Biology subjects

Nakamori, M.

Publications and source records attributed to Nakamori, M..

8 recordsLinked to original sources

bioRxiv2025

Interventionally targeting somatic CAG expansions can be a rapid disease-modifying therapeutic avenue: Preclinical evidence.

Huntington disease (HD) is caused by inherited CAG expansions, which continue expanding somatically in affected brain regions to hasten disease onset and progression. Therapeutically diminishing somatic expansions is expected to be clinically beneficial. However, it is not known if interventionally modifying somatic CAG expansions will actually modify in vivo clinically-relevant phenotypes, what the therapeutic window is, or which phenotypes will be altered. Here we show that acute (6-week) delivery of the contraction-inducing slipped-CAG DNA ligand naphthyridine-azaquinolone to young (4-week-old) (CAG)120 HD mice, induces contractions throughout brain regions, improves motor function (locomotion, balance, coordination, muscle strength), molecular disease landmarks (mHTT aggregates, nuclear envelope morphology, nucleocytoplasmic mRNA transport, transcriptomic dysregulation, neuroinflammation), and neurodegeneration. Beneficial effects of modifying somatic expansions were also evident in muscle and blood, where blood CAG instability correlated with brain instability and blood serum had diminished levels of neurofilament light (a biomarker for neurodegeneration) -- offering blood as having elements of target engagement and efficacy. These data support that targeting somatic repeat expansions can be a rapid disease-modifying therapeutic avenue for HD and possibly other repeat expansion diseases. Our findings support an etiologic pathway interconnected to somatic CAG expansions that will inform the design of clinical trials expecting clinical benefit by modulating somatic expansions.

genetics↗

bioRxiv2024

Establishment of a novel amyotrophic lateral sclerosis patient-derived blood-brain barrier model: Investigating barrier dysfunction and immune cell interaction

Amyotrophic lateral sclerosis (ALS) is a major neurodegenerative disease for which there is currently no effective treatment. The main feature of the disease is the loss of motor neurons in the central nervous system (CNS), but other CNS components and the immune system also appear to be involved in the pathogenesis of the disease. The blood-brain barrier (BBB) is formed by specialized brain microvascular endothelial cells (BMECs) and plays a crucial role in maintaining homeostasis within the central nervous system (CNS). Autopsy studies have reported BBB abnormalities in ALS patients, and studies in animal models suggest that BBB breakdown may precede neurodegeneration. However, the difficulty of obtaining patient samples has hampered further studies. We used the method of differentiating BMEC-like cells from human induced pluripotent stem cells (hiPSCs), which have robust barrier functions and express adhesion molecules necessary for immune cell adhesion, to investigate BBB functions in ALS patients. We also established a method using automated analysis techniques to analyze immune cell adhesion to the BBB in multiple samples simultaneously and with minimal bias. BMEC-like cells derived from ALS patients carrying TARDBP N345K/WT mutations exhibited increased permeability to small molecules due to loss of tight junction, as well as increased expression of cell surface adhesion molecules, leading to enhanced immune cell adhesion. BMEC-like cells derived from hiPSCs with other types of TARDBP gene mutations (TARDBP K263E/K263E and TARDBP G295S/G295S) introduced by genome editing technology did not show such BBB dysfunction compared to the isogenic control. These results indicate that our model can recapitulate BBB abnormalities reported in ALS patients using patient (TARDBP N345K/WT) -derived hiPSCs and that two types of missense mutation, TARDBP K263E/K263E and TARDBP G295S/G295S, do not contribute to the BBB dysfunction. This novel ALS patient-derived BBB model is useful for the challenging analysis of the involvement of BBB dysfunction in the pathogenesis and to promote therapeutic drug discovery.

cell biology↗

bioRxiv2023

Quercetin selectively reduces expanded repeat RNA levels in models of myotonic dystrophy

Myotonic dystrophy is a multisystemic neuromuscular disease caused by either a CTG repeat expansion in DMPK (DM1) or a CCTG repeat expansion in CNBP (DM2). Transcription of the expanded alleles produces toxic gain-of-function RNA that sequester the MBNL family of alternative splicing regulators into ribonuclear foci, leading to pathogenic mis-splicing. There are currently no approved treatments that target the root cause of disease which is the production of the toxic expansion RNA molecules. In this study, using our previously established HeLa DM1 repeat selective screening platform, we identified the natural product quercetin as a selective modulator of toxic RNA levels. Quercetin treatment selectively reduced toxic RNA levels and rescued MBNL dependent mis-splicing in DM1 and DM2 patient derived cell lines and in the HSALR transgenic DM1 mouse model where rescue of myotonia was also observed. Based on our data and its safety profile for use in humans, we have identified quercetin as a priority disease-targeting therapeutic lead for clinical evaluation for the treatment of DM1 and DM2. One Sentence SummaryThe natural product quercetin reduces toxic RNA in myotonic dystrophy.

molecular biology↗

bioRxiv2022

Analysis of splicing abnormalities in the white matter of myotonic dystrophy type 1 brain using RNA-sequence

Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by the genomic expansions of CTG repeats, in which RNA-binding proteins, such as muscleblind-like protein, are sequestered in the nucleus, and abnormal splicing is observed in various genes. Although abnormal splicing reportedly occurs in the brains of patients with DM1, it is relation to the central nervous system symptoms is unknown. Several imaging studies have indicated substantial white matter (WM) defects in patients with DM1. Here, we performed RNA-sequencing and analysis of CTG repeat lengths in the frontal lobe of patients with DM1, separating the grey matter (GM) and WM, to investigate the splicing abnormalities in the DM1 brain, especially in the WM. The results demonstrated the number of repeats in the GM tended to be increase, with several genes showing similar levels of splicing abnormalities in the GM and WM, suggesting that the WM defects in DM1 are not only caused by aberrant splicing of GM RNA but also of WM RNA, which could be attributed to abnormal splicing of glial cell RNAs.

molecular biology↗

bioRxiv2022

Deregulations of miR-1 and its target Multiplexin promote dilated cardiomyopathy associated with myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy. It is caused by the excessive expansion of non-coding CTG repeat, which when transcribed affect functions of RNA-binding factors. Specifically, MBNL1 is sequestered in nuclear foci while CELF1 is stabilised, with adverse effects on alternative splicing, processing and stability of a large set of muscular and cardiac transcripts. Among these effects, inefficient processing and down-regulation of muscle- and heart-specific miRNA, miR-1, has been reported in DM1 patients, but the impact of reduced miR-1 on DM1 pathogenesis was unknown. Here, we used Drosophila DM1 models to explore miR-1 involvement in cardiac dysfunction in DM1. We found that miR-1 down-regulation in the heart led to dilated cardiomyopathy (DCM), a DM1-associated phenotype. We then combined in silico screening for miR-1 targets with transcriptional profiling of DM1 cardiac cells to identify miR-1 target genes with potential roles in DCM. We identified Multiplexin (Mp) as a new cardiac miR-1 target involved in DM1. Mp and its human ortholog Col15A1 were both highly enriched in cardiac cells of DCM-developing DM1 flies and in heart samples from DM1 patients with DCM, respectively. Importantly, when overexpressed in the heart, Mp induced DCM, whereas its attenuation ameliorated the DCM phenotype in aged DM1 flies. Reduced levels of miR-1 and consecutive up-regulation of its target Mp/Col15A1 are thus critical in DM1-associated DCM.

genetics↗

bioRxiv2021

FAN1 nuclease processes and pauses on disease-associated slipped-DNA repeats: Mechanism against repeat expansions

FAN1 nuclease is a modifier of repeat expansion diseases, including Huntingtons disease (HD), fragile X syndrome, and autism. The age of HD onset correlates with ongoing inchworm-like repeat expansions (1-3 CAG units/event) in HD brains, and is regulated by three modifiers: The first two, repeat tract length and purity exert their effects by enhancing and slowing CAG expansions, respectively, by affecting the formation of slipped-DNAs -- mutagenic intermediates of instability; which are processed to expansions by the third modifiers, DNA repair proteins. FAN1 protects against hyper-expansions of repeats, by unknown mechanisms. We show FAN1, through iterative cycles bound, dimerized and cleaved slipped-DNAs, yielding striking patterns of distinct exo-nuclease pauses along slip-outs; 5'-C{downarrow}A{downarrow}GC{downarrow}A{downarrow}G-3' and 5'-C{downarrow}T{downarrow}G{downarrow}C{downarrow}T{downarrow}G-3'. The transcriptionally-displaced CAG strand was excised slower than its complementary CTG strand, required A*A and T*T mismatches, as fully-paired hairpins arrested excision progression, while disease-delaying CAA interruptions further slowed FAN1 excision. In contrast, endo-nucleolytic cleavage was insensitive to slip-outs. Rare FAN1 variants were found in autism individuals with CGG/CCG repeat expansions. Excision of CGG/CCG slip-outs were similarly excised, with CGG being slower than CCG. The slip-out specific ligand, Naphthyridine-Azaquinolone, shown to induce contractions of expanded repeats in cells, required FAN1 for its effect, and protected slip-outs from FAN1s exo- but not endo-nucleolytic digestion. FAN1s inchworm pausing of slip-out excision is suited to minimize incremental expansions and modulating disease onset.

genetics↗

bioRxiv2020

Tongue thickness measured by ultrasonography is associated with tongue pressure in the Japanese elderly

The term "oral frailty" reflects the fact that oral health is associated with physical frailty and mortality. Tongue thickness measurement is one of the evaluations for swallowing function. The aim of this study was to investigate the relationship between tongue thickness and tongue pressure in the Japanese elderly. We evaluated 254 elderly patients; all the participants underwent tongue ultrasonography and tongue pressure measurement. To determine tongue thickness, we measured the vertical distance from the surface of the mylohyoid muscle to the tongue dorsum using ultrasonography. Result analyses revealed that tongue thickness was linearly associated with tongue pressure in both sexes. In male participants, dyslipidemia, lower leg circumference, and tongue pressure were independently significantly associated with tongue thickness. In female participants, body mass index and tongue pressure were independently significantly associated with tongue thickness. Tongue thickness was significantly decreased by age for both men and women. The optimal cutoff for tongue thickness to predict the tongue pressure of < 20 kPa was 41.3 mm in males, and 39.3 mm in females. In the Japanese elderly, tongue thickness using ultrasonography is associated with tongue pressure. Tongue thickness and tongue pressure, which are sensitive markers for oral frailty, decrease in aging. The tongue ultrasonography provides a less invasive technique for determining tongue thickness and related aspiration risks for elderly patients.

neuroscience↗

bioRxiv2018

Straightjacket/α 2δ 3 deregulation is associated with cardiac conduction defects in Myotonic Dystrophy type 1

Cardiac conduction defects decrease life expectancy in myotonic dystrophy type 1 (DM1), a complex toxic CTG repeat disorder involving misbalance between two RNA- binding factors, MBNL1 and CELF1. How this pathogenic DM1 condition translates into cardiac conduction disorders remains poorly understood. Here, we simulated MBNL1 and CELF1 misbalance in the Drosophila heart and identified associated gene deregulations using TU-tagging based transcriptional profiling of cardiac cells. We detected deregulations of several genes controlling cellular calcium levels and among them increased expression of straightjacket/2{delta}3 that encodes a regulatory subunit of a voltage-gated calcium channel. Straightjacket overexpression in the fly heart leads to asynchronous heart beating, a hallmark of affected conduction, whereas cardiac straightjacket knockdown improves these symptoms in DM1 fly models. We also show that ventricular 2{delta}3 expression is low in healthy mice and humans but significantly elevated in ventricular muscles from DM1 patients with conduction defects. Taken together, this suggests that reducing the straightjacket/2{delta}3 transcript levels in ventricular cardiomyocytes could represent a strategy to prevent conduction defects and in particular intraventricular conduction delay associated with DM1 pathology.

genomics↗