (original) (raw)
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Journal of Cell Science, 1990
Summary In the developing eye of Drosophila cell fate is controlled by a cascade of inductive interactions. Little is known about how the specificity of positional signalling is achieved such that directly adjacent progenitor cells reproducibly choose distinct developmental pathways. The determination of the R7 photoreceptor in each ommatidium depends on the presence of the sevenless protein which acts as a receptor for positional information on the R7 precursor. The rough gene encodes a homeodomain protein that plays an instructive role in the determination of the R3 and R4 photoreceptor cells. The use of ectopic expression of sevenless and rough has provided insight into the mechanisms of positional signalling and the normal function of rough. Ubiquitous expression of sevenless does not alter cell fate suggesting that the inducing signal is both spatially and temporally controlled. Conversely, ectopic expression of rough in the R7 precursor causes a transformation of R7 cells into...
Genes & Development, 1992
Induction of the R7 photoreceptor cell fate in the developing eye of Drosophila depends on the activation of the sevenless receptor tyrosine kinase in the R7 precursor cell. The sevenless protein is expressed transiently in 8 of the 20 precursors of an ommatidium. Activation of the sevenless kinase in these eight cells indicates that six of them are competent to become R7 cells. To test the competence of all 20 ommatidial precursors in a temporally unrestricted manner we have used a constitutively activated sevenless kinase created by fusing the extracellular domain of a mutant torso protein, another Drosophila receptor tyrosine kinase, to the sevenless kinase. Our results show that competence to develop as neuronal cells in response to sevenless activity is spatially and temporally limited to the cells expressing sevenless. Therefore, the expression of sevenless marks a preexisting pattern of developmental potential in the disc epithelium.
Mechanisms of Development, 1992
Studies on the development of the R7 photoreceptor in the Drosophila eye thus far have identified three genes that specifically affect this cell: sevenless, boss and sina. In each of these mutants the R7 precursor develops instead as the equatorial cone cell (EQC). We have isolated an enhancer trap line, 1-1214, in which fl-galactosidase is primarily expressed in the R7 cell throughout its development. In mutations of sevenless, boss and sina, expression in H214 is initially reduced although still present in the R7 precursor and persists in the EQC into which it develops. The EQC in wild type never expresses /acZ in 1-1214. This result is in contrast to that seen with other enhancer trap lines that display expression in R7, and indicates that some aspect of R7 differentiation is independent of the genetic pathway(s) involving sevenless, boss and sina. Drosophila eye; H214; Positional information; sevenless; bride of sevenless; seven in absentia Correspondence to:
Neuroscience Research, 1996
Inhibitory signals of cellular differentiation from differentiating cells play an important role in regulating the number and spatial distribution of distinctive types of cells in developing tissues. Several types of inhibitory mechanisms of cellular differentiation have been identified by making full use of the developmental genetics of Drosophila compound eyes. These inhibitory mechanisms are distinct from each other in their signal transduction cascades and/or their role in the pattern formation of the developing Drosophila eye. The following events occur: firstly a diffusible protein, Scabrous (Sca), is required to confer regular spacings of the founder cells, R8 cells, or preommatidial clusters in the developing eye disc via an unknown signal transduction cascade, secondly the Notch-signalling is at least required for the single-out of the R8 cells within the pre-ommatidial cluster possibly by preventing other cells in the equivalent groups from adapting fates as R8 cells. Notch-signalling activates a simple signal cascade mediating communication between the plasma membrane and nucleus not via protein phosphorylation. In contrast, a novel diffusible ligand,.Argos, was likely to be required subsequently to the selection of R8 cells. Argos was shown to inhibit the activation of a receptor tyrosine kinase, DER, and the subsequent signal transduction in the Ras/MAPK cascade (the third inhibitory mechanism). We proposed that the role of Argos is to regulate the number of differentiated cells by controlling cellular differentiation and subsequent programmed cell death. The distinct roles of these inhibitory signals in the developing Drosophila eye are discussed in detail.
Dynamics of Drosophila eye development and temporal requirements of sevenless expression
Development, 1989
The development of the compound eye of Drosophila consists of a linear, stereotyped program starting at the posterior end of the eye imaginal disc and progressing towards the anterior border. The determination of the R7 photoreceptor cells is part of this process and is dependent on the sevenless gene. In this study, we used a heat-shock-inducible sevenless gene as a conditional allele to determine the exact temporal requirements of sevenless gene expression and to reveal the stages of ommatidial development during which the presumptive R7 cell can respond to the presence of sevenless protein. Our results indicate that sevenless gene function is only required during a brief, defined period for the initiation of R7 development; subsequently sevenless is dispensable for both differentiation and function of the R7 photoreceptors. Furthermore, using rescue of R7 cells as an internal marker to monitor the progression of eye development we could examine when and at what rate ommatidial co...
Journal of Cell Science, 2006
How cellular behaviors such as cell-to-cell communication, epithelial organization and cell shape reorganization are coordinated during development is poorly understood. The developing Drosophila eye offers an ideal model system to study these processes. Localized actin polymerization is required to constrict the apical surface of epithelial cells of the eye imaginal disc to maintain the refined arrangement of the developing ommatidia. The identity of each photoreceptor cell within the epithelium is determined by cell-to-cell contacts involving signal transduction events. The R7 photoreceptor cell requires the activity of the Sevenless RTK to adopt a proper cell fate. We performed an EP screen for negative regulators of this inductive process, and we identified the serine/threonine kinase Center divider (cdi) as a suppressor of the phenotype caused by an activated Sevenless receptor. Cdi is homologous to the human testis-specific kinase 1 (TESK1), a member of the LIM kinases involve...
Cell-fate determination in the developing Drosophila eye: role of the rough gene
Development, 1991
The homeobox-gene rough is required in photoreceptor cells R2 and R5 for normal ommatidial assembly in the developing Drosophila eye. We have used several celltype-specific markers and double mutant combinations to analyze cell-fate determination in rough. We show that the cells that would normally become R2 and/or R5 express a marker, a lacZ insertion in the seven-up (svp) gene, which is indicative of the Rl/3/4/6 cell fate. In addition, the analysis of mitotically induced svp,ro double mutant clones in the eye indicates that in rough all outer photoreceptors are under the genetic control of the svp gene. These results show that, in the absence of rough function, R2 and R5 fail to be correctly determined and appear to be transformed into cells of the R3/4/1/6 subtype. This transformation and the subsequent developmental defects do not preclude the recruitment of R7 cells. However, the presence of ommatidia containing more than one R7 and/or R8 cell in rough implies a complex network of cellular interactions underlying cell-fate determination in the Drosophila retina
Cell-fate determination in the developing Drosophila eye: role of the rough gene
Development (Cambridge, England), 1991
The homeobox-gene rough is required in photoreceptor cells R2 and R5 for normal ommatidial assembly in the developing Drosophila eye. We have used several cell-type-specific markers and double mutant combinations to analyze cell-fate determination in rough. We show that the cells that would normally become R2 and/or R5 express a marker, a lacZ insertion in the seven-up (svp) gene, which is indicative of the R1/3/4/6 cell fate. In addition, the analysis of mitotically induced svp,ro double mutant clones in the eye indicates that in rough all outer photoreceptors are under the genetic control of the svp gene. These results show that, in the absence of rough function, R2 and R5 fail to be correctly determined and appear to be transformed into cells of the R3/4/1/6 subtype. This transformation and the subsequent developmental defects do not preclude the recruitment of R7 cells. However, the presence of ommatidia containing more than one R7 and/or R8 cell in rough implies a complex netwo...