Biology subjects

Kakita, A.

Publications and source records attributed to Kakita, A..

13 recordsLinked to original sources

bioRxiv2026

Dysregulated flow responses drive pathogenesis in a cellular model of Sturge-Weber syndrome

Vascular diseases comprise a broad spectrum of conditions associated with organ dysfunction, yet how endothelial responses to mechanical forces drive their pathogenesis remains unclear. Sturge-Weber syndrome (SWS), a flow-associated vascular malformation caused by somatic GNAQ mutations, provides a model to investigate this question. Here, using isogenic induced pluripotent stem cell-derived endothelial cells (ECs), perfusable vascular models, and simplified systems under defined flow conditions, we show that SWS ECs exhibited maladaptive responses to laminar flow, including impaired flow alignment, reduced CLDN5 expression, and decreased transendothelial electrical resistance. Importantly, three-dimensional acoustic microscopy uncovered disturbed surface changes in SWS ECs, potentially contributing to changes in mechanosensing signaling. Transcriptomic and chromatin accessibility analyses revealed dysregulated flow-responsive gene programs, some of which were validated in human SWS samples. These findings provide insights into flow-dependent endothelial dysfunction and a framework for therapeutic modulation in SWS and other vascular disorders.

cell biology↗

bioRxiv2026

Vicious circle of amyloid and leptomeningeal macrophages evokes vascular dysfunction in CAA

The subarachnoid space contains leptomeningeal arteries and resident immune cells known as subarachnoid macrophages (SAMs). In Alzheimers disease (AD) and related cerebral amyloid angiopathy, amyloid-{beta} (A{beta}) frequently accumulates around the leptomeningeal arteries. Nevertheless, the local immune responses and their functional consequences remain poorly understood. Using longitudinal intravital imaging in a mouse model of AD, we tracked A{beta} deposition and identified a distinct SAM population that migrates to and phagocytoses these arterial A{beta} deposits. SAM recruitment correlated with vascular remodeling, including smooth muscle loss, aneurysm formation, and reduced cerebral perfusion. Transcriptomic profiling revealed a distinct SAM population in AD with upregulated CD39 expression. Pharmacological inhibition of CD39 attenuated arterial A{beta} deposition, identifying SAMs as a potential therapeutic target in AD.

neuroscience↗

bioRxiv2025

Guam amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) features CTE-like tau seeds in brain and spinal cord

Amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) is a fatal neurodegenerative disorder that was once hyperendemic in the island of Guam (Mariana Islands, US) and a few other Pacific locales. Despite extensive investigations into its origins, the etiology of ALS/PDC remains unclear. ALS/PDC is, at the neuropathology level, characterized by tau-dominant multiple proteinopathy in brain and spinal cord. It was recently reported that Guam ALS/PDC brain extracts exhibit tau seeding activity in fluorescence resonance energy transfer (FRET)-based biosensor cells. To build upon those findings and explore the nature of tau seeds in ALS/PDC in more detail, we used an alanine mutational scanning (Ala scan) approach to determine the seeding profile of tau in nervous tissues of Guam ALS/PDC cases. First, we confirmed the detection of tau seeding activity in ALS/PDC brain samples in tau biosensor cells. Notably, we could also detect potent tau seeding activity in spinal cord. Subsequent Ala scan assays demonstrated that ALS/PDC tau displays an aggregate incorporation pattern that resembles that of chronic traumatic encephalopathy (CTE)-type tau. This result is consistent with recent electron cryo-microscopy studies of tau, which revealed that ALS/PDC tau filaments are predominantly of the CTE-type. The structural characteristics and seeding behavior of ALS/PDC tau, as well as the regional distribution of tau pathology at post-mortem, suggest that ALS/PDC is a CTE-like tauopathy. Significance StatementNeurodegenerative tauopathies are characterized by proteinaceous deposits containing microtubule-associated tau in nervous tissue. Emerging evidence suggests that disease-associated tau proteins adopt abnormal, self-propagating conformations characteristic of prions. Here, we employed alanine mutational scanning (Ala scan) to determine the nature of prion-like tau seeds in ALS/PDC, a mysterious disorder that occurred formerly in high incidence in certain regions in the western Pacific. We show that the Ala scan incorporation profile of ALS/PDC tau is similar to that of abnormal tau proteins in chronic traumatic encephalopathy (CTE). The findings lend support to the idea that ALS/PDC can be classified structurally as a CTE-like tauopathy. This work may have important implications for our understanding of ALS/PDC as well as common neurological disorders beyond the Pacific.

neuroscience↗

bioRxiv2024

How Alzheimer's Abeta propagates and triggers tau pathology in intact neurons

Alzheimers disease begins with A{beta} accumulation, progresses to tau aggregates and results in widespread neurodegeneration1-3. Simultaneous propagation of A{beta} aggregates from very limited to wide and distant brain regions is one of the outstanding events in the early stage. Here, we demonstrate that the neurovascular unit4,5 comprising capillaries and pericytes, the machinery supplying oxygen and glucose to neurons, is also the machinery for propagating effector molecules that impose Alzheimers pathologies on intact neurons. We discovered two distinct signaling cascades, one activated in capillary endothelial cells and the other in pericytes. At the origin of either cascade, we identified amylospheroid (ASPD)6,7, a highly toxic 30-mer assembly of A{beta}, and its sole target NKA38, a neuron-specific isoform of Na+,K+-ATPase9,10 but present in endothelial cells and pericytes. In endothelial cells, ASPD binding to NKA3 releases angiotensin II, which increases {beta}-secretase in intact neurons, causing a huge increase of A{beta}42and resultant accumulation. In pericytes, ASPD binding to NKA3 releases an unknown effector molecule that activates {delta}-secretase in intact neurons, further augmenting A{beta}42and producing pathogenic tau1-368 fragment. Thus, A{beta} and tau pathologies are directly linked. Stopping the signaling cascades near the origin by inhibiting ASPD-NKA3 interaction8 may provide a new therapeutic approach.

neuroscience↗

bioRxiv2024

Extracellular disposal of nuclear waste by APP: a protective mechanism impaired in Alzheimer's disease

Although the amyloid beta (A{beta}) hypothesis1 has long been central to Alzheimers disease (AD) research, effective therapeutic strategies remain elusive2,3. Here we re-evaluate the functions of amyloid precursor protein (APP) and reveal its critical function in protecting against nuclear impairment-induced cell death and inflammation4,5. Overexpression of APP mitigated etoposide or lamin A knockdown-induced nuclear damage, while APP removal or mutations exacerbated these effects. Interestingly, neurons differentiated from induced pluripotent stem cells (iPSCs) exhibited similar patterns, and notably, familial AD-associated mutant APP failed to confer protection against nuclear impairment. We identify APPs interaction with a cytoplasmic structure of nuclear origin, termed "nuclear waste", and propose its role in extracellular waste disposal. Intriguingly, cells lacking APP showed impaired nuclear waste clearance, leading to abnormal cytoplasmic accumulation of the nuclear waste. Similarly, neuron-specific APP overexpression using adeno-associated virus (AAV) in mice reduced neuronal death and inflammation caused by nuclear damage. Conversely, shRNA-mediated APP exacerbated these effects, and mutant APP associated with familial AD lacked protective effects. Moreover, postmortem analysis of AD brains revealed accumulation of abnormal nuclear waste in the neurocytoplasm, irregular nuclear morphology, and reduced APP levels per neuron. Our data underscore APPs crucial role in disposing of nuclear waste, maintaining cellular homeostasis, and suggest its dysregulation as a potential contributor to AD pathogenesis. Restoring APP waste clearance in AD could be a promising target for disease-modifying therapies.

neuroscience↗

bioRxiv2023

Identification of Region-Specific Gene Isoforms in the Human Brain Using Long-Read Transcriptome Sequencing and Their Correlation with DNA Methylation

BackgroundSite specificity is known in neuropsychiatric disorders, and differences in gene expression patterns could potentially explain this mechanism. However, studies using long-read transcriptome sequencing to analyze gene expression in different regions of the human brain have been limited, and none have focused on the hypothalamus, which plays a crucial role in regulating autonomic functions. ResultsWe performed long-read RNA sequencing on 12 samples derived from three different brain regions of the same individuals; the cerebellum, hypothalamus, and temporal cortex. We found that, compared to other regions, many genes with higher expression levels in the cerebellum and temporal cortex were associated with neuronal pathways, whereas those with higher expression levels in the hypothalamus were primarily linked to immune pathways. In addition, we investigated genes with different major isoforms in each brain region, even with similar overall expression levels among regions, and identified several genes, such as GAS7, that express different major isoforms in different regions. Many of these genes are involved in "actin filament-based process" and "cell projection organization" pathways, suggesting that region-dependent isoforms may have distinct roles in dendritic spine and neuronal formation in each region. Furthermore, we investigated the involvement of DNA methylation in these isoforms and found that DNA methylation may be associated with isoforms that have different first exons. ConclusionsOur results provide potentially valuable findings for future research on brain disorders and shed light on the mechanisms underlying isoform diversity in the human brain.

genomics↗

bioRxiv2023

Tau Filaments from Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex (ALS/PDC) adopt the CTE Fold

The amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) of the island of Guam and the Kii peninsula of Japan is a fatal neurodegenerative disease of unknown cause that is characterised by the presence of abundant filamentous tau inclusions in brains and spinal cords. Here we used electron cryo-microscopy (cryo-EM) to determine the structures of tau filaments from the cerebral cortex of three cases of ALS/PDC from Guam and eight cases from Kii, as well as from the spinal cord of two of the Guam cases. Tau filaments had the chronic traumatic encephalopathy (CTE) fold, with variable amounts of Type I and Type II filaments. Paired helical tau filaments were also found in two Kii cases. We also identified a novel Type III CTE tau filament, where protofilaments pack against each other in an anti-parallel fashion. ALS/PDC is the third known tauopathy with CTE-type filaments and abundant tau inclusions in cortical layers II/III, the others being CTE and subacute sclerosing panencephalitis. Because these tauopathies are believed to have environmental causes, our findings support the hypothesis that ALS/PDC is caused by exogenous factors. SIGNIFICANCEA neurodegenerative disease of unknown cause on the island of Guam and the Kii peninsula of Japan has been widely studied, because patients can suffer from the combined symptoms of motor neuron disease, parkinsonism and dementia. Abnormal filamentous inclusions made of tau protein characterise this amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) and their formation closely correlates with neurodegeneration. Here we have used electron cryo-microscopy (cryo-EM) to show that tau filaments from ALS/PDC are identical to those from chronic traumatic encephalopathy (CTE), a disease caused by repetitive head impacts or blast waves. CTE tau filaments are also found in subacute sclerosing panencephalitis, which is a rare consequence of measles infection. ALS/PDC may therefore also be caused by environmental factors.

neuroscience↗

bioRxiv2021

Small Vessel Diseases: 3D Characteristics of the Vasculature and White Matter

Cerebral small vessel disease (SVD) is associated with white matter hyperintensities (WMHs), thereby contributing to vascular dementia and movement disorder. However, the pathomechanisms responsible for WMH-related small vessel degeneration remain poorly understood due to the technical limitations of current methods. The aim of this study was to clarify the 2- and 3-dimensional (2D and 3D) pathological features of small vessels and white matter (WM) in the brains of patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), HTRA1-autosomal dominant disease (HTRA1-AD) and sporadic SVD (sSVD). From a cohort of 86 consecutive autopsied patients with SVDs, we retrieved those with genetically confirmed CADASIL and HTRA1-AD (three and three, respectively), and four with sSVD. We quantitatively evaluated WM and vascular changes in the frontal portion of the centrum semiovale and temporal lobe using conventional 2D and chemically cleared 3D analytical methods with light-sheet fluorescence microscopy. Quantitatively, the WM pathology, including the density of myelin, axons and gliosis, was most severe in CADASIL, but unexpectedly sSVD was second in order of severity, followed by HTRA1-AD. The density of clasmatodendrocytes, known to be irreversibly injured astrocytes, was considerably highest in HTRA1-AD. The vascular pathology, including arteriole and capillary sclerosis and the extent of the perivascular space, was most severe in CADASIL, whereas the density of smooth muscle actin (SMA) positivity was most decreased in HTRA1-AD. 3D immunohistochemistry for SMA demonstrated two distinct patterns of SMA loss within the vessels: (1) CADASIL and sSVD: diffuse loss, being prominent in small branches, (2) HTRA1-AD: selective loss in main branches. Overall, the extent of WM and vascular degeneration is most severe in CADASIL, whereas SMA loss is most evident in HTRA1-AD. These differences in the size and distribution of affected vessels may be related to the heterogeneous WM pathology and underlying pathomechanisms of SVD.

pathology↗

bioRxiv2021

Structure-based Classification of Tauopathies

Ordered assembly of the tau protein into filaments characterizes multiple neurodegenerative diseases, which are called tauopathies. We previously reported that by electron cryo-microscopy (cryo-EM), tau filament structures from Alzheimers disease (1,2), chronic traumatic encephalopathy (CTE) (3), Picks disease (4) and corticobasal degeneration (CBD) (5) are distinct. Here we show that the structures of tau filaments from typical and atypical progressive supranuclear palsy (PSP), the most common tauopathy after Alzheimers disease, define a previously unknown, three-layered fold. Moreover, the tau filament structures from globular glial tauopathy (GGT, Types I and II) are similar to those from PSP. The tau filament fold of argyrophilic grain disease (AGD) differs from the above and resembles the four-layered CBD fold. The majority of tau filaments from aging-related tau astrogliopathy (ARTAG) also have the AGD fold. Surprisingly, tau protofilament structures from inherited cases with mutations +3/+16 in intron 10 of MAPT, the microtubule-associated protein tau gene, are identical to those from AGD, suggesting that a relative overproduction of four-repeat tau can give rise to the AGD fold. Finally, tau filament structures from cases of familial British dementia (FBD) and familial Danish dementia (FDD) are the same as those from Alzheimers disease and primary age-related tauopathy (PART). These structures provide the basis for a classification of tauopathies that also allows identification of new entities, as we show here for a case diagnosed as PSP, but with abundant spherical 4R tau inclusions in limbic and other brain areas. The structures of the tau fold of this new disease (Limbic-predominant Neuronal inclusion body 4R Tauopathy, LNT) were intermediate between those of GGT and PSP.

neuroscience↗

bioRxiv2021

Age-related demethylation of the TDP-43 autoregulatory region in the human motor cortex

In amyotrophic lateral sclerosis (ALS), TAR DNA-binding protein 43 (TDP-43), which is encoded by TARDBP, forms aggregates in the motor cortex. This aggregate formation may be triggered by an increase in the TDP-43 level with aging. However, the amount of TDP-43 is autoregulated by alternative splicing of the TARDBP 3UTR, and how this autoregulation is affected by aging remains to be elucidated. We found that DNA demethylation in the autoregulatory region in the TARDBP 3'UTR reduced alternative splicing and increased TARDBP mRNA expression. Furthermore, in the human motor cortex, we found that this region was demethylated with aging, resulting in increased expression of TARDBP mRNA. The acceleration of DNA demethylation in the motor cortex was associated with the age of ALS onset. In summary, the dysregulation of TDP-43 autoregulation by age-related DNA demethylation in the motor cortex may explain the contribution of aging and motor system selectivity in ALS.

molecular biology↗

bioRxiv2020

Alzheimer's Aβ assembly binds sodium pump and blocks endothelial NOS activity via ROS-PKC pathway

Amyloid {beta}-protein (A{beta}) may contribute to worsening of Alzheimers disease (AD) through vascular dysfunction, but the actual molecular mechanisms remain controversial. Using ex-vivo blood vessels and primary endothelial cells derived from human brain microvessels, we revealed that patient-derived A{beta} assemblies, termed amylospheroids (ASPD), exist on the microvascular surface in patient brains and inhibit vasorelaxation through binding to the 3 subunit of sodium, potassium-ATPase (NAK3) on endothelial cells. Interestingly, NAK3 also serves as the toxic target of ASPD in neurons. ASPD elicit neurodegeneration through calcium overload, while ASPD suppress vasorelaxation by inhibiting nitric oxide (NO) production. ASPD-NAK3 interaction on cerebrovascular endothelial cells disturbs the NO release by inactivating endothelial NO synthase through mitochondrial reactive oxygen species and protein kinase C. The findings suggest that ASPD may dually contribute to neuronal and vascular pathologies through binding to NAK3. Thus, blocking the ASPD-NAK3 interaction may be a useful target for AD therapy.

biochemistry↗

bioRxiv2019

Reciprocal connectivity between secondary auditory cortical field and amygdala in mice

Recent studies have examined the feedback pathway from the amygdala to the auditory cortex in conjunction with the feedforward pathway from the auditory cortex to the amygdala. However, these connections have not been fully characterized. Here, to visualize the comprehensive connectivity between the auditory cortex and amygdala, we injected cholera toxin subunit b (CTB), a bidirectional tracer, into multiple subfields in the mouse auditory cortex after identifying the location of these subfields using flavoprotein fluorescence imaging. After injecting CTB into the secondary auditory field (A2), we found densely innervated CTB-positive axon terminals that were mainly located in the lateral amygdala (La), and slight innervations in other divisions such as the basal amygdala. Moreover, we found a large number of retrogradely-stained CTB-positive neurons in La after injecting CTB into A2. When injecting CTB into the primary auditory cortex (A1), a small number of CTB-positive neurons and axons were visualized in the amygdala. Finally, we found a near complete absence of connections between the other auditory cortical fields and the amygdala. These data suggest that reciprocal connections between A2 and La are main conduits for communication between the auditory cortex and amygdala in mice.

neuroscience↗

bioRxiv2019

Investigation of betaine as a novel psychotherapeutic for schizophrenia

Betaine is known to act against various biological stresses and its levels were reported to be decreased in schizophrenia patients. Using Chdh (a gene for betaine synthesis)-deficient mice and betaine-supplemented inbred mice, we assessed the role of betaine in psychiatric pathophysiology, and its potential as a novel psychotherapeutic, by leveraging metabolomics, behavioral-, transcriptomics and DNA methylation analyses. The Chdh-deficient mice revealed remnants of psychiatric behaviors along with schizophrenia-related molecular perturbations. Betaine supplementation elicited genetic background-dependent improvement in cognitive performance, and suppressed methamphetamine (MAP)-induced behavioral sensitization. Furthermore, betaine rectified the altered antioxidative and proinflammatory responses induced by MAP and in vitro phencyclidine treatments. Notably, betaine levels were decreased in the postmortem brains from schizophrenia, and a coexisting elevated carbonyl stress, a form of oxidative stress, demarcated a subset of schizophrenia with \"betaine deficit-oxidative stress pathology\". We revealed the decrease of betaine levels in glyoxylase 1 (GLO1)-deficient hiPSCs, which shows elevated carbonyl stress, and the efficacy of betaine in alleviating it, thus supporting a causal link between betaine and oxidative stress conditions. Furthermore, a CHDH variant, rs35518479, was identified as a cis-expression quantitative trait locus (QTL) for CHDH expression in postmortem brains from schizophrenia, allowing genotype-based stratification of schizophrenia patients for betaine efficacy. In conclusion, the present study underscores the potential benefit of betaine in a subset of schizophrenia.

neuroscience↗