Biology subjects

Skoulakis, E. M.

Publications and source records attributed to Skoulakis, E. M..

5 recordsLinked to original sources

bioRxiv2026

Neurofibromin Regulates Sleep Consolidation via Cholinergic Neurons in a Drosophila Model of Neurofibromatosis 1

Neurofibromatosis type 1 (NF1) patients frequently present with fragmented, poor-quality sleep, but the neural circuits and molecular mechanisms underlying this deficit remain undefined. Using Drosophila, we show that loss of the NF1 ortholog dNf1 recapitulates the human phenotype: null mutants exhibit markedly reduced total sleep with blunted nighttime consolidation, reflected in fewer and shorter sleep bouts and elevated inter-bout activity, a recessive phenotype reproduced by independent null alleles and by pan-neuronal RNAi knockdown. Despite the broad expression of dNf1 across the adult CNS, including the mushroom bodies, ellipsoid body, dorsal fan-shaped body, and GABAergic neurons, cell-type-restricted knockdown showed the protein is dispensable for sleep regulation in each of these populations. Instead, dNf1 loss specifically in cholinergic neurons, the most abundant neuronal class in the fly brain, was sufficient to reproduce the deficient, fragmented sleep of null mutants, and restoring wild-type dNf1 to cholinergic neurons of null animals was both necessary and sufficient to rescue sleep. Mechanistically, cholinergic expression of the GAP-related domain (GRD) alone, which normalizes elevated Ras/MAPK signaling, fully restored sleep in nulls, whereas a catalytically dead GRD variant did not, establishing Ras/MAPK dysregulation in cholinergic neurons as the proximate cause. Two disease-associated missense mutations, dNf1C1045Y and dNf1R1861C, produced distinct, dose-graded sleep phenotypes. dNf1C1045Y showed severe deficits resembling the null and was resistant to pan-neuronal, but responded to cholinergic neuron-restricted rescue, consistent with a dominant-negative effect on dNf1 dimerization. In contrast, dNf1R1861C presented a milder phenotype that was largely reversible by wild-type dNf1 but only partially by the GRD domain, implicating an additional, GRD-independent mechanism. Collectively, these findings define cholinergic neurons as the key circuit through which Neurofibromin regulates sleep consolidation via Ras/MAPK signaling and reveal mutation-specific mechanisms that mirror the phenotypic heterogeneity seen in NF1 patients, with implications for genotype-informed understanding of sleep disturbance in this disorder.

neuroscience↗

bioRxiv2025

The Drosophila wing is a high-throughput and versatile screening tool for Tau-mediated disease mechanisms and drug discovery.

Tau protein contributes to microtubule stability, which is disrupted in Alzheimers disease and other Tauopathies. In these diseases, Tau molecules become hyperphosphorylated, misfolded and aggregated, propagating pathology across the brain. Studies dissecting disease mechanisms or screening disease-modifying therapies rely on animal models that unveil pathogenic events in vivo but also take several weeks or months to complete. Here we describe a versatile experimental paradigm that yields results in days and yet offers all the advantages of a genetically tractable in vivo system: the Drosophila wing disc. Mimicking neurotoxicity, human Tau expression causes cell death in the wing disc leading to quantifiable phenotypes in the adult wing. The neuroprotective peptide NAP ameliorates Tau toxicity in this system, validating it as a cost-effective drug screening tool. Phenocopying adult neurons, Tau toxicity in the wing disc is exacerbated by simulating hyper-phosphorylation and prevented by suppressing aggregation. Additionally, we show that the wing disc can dissect disease mechanisms that underpin clinically relevant Tau variants. Thus, the wing disc offers an in vivo experimental paradigm for fast and efficient exploration of disease mechanism and screening.

neuroscience↗

bioRxiv2025

Design of Tau Aggregation Inhibitors Using Iterative Machine Learning and a Polymorph-Specific Brain-Seeded Fibril Amplification Assay

The aggregation of tau into amyloid fibrils is associated with Alzheimers disease (AD) and related tauopathies. Since different tauopathies are characterised by the formation of distinct tau fibril morphologies, it is important to combine the search of tau aggregation inhibitors with the development of in vitro tau aggregation assays that recapitulate aggregation as it may occur in the brain. Here we address this problem by reporting an in vitro tau aggregation assay in which AD brain homogenates are used to seed the generation of first-generation tau fibrils in a polymorph-specific manner under quiescent conditions. These fibrils are then used to create amyloid seed libraries from which second-generation kinetic assays can be readily performed. Using this strategy, we illustrate an iterative machine learning method for the identification of small molecules for the polymorph-specific inhibition of the in vitro formation of tau fibrils. We further show that the small molecules selected by this procedure are potent inhibitors in a Drosophila tauopathy model.

biophysics↗

bioRxiv2025

Homosensory and heterosensory dishabituation engage distinct circuits in Drosophila

Habituation adaptively filters repeated, inconsequential sensory input, while the response to such stimuli re-emerges upon appearance of novel or salient cues (dishabituation).However, the neural circuits underlying dishabituation remain poorly defined, particularly in the central nervous system. Using Drosophila olfactory habituation to the odorant 3-octanol (OCT), we dissect the circuit basis of intramodal (odor-odor) and cross-modal (footshock-odor) dishabituation. A brief yeast odor puff dishabituates intramodally, whereas footshock cross-modally and neither operate through sensitization. Genetic silencing and optogenetics demonstrate that Mushroom Body (MBs) output drives both dishabituation forms. {beta} and {gamma} Kenyon cells (KCs) mediate dishabituation, while '{beta}' Kenyon cells mediate habituation. Dopaminergic neurons encode and PAM neurons mediating appetitive and PPL1 neurons aversive dishabituation, including that triggered by footshock and OCT itself. GABAergic APL neurons and specific MB output neurons tune the balance between habituation and dishabituation, relaying signals via MBONs to the Lateral Horn, a proposed decision node. Connectomic analysis reveals inhibitory interactions supporting this balance. Collectively, we reveal a multi-node circuit that dynamically overrides, rather than erases, habituation findings offering insight into habituation deficits in intellectual disability, autism, and schizophrenia. SIGNIFICANCE STATEMENTThis study identifies a multi-node neural circuit spanning the Mushroom Bodies, dopaminergic and GABAergic modulatory neurons and the Lateral Horn, that governs intramodal and cross-modal dishabituation in Drosophila. Showing that dishabituation dynamically overrides rather than erases habituation and that distinct dopaminergic populations encode stimulus valence to bias this switch, the work reveals a general logic for how the brain flexibly regulates sensory filtering.

animal behavior and cognition↗

bioRxiv2018

Drosophila mef2 is essential for normal mushroom body and wing development.

MEF2 (myocyte enhancer factor 2) transcription factors are found in the brain and muscle of insects and vertebrates and are essential for the differentiation of multiple cell types. We show that in the fruitfly Drosophila, MEF2 is essential for normal development of wing veins, and for mushroom body formation in the brain. In embryos mutant for D-mef2, there was a striking reduction in the number of mushroom body neurons and their axon bundles were not detectable. D-MEF2 expression coincided with the formation of embryonic mushroom bodies and, in larvae, expression onset was confirmed to be in post-mitotic neurons. With a D-mef2 point mutation that disrupts nuclear localization, we find that D-MEF2 is restricted to a subset of Kenyon cells that project to the /{beta}, and {gamma} axonal lobes of the mushroom bodies, but not to those forming the /{beta} lobes. Our findings that ancestral mef2 is specifically important in dopamine-receptive neurons has broad implications for its function in mammalian neurocircuits.

developmental biology↗