Biology subjects

Melkani, G. C.

Publications and source records attributed to Melkani, G. C..

6 recordsLinked to original sources

bioRxiv2026

Microbiome Integrity Protects Against Glial-Mediated Tau and Amyloid Pathology Through Circadian and Autophagy Homeostasis

Alzheimers disease (AD) is characterized not only by tau and amyloid-{beta} aggregation but also by systemic disruptions in circadian rhythms, metabolism, and gut-brain communication that exacerbate neuroinflammation and neurodegeneration. While glial cells play central roles in inflammatory signaling and proteostasis, the contribution of the gut microbiome to glia-driven AD pathology remains poorly understood. Here, we used Drosophila models with glial-specific expressions of human tau and amyloid-associated transgenes to investigate how microbiome integrity influences disease progression. AD models exhibited significant shifts in gut microbial composition, particularly in Lactobacillus and Acetobacter species, suggesting an adaptive microbial response to pathological stress. Strikingly, microbiome depletion (axenic condition) markedly worsened behavioral and physiological outcomes, including disrupted sleep-circadian rhythms, impaired memory, and reduced locomotor function. These deficits were accompanied by amplified neuroinflammatory signaling (Upd-Dome-Hop-Stat92e axis), increased apoptotic gene expression, lipid dysregulation, and altered synaptic markers. Moreover, microbiome loss induced energy stress marked by elevated phospho-AMPK (p-AMPK), yet failed to restore proteostasis, as evidenced by accumulation of ubiquitinated proteins and the autophagy adaptor Ref2p, indicating impaired autophagic flux. This dysfunction correlated with increased tau, phospho-tau, and A{beta}42 accumulation. Together, our findings demonstrate that microbiome depletion exacerbates glial-mediated inflammation, disrupts circadian and metabolic homeostasis, impairs, and accelerates cognitive and motor decline. This work highlights a previously underappreciated role of the gut microbiome in restraining glial dysfunction and mitigating AD-like pathology, positioning microbial homeostasis as a critical modulator of neurodegenerative disease progression.

neuroscience↗

bioRxiv2026

Exercise based Intervention For Metabolic Inflexibility Linked With Lipid Storage Myopathy Using Innovative CRISPR Etf-QO Mutant Knock-in Models

Multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare lipid storage myopathy caused predominantly by pathogenic variants in ETFDH, which encodes ETF-QO in Drosophila, a mitochondrial electron-transfer protein required for fatty acid {beta}-oxidation. Impaired ETF-QO function disrupts electron transfer from multiple acyl-CoA dehydrogenases to the ubiquinone pool, resulting in lipid accumulation, mitochondrial dysfunction, and progressive neuromuscular and cardiac abnormalities. Despite the availability of animal models of fatty acid oxidation disorders, genetically precise in vivo models carrying patient-relevant ETFDH missense variants and permitting longitudinal assessment of disease progression remain limited. Here, we generated CRISPR/Cas9 knock-in Drosophila melanogaster models of late-onset MADD harboring three conserved Etf-QO missense substitutions (L138R, S307C, and L409F), corresponding to human ETFDH mutations L127R, S296C, and L399F, respectively. These variants are located to the conserved FAD- and ubiquinone-binding regions of ETF-QO. Etf-QO mutant flies developed progressive deficits in locomotor activity and skeletal muscle performance accompanied by marked lipid droplet accumulation in indirect flight muscles, cardiac tissue, and fat bodies. Cardiac phenotyping further revealed impaired function, characterized by reduced fractional shortening, prolonged heart period, and increased arrhythmicity index. Consistent with mitochondrial bioenergetic dysfunction, Etf-QO mutants exhibited reduced oxygen consumption, increased oxidative stress, and decreased ATP levels. Molecular analyses indicated activation of cellular energy- and mitochondrial-stress responses, including increased AMPK and PGC-1 signaling, together with elevated Pink1, Parkin, and SOD2 expression, suggesting engagement of mitochondrial quality-control and antioxidant defense pathways in response to ETF-QO dysfunction. Importantly, exercise paradigm consisting of 15 min of daily exercise for 2.5 weeks significantly improved locomotor, skeletal muscle, and cardiac performance while reducing lipid accumulation and reactive oxygen species burden. Together, these findings establish innovative CRISPR knock-in Drosophila models that recapitulate key neuromuscular, metabolic, mitochondrial, and cardiac features of ETFDH-associated MADD. The models reveal coordinated mitochondrial stress and energy-signaling responses to ETF-QO dysfunction and demonstrate that exercise can ameliorate multiple disease phenotypes. These findings provide a tractable in vivo platform for dissecting MADD pathogenesis and evaluating potential therapeutic strategies targeting mitochondrial dysfunction and lipid storage myopathies.

cell biology↗

bioRxiv2025

An Application for Automated Drosophila Locomotor Assay with Integrated Device Design and Computer Vision Tracking

Drosophila has long served as a powerful model for investigating locomotor behavior, and geotaxis assays have generated valuable insights into genetics, aging, and neurobiology. Nonetheless, their use can be constrained by subjective scoring, modest throughput, and challenges in reproducibility. To complement and extend these classical approaches, we developed and validated an integrated hardware-software platform that enables automated, high-resolution locomotor analysis across 12 vials in parallel. The system integrates 3D-printed mechanical components, Raspberry Pi-based video acquisition, and programmable environmental controls to ensure standardized conditions. A deep learning pipeline segments vials with near-perfect accuracy (IoU > 0.95), while computer vision algorithms quantify climbing trajectories, velocity, and positional zone occupancy at 60 frames per second. The end-to-end workflow converts raw video into time-resolved metrics, supports sex-specific aggregation, and incorporates advanced statistical analyses, including Linear Mixed Effects regression, harmonic mean p-values, and Mann-Whitney U tests. Relative to manual scoring, this automated pipeline yields 2.8-fold faster processing and nearly 800-fold higher data density. Application of the platform uncovered reproducible phenotypes of multiple genotypes. For example, a circadian mutant known as Clockout, males displayed progressive climbing deficits with age, whereas females-maintained age-resilient trajectories. Moreover, male Clockout exhibited a reduced performance compared to age-matched control (w1118), however, female Clockout showed subtle reduction in performance. Additionally, glial-specific knockdown of PolG, encoding the DNA polymerase gamma catalytic subunit, revealed striking sex-dimorphic aging patterns: females outperformed controls at older age, while males exhibited marked decline. To promote broad adoption, a user-friendly Python interface (Tkinter GUI) enables accessibility independent of computational expertise. Collectively, this standardized, high-throughput framework advances the resolution of genotype-, age-, and sex-dependent locomotor dynamics, offering new opportunities in aging, circadian biology, and neurodegeneration research.

bioinformatics↗

bioRxiv2025

Drosophila Modeling Identifies Increased Sleep as a Link Between Insomnia and Cardiovascular Disease

Insomnia is a common sleep disorder associated with negative long-term health outcomes, including cardiovascular disease (CVD). We selected 16 genes from 13 insomnia- and CVD- associated genetic loci and disrupted Drosophila melanogaster orthologs in neuronal or cardiac tissue to characterize their roles in regulating sleep and cardiac physiology. Neuronal disruption of four orthologs (APOB, FUR, CYP17A1, and TCF4) resulted in short-sleeping flies, and three (MRAS, HDAC9, and TDRKH) resulted in long-sleeping flies. Short-sleeping fly lines impacted cardiac physiology consistent with links between short or poor-quality sleep and increased CVD in humans. Conversely, heart-specific disruption of five orthologs (RASD1, PHACTR1, CNNM2, MRAS, and TCF4) led to defects in cardiac physiology, with varied effects on sleep. Heart-specific knockdown lines that altered fractional shortening, a measure of cardiac contractility, also influenced long and short sleep states. These findings reveal bidirectional relationships between sleep states and cardiac performance, representing a potential feedback loop linking insomnia and CVD.

neuroscience↗

bioRxiv2025

Regulation of lipid dysmetabolism and neuroinflammation linked with Alzheimer's disease through modulation of Dgat2

Alzheimers disease (AD), an age-associated neurodegenerative disorder, is characterized by progressive cognitive decline, amyloid-{beta} (A{beta}) deposition, lipid dysregulation, and neuroinflammation. Although mutations in the amyloid precursor protein (APP) and accumulation of A{beta}42 are established drivers of pathology, the mechanisms connecting amyloid toxicity with lipid metabolism and inflammatory responses remain poorly understood. Here, we employed complementary Drosophila and mouse models to dissect these relationships. Expression of AppNLG and A{beta}42 in Drosophila resulted in locomotor deficits, disrupted sleep-circadian rhythms, memory impairments, lipid accumulation, synaptic loss, and neuroinflammatory signatures. Comparable lipid metabolic disturbances and inflammatory alterations were detected in the AppNLG-F knock-in mouse model, underscoring their conserved relevance to AD pathogenesis. We further identified diacylglycerol O-acyltransferase 2 (Dgat2), a key enzyme catalyzing the final step of triglyceride synthesis, as a critical modulator of AD-related phenotypes. Dgat2 expression was altered in both animal models and human AD tissues. Notably, panneuronal knockdown of Dgat2 in Drosophila attenuated lipid accumulation, restored synaptic integrity, and ameliorated locomotor and cognitive deficits, while also reducing neuroinflammation. Dgat2 suppression additionally improved sleep and circadian behavior, highlighting its pleiotropic protective effects. Together, these findings demonstrate a mechanistic link between amyloid pathology, lipid dysregulation, and neuroinflammatory processes. Targeting Dgat2 may therefore represent a novel therapeutic strategy to counteract AD-associated metabolic and neuronal dysfunction. The conservation of lipid homeostasis mechanisms across species underscores the translational potential of this approach for delaying or mitigating AD progression.

physiology↗

bioRxiv2023

Identifying novel links between cardiovascular disease and insomnia by Drosophila modeling of genes from a pleiotropic GWAS locus

Insomnia symptoms have been associated with cardiovascular disease (CVD), doubling the risk of incident CVD, but specific shared pathways remain poorly understood. Recently, genome-wide association studies (GWAS) identified genetic loci significantly associated with insomnia symptoms, including one locus (near ATP5G1, UBE2Z, SNF8, IGF2BP1, and GIP) that was previously linked with CVD in an independent GWAS. To evaluate the cell-autonomous role of genes within the 17q21 insomnia and CVD locus, we used Drosophila melanogaster models to perform tissue-specific RNAi knockdown of four conserved orthologues (ATPSynC, Lsn, Bruce, and Imp) in neurons and in the heart. To identify non-cell-autonomous mechanisms, we also assessed heart function in flies with neuronal-specific knockdown and sleep in flies with heart-specific knockdown. Neuronal and cardiac-specific RNAi knockdown of several of the genes conserved in Drosophila led to compromised sleep quality and impaired cardiac performance. Neuronal-specific knockdown of ATPSynC, Imp, and Lsn led to disruptions in sleep quantity and quality. Knockdown of ATPSynC and Lsn in the heart led to significantly reduced cardiac performance without and with cardiac dilation, respectively. Furthermore, Lsn and ATPSynC-suppressed hearts showed disruption in the actin-containing myofibrillar organization and led to a significantly shortened lifespan. Non-cell-autonomous effects were seen both from neurons to heart (Imp), and heart to neurons (ATPSynC and Lsn). Specifically, Imp neuronal knockdown led to a significantly compromised cardiac function, whereas knockdown of ATPSynC and Lsn in the heart led to compromised sleep characterized by increased sleep fragmentation, both accompanied by an increase in inflammation through Upd3, an inflammatory cytokine, in the heart or head, respectively. We also demonstrate disrupted cardiac function or sleep upon cardiac-specific or neuronal-specific overexpression of Upd3, respectively, showing a direct link between cardiac dysfunction and sleep disruption through inflammation. Our study reveals tissue-specific and cross-tissue consequences of Drosophila knockdown of multiple genes at this locus, providing novel insights into potential genetic mechanisms linking CVD and insomnia. Our study also highlights the key role of these four conserved genes in both sleep and cardiac function.

physiology↗