Biology subjects

Akamatsu, W.

Publications and source records attributed to Akamatsu, W..

4 recordsLinked to original sources

bioRxiv2026

Modeling the pathological brain-gut axis in Parkinson's disease using human iPSC derived brain-intestinal assembloids

Parkinson disease is increasingly recognized as a systemic disorder involving pathological communication along the brain-gut axis, yet the cellular mechanisms underlying inter-organ -synuclein propagation remain poorly defined. Here, we establish a human induced pluripotent stem cell-derived brain-intestinal assembloid that integrates a developmentally specified medullary hindbrain organoid with an enteric neuron-enriched intestinal organoid. Using this model, we show the propagation of -synuclein from brainstem neurons to enteric neurons. Ligand-receptor analysis combined with genetic perturbation identifies NRXN1-NLGN2 signaling as a key mediator of brain-to-gut -synuclein propagation, with NRXN1 being upregulated in Parkinsons disease patient datasets in vivo. Together, these findings establish a human stem cell-based platform for investigating brain-gut communication and uncover molecular mechanisms underlying -synuclein propagation in Parkinsons disease.

neuroscience↗

bioRxiv2023

Carvedilol suppresses ryanodine receptor-dependent Ca2+ bursts in human neurons bearing PSEN1 variants found in early onset Alzheimer's disease

Seizures are increasingly being recognized as the hallmark of Alzheimers disease (AD). Neuronal hyperactivity can be a consequence of neuronal damage caused by abnormal amyloid {beta} (A{beta}) depositions. However, it can also be a cell-autonomous phenomenon causing AD by A{beta}-independent mechanisms. Indeed, various studies using animal models showed that Ca2+ releases from the endoplasmic reticulum (ER) via type 1 inositol triphosphate receptors (InsP3R1s) and ryanodine receptors (RyRs). To investigate which is the main pathophysiological mechanism in human neurons, we measured Ca2+ signaling in neural cells derived from three early-onset AD patients harboring variants of Presenilin-1 (PSEN1 p.A246E, p.L286V, and p.M146L). Of these, it has been reported that PSEN1 p.A246E and p.L286V did not produce a significant amount of abnormal A{beta}. We found that all PSEN1-mutant neurons, but not wild-type, caused abnormal Ca2+-bursts in a manner dependent on the calcium channel, Ryanodine Receptor 2 (RyR2). Indeed, carvedilol, anRyR2 inhibitor, and VK-II-86, an analog of carvedilol without the {beta}-blocking effects, sufficiently eliminated the abnormal Ca2+ bursts. In contrast, Dantrolene, a RyR1 inhibitor, and Xestospongin c, an IP3R inhibitor, did not attenuate the Ca2+-bursts. The RNA-Seq data revealed that ER-stress responsive genes were increased, and mitochondrial Ca2+-transporter genes were decreased in PSEN1A246E cells compared to the WT neurons. Thus, we propose that aberrant Ca2+ signaling is a key link between human pathogenic PSEN1 variants and cell-intrinsic hyperactivity prior to deposition of abnormal A{beta}, offering prospects for the development of targeted prevention strategies for at-risk individuals. One Sentence SummaryAberrant Ca2+-signaling causes PSEN1-related early onset Alzheimers disease.

neuroscience↗

bioRxiv2021

Electrophysiological maturation and increased excitability of human iPSC-derived neurons in HTR2A variant-related sleep bruxism

Sleep bruxism (SB) is a sleep-related movement disorder characterized by grinding and clenching of the teeth during sleep. We previously found a significant association between SB and a single nucleotide polymorphism (SNP), rs6313, in the neuronal serotonin 2A receptor gene (HTR2A), and established human induced pluripotent stem cell (hiPSC)-derived neurons from SB patients with a genetic variant. To elucidate the electrophysiological characteristics of SB iPSC-derived neural cells bearing a SB-related genetic variant, we generated ventral hindbrain neurons from two SB patients and two unaffected controls and explored the intrinsic membrane properties of these neurons by patch-clamp technique. We found that the electrophysiological properties of the iPSC-derived neurons from the control line mature in a time-dependent manner in long-term cultures. In the early stage of neurogenesis, neurons from two SB lines tended to display shorter action potential (AP) half durations, which led to an increased cell capability of evoked firing. This is the first in vitro modelling of SB using disease-specific hiPSCs. The revealed electrophysiological characteristics may serve as a benchmark for further investigation of pathogenic mechanisms underlying SB. Summary StatementSleep bruxism patient-specific iPSC-derived neurons with the HTR2A variant show altered electrophysiological characteristics, providing the foremost narration of sleep bruxism neurological phenotypes in vitro from any species.

neuroscience↗

bioRxiv2020

IPSC-derived midbrain astrocytes from Parkinson's disease patients carrying pathogenic SNCA mutations exhibit alpha-synuclein aggregation, mitochondrial fragmentation and excess calcium release

Parkinsons disease (PD) is characterized by the loss of A9 midbrain dopaminergic neurons and the accumulation of alpha-synuclein aggregates in remaining neurons. Many studies of the molecular and cellular basis of neurodegeneration in PD have made use of iPSC-derived neurons from patients with familial PD mutations. However, approximately half of the cells in the brain are glia, and their role facilitating neurodegeneration is unclear. We developed a novel serum-free protocol to generate midbrain astrocytes from patient-derived iPSCs harbouring the pathogenic p.A30P, p.A53T mutations in SNCA, as well as duplication and triplication of the SNCA locus. In our cellular model, aggregates of alpha-synuclein occurred only within the GFAP+ astrocytes carrying the pathogenic SNCA mutations. Assessment of spontaneous cytosolic calcium (Ca2+) release using Fluo4 revealed that SNCA mutant astrocytes released excess Ca2+ compared to controls. Unbiased evaluation of 3D mitochondrial morphometric parameters showed that these SNCA mutant astrocytes had increased mitochondrial fragmentation and decreased mitochondrial connectivity compared to controls, and reduced mitochondrial bioenergetic function. This comprehensive assessment of different pathogenic SNCA mutations derived from PD patients using the same cellular model enabled assessment of the mutation effect, showing that p.A53T and triplication astrocytes were the most severely affected. Together, our results indicate that astrocytes harbouring the familial PD mutations in SNCA are dysfunctional, suggesting a contributory role for dysfunctional astrocytes in the disease mechanism and pathogenesis of PD. Table of Contents Image O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/053470v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@974d72org.highwire.dtl.DTLVardef@15d9da0org.highwire.dtl.DTLVardef@1177d4eorg.highwire.dtl.DTLVardef@123c0c2_HPS_FORMAT_FIGEXP M_FIG C_FIG Main PointsO_LIWe used a novel serum-free protocol to generate midbrain-specific functional astrocytes from Parkinsons disease patients carrying pathological mutations in SNCA C_LIO_LIPatient-derived astrocytes show morphological and functional impairments C_LI

neuroscience↗