Biology subjects

Sekiguchi, M.

Publications and source records attributed to Sekiguchi, M..

12 recordsLinked to original sources

bioRxiv2026

Auricular vagus nerve stimulation facilitates contextual fear extinction via insular-mPFC pathway without affecting reconsolidation

Cervical vagus nerve stimulation (VNS) suppresses conditioned fear in rodents and may serve as an adjunct to exposure-based therapy for anxiety disorders. Non-invasive auricular VNS reduces conditioned fear also in humans, although the underlying mechanisms remain unclear. Using a contextual fear conditioning paradigm, in which brief re-exposure induces reconsolidation and prolonged re-exposure promotes extinction learning in mice, we examined auricular VNS-induced attenuation of fear. Auricular VNS during prolonged but not during brief re-exposures reduced freezing, indicating selective facilitation of extinction learning. Stimulation during the latter half of prolonged re-exposure, while extinction learning was progressing, reduced fear responses. As a neural circuit mechanism, we focused on projections from the posterior insular cortex (pIC), which receives interoceptive signals, including vagal input, to the medial prefrontal cortex (mPFC), which regulates fear. Auricular VNS increased c-Fos expression in pIC neurons projecting to the mPFC subdivisions: infralimbic and dorsal peduncular cortex (IL/DP). Optogenetic activation of the pIC-IL/DP pathway mimicked the extinction-facilitating effects of auricular VNS, whereas inhibition blocked them. These results demonstrate that auricular VNS promotes extinction learning of contextual fear memory by activating the pIC-IL/DP circuit, providing insight into how vagal afferent stimulation engages insular-prefrontal networks to modulate fear.

neuroscience↗

bioRxiv2024

Viral vectors with cluster of differentiation gene promoters to target specific cell types in the brain

Understanding brain function and developing targeted therapies for neurological disorders require precise access to specific cell types, but current methods are limited. Here, we report the development of cell-type specific adeno-associated virus (AAV) vectors utilizing promoters of cluster of differentiation genes (CD promoters) for targeted gene delivery in the brain. We newly identified CD promoters that induce gene expression selectively in specific cell types in the mouse brain. These AAVs enable in vivo calcium imaging and chemogenetic applications in specific cerebellar cells, revealing distinct and shared roles of two types of cerebellar interneurons. Notably, chemogenetic modulation of cerebellar molecular layer interneurons using a CD promoter rescued social behavior and motor deficits in a mouse model of autism spectrum disorder. Our findings demonstrate the utility of these AAVs in elucidating the functions of individual cell types in brain function and in developing novel, cell-type specific therapies for brain diseases.

neuroscience↗

bioRxiv2024

Low-invasive, wide-field, and cellular resolution two-photon imaging of neural population activity in brainstem and nucleus tractus solitarii

Brain-viscera communication plays a crucial role in regulating mental health, with the vagus nerve being a key structure mediating this interaction. Clinically, artificial vagus nerve stimulation (VNS) is used to treat various neuropsychiatric disorders, highlighting the importance of vagal afferent fibers in regulating emotion. The nucleus tractus solitarii (NTS) is a brainstem structure proposed to receive signals from vagal afferents and relay them to brain networks for emotion regulation. However, due to the anatomical complexity and difficulty in accessing the deep-brain NTS region in living animals, the mechanisms remain unclear. Here, we developed a wide-field and deep-brain two-photon imaging method using a double-prism based optical interface. This approach enables the identification of cellular-resolution neural activities in the NTS while preserving the cerebellum, which covers the NTS and is important for emotion regulation, intact. We systematically evaluated how NTS neurons respond to VNS and a gastrointestinal hormone, suggesting the usefulness of this method for investigating the role of the vagus-NTS pathway in vivo.

neuroscience↗

bioRxiv2024

Oligodendrocyte dependent synchronized activity orchestrates circuit maturation and brain functionalization

Synchronized spontaneous neural activity is a fundamental feature of developing central nervous systems and is thought to be essential for proper brain development. However, the mechanisms that regulate this synchronization and its long-term impact on brain function remain unclear. Here, we identify a previously unrecognized role of oligodendrocytes in orchestrating synchronized spontaneous activity during a critical developmental window, with lasting consequences for adult behavior. Using oligodendrocyte-specific genetic manipulation in the mouse cerebellum, we demonstrate that oligodendrocyte deficiency during early postnatal development, but not after weaning, disrupts the synchronization of Purkinje cell activity both during development and in adulthood. The early disruption produced persistent deficits in cerebellar-dependent behaviors, including anxiety, sociality, and motor function. Optogenetic re-synchronization in adulthood restored motor and social functions but not anxiety-like behavior, demonstrating that reduced Purkinje cell synchrony specifically drives the motor and social impairments. Our findings establish a causal link between developmental oligodendrocyte-regulated neural synchrony and the emergence of complex brain functions, which depend on the proper developmental trajectory necessary for driving brain function.

neuroscience↗

bioRxiv2024

Metabolic resistance of Abeta3pE-42, epitope of the anti-Alzheimer therapeutic antibody, donanemab.

The amyloid {beta} peptide (A{beta}) starting with pyroglutamate (pE) at position 3 and ending at position 42 (A{beta}3pE-42) is a dominant species that accumulates in the Alzheimers disease (AD) brain. Consistently, a therapeutic antibody raised against this species, donanemab, has been shown to be effective in recent clinical trials. While the primary A{beta} species produced physiologically is A{beta}1-40/42, an explanation for how and why this physiological A{beta} is converted to the pathological form has remained elusive. The conversion of A{beta}1-42 to A{beta}3pE-42 is likely to take place after deposition of A{beta}1-42 given that A{beta}3pE-42 plaques arise significantly later than A{beta}1-42 deposition in the brains of single App knock-in and APP-transgenic mice. Here, we present experimental evidence that accounts for the aging-associated A{beta}3pE-42 deposition: [1] A{beta}3pE-42 is metabolically more stable than other A{beta}X-42 species; [2] Deficiency of neprilysin (NEP), the major A{beta}-degrading enzyme, induces a relatively selective deposition of A{beta}3pE-42 in APP-Tg mice. [3] A{beta}3pE-42 deposition always colocalizes with cored plaques in both APP-Tg and App knock-in mouse brains; [4] A{beta}3E-42, an immediate precursor of A{beta}3pE-42, as well as A{beta}2A-42 and A{beta}4F-42 are more short-lived than A{beta}1-42 in vivo, indicating that simple N-terminal truncation that can arise enzymatically or spontaneously makes A{beta}X-42 easier to catabolize. Consistently, newly generated knock-in mice, AppNL-({Delta}DA)-F and AppNL-({Delta}DA)-Q-F, showed no detectable A{beta} pathology even after aging, indicating that the A{beta}3E-42 and A{beta}3Q-42 species are extremely labile to the in vivo catabolic system and that the E/Q cyclase activity present in mouse brain is insufficient for A{beta}3pE-42 generation. In addition, a deficiency of NEP facilitated A{beta}3pE-42 deposition. Of note, we identified a trace amount of A{beta}3pE-42 and its immediate precursor, A{beta}3E-42, in the insoluble fraction of NEP-deficient APP-Tg mouse brains. A{beta}3pE-42 is thus likely to be a probabilistic by-product of A{beta}1-42 metabolism that selectively accumulates over a long-time range of brain aging. It is likely produced in the solid state or at the solid-liquid interface. Our findings suggest that anti-A{beta} therapies will probably be most effective if given before A{beta}3pE-42 deposition takes place.

neuroscience↗

bioRxiv2023

Synaptic and peptidergic connectomes of the Drosophila circadian clock

The circadian clock and its output pathways play a pivotal role in optimizing daily processes. To obtain novel insights into how diverse rhythmic physiology and behaviors are orchestrated, we have generated the first comprehensive connectivity map of an animal circadian clock using the Drosophila FlyWire brain connectome. Intriguingly, we identified additional dorsal clock neurons, thus showing that the Drosophila circadian network contains [~]240 instead of 150 neurons. We also revealed extensive contralateral synaptic connectivity within the network and discovered novel indirect light input pathways to the clock neurons. Interestingly, we observed sparse monosynaptic connectivity between clock neurons and down-stream higher-order brain centers and neurosecretory cells known to regulate behavior and physiology. Therefore, we integrated single-cell transcriptomics and receptor mapping to decipher putative paracrine peptidergic signaling by clock neurons. Our analyses identified additional novel neuropeptides expressed in clock neurons and suggest that peptidergic signaling significantly enriches interconnectivity within the clock network.

neuroscience↗

bioRxiv2021

An isogenic panel of single App knock-in mouse models of Alzheimer's disease confers differential profiles of β-secretase inhibition and endosomal abnormalities

We previously developed single App knock-in mouse models of Alzheimers disease (AD) that harbor the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL- G-F and AppNL-F mice). These models showed the development of amyloid {beta} peptide (A{beta}) pathology, neuroinflammation and cognitive impairment with aging. We have now generated App knock-in mice devoid of the Swedish mutations (AppG-F mice) and some additional mutants to address the following two questions: [1] Do the Swedish mutations influence the mode of {beta}-secretase inhibitor action in vivo? [2] Does the quantity of C-terminal fragment of amyloid precursor protein (APP) generated by {beta}-secretase (CTF-{beta}) affect endosomal properties as previously reported as well as other pathological events? A{beta} pathology was exhibited by AppG-F mice from 6 to 8 months of age, and was accompanied by microglial and astrocyte activation. We found that a {beta}-secretase inhibitor, verubecestat, inhibited A{beta} production in AppG-F mice, but not in AppNL-G-F mice, indicating that the AppG-F mice are more suitable for preclinical studies of {beta}-secretase inhibition given that most AD patients do not carry Swedish mutations. We also found that the quantity of CTF-{beta} generated by various App knock-in mutants failed to correlate with endosomal alterations or enlargement, implying that CTF-{beta}, endosomal abnormalities, or both are unlikely to play a major role in AD pathogenesis. This is the first AD mouse model ever described that recapitulates amyloid pathology in the brain without the presence of Swedish mutations and without relying on the overexpression paradigm. Thus, experimental comparisons between different App knock-in mouse lines will potentially provide new insights into our understanding of the etiology of AD.

neuroscience↗

bioRxiv2021

Neprilysin-sensitive amyloidogenic Aβ versus IDE-sensitive soluble Aβ: a probable mechanistic cause for sporadic Alzheimer's disease

Neprilysin (NEP) and insulin-degrading enzyme (IDE) are considered the two major catabolic enzymes that degrade amyloid {beta} peptide (A{beta}), the primary cause of Alzheimers disease (AD). However, their roles in A{beta} metabolism in vivo have never been compared in an impartial and side-by-side manner. Here, we crossbred single App knock-in mice with NEP (Mme) KO mice and with IDE (Ide) KO mice to generate double mutants that were analyzed for their biochemical and A{beta} pathology properties. We found that NEP is responsible for the metabolism of amyloidogenic insoluble A{beta} whereas IDE affects soluble A{beta}. A deficiency of NEP, but not of IDE, augmented the formation of A{beta} plaques, dystrophic neurites, and astrocytic and microglial activation, all of which are key pathological events in the development of AD. In addition, a deficiency of NEP had no significant impact on the levels of various neuropeptides (somatostatin, substance P, cholecystokinin, and neuropeptide Y), well known to be in vitro substrates for NEP, presumably because NEP is expressed in secretory vesicles and on the presynaptic membranes of excitatory neurons while most if not all neuropeptides are secreted from inhibitory neurons. This argues against the concern that NEP up-regulation for treatment of preclinical AD would reduce the levels of these neuropeptides. These findings indicate that NEP relatively selectively degrades A{beta} in the brain. Whereas familial AD (FAD) is unambiguously caused by an increased anabolism of A{beta}, and of A{beta} 42 and A{beta} 43 in particular, the anabolism of A{beta} appears unaffected before its deposition in the brain that subsequently leads to the onset of sporadic AD (SAD). These observations thus suggest that NEP-sensitive amyloidogenic A{beta} likely plays a primary pathogenic role in the etiology of SAD. Our findings are consistent with the aging-dependent decline of NEP expression in human brain and with recent genome-wide association studies (GWAS) indicating that variants of the gene encoding NEP (MME) are associated with the risk of SAD development. Taken together, our results imply that the aging-associated decrease in NEP expression is a primary cause of SAD and could thus be a target for the treatment of preclinical AD once other factors such as apolipoprotein E genotypes have also been considered.

neuroscience↗

bioRxiv2021

New App knock-in mice that accumulate wild-type human Aβ as rapidly as AppNL-G-F mice exhibit intensive cored plaque pathology and neuroinflammation.

We previously developed single App knock-in mouse models of Alzheimers disease (AD), harboring the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL-G-F and AppNL-F mice). These models showed amyloid {beta} peptide (A{beta}) pathology, neuroinflammation and cognitive impairment in an age-dependent manner. The former line exhibits extensive pathology as early as 6 months but is unsuitable for investigating A{beta} metabolism and clearance because the Arctic mutation renders A{beta} resistant to proteolytic degradation and prone to aggregation. In particular, it is inapplicable to preclinical immunotherapy studies due to its discrete affinity for anti-A{beta} antibodies. The weakness of the latter model is that it may take as long as 18 months for the pathology to become prominent. We have thus generated a new model that exhibits early deposition of wild-type human A{beta} by crossbreeding the AppNL-F line with the Psen1P117L/WT line. We show that the effects of the pathogenic mutations in the App and Psen1 genes are additive or synergistic. This new mouse model showed more cored plaque pathology and neuroinflammation than AppNL-G-F mice and will help accelerate the development of disease-modifying therapies to treat preclinical AD.

neuroscience↗

bioRxiv2020

Distinct synaptic and related transcriptional abnormalities in neonatal, childhood and mature autism model of primate: implications for early-age therapeutic intervention

Autism spectrum disorder (ASD) is a synapse-related disorder that is diagnosed at around 3 years of age. Earlier intervention is desirable for better ASD prognosis; however, there is limited biological literature regarding early-age ASD. This study aimed to assess altered cortical synapses and gene expression in the ASD model marmoset. There were distinct phenotypes in the model animals across the neonate, childhood, and mature stages in the dorsomedial prefrontal cortex (Brodmann area 8b/9). At the neonate stage, synapses were underdeveloped and modulated genes were enriched with synaptogenesis- and ASD-related genes. At the childhood stage, synaptic features and gene expressions associated with experience-dependent circuit remodeling were altered in model animals. At the mature stage, there were synapse overdevelopment and altered gene expression similar to those in human ASD. These early synaptic phenotypes and altered gene expressions could be novel targets of efficient therapy from a young age.

neuroscience↗

bioRxiv2020

Somatostatin receptor subtypes 1 and 4 redundantly regulate neprilysin, the major amyloid beta-degrading enzyme, in brain

Alzheimers disease (AD) brains are characterized by increased levels of the pathogenic amyloid beta (A{beta}) peptide, which accumulates into extracellular plaques. Finding a way to lower A{beta} levels is fundamental for the prevention and treatment of AD. Neprilysin is the major A{beta} degrading enzyme which is regulated by the neuropeptide somatostatin. Here we used a combination of in vitro and in vivo approaches to identify the subtype specificity of the five somatostatin receptors (SSTs) expressed in the brain, involved in the regulation of neprilysin. Using a battery of Sst double knockout (dKO) mice we show that neprilysin is regulated by SST1 and SST4 in a redundant manner. Sst1 and Sst4 dKO mice exhibit a specific decrease of presynaptic neprilysin in the Lacunosum molecular layer. Moreover, a genetic deficiency of Sst1 and Sst4 in amyloid beta precursor protein (App) knock-in mice, an AD mouse model, aggravates the A{beta} pathology in the hippocampus. As a first proof of concept towards an A{beta}-lowering strategy involving neprilysin, we demonstrate that treatment with an agonist selective for SST1 and SST4 ameliorates the A{beta} pathology and improves cognition in the App knock-in AD mouse model.

neuroscience↗

bioRxiv2018

Antibacterial effects of nanoimprinted moth-eye film in practical settings

Recent studies report that surfaces displaying micrometer-or nanometer-sized undulating structures exhibit antibacterial effects. In previous work, we described the use of an advanced nanofabrication technique to generate an artificial biomimetic moth-eye film by coating a polyethylene terephthalate (PET) film with nanoscale moth-eye protrusions made from a hydrophilic resin. This moth-eye film exhibited enhanced antibacterial effects in in vitro experiments. The aim of the present study was to verify the antibacterial efficacy of the Moth-eye film in practical environments. Three types of films (Moth-eye film, Flat film, and PET film) were used to compare antibacterial effects. Sample films were pasted onto hand-wash sinks at the testing locations. After several hours of elapsed time, bacteria from the surface of sample films were collected using one of three kinds of culture media stampers (to permit identification of bacterial species). The stampers were incubated for 48 hours at 35 {degrees}C, and the numbers of colonies were counted.\n\nThe number of common bacteria including E. coli and S. aureus from the Moth-eye film was significantly lower than that from the PET film (p<0.05) and that from the Flat film at 1 hour (p<0.05). This study found that the Moth-eye film had durability of antibacterial effect and the Moth-eye structure (PET coated with nanoscale cone-shaped pillars) had a physical antibacterial effect from the earlier time points. Therefore, the Moth-eye film might be useful for general-purpose applications in practical environments.

microbiology↗