Biology subjects

Saitoe, M.

Publications and source records attributed to Saitoe, M..

5 recordsLinked to original sources

bioRxiv2025

Pak, a downstream gene of ecdysone signaling, determines left-right polarity in the Drosophila brain through neuronal cell chirality

Left-right (LR) asymmetry is a conserved characteristic of the brain in various animals and is related to its higher-order functions. The Drosophila brain has an LR asymmetric structure known as an asymmetrical body (AB). LR asymmetric neurite remodeling lateralizes the AB, and ecdysone signaling determines LR specificity. However, the mechanisms underlying LR specificity remain unclear. We found that the Slit/Dreadlocks/Roundabout/p21-activated kinase (Pak) signaling axis determines the LR polarity of the AB downstream of ecdysone signaling in the type II neuroblast lineage before LR asymmetric neurite remodeling. In Drosophila, the intrinsic chirality of cells (cell chirality) defines the LR asymmetry of various non-neuronal organs. We suggested that neurons derived from type II neuroblasts exhibit cell chirality, which is established through Pak and ecdysone signaling and determines the LR polarity of the AB. As cell chirality is broadly observed in eukaryotes, our study reveals a novel mechanism underlying LR asymmetry of the brain.

neuroscience↗

bioRxiv2025

Forgetting in Drosophila consists of an increase in uncertainty rather than a stochastic loss of memory

While forgetting has been studied extensively in various organisms, its precise nature has often been unclear. Here, we used behavioral experiments in Drosophila to determine that a significant aspect of forgetting consists of a decrease in the ability of a memory to induce an appropriate behavior. We tested flies for memory retention at various times after training and then separately retested both flies that chose correctly and those that chose incorrectly. Although the ability to choose correctly decreased over time, we could not measure any differences in memory between flies that initially chose correctly and those that chose incorrectly upon retest. This suggests that forgetting is unlikely to consist of a spontaneous loss of a memory but instead consists of a decrease in the probability of flies that remember choosing the correct behavioral response. Thus, although flies maintain memory over time, there is an increase in uncertainty associated with this memory. We find that forgetting of long-term memories and accelerated forgetting in old flies occur in a similar manner.

neuroscience↗

bioRxiv2025

Neuropeptide signalling and perineurial barrier generate a persistent stress-induced internal state in Drosophila

Although fear conditioning has elucidated cue-evoked acute fear responses, the mechanisms by which stress experiences induce generalized internal states linked to anxiety are poorly understood. Here, we report that robust stress induces a persistent behavioral change characterized by avoidance of a confined space, claustrophobia-like behavior in Drosophila. Unlike aversive memory formation, the development of claustrophobia-like behavior does not require dopamine receptors. Our neuronal screening determined that neuropeptide signalling via Allatostatin-A inactivates the downstream neurons via its receptor AstA-R1, causally inducing claustrophobia-like behavior. Moreover, gene expression profiling of individual fly heads revealed that immune response activation in perineurial barrier is involved in claustrophobia-like behavior. Our data demonstrate that stress-induced persistent behavioral change would not be related to a canonical mechanism of aversive memory formation, rather involves neuropeptidergic signalling and perineurial barrier, providing the mechanism determining internal states which persistently change behavioral modes.

neuroscience↗

bioRxiv2022

A Drosophila model of diabetic neuropathy reveals a crucial role of proteasome activity in the glia

Diabetic peripheral neuropathy (DPN) is the most common chronic, progressive complication of diabetes mellitus. The main symptom is sensory loss; the molecular mechanisms are not fully understood. We found that Drosophila fed a high-sugar diet, which induces diabetes-like phenotypes, exhibit impairment of noxious heat avoidance. The impairment of heat avoidance was associated with shrinkage of the leg neurons expressing the Drosophila transient receptor potential channel Painless. Using a candidate genetic screening approach, we identified proteasome modulator 9 as one of the modulators of impairment of heat avoidance. We further showed that proteasome inhibition in the glia reversed the impairment of noxious heat avoidance, and heat-shock proteins and exosome secretion in the glia mediated the effect of proteasome inhibition. Our results establish Drosophila as a useful system for exploring molecular mechanisms of diet-induced peripheral neuropathy and propose that the glial proteasome is one of the candidate therapeutic targets for DPN.

neuroscience↗

bioRxiv2018

Carbon monoxide, a retrograde messenger generated in post-synaptic mushroom body neurons evokes local dopamine release

Dopaminergic neurons innervate extensive areas of the brain and release dopamine (DA) onto a wide range of target neurons. However, DA release is also precisely regulated, and in Drosophila, DA is released specifically onto mushroom body (MB) neurons, which have been coincidentally activated by cholinergic and glutamatergic inputs. The mechanism for this precise release has been unclear. Here we found that coincidentally activated MB neurons generate carbon monoxide (CO) which functions as a retrograde signal evoking local DA release from presynaptic terminals. CO production depends on activity of heme oxygenase in post-synaptic MB neurons, and CO-evoked DA release requires Ca2+ efflux through ryanodine receptors in DA terminals. CO is only produced in MB areas receiving coincident activation, and removal of CO using scavengers blocks DA release. We propose that DA neurons utilize two distinct modes of transmission to produce global and local DA signaling.\n\nSIGNIFICANCE STATEMENTDopamine (DA) is needed for various higher brain functions including memory formation. However, DA neurons form extensive synaptic connections, while memory formation requires highly specific and localized DA release. Here we identify a mechanism through which DA release from presynaptic terminals is controlled by postsynaptic activity. Postsynaptic neurons activated by cholinergic and glutamatergic inputs generate carbon monoxide, which acts as a retrograde messenger inducing presynaptic DA release. Released DA is required for memory-associated plasticity. Our work identifies a novel mechanism that restricts DA release to the specific postsynaptic sites that require DA during memory formation.

neuroscience↗