ase

..Our data indicate that coexpression is accomplished by activation of both ac and sc by the same set of position-specific enhancers...

..Our studies therefore serve as a cautionary note for the inference of normal gene function based on the gain-of-function phenotype after ectopic expression...

The asense (ase) gene of the achaete-scute complex (AS-C) is expressed in the precursors of all adult sensory organs (SOs), the sensory mother cells (SMCs) and in their immediate progeny...

..Thus there is a regulatory loop between Notch and Delta that is under the transcriptional control of the E(spl)-C and AS-C genes...

..We conclude that Dlg/Scrib/Lgl are important in regulating cortical polarity, cell size asymmetry and mitotic spindle asymmetry in Drosophila neuroblasts...

..Our results indicate that neuroepithelial cells have all the necessary components to execute asymmetric division, but that this pathway is normally overridden by the planar polarity cue provided by adherens junctions...

..These data suggest a mechanism for SMC committment...

..da is not required for the initial appearance of nascent neuronal precursors but is required for these cells to express multiple neuronal precursor genes and to produce the normal number of neurons...

..Sens is then in turn required to further activate and maintain proneural gene expression. This feedback mechanism is essential for selective enhancement and maintenance of proneural gene expression in the SOPs...

..It comprises 22 kb of DNA and contains two transcription units, only one of which, named asense (ase), seems involved in neurogenesis...

..Moreover, in prospero mutants, in which axon and dendrite outgrowth is defective, cato is strongly derepressed in the developing CNS...

..In some tissues cell fate appears to dictate the type of cell division, whereas in other tissues it is thought that stochastic variation in spindle position dictates subsequent sibling cell fate...

..Thus, regulation of mitotic activity during optic lobe development may, at least in part, involve deadpan and asense mediated regulation of the cyclin dependent kinase inhibitor gene dacapo. genesis 26:77-85, 2000...

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..asense differs from the other AS-C members in its expression pattern, regulation, mutant phenotype and some DNA-binding properities...

..The inscuteable mutant phenotype, together with these other observations, suggests a possible role for the protein in cytoskeleton organization...

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..The labral neuromere is confined to the posterior segmental compartment. Finally, similarities in the expression of DV patterning genes between the Drosophila and vertebrate brains are discussed...

..Neuroblasts or sensory organ mother cells are born within these clusters. Thus, the patterns of expression of the AS-C genes help to define the topology of the nervous system...

..We discuss the possible biochemical function of the AS-C in neurogenesis in the light of the homologies of the four genes with the mammalian myc family...

..We propose a model in which activation of Cdc2 initiates the release of Bora into the cytoplasm where it can bind and activate Aurora-A...

..Loss of amos function eliminates MD neurons that remain in ASC;atonal mutants. Misexpression of amos generates ectopic MD and other types of neurons...

..Some aspects of the transcriptional regulation have changed, however, and correlate in the notum with differences in the bristle pattern. The Ceratitis pannier gene was isolated and displays a conserved expression domain in the notum...

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..Our results suggest that direct binding to Bazooka mediates the asymmetric localization of Inscuteable and connects the asymmetric division of neuroblasts to the axis of epithelial apical-basal polarity...

..Thus, our results suggest that the Scutoid phenotype is due to an ectopic snail expression under the control of no-oceli enhancer, antagonizing neurogenesis through its inhibitory interaction with bHLH proteins...

..SOP recruitment is reiterative because the inductive signal comes from previously recruited SOPs...

..However, ubiquitous expression of sc or asense (ase) achieved with a heterologous promoter, in the absence of endogenous ac-sc expression, and the activity of the cis-..

..The question arose how these complexes evolved with regard to gene number in the evolution of insects concentrating on Diptera and the Hymenoptera Apis mellifera...

..In addition, Gbetagamma acts to restrict Galphai (and GoLoco proteins) to the apical cortex, where Galphai (and Pins) can mediate asymmetric spindle geometry...

..Genetic analysis shows that at least two proteins, Suppressor of Hairy wing and Modifier of MDG4, required for the activity of this insulator, are involved in the transcriptional regulation of Achaete-scute...

..Furthermore, the multiple equal cleavages of G beta mutant neuroblasts accompany neural defects; this finding suggests indispensable roles of eccentric division in assuring the stem cell properties of neuroblasts...

..However, despite lacking a histone deacetylase subunit, only dMec contributes to the repression of proneural genes. These results reveal an unexpected complexity in the composition and function of Mi-2 complexes...

..Overall, none of the data analyzed were consistent with recent introgression exclusively between D. simulans and D. mauritiana...

..Our results provide the first example that bHLH proneural proteins promote neurogenesis through regulation of protein degradation...

..This probably coincided in time with gene duplication events, raising the possibility that an increase in gene copy number might have provided the flexibility necessary for more complex transcriptional regulation...

..What triggers the asymmetric localization of Numb at the onset of mitosis is unclear...

..These findings also emphasize the requirement for both spatial and temporal glide/gcm regulation to achieve proper cell specification within the nervous system...

..The potent modulatory effect of Neur on Dl activity makes Neur a candidate for establishing signaling asymmetries within cellular equivalence groups...

..Thus, asymmetric activation of heterotrimeric G proteins by a receptor-independent mechanism may orient asymmetric cell divisions in different cell types...

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..These findings indicate that proneural and E(spl) proteins exert antagonistic functions...

..Two additional polyadenylated RNAs are transcribed from the achaete (1.1 kb) and yellow (1.9 kb) loci...

..Synergistic interactions between pyd and Notch, Delta and extramacrochaetae mutations support this model. We also demonstrate that pyd is required for normal eye development...

..With respect to their position and the expression of the markers asense (ase) and seven-up (svp), 23 small groups of one to five neuroblasts each were identified...

..These observations lead to the hypothesis that gliogenesis is induced by the presence of sensory organ cells, either the precursor or its progeny...

..Both recurrent nerve and frontal connectives are pioneered by small subpopulations of early differentiating stomatogastric neurons that most likely derive from among the dSNSPs and iSNSPs...

..Selective expression of certain neuronal-type selector genes further specifies the type of neuron(s) that a neural precursor will produce...

..Immunohistochemical detection of Mam on polytene chromosomes revealed binding at > 100 sites. Chromosome colocalization studies with RNA polymerase and the groucho corepressor protein implicate Mam in transcriptional regulation...

..The results suggest that H insulates SOP cells from inhibition and indicate that H activity is suppressed by Notch signaling...

..Three of these argos-expressing cells differentiate into the three remaining COPs and they prevent neighboring cells from becoming extra COPs...

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..runt is distinguished from previously identified regulators of Sxl by its nonuniform role and by the absence of an identifiable helix-loop-helix (HLH) motif, indicating that the activation of Sxl is not controlled solely by HLH proteins...

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..This general function in cell fate specification has been conserved from Drosophila to vertebrates and has implications for human disease pathogenesis...

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..We investigated the structural requirements for some of these interactions by site-specific and deletion mutagenesis...

..These results are consistent with bib acting as a channel protein in proneural cluster cells that adopt the epidermal cell fate, and serving a necessary function in the response of these cells to the lateral inhibition signal...

..Furthermore, reptile class III POU sequences revealed no evolutionary directionality increasing the GC contents from cold- to warm-blooded vertebrates...

..At least one of these genes is transiently expressed in the embryonic rat nervous system, is not detected in non-neuronal tissues or cell lines, and is induced by nerve growth factor in PC12 cells...

..These findings provide evidence that some lipid-processing functions of the mammalian liver are performed in insects by oenocytes...

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..Finally, the bHLH domain is necessary and sufficient to mediate the proneural function, to activate neurogenic genes, and to allow lateral inhibition...

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..Use of cell type markers suggests that the defect does not lie in cell fate decisions during bristle development, but in the maintenance of neural fate and/or differentiation of the descendants of sensory mother cells...

..Drawing on several lines of evidence, we suggest that modular evolution by domain shuffling may have played an important role in the evolution of this large group of transcriptional regulators...

..Sequence comparisons suggest that tap is most closely related to two bHLH genes identified in several vertebrate species, neurogenin and neuroD, which are involved respectively in neural determination and in neuronal differentiation...

..The bHLH domain is sufficiently different from previously described bHLH domains to imply a novel function...

..I propose that Tramtrack ensures stable mature glial identity by both repressing neuroblast-specific genes and controlling glial cell proliferation...

..Due to their intricate organization, these genes have occupied geneticists and developmental biologists for many years. Here, genetic studies on the complex are discussed from a historical point of view...

..While lineage identity genes allow the various lineages to acquire specific identities, neuronal precursor genes presumably regulate functional and developmental characteristics common to all neuronal precursor cells...

..Importantly, our results have also revealed a novel aspect of apical complex function, that is, the two apical pathways act redundantly to suppress the formation of basal astral microtubules in neuroblasts...

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