RESUMO
Many animals use visual information to navigate1-4, but how such information is encoded and integrated by the navigation system remains incompletely understood. In Drosophila melanogaster, EPG neurons in the central complex compute the heading direction5 by integrating visual input from ER neurons6-12, which are part of the anterior visual pathway (AVP)10,13-16. Here we densely reconstruct all neurons in the AVP using electron-microscopy data17. The AVP comprises four neuropils, sequentially linked by three major classes of neurons: MeTu neurons10,14,15, which connect the medulla in the optic lobe to the small unit of the anterior optic tubercle (AOTUsu) in the central brain; TuBu neurons9,16, which connect the AOTUsu to the bulb neuropil; and ER neurons6-12, which connect the bulb to the EPG neurons. On the basis of morphologies, connectivity between neural classes and the locations of synapses, we identify distinct information channels that originate from four types of MeTu neurons, and we further divide these into ten subtypes according to the presynaptic connections in the medulla and the postsynaptic connections in the AOTUsu. Using the connectivity of the entire AVP and the dendritic fields of the MeTu neurons in the optic lobes, we infer potential visual features and the visual area from which any ER neuron receives input. We confirm some of these predictions physiologically. These results provide a strong foundation for understanding how distinct sensory features can be extracted and transformed across multiple processing stages to construct higher-order cognitive representations.
Assuntos
Conectoma , Drosophila melanogaster , Neurônios , Neurópilo , Navegação Espacial , Sinapses , Vias Visuais , Animais , Drosophila melanogaster/fisiologia , Drosophila melanogaster/citologia , Vias Visuais/fisiologia , Navegação Espacial/fisiologia , Neurônios/fisiologia , Neurópilo/citologia , Masculino , Feminino , Lobo Óptico de Animais não Mamíferos/citologia , Microscopia EletrônicaRESUMO
The fruit fly Drosophila melanogaster has emerged as a key model organism in neuroscience, in large part due to the concentration of collaboratively generated molecular, genetic and digital resources available for it. Here we complement the approximately 140,000 neuron FlyWire whole-brain connectome1 with a systematic and hierarchical annotation of neuronal classes, cell types and developmental units (hemilineages). Of 8,453 annotated cell types, 3,643 were previously proposed in the partial hemibrain connectome2, and 4,581 are new types, mostly from brain regions outside the hemibrain subvolume. Although nearly all hemibrain neurons could be matched morphologically in FlyWire, about one-third of cell types proposed for the hemibrain could not be reliably reidentified. We therefore propose a new definition of cell type as groups of cells that are each quantitatively more similar to cells in a different brain than to any other cell in the same brain, and we validate this definition through joint analysis of FlyWire and hemibrain connectomes. Further analysis defined simple heuristics for the reliability of connections between brains, revealed broad stereotypy and occasional variability in neuron count and connectivity, and provided evidence for functional homeostasis in the mushroom body through adjustments of the absolute amount of excitatory input while maintaining the excitation/inhibition ratio. Our work defines a consensus cell type atlas for the fly brain and provides both an intellectual framework and open-source toolchain for brain-scale comparative connectomics.
Assuntos
Encéfalo , Conectoma , Drosophila melanogaster , Neurônios , Animais , Drosophila melanogaster/citologia , Drosophila melanogaster/fisiologia , Neurônios/citologia , Neurônios/fisiologia , Neurônios/classificação , Encéfalo/citologia , Encéfalo/fisiologia , Reprodutibilidade dos Testes , Masculino , Curadoria de Dados , Feminino , Contagem de Células , Corpos Pedunculados/citologia , Corpos Pedunculados/fisiologiaRESUMO
As connectomics advances, it will become commonplace to know far more about the structure of a nervous system than about its function. The starting point for many investigations will become neuronal wiring diagrams, which will be interpreted to make theoretical predictions about function. Here I demonstrate this emerging approach with the Drosophila optic lobe, analysing its structure to predict that three Dm3 (refs. 1-4) and three TmY (refs. 2,4) cell types are part of a circuit that serves the function of form vision. Receptive fields are predicted from connectivity, and suggest that the cell types encode the local orientation of a visual stimulus. Extraclassical5,6 receptive fields are also predicted, with implications for robust orientation tuning7, position invariance8,9 and completion of noisy or illusory contours10,11. The TmY types synapse onto neurons that project from the optic lobe to the central brain12,13, which are conjectured to compute conjunctions and disjunctions of oriented features. My predictions can be tested through neurophysiology, which would constrain the parameters and biophysical mechanisms in neural network models of fly vision14.
Assuntos
Drosophila melanogaster , Modelos Neurológicos , Neurônios , Lobo Óptico de Animais não Mamíferos , Animais , Lobo Óptico de Animais não Mamíferos/citologia , Lobo Óptico de Animais não Mamíferos/fisiologia , Drosophila melanogaster/fisiologia , Drosophila melanogaster/citologia , Neurônios/fisiologia , Visão Ocular/fisiologia , Vias Visuais/fisiologia , Sinapses/fisiologia , Orientação/fisiologiaRESUMO
Connections between neurons can be mapped by acquiring and analysing electron microscopic brain images. In recent years, this approach has been applied to chunks of brains to reconstruct local connectivity maps that are highly informative1-6, but nevertheless inadequate for understanding brain function more globally. Here we present a neuronal wiring diagram of a whole brain containing 5 × 107 chemical synapses7 between 139,255 neurons reconstructed from an adult female Drosophila melanogaster8,9. The resource also incorporates annotations of cell classes and types, nerves, hemilineages and predictions of neurotransmitter identities10-12. Data products are available for download, programmatic access and interactive browsing and have been made interoperable with other fly data resources. We derive a projectome-a map of projections between regions-from the connectome and report on tracing of synaptic pathways and the analysis of information flow from inputs (sensory and ascending neurons) to outputs (motor, endocrine and descending neurons) across both hemispheres and between the central brain and the optic lobes. Tracing from a subset of photoreceptors to descending motor pathways illustrates how structure can uncover putative circuit mechanisms underlying sensorimotor behaviours. The technologies and open ecosystem reported here set the stage for future large-scale connectome projects in other species.
Assuntos
Encéfalo , Conectoma , Drosophila melanogaster , Neurônios , Sinapses , Animais , Drosophila melanogaster/fisiologia , Drosophila melanogaster/citologia , Feminino , Encéfalo/citologia , Encéfalo/fisiologia , Neurônios/fisiologia , Neurônios/citologia , Vias Neurais/fisiologia , Vias Neurais/citologia , Neurotransmissores/metabolismo , Lobo Óptico de Animais não Mamíferos/citologia , Lobo Óptico de Animais não Mamíferos/fisiologia , Vias Eferentes/fisiologia , Vias Eferentes/citologia , Células Fotorreceptoras de Invertebrados/fisiologia , Células Fotorreceptoras de Invertebrados/citologiaRESUMO
A catalogue of neuronal cell types has often been called a 'parts list' of the brain1, and regarded as a prerequisite for understanding brain function2,3. In the optic lobe of Drosophila, rules of connectivity between cell types have already proven to be essential for understanding fly vision4,5. Here we analyse the fly connectome to complete the list of cell types intrinsic to the optic lobe, as well as the rules governing their connectivity. Most new cell types contain 10 to 100 cells, and integrate information over medium distances in the visual field. Some existing type families (Tm, Li, and LPi)6-10 at least double in number of types. A new serpentine medulla (Sm) interneuron family contains more types than any other. Three families of cross-neuropil types are revealed. The consistency of types is demonstrated by analysing the distances in high-dimensional feature space, and is further validated by algorithms that select small subsets of discriminative features. We use connectivity to hypothesize about the functional roles of cell types in motion, object and colour vision. Connectivity with 'boundary types' that straddle the optic lobe and central brain is also quantified. We showcase the advantages of connectomic cell typing: complete and unbiased sampling, a rich array of features based on connectivity and reduction of the connectome to a substantially simpler wiring diagram of cell types, with immediate relevance for brain function and development.
Assuntos
Conectoma , Drosophila melanogaster , Neurônios , Lobo Óptico de Animais não Mamíferos , Vias Visuais , Animais , Lobo Óptico de Animais não Mamíferos/citologia , Drosophila melanogaster/citologia , Drosophila melanogaster/fisiologia , Vias Visuais/fisiologia , Neurônios/fisiologia , Neurônios/citologia , Interneurônios/fisiologia , Interneurônios/citologia , Feminino , Visão de Cores/fisiologia , Neurópilo/citologia , Neurópilo/fisiologia , Percepção de Movimento/fisiologia , Masculino , Algoritmos , Modelos Neurológicos , Campos Visuais/fisiologiaRESUMO
Cell division is fundamental to all healthy tissue growth, as well as being rate-limiting in the tissue repair response to wounding and during cancer progression. However, the role that cell divisions play in tissue growth is a collective one, requiring the integration of many individual cell division events. It is particularly difficult to accurately detect and quantify multiple features of large numbers of cell divisions (including their spatio-temporal synchronicity and orientation) over extended periods of time. It would thus be advantageous to perform such analyses in an automated fashion, which can naturally be enabled using deep learning. Hence, we develop a pipeline of deep learning models that accurately identify dividing cells in time-lapse movies of epithelial tissues in vivo. Our pipeline also determines their axis of division orientation, as well as their shape changes before and after division. This strategy enables us to analyse the dynamic profile of cell divisions within the Drosophila pupal wing epithelium, both as it undergoes developmental morphogenesis and as it repairs following laser wounding. We show that the division axis is biased according to lines of tissue tension and that wounding triggers a synchronised (but not oriented) burst of cell divisions back from the leading edge.
Assuntos
Divisão Celular , Aprendizado Profundo , Drosophila melanogaster , Morfogênese , Asas de Animais , Animais , Epitélio/fisiologia , Epitélio/crescimento & desenvolvimento , Asas de Animais/crescimento & desenvolvimento , Asas de Animais/citologia , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/fisiologia , Drosophila melanogaster/citologia , Células Epiteliais/fisiologia , Células Epiteliais/citologia , Drosophila/fisiologia , Cicatrização/fisiologia , Imagem com Lapso de Tempo/métodosRESUMO
The number of neural stem cells reflects the total number of neurons in the mature brain. As neural stem cells arise from neuroepithelial cells, the neuroepithelial cell population must be expanded to secure a sufficient number of neural stem cells. However, molecular mechanisms that regulate timely differentiation from neuroepithelial to neural stem cells are largely unclear. Here, we show that TCF4/Daughterless is a key factor that determines the timing of the differentiation in Drosophila. The neuroepithelial cells initiated but never completed the differentiation in the absence of TCF4/Daughterless. We also found that TCF4/Daughterless binds to the Notch locus, suggesting that Notch is one of its downstream candidate genes. Consistently, Notch expression was ectopically induced in the absence of TCF4/Daughterless. Furthermore, ectopic activation of Notch signaling phenocopied loss of TCF4/Daughterless. Our findings demonstrate that TCF4/Daughterless directly inactivates Notch signaling pathway, resulting in completion of the differentiation from neuroepithelial cells into neural stem cells with optimal timing. Thus, the present results suggest that TCF4/Daughterless is essential for determining whether to move to the next state or stay in the current state in differentiating neuroepithelial cells.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos , Diferenciação Celular , Proteínas de Drosophila , Células-Tronco Neurais , Células Neuroepiteliais , Receptores Notch , Transdução de Sinais , Animais , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Receptores Notch/metabolismo , Receptores Notch/genética , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Células Neuroepiteliais/metabolismo , Células Neuroepiteliais/citologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Diferenciação Celular/genética , Regulação da Expressão Gênica no Desenvolvimento , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/citologia , Fatores de Tempo , Drosophila/metabolismoRESUMO
Alternative cleavage and polyadenylation (APA) often results in production of mRNA isoforms with either longer or shorter 3' UTRs from the same genetic locus, potentially impacting mRNA translation, localization, and stability. Developmentally regulated APA can thus make major contributions to cell type-specific gene expression programs as cells differentiate. During Drosophila spermatogenesis, â¼500 genes undergo APA when proliferating spermatogonia differentiate into spermatocytes, producing transcripts with shortened 3' UTRs, leading to profound stage-specific changes in the proteins expressed. The molecular mechanisms that specify usage of upstream polyadenylation sites in spermatocytes are thus key to understanding the changes in cell state. Here, we show that upregulation of PCF11 and Cbc, the two components of cleavage factor II (CFII), orchestrates APA during Drosophila spermatogenesis. Knockdown of PCF11 or cbc in spermatocytes caused dysregulation of APA, with many transcripts normally cleaved at a proximal site in spermatocytes now cleaved at their distal site, as in spermatogonia. Forced overexpression of CFII components in spermatogonia switched cleavage of some transcripts to the proximal site normally used in spermatocytes. Our findings reveal a developmental mechanism where changes in expression of specific cleavage factors can direct cell type-specific APA at selected genes.
Assuntos
Linhagem da Célula , Poliadenilação , Espermatócitos , Espermatogênese , Animais , Poliadenilação/genética , Masculino , Espermatogênese/genética , Espermatócitos/metabolismo , Espermatócitos/citologia , Linhagem da Célula/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Células-Tronco Adultas/metabolismo , Células-Tronco Adultas/citologia , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Espermatogônias/citologia , Espermatogônias/metabolismo , Fatores de Poliadenilação e Clivagem de mRNA/metabolismo , Fatores de Poliadenilação e Clivagem de mRNA/genéticaRESUMO
The Ras family genes are proto-oncogenes that are highly conserved from Drosophila to humans. In Drosophila, RasV12 is a constitutively activated form of the Ras oncoprotein, and its function in cell-cycle progression is context dependent. However, how it influences the cell cycle of female germline stem cells (GSCs) still remains unknown. Using both wild-type GSCs and bam mutant GSC-like cells as model systems, here we determined that RasV12 overexpression promotes GSC division, not growth, opposite to that in somatic wing disc cells. Ras performs this function through activating the mitogen-activated protein kinase (MAPK) signaling. This signaling is activated specifically in the M phase of mitotic germ cells, including both wild-type GSCs and bam mutant GSC-like cells. Furthermore, RasV12 overexpression triggers polyploid nurse cells to die through inducing mitotic stress. Given the similarities between Drosophila and mammalian GSCs, we propose that the Ras/MAPK signaling also promotes mammalian GSC division.
Assuntos
Divisão Celular , Proteínas de Drosophila , Ovário , Proteínas ras , Animais , Feminino , Ovário/citologia , Ovário/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas ras/metabolismo , Proteínas ras/genética , Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Sistema de Sinalização das MAP Quinases , Células Germinativas/metabolismo , Células Germinativas/citologia , Células-Tronco/metabolismo , Células-Tronco/citologia , Mitose , Drosophila/metabolismo , Transdução de SinaisRESUMO
Drosophila border cell clusters model collective cell migration. Airyscan super-resolution microscopy enables fine-scale description of cluster shape and texture. Here we describe how to convert Airyscan images of border cell clusters into 3D models of the surface and detect regions of convex and concave curvature. We use spectral decomposition analysis to compare surface textures across genotypes to determine how genes of interest impact cluster surface geometry. This protocol applies to border cells and could generalize to additional cell types. For complete details on the use and execution of this protocol, please refer to Gabbert et al.1.
Assuntos
Imageamento Tridimensional , Animais , Imageamento Tridimensional/métodos , Movimento Celular/fisiologia , Movimento Celular/genética , Drosophila/citologia , Drosophila melanogaster/citologia , Drosophila melanogaster/genéticaRESUMO
A deep understanding of how the brain controls behaviour requires mapping neural circuits down to the muscles that they control. Here, we apply automated tools to segment neurons and identify synapses in an electron microscopy dataset of an adult female Drosophila melanogaster ventral nerve cord (VNC)1, which functions like the vertebrate spinal cord to sense and control the body. We find that the fly VNC contains roughly 45 million synapses and 14,600 neuronal cell bodies. To interpret the output of the connectome, we mapped the muscle targets of leg and wing motor neurons using genetic driver lines2 and X-ray holographic nanotomography3. With this motor neuron atlas, we identified neural circuits that coordinate leg and wing movements during take-off. We provide the reconstruction of VNC circuits, the motor neuron atlas and tools for programmatic and interactive access as resources to support experimental and theoretical studies of how the nervous system controls behaviour.
Assuntos
Conectoma , Drosophila melanogaster , Neurônios Motores , Tecido Nervoso , Vias Neurais , Sinapses , Animais , Feminino , Conjuntos de Dados como Assunto , Drosophila melanogaster/anatomia & histologia , Drosophila melanogaster/citologia , Drosophila melanogaster/fisiologia , Drosophila melanogaster/ultraestrutura , Extremidades/fisiologia , Extremidades/inervação , Holografia , Microscopia Eletrônica , Neurônios Motores/citologia , Neurônios Motores/fisiologia , Neurônios Motores/ultraestrutura , Movimento , Músculos/inervação , Músculos/fisiologia , Tecido Nervoso/anatomia & histologia , Tecido Nervoso/citologia , Tecido Nervoso/fisiologia , Tecido Nervoso/ultraestrutura , Vias Neurais/citologia , Vias Neurais/fisiologia , Vias Neurais/ultraestrutura , Sinapses/fisiologia , Sinapses/ultraestrutura , Tomografia por Raios X , Asas de Animais/inervação , Asas de Animais/fisiologiaRESUMO
Animal movement is controlled by motor neurons (MNs), which project out of the central nervous system to activate muscles1. MN activity is coordinated by complex premotor networks that facilitate the contribution of individual muscles to many different behaviours2-6. Here we use connectomics7 to analyse the wiring logic of premotor circuits controlling the Drosophila leg and wing. We find that both premotor networks cluster into modules that link MNs innervating muscles with related functions. Within most leg motor modules, the synaptic weights of each premotor neuron are proportional to the size of their target MNs, establishing a circuit basis for hierarchical MN recruitment. By contrast, wing premotor networks lack proportional synaptic connectivity, which may enable more flexible recruitment of wing steering muscles. Through comparison of the architecture of distinct motor control systems within the same animal, we identify common principles of premotor network organization and specializations that reflect the unique biomechanical constraints and evolutionary origins of leg and wing motor control.
Assuntos
Conectoma , Drosophila melanogaster , Extremidades , Neurônios Motores , Vias Neurais , Sinapses , Asas de Animais , Animais , Feminino , Masculino , Drosophila melanogaster/anatomia & histologia , Drosophila melanogaster/citologia , Drosophila melanogaster/fisiologia , Extremidades/inervação , Extremidades/fisiologia , Neurônios Motores/fisiologia , Movimento/fisiologia , Músculos/inervação , Músculos/fisiologia , Rede Nervosa/anatomia & histologia , Rede Nervosa/citologia , Rede Nervosa/fisiologia , Vias Neurais/anatomia & histologia , Vias Neurais/citologia , Vias Neurais/fisiologia , Sinapses/fisiologia , Asas de Animais/inervação , Asas de Animais/fisiologiaRESUMO
Senescence is a cellular state linked to ageing and age-onset disease across many mammalian species1,2. Acutely, senescent cells promote wound healing3,4 and prevent tumour formation5; but they are also pro-inflammatory, thus chronically exacerbate tissue decline. Whereas senescent cells are active targets for anti-ageing therapy6-11, why these cells form in vivo, how they affect tissue ageing and the effect of their elimination remain unclear12,13. Here we identify naturally occurring senescent glia in ageing Drosophila brains and decipher their origin and influence. Using Activator protein 1 (AP1) activity to screen for senescence14,15, we determine that senescent glia can appear in response to neuronal mitochondrial dysfunction. In turn, senescent glia promote lipid accumulation in non-senescent glia; similar effects are seen in senescent human fibroblasts in culture. Targeting AP1 activity in senescent glia mitigates senescence biomarkers, extends fly lifespan and health span, and prevents lipid accumulation. However, these benefits come at the cost of increased oxidative damage in the brain, and neuronal mitochondrial function remains poor. Altogether, our results map the trajectory of naturally occurring senescent glia in vivo and indicate that these cells link key ageing phenomena: mitochondrial dysfunction and lipid accumulation.
Assuntos
Envelhecimento , Encéfalo , Senescência Celular , Drosophila melanogaster , Metabolismo dos Lipídeos , Mitocôndrias , Neuroglia , Animais , Feminino , Humanos , Masculino , Envelhecimento/metabolismo , Envelhecimento/patologia , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/citologia , Drosophila melanogaster/metabolismo , Drosophila melanogaster/citologia , Fibroblastos/metabolismo , Fibroblastos/patologia , Longevidade , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Neuroglia/metabolismo , Neuroglia/patologia , Neurônios/metabolismo , Neurônios/patologia , Estresse Oxidativo , Fator de Transcrição AP-1/metabolismo , Lipídeos , Inflamação/metabolismo , Inflamação/patologiaRESUMO
Regulation of codon optimality is an increasingly appreciated layer of cell- and tissue-specific protein expression control. Here, we use codon-modified reporters to show that differentiation of Drosophila neural stem cells into neurons enables protein expression from rare-codon-enriched genes. From a candidate screen, we identify the cytoplasmic polyadenylation element binding (CPEB) protein Orb2 as a positive regulator of rare-codon-dependent mRNA stability in neurons. Using RNA sequencing, we reveal that Orb2-upregulated mRNAs in the brain with abundant Orb2 binding sites have a rare-codon bias. From these Orb2-regulated mRNAs, we demonstrate that rare-codon enrichment is important for mRNA stability and social behavior function of the metabotropic glutamate receptor (mGluR). Our findings reveal a molecular mechanism by which neural stem cell differentiation shifts genetic code regulation to enable critical mRNA stability and protein expression.
Assuntos
Diferenciação Celular , Proteínas de Drosophila , Células-Tronco Neurais , Neurônios , Estabilidade de RNA , RNA Mensageiro , Animais , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Neurônios/metabolismo , Neurônios/citologia , RNA Mensageiro/metabolismo , RNA Mensageiro/genética , Diferenciação Celular/genética , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Códon/genética , Drosophila melanogaster/genética , Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Receptores de Glutamato Metabotrópico/genética , Fatores de Poliadenilação e Clivagem de mRNA/metabolismo , Fatores de Poliadenilação e Clivagem de mRNA/genética , Drosophila/genética , Drosophila/metabolismo , Encéfalo/metabolismo , Encéfalo/citologia , Fatores de TranscriçãoRESUMO
Insect respiration has long been thought to be solely dependent on an elaborate tracheal system without assistance from the circulatory system or immune cells1,2. Here we describe that Drosophila crystal cells-myeloid-like immune cells called haemocytes-control respiration by oxygenating Prophenoloxidase 2 (PPO2) proteins. Crystal cells direct the movement of haemocytes between the trachea of the larval body wall and the circulation to collect oxygen. Aided by copper and a neutral pH, oxygen is trapped in the crystalline structures of PPO2 in crystal cells. Conversely, PPO2 crystals can be dissolved when carbonic anhydrase lowers the intracellular pH and then reassembled into crystals in cellulo by adhering to the trachea. Physiologically, larvae lacking crystal cells or PPO2, or those expressing a copper-binding mutant of PPO2, display hypoxic responses under normoxic conditions and are susceptible to hypoxia. These hypoxic phenotypes can be rescued by hyperoxia, expression of arthropod haemocyanin or prevention of larval burrowing activity to expose their respiratory organs. Thus, we propose that insect immune cells collaborate with the tracheal system to reserve and transport oxygen through the phase transition of PPO2 crystals, facilitating internal oxygen homeostasis in a process that is comparable to vertebrate respiration.
Assuntos
Catecol Oxidase , Proteínas de Drosophila , Drosophila melanogaster , Precursores Enzimáticos , Hemócitos , Oxigênio , Transição de Fase , Respiração , Animais , Feminino , Masculino , Transporte Biológico , Anidrases Carbônicas/metabolismo , Catecol Oxidase/metabolismo , Cobre/metabolismo , Cristalização , Drosophila melanogaster/anatomia & histologia , Drosophila melanogaster/citologia , Drosophila melanogaster/enzimologia , Drosophila melanogaster/imunologia , Drosophila melanogaster/metabolismo , Proteínas de Drosophila/metabolismo , Precursores Enzimáticos/metabolismo , Hemocianinas/metabolismo , Hemócitos/imunologia , Hemócitos/metabolismo , Homeostase , Concentração de Íons de Hidrogênio , Hiperóxia/metabolismo , Hipóxia/metabolismo , Larva/anatomia & histologia , Larva/citologia , Larva/imunologia , Larva/metabolismo , Oxigênio/metabolismoRESUMO
Regulated cell shape change requires the induction of cortical cytoskeletal domains. Often, local changes to plasma membrane (PM) topography are involved. Centrosomes organize cortical domains and can affect PM topography by locally pulling the PM inward. Are these centrosome effects coupled? At the syncytial Drosophila embryo cortex, centrosome-induced actin caps grow into dome-like compartments for mitoses. We found the nascent cap to be a collection of PM folds and tubules formed over the astral centrosomal MT array. The localized infoldings require centrosome and dynein activities, and myosin-based surface tension prevents them elsewhere. Centrosome-engaged PM infoldings become specifically enriched with an Arp2/3 induction pathway. Arp2/3 actin network growth between the infoldings counterbalances centrosomal pulling forces and disperses the folds for actin cap expansion. Abnormal domain topography with either centrosome or Arp2/3 disruption correlates with decreased exocytic vesicle association. Together, our data implicate centrosome-organized PM infoldings in coordinating Arp2/3 network growth and exocytosis for cortical domain assembly.
Assuntos
Complexo 2-3 de Proteínas Relacionadas à Actina , Actinas , Membrana Celular , Centrossomo , Proteínas de Drosophila , Drosophila melanogaster , Animais , Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Actinas/metabolismo , Membrana Celular/metabolismo , Centrossomo/metabolismo , Drosophila melanogaster/citologia , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Dineínas/metabolismo , Exocitose , Microtúbulos/metabolismoRESUMO
To convert intentions into actions, movement instructions must pass from the brain to downstream motor circuits through descending neurons (DNs). These include small sets of command-like neurons that are sufficient to drive behaviours1-the circuit mechanisms for which remain unclear. Here we show that command-like DNs in Drosophila directly recruit networks of additional DNs to orchestrate behaviours that require the active control of numerous body parts. Specifically, we found that command-like DNs previously thought to drive behaviours alone2-4 in fact co-activate larger populations of DNs. Connectome analyses and experimental manipulations revealed that this functional recruitment can be explained by direct excitatory connections between command-like DNs and networks of interconnected DNs in the brain. Descending population recruitment is necessary for behavioural control: DNs with many downstream descending partners require network co-activation to drive complete behaviours and drive only simple stereotyped movements in their absence. These DN networks reside within behaviour-specific clusters that inhibit one another. These results support a mechanism for command-like descending control in which behaviours are generated through the recruitment of increasingly large DN networks that compose behaviours by combining multiple motor subroutines.
Assuntos
Encéfalo , Conectoma , Drosophila melanogaster , Neurônios Motores , Rede Nervosa , Animais , Feminino , Comportamento Animal/fisiologia , Encéfalo/citologia , Encéfalo/fisiologia , Drosophila melanogaster/citologia , Drosophila melanogaster/fisiologia , Neurônios Motores/fisiologia , Movimento/fisiologia , Rede Nervosa/fisiologiaRESUMO
The brain is consisted of diverse neurons arising from a limited number of neural stem cells. Drosophila neural stem cells called neuroblasts (NBs) produces specific neural lineages of various lineage sizes depending on their location in the brain. In the Drosophila visual processing centre - the optic lobes (OLs), medulla NBs derived from the neuroepithelium (NE) give rise to neurons and glia cells of the medulla cortex. The timing and the mechanisms responsible for the cessation of medulla NBs are so far not known. In this study, we show that the termination of medulla NBs during early pupal development is determined by the exhaustion of the NE stem cell pool. Hence, altering NE-NB transition during larval neurogenesis disrupts the timely termination of medulla NBs. Medulla NBs terminate neurogenesis via a combination of apoptosis, terminal symmetric division via Prospero, and a switch to gliogenesis via Glial Cell Missing (Gcm); however, these processes occur independently of each other. We also show that temporal progression of the medulla NBs is mostly not required for their termination. As the Drosophila OL shares a similar mode of division with mammalian neurogenesis, understanding when and how these progenitors cease proliferation during development can have important implications for mammalian brain size determination and regulation of its overall function.
Every cell in the body can be traced back to a stem cell. For instance, most cells in the adult brains of fruit flies come from a type of stem cell known as a neuroblast. This includes neurons and glial cells (which support and protect neurons) in the optic lobe, the part of the brain that processes visual information. The numbers of neurons and glia in the optic lobe are tightly regulated such that when the right numbers are reached, the neuroblasts stop making more and are terminated. But how and when this occurs is poorly understood. To investigate, Nguyen and Cheng studied when neuroblasts disappear in the optic lobe over the course of development. This revealed that the number of neuroblasts dropped drastically 12 to 18 hours after the fruit fly larvae developed in to pupae, and were completely gone by 30 hours in to pupae life. Further experiments revealed that the timing of this decrease is influenced by neuroepithelium cells, the pool of stem cells that generate neuroblasts during the early stages of development. Nguyen and Cheng found that speeding up this transition so that neuroblasts arise from the neuroepithelium earlier, led neuroblasts to disappear faster from the optic lobe; whereas delaying the transition caused neuroblasts to persist for much longer. Thus, the time at which neuroblasts are born determines when they are terminated. Furthermore, Nguyen and Cheng showed that the neuroblasts were lost through a combination of means. This includes dying via a process called apoptosis, dividing to form two mature neurons, or switching to a glial cell fate. These findings provide a deeper understanding of the mechanisms regulating stem cell pools and their conversion to different cell types, a process that is crucial to the proper development of the brain. How cells divide to form the optic lobe of fruit flies is similar to how new neurons arise in the mammalian brain. Understanding how and when stem cells in the fruit fly brain stop proliferating could therefore provide new insights in to the development of the human brain.
Assuntos
Apoptose , Diferenciação Celular , Proteínas de Drosophila , Células-Tronco Neurais , Células Neuroepiteliais , Neurogênese , Animais , Células-Tronco Neurais/fisiologia , Células-Tronco Neurais/citologia , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Neurogênese/fisiologia , Células Neuroepiteliais/fisiologia , Células Neuroepiteliais/citologia , Neuroglia/fisiologia , Neuroglia/citologia , Drosophila/fisiologia , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/fisiologia , Drosophila melanogaster/citologia , Lobo Óptico de Animais não Mamíferos/citologia , Lobo Óptico de Animais não Mamíferos/crescimento & desenvolvimento , Pupa/crescimento & desenvolvimento , Proteínas de Ligação a DNA , Fatores de TranscriçãoRESUMO
The fruit fly Drosophila is a well-established invertebrate model that enables in vivo imaging of innate immune cell (e.g., macrophage) migration and signaling at high spatiotemporal resolution within the intact, living animal. While optimized methods already exist to enable flow cytometry-based macrophage isolation from Drosophila at various stages of development, there remains a need for more rapid and gentle methods to isolate living macrophages for downstream ex vivo applications. Here, we describe techniques for rapid and direct isolation of living macrophages from mature Drosophila pupae and their downstream ex vivo preparation for live imaging and immunostaining. This strategy enables straightforward access to physiologically relevant innate immune cells, both circulating and tissue-resident populations, for subsequent imaging of signal transduction.