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1
Baccino-Calace, Martin, Daniel Prieto, Rafael Cantera et Boris Egger. « Compartment and cell-type specific hypoxia responses in the developing Drosophila brain ». Biology Open 9, no 8 (15 août 2020) : bio053629. http://dx.doi.org/10.1242/bio.053629.
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ABSTRACTEnvironmental factors such as the availability of oxygen are instructive cues that regulate stem cell maintenance and differentiation. We used a genetically encoded biosensor to monitor the hypoxic state of neural cells in the larval brain of Drosophila. The biosensor reveals brain compartment and cell-type specific levels of hypoxia. The values correlate with differential tracheolation that is observed throughout development between the central brain and the optic lobe. Neural stem cells in both compartments show the strongest hypoxia response while intermediate progenitors, neurons and glial cells reveal weaker responses. We demonstrate that the distance between a cell and the next closest tracheole is a good predictor of the hypoxic state of that cell. Our study indicates that oxygen availability appears to be the major factor controlling the hypoxia response in the developing Drosophila brain and that cell intrinsic and cell-type specific factors contribute to modulate the response in an unexpected manner.This article has an associated First Person interview with the first author of the paper.
2
Datta, S. « Control of proliferation activation in quiescent neuroblasts of the Drosophila central nervous system ». Development 121, no 4 (1 avril 1995) : 1173–82. http://dx.doi.org/10.1242/dev.121.4.1173.
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Stem cell proliferation is controlled through cell cycle arrest and activation. In the central nervous system of Drosophila melanogaster, neuroblast quiescence and activation takes place in defined spatial and temporal patterns. Two genes have been identified that regulate the pattern of neuroblast quiescence and proliferation. ana, which has been previously described by Ebens and coworkers (Ebens, A., Garren, H., Cheyette, B. N. R. and Zipursky, S. L. (1993). Cell 74, 15–28), encodes a secreted glial glycoprotein that inhibits premature neuroblast proliferation. We previously showed that trolsd causes a dramatic drop in the number of dividing cells in the larval brain late in development. This study presents evidence that this decrease results from a failure to activate proliferation in the quiescent neuroblast population at the appropriate time. However, trolsd does not affect the maintenance of cell division in already dividing mushroom body neuroblasts. The quiescent optic lobe and thoracic neuroblasts affected by trolsd proliferate in a trol mutant background if they have been activated by a lack of the ana proliferation repressor, demonstrating that trolsd does not affect cellular viability, nor does trol represent a celltype-specific mitotic factor. This also shows that trol acts downstream of ana to activate proliferation of quiescent neuroblasts in an ana-dependent pathway, possibly by inactivating or bypassing the ana repressor. These results suggest that trol and ana are components of a novel developmental pathway for the control of cell cycle activation in quiescent neuroblasts.
3
Truman, J. W., W. S. Talbot, S. E. Fahrbach et D. S. Hogness. « Ecdysone receptor expression in the CNS correlates with stage-specific responses to ecdysteroids during Drosophila and Manduca development ». Development 120, no 1 (1 janvier 1994) : 219–34. http://dx.doi.org/10.1242/dev.120.1.219.
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In insects, the ecdysteroids act to transform the CNS from its larval to its adult form. A key gene in this response is the ecdysone receptor (EcR), which has been shown in Drosophila to code for 3 protein isoforms. Two of these isoforms, EcR-A and EcR-B1, are prominently expressed in the CNS and we have used isoform-specific antibodies to examine their fluctuations through postembryonic life. EcR expression at the onset of metamorphosis is extremely diverse but specific patterns of EcR expression correlate with distinct patterns of steroid response. Most larval neurons show high levels of EcR-B1 at the start of metamorphosis, a time when they lose larval features in response to ecdysteroids. Earlier, during the larval molts, the same cells have no detectable receptors and show no response to circulating ecdysteroids; later, during the pupal-adult transformation, they switch to EcR-A expression and respond by maturing to their adult form. During the latter period, a subset of the larval neurons hyperexpress EcR-A and these cells are fated to die after the emergence of the adult. The stem cells for the imaginal neurons show prominent EcR-B1 expression during the last larval stage correlated with their main proliferative period. Most imaginal neurons, by contrast, express only EcR-A when they subsequently initiate maturation at the start of metamorphosis. The imaginal neurons of the mushroom bodies are unusual amongst imaginal neurons in expressing the B1 isoform at the start of metamorphosis but they also show regressive changes at this time as they lose their larval axons. Imaginal neurons of the optic lobe show a delayed expression of EcR-B1 through the period when cell-cell interactions are important for establishing connections within this region of the CNS. Overall, the appearance of the two receptor isoforms in cells correlates with different types of steroid responses: EcR-A predominates when cells are undergoing maturational responses whereas EcR-B1 predominates during proliferative activity or regressive responses. The heterogeneity of EcR expression at the start of metamorphosis presumably reflects the diverse origins and requirements of the neurons that nevertheless are all exposed to a common hormonal signal.
4
Tix, S., J. S. Minden et G. M. Technau. « Pre-existing neuronal pathways in the developing optic lobes of Drosophila ». Development 105, no 4 (1 avril 1989) : 739–46. http://dx.doi.org/10.1242/dev.105.4.739.
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We have identified a set of larval neurones in the developing adult optic lobes of Drosophila by selectively labelling cells that have undergone only a few mitoses. A cluster of three cells is located in each of the optic lobes near the insertion site of the optic stalk. Their axons fasciculate with fibres of the larval optic nerve, the Bolwig's nerve, and then form part of the posterior optic tract. These cells are likely to be first order interneurones of the larval visual system. Unlike the Bolwig's nerve, they persist into the adult stage. The possibility of a pioneering function of the larval visual system during formation of the adult optic lobe neuropil is discussed.
5
Poeck, B., A. Hofbauer et G. O. Pflugfelder. « Expression of the Drosophila optomotor-blind gene transcript in neuronal and glial cells of the developing nervous system ». Development 117, no 3 (1 mars 1993) : 1017–29. http://dx.doi.org/10.1242/dev.117.3.1017.
Texte intégralRésumé :
Mutations in the complex gene locus optomotor-blind (omb) can lead to defects in the development of both the optic lobes and external features of the adult fly. We describe here the expression of omb in the developing and adult nervous system using in situ hybridization. During embryogenesis, omb expression is first observed in the optic lobe anlagen. It later expands to a larger part of the developing larval brain and to the gnathal lobes. Cells in the ventral and peripheral nervous systems begin to express omb after completion of germ band extension. Later in embryonic development, expression declines and only persists in the antennomaxillary complex and in part of the brain hemispheres. During the larval and pupal stages, omb expression in the brain is confined to the developing optic lobes and contiguous regions of the central brain. At these stages, only a few cells show expression in the ventral ganglion. In the eye imaginal disc, transcript accumulation is most conspicuous in a group of presumptive glia precursor cells posterior to the morphogenetic furrow and in the optic stalk. In the adult brain, expression is prominent in several regions of the optic lobe cortex and along the border between central brain and optic lobes. In the mutation In(1)ombH31, 40 kb of regulatory DNA, downstream from the transcription unit, are removed from the omb gene. In(1)ombH31 is characterized by the lack of a set of giant interneurons from the lobula plate of the adult optic lobes. We find that, already during embryogenesis, there is a drastic difference between wild type and In(1)ombH31 in the level of the omb transcript in the optic lobe primordia. The adult mutant phenotype may thus be caused by omb misexpression during embryonic development.
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Campos, A. R., K. F. Fischbach et H. Steller. « Survival of photoreceptor neurons in the compound eye of Drosophila depends on connections with the optic ganglia ». Development 114, no 2 (1 février 1992) : 355–66. http://dx.doi.org/10.1242/dev.114.2.355.
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The importance of retinal innervation for the normal development of the optic ganglia in Drosophila is well documented. However, little is known about retrograde effects of the optic lobe on the adult photoreceptor cells (R-cells). We addressed this question by examining the survival of R-cells in mutant flies where R-cells do not connect to the brain. Although imaginal R-cells develop normally in the absence of connections to the optic lobes, we find that their continued survival requires these connections. Genetic mosaic studies with the disconnected (disco) mutation demonstrate that survival of R-cells does not depend on the genotype of the eye, but is correlated with the presence of connections to the optic ganglia. These results suggest the existence of retrograde interactions in the Drosophila visual system reminiscent of trophic interactions found in vertebrates.
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Holmes, A. L., et J. S. Heilig. « Fasciclin II and Beaten path modulate intercellular adhesion in Drosophila larval visual organ development ». Development 126, no 2 (15 janvier 1999) : 261–72. http://dx.doi.org/10.1242/dev.126.2.261.
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Previous studies demonstrated that Fasciclin II and Beaten path are necessary for regulating cell adhesion events that are important for motoneuron development in Drosophila. We observe that the cell adhesion molecule Fasciclin II and the secreted anti-adhesion molecule Beaten path have additional critical roles in the development of at least one set of sensory organs, the larval visual organs. Taken together, phenotypic analysis, genetic interactions, expression studies and rescue experiments suggest that, in normal development, secretion of Beaten path by cells of the optic lobes allows the Fasciclin II-expressing larval visual organ cells to detach from the optic lobes as a cohesive cell cluster. Our results also demonstrate that mechanisms guiding neuronal development may be shared between motoneurons and sensory organs, and provide evidence that titration of adhesion and anti-adhesion is critical for early steps in development of the larval visual system.
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Wang, Wei, Wenke Liu, Yue Wang, Liya Zhou, Xiaofang Tang et Hong Luo. « Notch signaling regulates neuroepithelial stem cell maintenance and neuroblast formation in Drosophila optic lobe development ». Developmental Biology 350, no 2 (février 2011) : 414–28. http://dx.doi.org/10.1016/j.ydbio.2010.12.002.
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Wang, Wei, Yonggang Li, Liya Zhou, Haitao Yue et Hong Luo. « Role of JAK/STAT signaling in neuroepithelial stem cell maintenance and proliferation in the Drosophila optic lobe ». Biochemical and Biophysical Research Communications 410, no 4 (juillet 2011) : 714–20. http://dx.doi.org/10.1016/j.bbrc.2011.05.119.
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Serikaku, M. A., et J. E. O'Tousa. « sine oculis is a homeobox gene required for Drosophila visual system development. » Genetics 138, no 4 (1 décembre 1994) : 1137–50. http://dx.doi.org/10.1093/genetics/138.4.1137.
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Abstract The somda (sine oculis-medusa) mutant is the result of a P element insertion at position 43C on the second chromosome. somda causes aberrant development of the larval photoreceptor (Bolwig's) organ and the optic lobe primordium in the embryo. Later in development, adult photoreceptors fail to project axons into the optic ganglion. Consequently optic lobe development is aborted and photoreceptor cells show age-dependent retinal degeneration. The so gene was isolated and characterized. The gene encodes a homeodomain protein expressed in the optic lobe primordium and Bolwig's organ of embryos, in the developing adult visual system of larvae, and in photoreceptor cells and optic lobes of adults. In addition, the SO product is found at invagination sites during embryonic development: at the stomadeal invagination, the cephalic furrow, and at segmental boundaries. The mutant somda allele causes severe reduction of SO embryonic expression but maintains adult visual system expression. Ubiquitous expression of the SO gene product in 4-8-hr embryos rescues all somda mutant abnormalities, including the adult phenotypes. Thus, all deficits in adult visual system development and function results from failure to properly express the so gene during embryonic development. This analysis shows that the homeodomain containing SO gene product is involved in the specification of the larval and adult visual system development during embryogenesis.
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Raji, Joshua I., et Christopher J. Potter. « The number of neurons in Drosophila and mosquito brains ». PLOS ONE 16, no 5 (14 mai 2021) : e0250381. http://dx.doi.org/10.1371/journal.pone.0250381.
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Various insect species serve as valuable model systems for investigating the cellular and molecular mechanisms by which a brain controls sophisticated behaviors. In particular, the nervous system of Drosophila melanogaster has been extensively studied, yet experiments aimed at determining the number of neurons in the Drosophila brain are surprisingly lacking. Using isotropic fractionator coupled with immunohistochemistry, we counted the total number of neuronal and non-neuronal cells in the whole brain, central brain, and optic lobe of Drosophila melanogaster. For comparison, we also counted neuronal populations in three divergent mosquito species: Aedes aegypti, Anopheles coluzzii and Culex quinquefasciatus. The average number of neurons in a whole adult brain was determined to be 199,380 ±3,400 cells in D. melanogaster, 217,910 ±6,180 cells in Ae. aegypti, 223,020 ± 4,650 cells in An. coluzzii and 225,911±7,220 cells in C. quinquefasciatus. The mean neuronal cell count in the central brain vs. optic lobes for D. melanogaster (101,140 ±3,650 vs. 107,270 ± 2,720), Ae. aegypti (109,140 ± 3,550 vs. 112,000 ± 4,280), An. coluzzii (105,130 ± 3,670 vs. 107,140 ± 3,090), and C. quinquefasciatus (108,530 ±7,990 vs. 110,670 ± 3,950) was also estimated. Each insect brain was comprised of 89% ± 2% neurons out of its total cell population. Isotropic fractionation analyses did not identify obvious sexual dimorphism in the neuronal and non-neuronal cell population of these insects. Our study provides experimental evidence for the total number of neurons in Drosophila and mosquito brains.
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Winberg, M. L., S. E. Perez et H. Steller. « Generation and early differentiation of glial cells in the first optic ganglion of Drosophila melanogaster ». Development 115, no 4 (1 août 1992) : 903–11. http://dx.doi.org/10.1242/dev.115.4.903.
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We have examined the generation and development of glial cells in the first optic ganglion, the lamina, of Drosophila melanogaster. Previous work has shown that the growth of retinal axons into the developing optic lobes induces the terminal cell divisions that generate the lamina monopolar neurons. We investigated whether photoreceptor ingrowth also influences the development of lamina glial cells, using P element enhancer trap lines, genetic mosaics and birthdating analysis. Enhancer trap lines that mark the differentiating lamina glial cells were found to require retinal innervation for expression. In mutants with only a few photoreceptors, only the few glial cells near ingrowing axons expressed the marker. Genetic mosaic analysis indicates that the lamina neurons and glial cells are readily separable, suggesting that these are derived from distinct lineages. Additionally, BrdU pulse-chase experiments showed that the cell divisions that produce lamina glia, unlike those producing lamina neurons, are not spatially or temporally correlated with the retinal axon ingrowth. Finally, in mutants lacking photoreceptors, cell divisions in the glial lineage appeared normal. We conclude that the lamina glial cells derive from a lineage that is distinct from that of the L-neurons, that glia are generated independently of photoreceptor input, and that completion of the terminal glial differentiation program depends, directly or indirectly, on an inductive signal from photoreceptor axons.
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Pflugfelder, G. O., H. Schwarz, H. Roth, B. Poeck, A. Sigl, S. Kerscher, B. Jonschker, W. L. Pak et M. Heisenberg. « Genetic and molecular characterization of the optomotor-blind gene locus in Drosophila melanogaster. » Genetics 126, no 1 (1 septembre 1990) : 91–104. http://dx.doi.org/10.1093/genetics/126.1.91.
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Abstract The Drosophila gene optomotor-blind (omb) is involved in the development of a set of giant neurons in the optic lobes and possibly other structures in the imaginal brain. Adult flies have discrete defects in optomotor behavior. The gene has previously been mapped in chromomeres 4C5-6, together with three other genes, bifid, Quadroon and lacqueredgls. We have localized the gene in a genomic walk of 340 kb of DNA. By mapping seven chromosome breakpoints with omb phenotype we determined its minimum size to about 80 kb. From this region more than 20 RNAs of different size and temporal expression pattern are transcribed. Three of them (T3, T7 and T7') stem from primary transcripts of 40-80 kb in length. In its distal part the omb gene overlaps in at least 19 kb with four other complementation units, bifid, l(1)bifid, Quadroon and lacqueredgls. The three nonlethals affect the external appearance of the fly and seem to be unrelated to brain development.
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Zhang, Stephanie, Miles Markey, Caroline D. Pena, Tadmiri Venkatesh et Maribel Vazquez. « A Micro-Optic Stalk (μOS) System to Model the Collective Migration of Retinal Neuroblasts ». Micromachines 11, no 4 (31 mars 2020) : 363. http://dx.doi.org/10.3390/mi11040363.
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Contemporary regenerative therapies have introduced stem-like cells to replace damaged neurons in the visual system by recapitulating critical processes of eye development. The collective migration of neural stem cells is fundamental to retinogenesis and has been exceptionally well-studied using the fruit fly model of Drosophila Melanogaster. However, the migratory behavior of its retinal neuroblasts (RNBs) has been surprisingly understudied, despite being critical to retinal development in this invertebrate model. The current project developed a new microfluidic system to examine the collective migration of RNBs extracted from the developing visual system of Drosophila as a model for the collective motile processes of replacement neural stem cells. The system scales with the microstructure of the Drosophila optic stalk, which is a pre-cursor to the optic nerve, to produce signaling fields spatially comparable to in vivo RNB stimuli. Experiments used the micro-optic stalk system, or μOS, to demonstrate the preferred sizing and directional migration of collective, motile RNB groups in response to changes in exogenous concentrations of fibroblast growth factor (FGF), which is a key factor in development. Our data highlight the importance of cell-to-cell contacts in enabling cell cohesion during collective RNB migration and point to the unexplored synergy of invertebrate cell study and microfluidic platforms to advance regenerative strategies.
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Saez, L., et M. W. Young. « In situ localization of the per clock protein during development of Drosophila melanogaster. » Molecular and Cellular Biology 8, no 12 (décembre 1988) : 5378–85. http://dx.doi.org/10.1128/mcb.8.12.5378.
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The per locus influences biological rhythms in Drosophila melanogaster. In this study, per transcripts and proteins were localized in situ in pupae and adults. Earlier genetic studies have demonstrated that per expression is required in the brain for circadian locomotor activity rhythms and in the thorax for ultradian rhythmicity of the Drosophila courtship song. per RNA and proteins were detected in a restricted group of cells in the eyes and optic lobes of the adult brain and in many cell bodies in the adult and pupal thoracic ganglia. per products were also found in the pupal ring gland complex, a tissue involved in rhythmic aspects of Drosophila development. Abundant expression was seen in gonadal tissue. No biological clock phenotypes have been reported for this tissue in any of the per mutants, per protein mapped to different subcellular locations in different tissues. The protein accumulated in or around nuclei in some cells and appeared to be cytoplasmic in others.
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Saez, L., et M. W. Young. « In situ localization of the per clock protein during development of Drosophila melanogaster ». Molecular and Cellular Biology 8, no 12 (décembre 1988) : 5378–85. http://dx.doi.org/10.1128/mcb.8.12.5378-5385.1988.
Texte intégralRésumé :
The per locus influences biological rhythms in Drosophila melanogaster. In this study, per transcripts and proteins were localized in situ in pupae and adults. Earlier genetic studies have demonstrated that per expression is required in the brain for circadian locomotor activity rhythms and in the thorax for ultradian rhythmicity of the Drosophila courtship song. per RNA and proteins were detected in a restricted group of cells in the eyes and optic lobes of the adult brain and in many cell bodies in the adult and pupal thoracic ganglia. per products were also found in the pupal ring gland complex, a tissue involved in rhythmic aspects of Drosophila development. Abundant expression was seen in gonadal tissue. No biological clock phenotypes have been reported for this tissue in any of the per mutants, per protein mapped to different subcellular locations in different tissues. The protein accumulated in or around nuclei in some cells and appeared to be cytoplasmic in others.
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Mamon, Ludmila, Anna Yakimova, Daria Kopytova et Elena Golubkova. « The RNA-Binding Protein SBR (Dm NXF1) Is Required for the Constitution of Medulla Boundaries in Drosophila melanogaster Optic Lobes ». Cells 10, no 5 (10 mai 2021) : 1144. http://dx.doi.org/10.3390/cells10051144.
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Drosophila melanogaster sbr (small bristles) is an orthologue of the Nxf1 (nuclear export factor 1) genes in different Opisthokonta. The known function of Nxf1 genes is the export of various mRNAs from the nucleus to the cytoplasm. The cytoplasmic localization of the SBR protein indicates that the nuclear export function is not the only function of this gene in Drosophila. RNA-binding protein SBR enriches the nucleus and cytoplasm of specific neurons and glial cells. In sbr12 mutant males, the disturbance of medulla boundaries correlates with the defects of photoreceptor axons pathfinding, axon bundle individualization, and developmental neurodegeneration. RNA-binding protein SBR participates in processes allowing axons to reach and identify their targets.
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Schmidt, C. J., S. Garen-Fazio, Y. K. Chow et E. J. Neer. « Neuronal expression of a newly identified Drosophila melanogaster G protein alpha 0 subunit. » Cell Regulation 1, no 1 (novembre 1989) : 125–34. http://dx.doi.org/10.1091/mbc.1.1.125.
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Guanine nucleotide-binding proteins (G proteins) mediate signals between activated cell-surface receptors and cellular effectors. A bovine G-protein alpha-subunit cDNA has been used to isolate similar sequences from Drosophila genomic and cDNA libraries. One class, which we call DG alpha 0, hybridized to position 47A on the second chromosome of Drosophila. The nucleotide sequence of the protein coding region of one cDNA has been determined, revealing an alpha subunit that is 81% identical with rat alpha 0. The cDNA hybridizes strongly to a 3.8 kb mRNA and weakly with a 5.3 kb message. Antibodies raised against a trp-E-DG alpha 0 fusion protein recognized a 39,000 Da protein in Drosophila extracts. In situ hybridization to adult Drosophila sections combined with immunohistochemical studies revealed expression throughout the optic lobes and central brain and in the thoracic and abdominal ganglia. DG alpha 0 message and protein were also detected in the antennae, oocytes, and ovarian nurse cells. The neuronal expression of this gene is similar to mammalian alpha 0, which is most abundantly expressed in the brain.
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Bentley, A. M., Byron C. Williams, Michael L. Goldberg et Andrew J. Andres. « Phenotypic characterization ofDrosophila idamutants : defining the role of APC5 in cell cycle progression ». Journal of Cell Science 115, no 5 (1 mars 2002) : 949–61. http://dx.doi.org/10.1242/jcs.115.5.949.
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We have cloned and characterized the ida gene that is required for proliferation of imaginal disc cells during Drosophila development. IDA is homologous to APC5, a subunit of the anaphase-promoting complex(APC/cyclosome). ida mRNA is detected in most cell types throughout development, but it accumulates to its highest levels during early embryogenesis. A maternal component of IDA is required for the production of eggs and viable embryos. Homozygous ida mutants display mitotic defects: they die during prepupal development, lack all mature imaginal disc structures, and have abnormally small optic lobes. Cytological observations show that ida mutant brains have a high mitotic index and many imaginal cells contain an aneuploid number of aberrant overcondensed chromosomes. However, cells are not stalled in metaphase, as mitotic stages in which chromosomes are orientated at the equatorial plate are never observed. Interestingly, some APC/C-target substrates such as cyclin B are not degraded in ida mutants, whereas others controlling sister-chromatid separation appear to be turned over. Taken together, these results suggest a model in which IDA/APC5 controls regulatory subfunctions of the anaphase-promoting complex.
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Beer, Katharina, Esther Kolbe, Noa B. Kahana, Nadav Yayon, Ron Weiss, Pamela Menegazzi, Guy Bloch et Charlotte Helfrich-Förster. « Pigment-Dispersing Factor-expressing neurons convey circadian information in the honey bee brain ». Open Biology 8, no 1 (janvier 2018) : 170224. http://dx.doi.org/10.1098/rsob.170224.
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Pigment-Dispersing Factor (PDF) is an important neuropeptide in the brain circadian network of Drosophila and other insects, but its role in bees in which the circadian clock influences complex behaviour is not well understood. We combined high-resolution neuroanatomical characterizations, quantification of PDF levels over the day and brain injections of synthetic PDF peptide to study the role of PDF in the honey bee Apis mellifera . We show that PDF co-localizes with the clock protein Period (PER) in a cluster of laterally located neurons and that the widespread arborizations of these PER/PDF neurons are in close vicinity to other PER-positive cells (neurons and glia). PDF-immunostaining intensity oscillates in a diurnal and circadian manner with possible influences for age or worker task on synchrony of oscillations in different brain areas. Finally, PDF injection into the area between optic lobes and the central brain at the end of the subjective day produced a consistent trend of phase-delayed circadian rhythms in locomotor activity. Altogether, these results are consistent with the hypothesis that PDF is a neuromodulator that conveys circadian information from pacemaker cells to brain centres involved in diverse functions including locomotion, time memory and sun-compass orientation.
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Ambrosini, Arnaud, et Katja Röper. « “Neur”al brain wave : Coordinating epithelial-to-neural stem cell transition in the fly optic lobe ». Journal of Cell Biology 219, no 11 (15 octobre 2020). http://dx.doi.org/10.1083/jcb.202009040.
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In the Drosophila larval optic lobe, the generation of neural stem cells involves an epithelial-to-mesenchymal–like transition of a continuous stripe of cells that sweeps across the neuroepithelium, but the dynamics at cell and tissue level were unknown until now. In this issue, Shard et al. (2020. J. Cell Biol.https://doi.org/10.1083/jcb.202005035) identify that Neuralized controls a partial epithelial-to-mesenchymal transition through regulation of the apical Crumbs complex and through the coordination of cell behaviors such as apical constriction and cell alignment.
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Shard, Chloé, Juan Luna-Escalante et François Schweisguth. « Tissue-wide coordination of epithelium-to-neural stem cell transition in the Drosophila optic lobe requires Neuralized ». Journal of Cell Biology 219, no 11 (18 septembre 2020). http://dx.doi.org/10.1083/jcb.202005035.
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Many tissues are produced by specialized progenitor cells emanating from epithelia via epithelial-to-mesenchymal transition (EMT). Most studies have so far focused on EMT involving single or isolated groups of cells. Here we describe an EMT-like process that requires tissue-level coordination. This EMT-like process occurs along a continuous front in the Drosophila optic lobe neuroepithelium to produce neural stem cells (NSCs). We find that emerging NSCs remain epithelial and apically constrict before dividing asymmetrically to produce neurons. Apical constriction is associated with contractile myosin pulses and involves RhoGEF3 and down-regulation of the Crumbs complex by the E3 ubiquitin ligase Neuralized. Anisotropy in Crumbs complex levels also results in accumulation of junctional myosin. Disrupting the regulation of Crumbs by Neuralized lowered junctional myosin and led to imprecision in the integration of emerging NSCs into the front. Thus, Neuralized promotes smooth progression of the differentiation front by coupling epithelium remodeling at the tissue level with NSC fate acquisition.
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Islam, Ishrat Maliha, June Ng, Priscilla Valentino et Ted Erclik. « Identification of enhancers that drive the spatially restricted expression of Vsx1 and Rx in the outer proliferation center of the developing Drosophila optic lobe ». Genome, 15 octobre 2020, 1–9. http://dx.doi.org/10.1139/gen-2020-0034.
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Combinatorial spatial and temporal patterning of stem cells is a powerful mechanism for the generation of neural diversity in insect and vertebrate nervous systems. In the developing Drosophila medulla, the neural stem cells of the outer proliferation center (OPC) are spatially patterned by the mutually exclusive expression of three homeobox transcription factors: Vsx1 in the center of the OPC crescent (cOPC), Optix in the main arms (mOPC), and Rx in the posterior tips (pOPC). These spatial factors act together with a temporal cascade of transcription factors in OPC neuroblasts to specify the greater than 80 medulla cell types. Here, we identify the enhancers that are sufficient to drive the spatially restricted expression of the Vsx1 and Rx genes in the OPC. We show that removal of the cOPC enhancer in the Muddled inversion mutant leads to the loss of Vsx1 expression in the cOPC. Analysis of the evolutionarily conserved sequences within these enhancers suggests that direct repression by Optix may restrict the expression of Vsx1 and Rx to the cOPC and pOPC, respectively.
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Guzmán-Palma, Pablo, Esteban G. Contreras, Natalia Mora, Macarena Smith, M. Constanza González-Ramírez, Jorge M. Campusano, Jimena Sierralta, Bassem A. Hassan et Carlos Oliva. « Slit/Robo Signaling Regulates Multiple Stages of the Development of the Drosophila Motion Detection System ». Frontiers in Cell and Developmental Biology 9 (21 avril 2021). http://dx.doi.org/10.3389/fcell.2021.612645.
Texte intégralRésumé :
Neurogenesis is achieved through a sequence of steps that include specification and differentiation of progenitors into mature neurons. Frequently, precursors migrate to distinct positions before terminal differentiation. The Slit-Robo pathway, formed by the secreted ligand Slit and its membrane bound receptor Robo, was first discovered as a regulator of axonal growth. However, today, it is accepted that this pathway can regulate different cellular processes even outside the nervous system. Since most of the studies performed in the nervous system have been focused on axonal and dendritic growth, it is less clear how versatile is this signaling pathway in the developing nervous system. Here we describe the participation of the Slit-Robo pathway in the development of motion sensitive neurons of theDrosophila visualsystem. We show that Slit and Robo receptors are expressed in different stages during the neurogenesis of motion sensitive neurons. Furthermore, we find that Slit and Robo regulate multiple aspects of their development including neuronal precursor migration, cell segregation between neural stem cells and daughter cells and formation of their connectivity pattern. Specifically, loss of function ofslitorroboreceptors in differentiated motion sensitive neurons impairs dendritic targeting, while knocking downroboreceptors in migratory progenitors or neural stem cells leads to structural defects in the adult optic lobe neuropil, caused by migration and cell segregation defects during larval development. Thus, our work reveals the co-option of the Slit-Robo signaling pathway in distinct developmental stages of a neural lineage.
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Haag, Juergen, Alexander Arenz, Etienne Serbe, Fabrizio Gabbiani et Alexander Borst. « Complementary mechanisms create direction selectivity in the fly ». eLife 5 (9 août 2016). http://dx.doi.org/10.7554/elife.17421.
Texte intégralRésumé :
How neurons become sensitive to the direction of visual motion represents a classic example of neural computation. Two alternative mechanisms have been discussed in the literature so far: preferred direction enhancement, by which responses are amplified when stimuli move along the preferred direction of the cell, and null direction suppression, where one signal inhibits the response to the subsequent one when stimuli move along the opposite, i.e. null direction. Along the processing chain in the Drosophila optic lobe, directional responses first appear in T4 and T5 cells. Visually stimulating sequences of individual columns in the optic lobe with a telescope while recording from single T4 neurons, we find both mechanisms at work implemented in different sub-regions of the receptive field. This finding explains the high degree of directional selectivity found already in the fly’s primary motion-sensing neurons and marks an important step in our understanding of elementary motion detection.
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Nandakumar, Shyama, Olga Grushko et Laura A. Buttitta. « Polyploidy in the adult Drosophila brain ». eLife 9 (25 août 2020). http://dx.doi.org/10.7554/elife.54385.
Texte intégralRésumé :
Long-lived cells such as terminally differentiated postmitotic neurons and glia must cope with the accumulation of damage over the course of an animal’s lifespan. How long-lived cells deal with ageing-related damage is poorly understood. Here we show that polyploid cells accumulate in the adult fly brain and that polyploidy protects against DNA damage-induced cell death. Multiple types of neurons and glia that are diploid at eclosion, become polyploid in the adult Drosophila brain. The optic lobes exhibit the highest levels of polyploidy, associated with an elevated DNA damage response in this brain region. Inducing oxidative stress or exogenous DNA damage leads to an earlier onset of polyploidy, and polyploid cells in the adult brain are more resistant to DNA damage-induced cell death than diploid cells. Our results suggest polyploidy may serve a protective role for neurons and glia in adult Drosophila melanogaster brains.
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Vogt, Katrin, Yoshinori Aso, Toshihide Hige, Stephan Knapek, Toshiharu Ichinose, Anja B. Friedrich, Glenn C. Turner, Gerald M. Rubin et Hiromu Tanimoto. « Direct neural pathways convey distinct visual information to Drosophila mushroom bodies ». eLife 5 (15 avril 2016). http://dx.doi.org/10.7554/elife.14009.
Texte intégralRésumé :
Previously, we demonstrated that visual and olfactory associative memories of Drosophila share mushroom body (MB) circuits (<xref ref-type="bibr" rid="bib46">Vogt et al., 2014</xref>). Unlike for odor representation, the MB circuit for visual information has not been characterized. Here, we show that a small subset of MB Kenyon cells (KCs) selectively responds to visual but not olfactory stimulation. The dendrites of these atypical KCs form a ventral accessory calyx (vAC), distinct from the main calyx that receives olfactory input. We identified two types of visual projection neurons (VPNs) directly connecting the optic lobes and the vAC. Strikingly, these VPNs are differentially required for visual memories of color and brightness. The segregation of visual and olfactory domains in the MB allows independent processing of distinct sensory memories and may be a conserved form of sensory representations among insects.
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Rodrigues, Diana, Yoan Renaud, K. VijayRaghavan, Lucas Waltzer et Maneesha S. Inamdar. « Differential activation of JAK-STAT signaling reveals functional compartmentalization in Drosophila blood progenitors ». eLife 10 (17 février 2021). http://dx.doi.org/10.7554/elife.61409.
Texte intégralRésumé :
Blood cells arise from diverse pools of stem and progenitor cells. Understanding progenitor heterogeneity is a major challenge. TheDrosophilalarval lymph gland is a well-studied model to understand blood progenitor maintenance and recapitulates several aspects of vertebrate hematopoiesis. However in-depth analysis has focused on the anterior lobe progenitors (AP), ignoring the posterior progenitors (PP) from the posterior lobes. Using in situ expression mapping and developmental and transcriptome analysis, we reveal PP heterogeneity and identify molecular-genetic tools to study this abundant progenitor population. Functional analysis shows that PP resist differentiation upon immune challenge, in a JAK-STAT-dependent manner. Upon wasp parasitism, AP downregulate JAK-STAT signaling and form lamellocytes. In contrast, we show that PP activate STAT92E and remain undifferentiated, promoting survival.Stat92Eknockdown or genetically reducing JAK-STAT signaling permits PP lamellocyte differentiation. We discuss how heterogeneity and compartmentalization allow functional segregation in response to systemic cues and could be widely applicable.