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. 2018 Nov 22;13(1):25.
doi: 10.1186/s13064-018-0123-8.

Dynamic Notch signalling regulates neural stem cell state progression in the Drosophila optic lobe

Esteban G Contreras  1 , Boris Egger  1   2 , Katrina S Gold  1 , Andrea H Brand  3
Affiliations

Dynamic Notch signalling regulates neural stem cell state progression in the Drosophila optic lobe

Esteban G Contreras et al. Neural Dev. .

Abstract

Background: Neural stem cells generate all of the neurons and glial cells in the central nervous system, both during development and in the adult to maintain homeostasis. In the Drosophila optic lobe, neuroepithelial cells progress through two transient progenitor states, PI and PII, before transforming into neuroblasts. Here we analyse the role of Notch signalling in the transition from neuroepithelial cells to neuroblasts.

Results: We observed dynamic regulation of Notch signalling: strong activity in PI progenitors, low signalling in PII progenitors, and increased activity after neuroblast transformation. Ectopic expression of the Notch ligand Delta induced the formation of ectopic PI progenitors. Interestingly, we show that the E3 ubiquitin ligase, Neuralized, regulates Delta levels and Notch signalling activity at the transition zone. We demonstrate that the proneural transcription factor, Lethal of scute, is essential to induce expression of Neuralized and promote the transition from the PI progenitor to the PII progenitor state.

Conclusions: Our results show dynamic regulation of Notch signalling activity in the transition from neuroepithelial cells to neuroblasts. We propose a model in which Lethal of scute activates Notch signalling in a non-cell autonomous manner by regulating the expression of Neuralized, thereby promoting the progression between different neural stem cell states.

Keywords: Neural stem cell; Neuralized; Notch; Optic lobe.

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Figures

Fig. 1
Fig. 1
E(spl)mγ expression reports Notch signalling at the transition zone. (a) Schematic model of the optic lobe transition (TZ) between NE cells into NBs. NE cells divide symmetrically to amplify their pool and transform into PI progenitors, expressing low levels of nuclear Dpn (blue). PI progenitors transform into PII progenitors, characterised by the expression of L’sc (red), and PII progenitors transform into NBs that divides asymmetrically and generate differentiated progeny. Modified from [8]. (b-b”’) Immunostaining of the optic lobe transition zone expressing the Notch reporter (b’) E(spl)mγ-GFP (green) and stained for (b”) Dl (red) and (b”’) Dpn (blue). (c) Schematic model of Notch signalling activation at the optic lobe transition zone, showing two peaks of Notch signalling activation in PI progenitors and in NBs. Scale bars are 20 μm
Fig. 2
Fig. 2
Notch signalling regulates PI progenitor fate and prevents PII progenitor conversion into neuroblasts. (a-Aa”) Staining of clone misexpressing the NICD in the optic lobe transition zone. Clone was marked by β-gal expression (blue) and marked by dotted lines; E(spl)mγ expression in green, and Dpn in red. (b-b”) Wild-type brain transition zone stained for E(spl)mγ in green, Dpn in red and Notch receptor in blue (b) or grey (b”). Arrows indicate the end of Notch receptor and Notch signalling activation (c-d”) Staining of clones misexpressing a full length Notch receptor (NFL) for (c - d”) E(spl)mγ in green, Dpn in red (c, c”) and L’sc in red (d, d”). Arrows indicate E(spl)mγ activation after PI progenitor formation and (d-d”) a delay in PII progenitor transformation into NBs. Arrowheads show cells in the clone that do not activate Notch signalling (c-c”). Scale bars are 20 μm
Fig. 3
Fig. 3
Delta necessary ans sufficient for Notch signalling inducing PI progenitor formation. (a-b”) Immunostaining of Dl misexpressing clones, E(spl)mγ in green, and Dpn in red. Clones were marked by β-gal staining in blue and dotted line. Arrowheads show E(spl)mγ activation in clone neighbouring cells. (c-d”’) Dlrev10 mutant clones stained for E(spl)mγ in green, Dpn in blue, and Dl in gray. Clones were marked by the absence of RFP expression and dotted lines. Arrows show E(spl)mγ expression inside mutant cells that were in contact with wild-type cells. Arrowheads show NBs not expressing E(spl)mγ. Scale bars are 20 μm
Fig. 4
Fig. 4
neuralized is expressed in PII progenitors and in optic lobe neuroblasts. (a) Immunostaining of neur-lacZ larval brains for β-gal/neur in green, Dl in red and L’sc in blue. Arrowheads show PII progenitor expressing neur, Dl and L’sc. (b) Schematic representation of neur expression during the transition between NE cells into NBs. Scale bars are 20 μm
Fig. 5
Fig. 5
Notch signalling activation requires Neuralized function at the transition zone. (a-b”’) neur1 mutant clones stained for E(spl)mγ in green, (a,a”) Dpn in blue, (b,b”) L’sc in blue, (a”’) Dl in gray and (b”’) Asense (Ase), as a neuroblast marker, in gray. Clones were marked by the absence of RFP expression and dotted lines. (a-a”) Arrows show decrease in E(spl)mγ staining in PI progenitors and arrowheads in NBs. (b-b”) Arrows pointed L’sc-positive PII progenitor inside neur mutant clone. Scale bars are 20 μm
Fig. 6
Fig. 6
Lethal of scute regulates neutralized expression and generates ectopic transition zone in a cell non-autonomous manner. (a-c”’) Immunostaining of L’sc misexpressing clones in neur-lacZ larval brain for β-gal/neur in green, Dpn in and Notch in gray. Clones were marked by GFP expression in blue and dotted lines. Arrows show ectopic activation of neur expression (a-a”’) inside and (b-c”’) outside L’sc misexpressing clones. Note that in (c-c”’) there is no NE cell misexpressing L’sc (no GFP expression, blue). Scale bars are 20 μm
Fig. 7
Fig. 7
Working models of Notch signalling during the transition of neural stem cell states. Two models showing the progression of the transition between NE cells into NBs. a Long-range activation of Notch signalling in PI progenitors can be controlled by L’sc in PII progenitors. L’sc regulates neur expression that activates Dl function. b Activation of Notch signalling is regulated by L’sc-positive/Neur-positive/Dl-positive PII progenitors inducing Dl expression in the closer neighbour and generating a gradient of E(spl)mγ expression in PI progenitors. In both models, PII progenitors are able to induce the PII fate in PI progenitor, while PI progenitors promote NE cells transformation intro PI state. When PII progenitors convert into NB, PI progenitors replace PII progenitors and NE cells convert into PI progenitors, promoting the progression of the proneural wave
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References

    1. Brand AH, Livesey FJ. Neural stem cell biology in vertebrates and invertebrates: more alike than different? Neuron. 2011;70(4):719–729. doi: 10.1016/j.neuron.2011.05.016. - DOI - PubMed
    1. Lanet E, Gould A, Maurange C. Protection of neuronal diversity at the expense of neuronal numbers during nutrient restriction in the Drosophila visual system. Cell Rep. 2013;3(3):587–594. doi: 10.1016/j.celrep.2013.02.006. - DOI - PMC - PubMed
    1. Egger B, Boone JQ, Stevens NR, Brand AH, Doe CQ. Regulation of spindle orientation and neural stem cell fate in the Drosophila optic lobe. Neural Dev. 2007;2:1. doi: 10.1186/1749-8104-2-1. - DOI - PMC - PubMed
    1. Hofbauer A, Campos-Ortega J. Proliferation pattern and early differentiation of the optic lobes in Drosophila melanogaster. Roux Arch Dev Biol. 1990;198(5):264–274. doi: 10.1007/BF00377393. - DOI - PubMed
    1. Rujano MA, Sanchez-Pulido L, Pennetier C, le Dez G, Basto R. The microcephaly protein Asp regulates neuroepithelium morphogenesis by controlling the spatial distribution of myosin II. Nat Cell Biol. 2013;15(11):1294–1306. doi: 10.1038/ncb2858. - DOI - PubMed

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