Biology subjects

Barnhart, E. L.

Publications and source records attributed to Barnhart, E. L..

5 recordsLinked to original sources

bioRxiv2026

Time-restricted eating promotes sustained fat loss in Drosophila

While current therapeutics restricting calorie intake, such as GLP-1 agonists, induce fat loss for many people, they are ineffective for others and concerns remain about their long-term effects on health, particularly loss of lean muscle mass. Moreover, many quickly regain fat if they stop treatment. In contrast, time-restricted eating does not restrict calorie intake but instead restricts the time window for eating and prevents obesity in mice and humans. Here we investigated the effects of intermittent Time-Restricted Feeding (iTRF), which extends lifespan and delays markers of aging, on stored fat in Drosophila. Ten days of iTRF caused significant fat loss relative to ad lib diet, an effect that persisted even after return to ad lib diet. Unlike iTRF-induced lifespan extension, iTRF-induced fat loss did not depend on circadian-regulated autophagy. iTRF treated both diet-induced and genetically induced obesity and significantly reduced lipid droplet size in the fat body (adipose tissue). Instead of causing muscle loss, iTRF increased total and muscle-specific protein levels and enhanced flight performance, suggesting a shift in body composition. We found that iTRF evoked fasting-induced hyperactivity, partially mediated by octopamine, the fly ortholog of the human stress hormone norepinephrine. Ablation of octopaminergic neurons (OANs) prevented iTRF-mediated effects: fat loss, increased protein, and enhanced flight performance. Our results suggest that Drosophila iTRF causes rapid, permanent fat loss and increased muscle function through a "fight or flight" response. Understanding the mechanisms driving differences between Drosophila and human responses to TRE could be critical for identifying effective therapeutic targets for obesity.

physiology↗

bioRxiv2025

Visual input drives diverse ER calcium signals in neurons in vivo

The endoplasmic reticulum (ER) has long been thought to shape calcium signals in neurons, but stimulus-driven ER calcium fluctuations have not been directly measured in vivo. To measure neuronal ER calcium signals in vivo, we paired visual stimulus presentation with two photon imaging of ER and cytosolic calcium reporters in four different cell types in the Drosophila visual system. We found that visual input elicits diverse ER calcium signals, with the ER acting as a calcium sink or source depending on the cell type, subcellular compartment (dendrite versus axon), and type of visual stimulus. ER calcium signals were not simply a reflection of cytosolic signals, indicating that the ER, rather than acting as a passive calcium buffer, actively processes calcium signals in neurons in a context-specific fashion. Thus, ER-based signal processing may contribute to functional diversity across neuronal cell types, thereby enhancing the computational capacity of neural circuits.

neuroscience↗

bioRxiv2025

Drosophila HS dendrites are resilient to adult-onset deficits in mitochondrial dynamics

Mitochondrial transport, fusion, and fission are necessary for neuronal development, but the role of mitochondrial dynamics in neuronal maintenance remains unclear. In this work, we employed functional in vivo imaging of neurons in the Drosophila visual system, HS ("horizontal system") cells, to determine how adult-onset deficits in mitochondrial dynamics affect mitochondrial localization, local regulation of ATP, and dendrite maintenance. In mature HS neurons, inhibition of mitochondrial transport or fusion depleted mitochondria from the dendrite over time but, surprisingly, had no effect on dendrite morphology. Moreover, adult-restricted mitochondrial mis- localization affected neither visual stimulus-driven dendritic calcium responses nor local, dynamic regulation of ATP levels. In contrast, when induced during development, the same perturbations caused mitochondrial mis-localization, loss of dendrite complexity, abrogation of stimulus-locked calcium responses and ATP fluctuations, and age-dependent dendrite degeneration. Thus, although mitochondrial dynamics are necessary during neuronal development, mature dendrites are capable of maintaining form and function in vivo in the absence of properly-positioned mitochondria.

cell biology↗

bioRxiv2022

Dendrite architecture determines mitochondrial distribution patterns in vivo

Mitochondria are critical for neuronal function and must be reliably distributed through complex neuronal architectures. By quantifying in vivo mitochondrial transport and localization patterns in the dendrites of Drosophila visual system neurons, we show that mitochondria make up a dynamic system at steady-state, with significant transport of individual mitochondria within a stable global pattern. Mitochondrial motility patterns are unaffected by visual input, suggesting that neuronal activity does not directly regulate mitochondrial localization in vivo. Instead, we present a mathematical model in which four simple scaling rules enable the robust self-organization of the mitochondrial population. Experimental measurements of dendrite morphology validate key model predictions: to maintain equitable distribution of mitochondria across asymmetrically branched subtrees, dendritic branch points obey a parent-daughter power law that preserves cross-sectional area, and thicker trunks support proportionally bushier subtrees. Altogether, we propose that "housekeeping" requirements, including the need to maintain steady-state mitochondrial distributions, impose constraints on neuronal architecture.

cell biology↗

bioRxiv2018

Cell Mechanics at the Rear Act To Steer the Direction of Cell Migration

Motile cells navigate complex environments by changing their direction of travel, generating left-right asymmetries in their mechanical subsystems to physically turn. Currently little is known about how external directional cues are propagated along the length scale of the whole cell and integrated with its force-generating apparatus to steer migration mechanically. We examine the mechanics of spontaneous cell turning in fish epidermal keratocytes and find that the mechanical asymmetries responsible for turning behavior predominate at the rear of the cell, where there is asymmetric centripetal actin flow. Using experimental perturbations we identify two linked feedback loops connecting myosin II contractility, adhesion strength and actin network flow in turning cells that are sufficient to recreate observed cell shapes and trajectories in a computational model. Surprisingly, asymmetries in actin polymerization at the cell leading edge play only a minor role in the mechanics of cell turning - that is, cells steer from the rear.\n\nHighlightsO_LIFish keratocytes can migrate with persistent angular velocity, straight or in circles.\nC_LIO_LIAsymmetry in protrusion at the leading edge is not sufficient to generate persistent turning.\nC_LIO_LIAsymmetries in myosin II contraction, actin flow and adhesion at the cell rear cause turns.\nC_LIO_LIOur new computational model of migration predicts observed cell trajectories.\nC_LI

cell biology↗