Biology subjects

Barber, A. F.

Publications and source records attributed to Barber, A. F..

5 recordsLinked to original sources

bioRxiv2026

AP-1 activation in Drosophila neuropil ensheathing glia improves traumatic brain injury survival

Traumatic brain injury (TBI) impacts millions of individuals annually causing death, disability, and a heightened risk for long-term neurological and neuropsychiatric disorders. In recent years the fruit fly, Drosophila melanogaster has become a valuable model organism to study the cellular and molecular responses following TBI. AP-1 mediated transcriptional responses to TBI have previously been identified in Drosophila using pan-glial approaches. Fruit flies possess multiple glial subtypes which vary greatly in both cellular morphology and function, including glia of the blood hemolymph barrier, cortex, astrocyte-like, and ensheathing glia. By generating and utilizing a nuclear localized AP-1 transcriptional reporter, we identified glial subtype-specific differences in the extent of AP-1 activation following injury. Our findings identify a strong AP-1 response in the blood hemolymph barrier and ensheathing glia, a moderate response in cortex glia and little to no AP-1 activation in astrocyte-like glia. In addition, we inhibited AP-1 signaling in each glial subtype and tested the effect on acute survival. We found that inhibition of the AP-1 response in neuropil ensheathing glia leads to increased mortality following mild and moderate TBI. These results show that AP-1 activation levels vary across glial subtypes after TBI, with activation in neuropil ensheathing glia having a particularly important role in promoting post-injury survival. ARTICLE SUMMARYUsing Drosophila as a model organism, we investigated the early molecular and cellular response to traumatic brain injury. Our findings substantiate the requirement of a functional glial associated AP-1 transcriptional activation response for survival. Using colocalization studies, we characterized the AP-1 glial response in six morphologically and functionally distinct glia subtypes. After TBI, we find high levels of AP-1 activation in glia of the hemolymph brain barrier, cortex glia, and ensheathing glia. We further show the importance of AP-1 transcription within the neuropil ensheathing glia subtype for optimal survival following TBI.

neuroscience↗

bioRxiv2026

Fat body CLOCK restrains innate immunity and maintains survival under dietary stress in Drosophila

Both aging and a high-fat diet (HFD) dampen circadian gene transcription rhythms and promote chronic inflammation. How aging and HFD interact to affect peripheral molecular clocks and circadian behavior remains unclear. Using Drosophila melanogaster, we showed that aging and HFD additively dampened circadian behavior, with their adverse effects converging on the fat body (FB), a tissue that regulates systemic metabolism and innate immunity. Applying longitudinal in vivo bioluminescence recording in small, genetically defined cell populations, we found that molecular clocks in the FB were uniquely vulnerable to aging- and HFD-induced dampening of rhythm amplitude, whereas those in the clock neurons declined with age but were resistant to dietary stress. To test the consequences of this FB clock decline, we disrupted individual components of the core molecular clock specifically in the FB. We found that only CLOCK (CLK) disruption shortened lifespan on HFD, whereas disrupting its binding partner CYCLE (CYC), or the repressors PERIOD and TIMELESS, did not. Furthermore, CLK, but not CYC, disruption upregulated antimicrobial peptide expression in the FB, dampened behavioral rhythms, and suppressed locomotor activity, even though both CLK and CYC disruption comparably dampened clock gene oscillation in the FB. Together, these results indicate that FB CLK has a unique role in suppressing pro-inflammatory signals independently of CYC. Our findings provide insight into how stressors such as aging and HFD selectively disrupt the peripheral metabolic clock, and into the distinct roles of individual clock components, with implications for age-related inflammation and metabolic disease.

molecular biology↗

bioRxiv2026

Drosophila core circadian clock neurons peptidergically regulate activity of insulin-producing cells

Central pacemaker neurons use a combination of external stimuli and neuropeptide signaling to synchronize molecular oscillations leading to circadian behaviors. The clock network structure and signaling between these pacemaker neuron groups have been well described, but how these pacemakers communicate with specific brain output regions remains poorly understood. Here, we identified how "core" clock neurons in Drosophila, the ventrolateral neurons (LNvs), signal to the proto-hypothalamic region, the pars intercerebralis (PI). We provide evidence to show that LNvs functionally modulate insulin-producing cells (IPCs) of the PI in a time-of-day-dependent manner. This functional connectivity relies on neuropeptidergic signaling of two classical clock neuropeptides: pigment dispersing factor (PDF) and short Neuropeptide F (sNPF). Connectomic analysis does not identify any direct synaptic inputs from clock neurons to IPCs. Small ventrolateral clock neurons, which secrete both PDF and sNPF are 15-20 mm away from IPCs, suggesting that volume transmission across these distances may be possible in the fly dorsal protocerebrum. Peptide application with functional imaging of IPCs provides insight into how these two neuropeptides may act synergistically via their receptors to signal to IPCs. Our findings indicate that LNvs can signal to IPCs by volume transmission and also form indirect multisynaptic circuits with IPCs. Thus, neuropeptides associated with intra-clock signaling also serve as circadian cues to non-clock neurons, which may model more broadly how clock peptides communicate to clock output regions. Author SummaryCircadian clocks in the brains of animals from flies to humans allow animals to anticipate daily environmental changes and temporally coordinate internal processes. The central clock in the brain serves as a master pacemaker that sets the pace of circadian clocks in all other tissues. Fruit flies have been an essential model system for discovering the genetic and cellular underpinnings of circadian rhythms, with work in flies being awarded the 2017 Nobel Prize in Physiology or Medicine. Brain clocks in flies and mammals use classical synaptic communication and neuromodulatory peptides to signal between the neurons that make up the brain clock. Our study asks whether the neuropeptides that signal between clock neurons also signal from clock to non-clock neurons. We found that the signature fly clock neuropeptide pigment dispersing factor signals outside the brain clock to insulin producing cells of the brain. There are no synaptic connections from clock neurons to insulin producing cells, instead signaling occurs by diffusion of peptide signals across tens of microns, termed volume transmission. Our findings point to the possibility that neuropeptide volume transmission may be a general feature not only of intra-clock signaling but also of brain clock output signaling to non-clock neurons.

neuroscience↗

bioRxiv2020

Drosophila clock cells use multiple mechanisms to transmit time-of-day signals in the brain

Regulation of circadian behavior and physiology by the Drosophila brain clock requires communication from central clock neurons to downstream output regions, but the mechanism by which clock cells regulate downstream targets is not known. We show here that the pars intercerebralis (PI), previously identified as a target of the morning cells in the clock network, also receives input from evening cells. We determined that morning and evening clock neurons have time of day dependent connectivity to the PI, which is regulated by specific peptides as well as by fast neurotransmitters. Interestingly, PI cells that secrete the peptide DH44, and control rest:activity rhythms, are inhibited by clock inputs while insulin-producing cells are activated, indicating that the same clock cells can use different mechanisms to drive cycling in output neurons. Inputs of morning cells to the DILP2+ neurons are relevant for the circadian rhythm of feeding, reinforcing the role of the PI as a circadian relay that controls multiple behavioral outputs. Our findings provide mechanisms by which clock neurons signal to non-clock cells to drive rhythms of behavior. Significance StatementDespite our growing understanding of how the fly clock network maintains free-running rhythms of behavior and physiology, little is known about how information is communicated from the clock network to the rest of the brain to regulate behavior. We identify glutamate and acetylcholine as key neurotransmitters signaling from clock neurons to the pars interecerebralis (PI), a clock output region regulating circadian rhythms of sleep and metabolism. We report a novel link between Drosophila evening clock neurons and the PI, and find that the effect of clock neurons on output neuron physiology varies, suggesting that the same clock cells use multiple mechanisms simultaneously to drive cycling in output neurons.

neuroscience↗

bioRxiv2020

A Circuit Mechanism Underlying Suppression of Circadian Signals by Homeostatic Sleep Drive

Sleep is controlled by homeostatic mechanisms, which drive sleep after wakefulness, and a circadian clock, which confers the 24-hour rhythm of sleep. These processes interact with each other to control the timing of sleep in a daily cycle as well as following sleep deprivation. However, the mechanisms by which they interact are poorly understood. We show here that hugin+ neurons, previously identified as neurons that function downstream of the clock to regulate rhythms of locomotor activity, are also targets of the sleep homeostat. Sleep deprivation decreases activity of hugin+ neurons, likely to suppress circadian-driven activity during recovery sleep, and manipulations of hugin+ neurons affect sleep increases generated by activation of the homeostatic sleep locus, the dorsal fanshaped body (dFB). Also, mutations in peptides produced by the hugin+ locus increase recovery sleep following deprivation. Trans-synaptic mapping reveals that hugin+ neurons feed-back onto central clock neurons, which also show decreased activity upon sleep loss, in a Hugin-peptide dependent fashion. We propose that hugin+ neurons integrate circadian and sleep signals to modulate circadian circuitry and regulate the timing of sleep.

neuroscience↗