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Masayuki Nakamori

Publications and source records attributed to Masayuki Nakamori.

7 recordsLinked to original sources
PubMed2026

Multiancestry genome-wide association and multiomics analyses elucidate spatiocellular features of multiple sclerosis genetics.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by demyelination disseminated in space and time. Here we performed a genome-wide association study (GWAS) using 688 MS cases and 205,199 controls from the Japanese population and identified significant associations in the major histocompatibility complex region and a population-specific risk variant in 11q24. Through cross-population GWAS meta-analyses using a total of 29,374 cases and 1,843,563 controls from 4 ancestral populations, we identified 22 novel susceptibility loci. Integration of GWAS and single-cell and single-nucleus RNA sequencing of peripheral blood mononuclear cells and subcortical lesions from patients with MS revealed enrichment of genetic risk factors for MS in CD4+ T helper cell lineage and regulatory T cells, as well as in endothelial cells. Furthermore, spatial transcriptomics of subcortical lesions demonstrated spatial and temporal heterogeneity in associations with MS genetic risk. Our study demonstrates the value of investigation of spatiocellular features of disease genetics across diverse populations and omics modalities.

Humans↗
PubMed2025

Pentatricopeptide repeat protein targeting CUG repeat RNA ameliorates RNA toxicity in a myotonic dystrophy type 1 mouse model.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder caused by the expansion of a CTG-triplet repeat in the 3' untranslated region of the dystrophia myotonica protein kinase (DMPK) gene. It results in the transcription of toxic RNAs that contain expanded CUG repeats (CUGexp). Splicing factors, such as muscleblind-like 1 (MBNL1), are sequestered by CUGexp, thereby disrupting the normal splicing program that is essential for various cellular functions. Pentatricopeptide repeat (PPR) proteins, originally found in plants, regulate RNA in organelles by binding in a sequence-specific manner. Here, we designed PPR proteins that specifically bind to the hexamer of CUG repeat RNAs (CUG-PPRs) and showed that CUG-PPR1 could ameliorate RNA toxicity induced by CUGexp in cell models of DM1. A single systemic recombinant adeno-associated virus (AAV9) vector-mediated gene delivery of CUG-PPR1 demonstrated long-term therapeutic effects on myotonia and restored splicing activity in a mouse model of DM1. These results highlight the potential of PPR molecules to target pathogenic RNA sequences in DM1 and potentially other RNA-mediated disorders.

Animals↗
PubMed2005

Altered mRNA splicing of the skeletal muscle ryanodine receptor and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase in myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is a debilitating multisystemic disorder caused by a CTG repeat expansion in the DMPK gene. Aberrant splicing of several genes has been reported to contribute to some symptoms of DM1, but the cause of muscle weakness in DM1 and elevated Ca2+ concentrations in cultured DM muscle cells is unknown. Here, we investigated the alternative splicing of mRNAs of two major proteins of the sarcoplasmic reticulum, the ryanodine receptor 1 (RyR1) and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) 1 or 2. The fetal variants, ASI(-) of RyR1 which lacks residue 3481-3485, and SERCA1b which differs at the C-terminal were significantly increased in skeletal muscles from DM1 patients and the transgenic mouse model of DM1 (HSA(LR)). In addition, a novel variant of SERCA2 was significantly decreased in DM1 patients. The total amount of mRNA for RyR1, SERCA1 and SERCA2 in DM1 and the expression levels of their proteins in HSA(LR) mice were not significantly different. However, heterologous expression of ASI(-) in cultured cells showed decreased affinity for [3H]ryanodine but similar Ca2+ dependency, and decreased channel activity in single-channel recording when compared with wild-type (WT) RyR1. In support of this, RyR1-knockout myotubes expressing ASI(-) exhibited a decreased incidence of Ca2+ oscillations during caffeine exposure compared with that observed for myotubes expressing WT-RyR1. We suggest that aberrant splicing of RyR1 and SERCA1 mRNAs might contribute to impaired Ca2+ homeostasis in DM1 muscle.

Alternative Splicing↗
PubMed2004

[A clinical trial of creatine monohydrate in muscular dystrophy patients].

To investigate the effects of creatine monohydrate on muscle performance and cognitive functions in muscular dystrophy patients, we made an open trial. Twenty-nine individuals, including 14 myotonic dystrophy (DM), seven facioscapurohumeral muscular dystrophy (FSHD), two limb-girdle muscular dystrophy and six healthy volunteers, were enrolled in this study and 27 participants completed it. All participants took creatine 20g/day for an initial week and 5g/day for successive eight weeks. Somatotonic measurements, global subjective assessment, muscle performance, cardiopulmonary function, cognitive function, laboratory studies and magnetic resonance spectroscopy (MRS) were evaluated at both pre and post examination. Subjective improvements were reported from twelve individuals. Contrary adverse effects were also complained from ten individuals, although all these problems were not serious. Quantitative muscle power was slightly but significantly increased in the patients and the number of the patients who failed to complete cycle ergometer test was decreased. Phosphocreatine concentrations of left calf muscle were not different between pre and post trial examination. No obvious changes were detected in cardiopulmonary assessment, cognitive function and laboratory date. Creatine has certain expectance for muscular dystrophy patients in motor performance. The effect may be achieved not only by increase of energy buffer, because clinical improvements were observed in our study nevertheless no increase was detected in phosphocreatine concentration. The usage of creatine should be managed under medical monitoring since ideal protocol has not yet been established and adverse effects can not be ignored.

Activities of Daily Living↗
PubMed2004

[Erythrocyte from Duchenne muscular dystrophy is fragile].

Intermittent indirect hyperbilirubinemia was occasionally observed in Duchenne muscular dystrophy (DMD) patients. We suspected that hyperbilirubinemia might be caused by hemolysis of fragile erythrocytes due to damaged endothelium, which was reported in DMD. To examine the fragility of erythrocytes, we performed osmotic resistance test in 25 DMD, 12 myotonic dystrophy (DM), 12 amyotrophic lateral sclerosis (ALS) and 24 healthy volunteers (male 15, female 9). Minimum resistance (beginning point of hemolysis) of DMD (0.447 +/- 0.016%) was higher than that of age matched male controls (0.425 +/- 0.018%: p = 0.0008) and that of DM (0.440 +/- 0.015%) was also higher than that of total controls (0.423 +/- 0.016%, p = 0.0077). The number of poikilocytes was increased in DMD (35.45 +/- 41.17 per a high magnitude field), however no obvious correlation was detected between the ratio of poikilocytes and resistances. Total bilirubin showed correlation (p = 0.029) to minimum resistance. These findings suggested that erythrocyte membrane is fragile in DMD. Involvement of endothelial damage could not be proven, because all investigated patients showed normal tissue plasminogen activator inhibitor-1. Although the mechanism of fragile erythrocytes in DMD is still unknown, we should pay attention to interpret bilirubin in DMD, because hemolysis due to erythrocyte fragility may influence the value.

Aged↗
PubMed2003

[A case of thymoma-associated myasthenia gravis with antibodies against interferon-alpha--a clinico-immunological follow up of the symptoms and its titer].

A 73-year-old woman developed myasthenia gravis (MG) with thymoma. She had a very high level of serum antibodies against interferon-alfa (IFN-alpha). We observed the changes to her clinical symptoms and titer of the antibody during therapeutic course. Although she underwent thymectomy, intravenous methylprednisolone therapy, and oral tacrolimus administration, MG symptoms of the patient were not significantly improved and the antibody titer remained at a high level. IFN-alpha is a potent immunomodulating cytokine that regulates MHC class II expression on antigen presenting cells and activities of NK cells, B cells, and helper/suppressor T cells. This case suggests that IFN-alpha related immunological perturbation participates in the pathogenesis of thymoma-associated myasthenia gravis.

Aged↗