Biology subjects

Sasaguri, H.

Publications and source records attributed to Sasaguri, H..

14 recordsLinked to original sources

bioRxiv2025

Repetitive Hibernation-Like State Suppresses the Progression of Amyloid Pathology

Alzheimers disease (AD) is characterized by the gradual accumulation of amyloid pathology before the onset of cognitive impairment, yet effective strategies to alter disease progression remain limited. Here, we tested whether induction of a hibernation-like physiological state can slow amyloid pathology in an AD mouse model. To achieve sustained effects, we developed a protocol for repeated induction of a hypometabolic/hypothermic state and found that it significantly slowed plaque accumulation in a duration-dependent manner. This intervention also attenuated neuroinflammation and the formation of dystrophic neurites associated with plaques. Notably, this approach does not target specific molecular pathways but instead modulates global brain state. Our findings establish a proof-of-concept for a brain-state- based therapeutic paradigm for modifying disease progression in AD.

neuroscience↗

bioRxiv2025

Human-specific fast synaptic kinetics enable rapid detection of predictive features

Humans can discern the underlying principles in complex environments, but the cellular basis of this ability is unclear. By comparing layer 2/3 cortical pyramidal neurons in five mammals (mouse, rat, marmoset, macaque and human), we found that human neurons exhibited distinctively faster kinetics of excitatory synaptic transmissions. In a computational model, neurons with human-type synapses detected hidden patterns more quickly in noise, and this superiority was only evident in unsupervised learning. Tracking synaptic weights revealed that human synapses were potentiated sharply and persistently by the patterns, while macaque-type synapses were broadly potentiated, which were easily eroded. These data suggest that the human-specific acceleration of synaptic kinetics enables the rapid extraction of latent structures in complex environments, providing a cellular basis for our efficient cognitive abilities.

neuroscience↗

bioRxiv2025

Involvement of orexin nerves in early stage of Alzheimer's disease model mice and preventive effect of orexin receptor antagonists

BackgroundMild cognitive impairment (MCI) is a condition between healthy cognition and dementia with a high probability of progression to Alzheimers disease (AD). Elevated levels of orexin (OX) have been reported in the cerebrospinal fluid of patients with MCI and AD. ObjectiveTo investigate the efficacy of dual OX receptor antagonists (suvorexant and lemborexant) in an early-stage AD mouse model (App-KI). MethodsThe expression of the OX receptor gene, the levels of suvorexant and lemborexant in the brain after a single oral dose, and their effects on locomotor activity were investigated in wild-type mice. In addition, the cognitive function of wild-type and App-KI mice was assessed using the Y-maze test after oral administration of suvorexant or lemborexant once a day for 60 d. After the behavioral test, amyloid-beta levels were quantified in the hippocampal CA1 region of App-KI mice. ResultsThe expression of the OX receptor gene was highest in the lateral hypothalamus and was also observed in other brain regions. Drug levels peaked at 20-40 min for suvorexant and 15 min for lemborexant and declined, still detectable 24 h later. Locomotor activity was reduced after suvorexant or lemborexant administration; however, 24 h after administration, locomotor activity did not differ from the control group. In particular, the Y-maze test showed that suvorexant and lemborexant prevented cognitive impairment in App-KI mice. Furthermore, suvorexant and lemborexant suppressed amyloid-beta accumulation in the hippocampal CA1 region of App-KI mice. ConclusionThe results suggest that suvorexant and lemborexant effectively suppress the early stages of AD.

animal behavior and cognition↗

bioRxiv2025

Misclassification in memory modification in AppNL-G-F knock-in mouse model of Alzheimers disease

Alzheimers disease (AD), the leading cause of dementia, could potentially be mitigated through early detection and interventions. However, it remains challenging to assess subtle cognitive changes in the early AD continuum. Computational modeling is a promising approach to explain a generative process underlying subtle behavioral changes with a number of putative variables. Nonetheless, internal models of the patient remain underexplored in AD. Determining the states of an internal model between measurable pathological states and behavioral phenotypes would advance explanations about the generative process in earlier disease stages beyond assessing behavior alone. In this study, we assumed the latent cause model as an internal model and estimated internal states defined by the model parameters being in conjunction with measurable behavioral phenotypes. The 6- and 12-month-old AppNL-G-F knock-in AD model mice and the age-matched control mice underwent memory modification learning, which consisted of classical fear conditioning, extinction, and reinstatement. The results showed that AppNL-G-F mice exhibited a lower extent of reinstatement of fear memory. Computational modeling revealed that the deficit in the AppNL-G-F mice would be due to their internal states being biased toward overgeneralization or overdifferentiation of their observations, and consequently the competing memories were not retained. This deficit was replicated in another type of memory modification learning in the reversal Barnes maze task. Following reversal learning, AppNL- G-F mice, given spatial cues, failed to infer coexisting memories for two goal locations during the trial. We concluded that the altered internal states of AppNL-G-F mice illustrated their misclassification in the memory modification process. This novel approach highlights the potential of investigating internal states to precisely assess cognitive changes in early AD and multidimensionally evaluate how early interventions may work.

neuroscience↗

bioRxiv2024

Single MAPT knock-in mouse models of frontotemporal dementia for sharing with the neurodegenerative research community

We recently reported development of human MAPT knock-in mice that carry single or double pathogenic mutations of frontotemporal dementia. However, it takes more than 14 months for the line with the most aggressive phenotypes to exhibit tau pathology without forming high-order tau oligomers, along with concomitant abnormal behavior. We thus generated MAPT knock-in mice carrying triple mutations, among which the MAPTP301S;Int10+3;S320F line exhibited robust pathology starting earlier than 6 months. Tau accumulation took place mainly in the thalamus, hypothalamus, amygdala and entorhinal cortex, but less so in the hippocampus, leading to synaptic loss, atrophy and behavioral abnormalities. Crossbreeding MAPTP301S;Int10+3;S320F with App knock-in mice AppNL-G-F resulted in the manifestation of tau pathology in the hippocampus and cortex. These mutant mice will be valuable tools for understanding the mechanisms of frontotemporal dementia, Alzheimers disease and other tauopathies.

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↗

bioRxiv2022

Cystatin F (Cst7) drives sex-dependent changes in microglia in an amyloid-driven model of Alzheimer's Disease

Microglial endolysosomal (dys)function is strongly implicated in neurodegeneration. Transcriptomic studies show that a microglial state characterised by a set of genes involved in endolysosomal function is induced in both mouse Alzheimers Disease (AD) models and in human AD brain and that the onset of this state is emphasized in females. Cst7 (encoding protein Cystatin F) is among the most highly upregulated genes in these microglia. However, despite such striking and robust upregulation, the sex-specific function of Cst7 in neurodegenerative disease is not understood. Here, we crossed Cst7-/- mice with the AppNL-G-F mouse to test the role of Cst7 in a model of amyloid-driven AD. Surprisingly, we found that Cst7 plays a sexually dimorphic role regulating microglia in this model. In females, Cst7-deficient microglia had greater endolysosomal gene expression, lysosomal burden, and amyloid beta (A{beta}) burden in vivo and were more phagocytic in vitro. However, in males, Cst7-deficient microglia were less inflammatory and had a reduction in lysosomal burden but had no change in A{beta} burden. This study has important implications for AD research, confirming the functional role of a gene which is commonly upregulated in disease models, but also raising crucial questions on sexual dimorphism in neurodegenerative disease and the interplay between endolysosomal and inflammatory pathways in AD pathology.

neuroscience↗

bioRxiv2022

A novel fully-automated system for lifelong continuous phenotyping of mouse cognition and behaviour

Comprehensive ethologically-relevant behavioural phenotyping in rodent experiments is essential for deciphering the neural basis of animal cognition. Automated home-cage monitoring systems present a valuable tool to fulfil this need. However, they often involve complex animal training routines, water or food deprivation, and probe a limited range of behaviours. Here, we present a new fully automated AI-driven home-cage system for cognitive and behavioural phenotyping in mice. The system incorporates spontaneous alternation T-maze, novel-object recognition and object-in-place recognition tests combined with monitoring of an animals position, water consumption, quiescence and locomotion patterns, all carried out continuously and simultaneously in an unsupervised fashion over long periods of time. Mice learnt the tasks rapidly without any need for water or food restrictions. We applied ethomics approach to show that combined statistical properties of multiple behaviours can be used to discriminate between mice with hippocampal, medial entorhinal and sham lesions and accurately predict genotype of Alzheimers disease mouse models on an individual animal level, surpassing the performance of several gold standard cognitive tests. This technology could enable large-scale behavioural screening for genes and neural circuits underlying spatial memory and other cognitive processes.

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

α-Endosulfine regulates amyloid β42 via the modulation of neprilysin activity

The neuropeptide somatostatin (SST) regulates amyloid {beta} peptide (A{beta}) catabolism by enhancing neprilysin (NEP)-catalyzed proteolytic degradation. However, the mechanism by which SST regulates NEP activity remains unclear. Here we report the identification by differential proteomics of -endosulfine (ENSA), an endogenous ligand of the ATP-sensitive potassium (KATP) channel, as a negative regulator of NEP activity downstream of SST signaling. Genetic deficiency of ENSA resulted in enhanced NEP activity and decreased A{beta} deposition in the brains of wild-type and Alzheimers disease (AD) model mice. Pharmacological intervention to increase the probability of KATP channel opening reduced A{beta} deposition in AD model mice. Our findings provide new insights into possible mechanisms to prevent AD.

neuroscience↗

bioRxiv2020

A non-human primate model of familial Alzheimer's disease

Alzheimers disease (AD) is a major cause of dementia, with the number of patients with this condition anticipated to exceed 50 million worldwide in the near future. Despite extensive research efforts, no effective measures are available to facilitate the prevention or treatment of AD, which is due in part to a lack of animal models able to closely replicate a human-like disease state. Here, we describe the generation of three mutant marmoset individuals in which exon 9 of PSEN1 gene product has been deleted (PSEN1-{Delta}E9). Such {Delta}E9 mutations have been reported to cause early on-set familial AD (references1-5). We used Transcription Activator-Like Effector Nuclease (TALEN) to destroy the 3 splice site of exon 9 in the marmoset PSEN1 gene. To this end, TALEN exhibits high genome-editing efficacy, generates few off-target effects, and produces minimal mosaicism. Indeed, whole genome sequencing and other analyses illustrated an absence of off-target effects and an apparent absence of mosaicism. Fibroblasts obtained from newborn marmosets exhibited uncleaved full-length presenilin 1 protein (PS1) caused by the perturbation of PS1 endoproteolysis as well as an increased ratio of A{beta}42/A{beta}40 production, a signature of familial AD pathogenesis. To our knowledge, this is the first non-human primate model of familial AD. We intend to make our marmoset model available to the research community to facilitate the global fight against AD.

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↗