Biology subjects

Buhl, E.

Publications and source records attributed to Buhl, E..

7 recordsLinked to original sources

bioRxiv2026

Conserved circadian membrane rhythms arise from divergent cellular mechanisms in pacemaker neurons of mice and Drosophila

Circadian clocks align physiology and behaviour with daily environmental cycles, requiring neuronal networks that reliably encode and transmit time-of-day information. A fundamental yet unresolved question is how membrane properties support this function and whether conserved principles arise across evolutionarily distant organisms. We compared the intrinsic electrophysiological properties of identified circadian neurons from a nocturnal mammal (mouse, Mus musculus SCN VIP neurons) and a diurnal insect (fly, Drosophila melanogaster l-LNv PDF neurons) across the 24-h light-dark cycle. Despite [~]700 million years of evolutionary divergence and opposite temporal niches, we found neurons from both species exhibited similar rhythmic patterns in key parameters for encoding time-of-day, including resting membrane potential, spontaneous firing rate and cell capacitance, indicating convergent strategies for generating daily variation in excitability despite dramatically different network scales ([~]2200 VIPs vs. 8 l-LNvs). These shared outputs arose through distinct mechanisms: flies exhibited higher input resistance, greater excitability and relatively larger A-type potassium currents, while mice displayed larger sustained outward currents and post-inhibitory rebound excitation, absent in flies. Rheobase troughs occurred during the inactive phase in both species, while other parameters did not cycle. These differences likely shape how each neuronal type integrates salient inputs, consistent with their respective roles in processing sustained daytime light (flies) versus nocturnal cues (mice). Our findings reveal conserved functional goals but divergent electrophysiological strategies in circadian neurons, reflecting evolutionary adaptation to species-specific environmental demands. Such neurophysiological diversity highlights how evolution shapes cellular mechanisms to meet the requirements of temporal niche while preserving robust circadian timekeeping.

neuroscience↗

bioRxiv2025

Alzheimer's disease risk gene Wwox protects against amyloid pathology through metabolic reprogramming

Genome wide association studies have identified multiple loci that mediate the risk of developing late-onset Alzheimers Disease (LOAD). The gene WW-domain containing oxidoreductase (WWOX) has been identified in recent LOAD risk meta-analyses, yet its function in the brain is poorly understood. Using Drosophila, we discovered that knockdown of the highly conserved Wwox gene impacts longevity and sleep, having roles in both neuronal and glial subtypes. In an amyloid beta 42 (A{beta}42) transgenic model of AD, RNAi-mediated knockdown of Wwox significantly decreased both lifespan and locomotion whilst elevating soluble A{beta}42. Transcriptomic and metabolomic analyses revealed that these effects were accompanied by elevated lactate dehydrogenase (Ldh) mRNA and lactate levels, downstream of an increase in the key unfolded protein response protein Atf4. Strikingly, we found that upregulation of Wwox in the A{beta}42 model through CRISPR activation significantly reduced amyloid load, improved longevity and locomotion. Multi-omics analysis revealed Wwox upregulation partially reversed several key A{beta}42-induced transcriptional pathways in the brain and reduced levels of L-methionine and associated enzymes. These findings support a role for reduced WWOX levels in the genetic risk of developing LOAD via pyruvate metabolism and point towards WWOX activation as a protective therapeutic strategy.

neuroscience↗

bioRxiv2021

The opposing Chloride Cotransporters KCC and NKCC control locomotor activity inconstant light and during long days.

Cation Chloride Cotransporters (CCCs) regulate intracellular chloride ion concentration ([Cl-]i) within neurons, which can reverse the direction of the neuronal response to the neurotransmitter GABA. Na+ K+ Cl- (NKCC) and K+ Cl- (KCC) cotransporters transport Cl- into or out of the cell, respectively. When NKCC activity dominates, the resulting high [Cl-]i can lead to an excitatory and depolarizing response of the neuron upon GABAA receptor opening, while KCC dominance has the opposite effect. This inhibitory-to-excitatory GABA switch has been linked to seasonal adaption of circadian clock function to changing day length, and its dysregulation is associated with neurodevelopmental disorders such as epilepsy. Constant light normally disrupts circadian clock function and leads to arrhythmic behavior. Here, we demonstrate a function for KCC in regulating Drosophila locomotor activity and GABA responses in circadian clock neurons because alteration of KCC expression in circadian clock neurons elicits rhythmic behavior in constant light. We observed the same effects after downregulation of the Wnk and Fray kinases, which modulate CCC activity in a [Cl-]i-dependent manner. Patch-clamp recordings from clock neurons show that downregulation of KCC results in a more positive GABA reversal potential, while KCC overexpression has the opposite effect. Finally, KCC downregulation represses morning behavioral activity during long photoperiods, while downregulation of NKCC promotes morning activity. In summary, our results support a model in which the regulation of [Cl-]i by a KCC/NKCC/Wnk/Fray feedback loop determines the response of clock neurons to GABA, which is important for adjusting behavioral activity to constant light and long-day conditions.

neuroscience↗

bioRxiv2020

Neonicotinoids disrupt memory, circadian behaviour and sleep

Globally, neonicotinoids are still the most used insecticides, despite their well-documented sub-lethal effects on beneficial insects1. Neonicotinoids are agonists at the nicotinic acetylcholine receptors, the main mediator of synaptic transmission in the insect brain2-5, making them highly potent neurotoxins and insecticides6,7. Memory, circadian rhythmicity and sleep are essential for efficient foraging in many pollinating insects, and involve nicotinic acetylcholine receptor signalling2,4,8-10. The effect of field-relevant concentrations of European Union-banned neonicotinoids: imidacloprid, clothianidin and thiamethoxam, as well as the currently unbanned thiacloprid were tested on Drosophila memory, circadian rhythms and sleep. Field-relevant concentrations of imidacloprid, clothianidin and thiamethoxam disrupted learning, behavioural rhythmicity and sleep whilst thiacloprid exposure only affected sleep. Exposure to imidacloprid and clothianidin directly affected neurophysiology, preventing the day/night remodelling and accumulation of pigment dispersing factor neuropeptide in the dorsal terminals of clock neurons. Knockdown of the neonicotinoid susceptible D1 and D{beta}2 nicotinic acetylcholine receptor subunits in the mushroom bodies or clock neurons recapitulated the neonicotinoid like deficits in memory or circadian/sleep behaviour demonstrating that neonicotinoid effects are likely mediated in the mushroom body and clock circuitry. Disruption to learning, circadian rhythmicity and sleep are likely to have far-reaching detrimental effects on beneficial insects in the field.

pharmacology and toxicology↗

bioRxiv2020

A knock-in Drosophila model supports a conserved link between potassium channelopathy and involuntary movement

BackgroundGenetic and in vitro studies have linked a heterozygous gain-of-function mutation (D434G) in the hSlo1 BK (Big potassium) channel to paroxysmal dyskinesia. However, support for this linkage from in vivo models has been lacking. ObjectivesWe aimed to re-create the equivalent mutation to hSlo1 D434G in the fruit fly, Drosophila, and examine how this mutation altered movement and action potential waveforms. MethodsWe generated a knock-in Drosophila model of hSlo1 D434G. We used video-tracking and infra-red beam-break systems to test whether locomotion was altered in this model, and patch-clamp electrophysiology to determine how the mutation affected action potential waveforms. ResultsWe identified profound motor dysfunction and sporadic leg twitches, as well as a reduced width and an enhancement of the afterhyperpolarization phase of action potentials, in the model background. ConclusionOur results support a conserved relationship between enhanced BK channel function and disrupted motor control across distantly related species.

neuroscience↗

bioRxiv2018

Mis-expression of the Alzheimers disease associated gene Ankyrin causes memory loss and shortened lifespan in Drosophila

Alzheimers disease (AD) is the most common form of dementia and is characterized by the accumulation of extracellular amyloid beta (A{beta}) plaques and intracellular neurofibrillary tangles of hyperphosphorylated Tau, including the 4R0N isoform. Recent epigenome-wide association studies (EWAS) of AD have identified a number of loci that are differentially methylated in AD cortex. Indeed, hypermethylation of the Ankyrin 1 (ANK1) gene in AD has been reported in the cortex in numerous different post-mortem brain cohorts. Little is known about the normal function of ANK1 in the healthy brain, nor the role it may play in AD. We have generated Drosophila models to allow us to functionally characterize Drosophila Ank2, the ortholog of human ANK1. These models have targeted reduction in the expression of Ank2 in neurons. We find that Drosophila with reduced neuronal Ank2 expression have shortened lifespan, reduced locomotion, reduced memory and reduced neuronal excitability similar to flies overexpressing either human mutant APP (that leads to A{beta}42 production) and MAPT (that leads to 0N4R Tau). Therefore, we show that the mis-expression of Ank2 can drive disease relevant processes and phenocopy some features of AD and we propose targeting ANK1 may have therapeutic potential. This represents the first study to characterize a gene implicated in AD, which was nominated from EWAS.\n\nAuthor summaryThe majority (>95%) of Alzheimers disease (AD) cases are sporadic, with their incidence attributed to common genetic mutations, epigenetic variation, aging and the environment. There is no cure for AD and only limited treatment options which only treat the symptoms of AD and only work in some people. Recent epigenome-wide association studies (EWAS) in AD have highlighted hypermethylation of the Ankyrin1 (ANK1) gene in AD cortex. Little is known of the normal role of the gene in the brain. Here, we have demonstrated that Drosophila with reduced neuronal expression of the Drosophila ortholog of human ANK1 (Ank2), can drive AD relevant processes including locomotor difficulties, memory loss and shortened lifespan similar to expression of human amyloid-Beta or tau mutant proteins. Furthermore, increasing Ank2 expression reversed the memory loss caused by expression of human amyloid-Beta or tau mutant proteins, suggesting that targeting ANK1 may have therapeutic potential. This represents the first study to characterize a gene implicated in AD, which was nominated from EWAS.

neuroscience↗

bioRxiv2017

A lineage-related reciprocal inhibition circuitry for sensory-motor action selection

The insect central complex and vertebrate basal ganglia are forebrain centres involved in selection and maintenance of behavioural actions. However, little is known about the formation of the underlying circuits, or how they integrate sensory information for motor actions. Here, we show that paired embryonic neuroblasts generate central complex ring neurons that mediate sensory-motor transformation and action selection in Drosophila. Lineage analysis resolves four ring neuron subtypes, R1-R4, that form GABAergic inhibition circuitry among inhibitory sister cells. Genetic manipulations, together with functional imaging, demonstrate subtype-specific R neurons mediate the selection and maintenance of behavioural activity. A computational model substantiates genetic and behavioural observations suggesting that R neuron circuitry functions as salience detector using competitive inhibition to amplify, maintain or switch between activity states. The resultant gating mechanism translates facilitation, inhibition and disinhibition of behavioural activity as R neuron functions into selection of motor actions and their organisation into action sequences.

neuroscience↗