Biology subjects

Inami, S.

Publications and source records attributed to Inami, S..

6 recordsLinked to original sources

bioRxiv2025

Increased neuronal activity restores circadian functionin Drosophila models of C9orf72-ALS/FTD

Circadian rhythm disruptions are common across neurodegenerative diseases, but their link to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) remains unclear. The C9orf72 hexanucleotide repeat expansion is the most prevalent genetic cause of ALS/FTD. Here, we used Drosophila models expressing toxic arginine-rich dipeptides (PR or GR) or GGGGCC hexanucleotide repeats to investigate circadian deficits in C9orf72-ALS/FTD. We found that circadian rhythmicity and period length were disrupted in a repeat number-, dosage-, and age-dependent manner. Additionally, we observed lower levels of the neuropeptide PDF, a key regulator of free-running circadian rhythms, as well as decreased projection complexity and reduced neuronal activity in PDF-expressing neurons. Importantly, increases in neuronal activity significantly restored circadian function under select conditions. These results implicate reduced neuronal activity in C9orf72-ALS/FTD circadian deficits, underscoring the importance of precisely tuned, circuit- and stage-specific interventions. HighlightsO_LIC9orf72 dipeptide and nucleotide repeats disrupt circadian rhythms in Drosophila C_LIO_LICircadian dysfunction with reduced PDF and neurites emerges before neuron loss C_LIO_LIIncreased neuronal activity rescues mild circadian dysfunction C_LIO_LIActivity-based rescue is effective across ages and models when precisely tuned C_LI

neuroscience↗

bioRxiv2024

Sleep induced by mechanosensory stimulation provides cognitive and health benefits in Drosophila

Study ObjectivesSleep is a complex phenomenon regulated by various factors, including sensory input. Anecdotal observations have suggested that gentle rocking helps babies fall asleep, and experimental studies have verified that rocking promotes sleep in both humans and mice. Recent studies have expanded this understanding, demonstrating that gentle vibration also induces sleep in Drosophila. Natural sleep serves multiple functions, including learning and memory, synaptic downscaling, and clearance of harmful substances associated with neurodegenerative diseases. Here, we investigated whether vibration-induced sleep provides similar cognitive and health benefits in Drosophila. MethodsWe administered gentle vibration to flies that slept very little due to a forced activation of wake-promoting neurons and investigated how the vibration influenced learning and memory in the courtship conditioning paradigm. Additionally, we examined the effects of VIS on synaptic downscaling by counting synapse numbers of select neurons. Finally, we determined whether vibration could induce sleep in Drosophila models of Alzheimers disease (AD) and promote the clearance of Amyloid {beta} (A{beta}) and Tubulin Associated Unit (TAU). ResultsVibration-induced sleep enhanced performance in a courtship conditioning paradigm and reduced the number of synapses in select neurons. Moreover, vibration improved sleep in Drosophila models of AD, promoting the clearance of A{beta} and TAU. ConclusionsMechanosensory stimulation offers a promising non-invasive avenue for enhancing sleep, potentially providing associated cognitive and health benefits. Significance StatementSleep is critical for a healthy mind and body, and sleep disturbances are commonly associated with neurodegenerative diseases such as Alzheimers disease. Sleep is influenced by sensory input, and mechanical stimulation, such as gentle rocking and vibration, has been shown to promote sleep in various species, including humans, mice, and fruit flies. This study demonstrates that gentle vibration not only helps flies sleep better but also improves their performance in a learning and memory task and makes their brains more efficient in clearing harmful substances. Notably, vibration can facilitate the clearance of Amyloid {beta} and the TAU proteins, which accumulate in Alzheimers disease. These results highlight the potential for gentle mechanosensory stimulation to promote sleep and cognitive health.

neuroscience↗

bioRxiv2023

Modulation and Neural Correlates of Postmating Sleep Plasticity in Drosophila Females

Sleep is essential, but animals may forgo sleep to engage in other critical behaviors, such as feeding and reproduction. Previous studies have shown that female flies show decreased sleep after mating, but our understanding of the process is limited. Here, we report that postmating nighttime sleep loss is modulated by diet and sleep deprivation, demonstrating a complex interaction among sleep, reproduction, and diet. We also report that female-specific pC1 neurons and sleep-promoting dorsal fan-shaped body (dFB) neurons are required for postmating sleep plasticity. Activating pC1 neurons leads to sleep suppression on standard fly culture media but has little sleep effect on sucrose-only food. Published connectome data suggest indirect, inhibitory connections among pC1 subtypes. Using calcium imaging, we show that activating the pC1e subtype inhibits dFB neurons. We propose that pC1 and dFB neurons integrate the mating status, food context, and sleep drive to modulate postmating sleep plasticity. HighlightsO_LIDiet and sleep drive modulate female nighttime postmating sleep loss C_LIO_LIFemale-specific pC1 neurons are required for postmating sleep loss C_LIO_LISleep-promoting dFB-projecting neurons are required for postmating sleep loss C_LIO_LIActivating pC1 subtypes promotes wakefulness and inhibits dFB-projecting neurons C_LI eTOC blurbAnimals evaluate environmental conditions and internal states to make behavioral choices. Duhart et al. show that the decision to stay awake after mating in Drosophila females is modulated by food composition and sleep history and mediated by female-specific pC1 neurons acting upstream of the dFB sleep center.

neuroscience↗

bioRxiv2020

Consolidation and maintenance of Drosophila long-term memory require LIM homeodomain protein Apterous in distinct brain neurons

The LIM-homeodomain (LIM-HD) transcription factor Apterous (Ap) and its cofactor Chip (Chi) form a complex that regulates various developmental events in Drosophila. Although Ap continues to be expressed in the adult brain, the functions of the centrally expressed Ap remain incompletely understood. Here, we show that Ap and Chi in the Drosophila memory center, the mushroom bodies (MBs), are indispensable for long-term memory (LTM) maintenance, whereas Ap in a subset of clock neurons [large ventral-lateral neurons (l-LNvs)] plays a crucial role in memory consolidation in a Chi-independent manner. Ex vivo imaging revealed that Ap, but not Chi, in l-LNvs is essential for the appropriate Cl- responses to GABA. Furthermore, knockdown of GABAA receptor in l-LNvs compensated for the impairment of memory consolidation in ap null mutant flies. Our results indicate that Drosophila Ap functions differently in l-LNvs and MBs, and it contributes to the consolidation and maintenance of LTM.

neuroscience↗

bioRxiv2020

Sleep Induction by Mechanosensory Stimulation in Drosophila

People tend to fall asleep when gently rocked or vibrated. Experimental studies have shown rocking promotes sleep in humans and mice. The prevailing "synchronization" model proposes synchronization of brain activity to mechanosensory stimuli mediates the phenomenon. The alternative "habituation" model proposes habituation, a form of non-associative learning, mediates sleep induction by monotonous stimulation. Here we show that gentle vibration promotes sleep in Drosophila in part through habituation. Vibration-induced sleep (VIS) leads to the accrual of homeostatic sleep credit, is associated with reduced arousability, and can be suppressed by heightened arousal. Sleep induction improves over successive blocks of vibration and exhibits stimulus specificity, supporting the habituation model. Multiple mechanosensory organs mediate VIS, and the magnitude of sleep gain depends on the vibration frequency and genetic background. Our findings suggest habituation is a major contributor to VIS, but synchronization of brain activity may play a role under certain stimulus conditions.

neuroscience↗

bioRxiv2019

Environmental light is required for maintenance of long-term memory in Drosophila

Long-term memory (LTM) is stored as functional modifications of relevant neural circuits in the brain. A large body of evidence indicates that the initial establishment of such modifications through the process known as memory consolidation requires learning-dependent transcriptional activation and de novo protein synthesis. However, it remains poorly understood how the consolidated memory is maintained for a long period in the brain, despite constant turnover of molecular substrates. Using the Drosophila courtship-conditioning assay of adult males as a memory paradigm, here, we show that in Drosophila, environmental light plays a critical role in LTM maintenance. LTM is impaired when flies are kept in constant darkness (DD) during the memory maintenance phase. Because light activates the brain neurons expressing the neuropeptide Pigment-dispersing factor (Pdf), we examined the possible involvement of Pdf neurons in LTM maintenance. Temporal activation of Pdf neurons compensated for the DD-dependent LTM impairment, whereas temporal knockdown of Pdf during the memory maintenance phase impaired LTM in light-dark cycles. Furthermore, we demonstrated that the transcription factor cAMP response element-binding protein (CREB) is required in the memory center, mushroom bodies (MBs), for LTM maintenance, and Pdf signaling regulates light-dependent transcription via CREB. Our results demonstrate for the first time that universally available environmental light plays a critical role in LTM maintenance by activating the evolutionarily conserved memory modulator CREB in MBs via the Pdf signaling pathway.\n\nSignificant StatementTemporary memory can be consolidated into long-term memory (LTM) through de novo protein synthesis and functional modifications of neuronal circuits in the brain. Once established, LTM requires continual maintenance so that it is kept for an extended period against molecular turnover and cellular reorganization that may disrupt memory traces. How is LTM maintained mechanistically? Despite its critical importance, the molecular and cellular underpinnings of LTM maintenance remain elusive. This study using Drosophila is significant because it revealed for the first time in any organism that universally available environmental light plays an essential role in LTM maintenance. Interestingly, light does so by activating the evolutionarily conserved transcription factor cAMP response element-binding protein via peptidergic signaling.

neuroscience↗