Takashi Kimura

Myasthenia gravis (MG) is an autoimmune disorder characterized by impaired neuromuscular transmission and motor symptoms. Its genetic background remains unclear, particularly beyond specific subtypes reported in European populations. Here, we perform a genome-wide association study (GWAS) of 1,434 MG cases covering all disease subtypes and 42,913 controls of Japanese, which newly identify the TERT locus (odds ratio [OR] = 1.31, P = 1.7×10^-10). Subtype-stratified GWASs show stronger signals for generalized MG (gMG; OR = 1.38, P = 1.6×10^-12), anti AChR antibody-positive gMG (g-AChR-Ab(+)MG; OR= 1.49, P = 2.1×10^-15), and thymoma-associated gMG (g-TAMG; OR = 1.92, P = 1.1×10^-15). Fine-mapping of the major histocompatibility complex region reveal distinct associations of HLA-DRB1 with late onset gMG (g-LOMG) and HLA-A with early onset gMG (g-EOMG). The MG risk TERT lead variant rs2736099 is associated with poor treatment response, especially in g-AChR-Ab(+)MG and g-EOMG (P < 0.0042). The biobank-based phenome-wide association study identify pleiotropic effects on lung cancer, hematological traits, and telomere length. Single cell transcriptomics and immunohistochemistry identified immature lymphocyte-specific TERT expression in thymoma specimens. Full-length transcriptomics reveal allele-specific decreasing effect of rs2736099-A on TERT expression. Our study unveils genetics of MG distinctly across disease subtypes, and involvement of TERT in its pathogenesis.

Introduction Parkinsonism–hyperpyrexia syndrome (PHS) is a potentially fatal complication of Parkinson’s disease (PD) often triggered by antiparkinsonian medication discontinuation or reduction. Rotigotine, a transdermal dopamine agonist, provides continuous drug delivery and can be administered even when oral administration is difficult. However, the association between rotigotine use and development of PHS remains unclear. Methods We retrospectively reviewed 166 episodes of emergency hospitalization for PD at Hyogo Medical University Hospital (2010–2024). After excluding 19 episodes with insufficient data, 147 were analyzed. Thirty episodes met the diagnostic criteria for PHS (PHS group), and 117 episodes did not (non-PHS group). Clinical characteristics, antiparkinsonian medications, and precipitating events during hospitalization were assessed. A multivariable logistic regression analysis was performed using age, sex, disease duration, and rotigotine administration as covariates. Results The PHS group had a shorter disease duration, lower modified Hoehn and Yahr stages, and a lower levodopa equivalent dose than the non-PHS group. Poor medication compliance was the most common precipitating factor among PHS cases (n=11, 36.7%). Rotigotine was administered in five PHS and 41 non-PHS episodes. In the multivariable analysis, age was significantly negatively associated with the development of PHS (odds ratio [OR], 0.894; 95% confidence interval [CI], 0.840–0.952; p=0.0005). And rotigotine administration showed a tendency to suppress the development of PHS (OR, 0.353; 95% CI, 0.121–1.031; p=0.0569). Conclusion Rotigotine use tends to be associated with a lower incidence of PHS, suggesting its potential protective effects. Maintaining good medication adherence is critical for preventing PHS, and rotigotine may be a useful therapeutic option.

Efgartigimod, which has been well tolerated and efficacious in individuals with generalized myasthenia gravis (MG), is available in Japan not only for the treatment of anti–acetylcholine receptor–positive (AChR+) but also anti–muscle-specific receptor tyrosine kinase (MuSK+) and seronegative generalized MG. We report details of the use of efgartigimod for generalized MG in clinical practice in Japan. We included patients with generalized MG in the 2021 survey of Japan Myasthenia Gravis Registry (JAMG-R) study group who received an initial cycle of efgartigimod between May and September 2022. We defined “responders” as patients who achieved a score ≥2 points for MG activities of daily living (MG-ADL) in the first treatment cycle. The MG composite and the Revised scale of the 15-item Myasthenia Gravis–Quality of Life scale (MG-QOL15-r) were also evaluated. Of 1,343 JAMG-R patients, 36 (2.7%) started efgartigimod (female 68%, age 53 years). Their serologic profiles were as follows: AChR+, n = 19 (53%); MuSK+, n = 6 (17%); and seronegative, n = 11 (31%). Twenty-six patients (72%) had refractory MG. There were 81 cycles of efgartigimod during the 26-week observation in 34 patients (average, 2.4 cycles). The mean interval between cycles was 5.9 weeks. A continuous 4-weekly infusion of efgartigimod was performed in 65 (80%) of 81 cycles. In the first cycle, the MG-ADL score of the 34 patients decreased significantly from 10.5 ± 4.3 to 6.9 ± 5.1 (p = 0.003). Similarly, the mean MG composite and MG-QOL15-r decreased from 18.4 ± 13.6 to 11.8 ± 9.6 (p = 0.004) and from 19.2 ± 6.3 to 14.2 ± 8.3 (p = 0.007), respectively. Twenty-one (62%) patients were responders. Therapeutic responses were observed in the subsequent cycles. The duration of effectiveness of efgartigimod was varied among the responders; 4 responders had only a single effective cycle. Significant improvement was observed in the MuSK+ patients. Prednisolone dose of 7 patients was reduced. Our examination of the patients' postintervention status revealed that 6 patients achieved minimal manifestations. COVID-19 occurred in 5 patients. We failed to detect clinical or laboratory findings associated with responders. Efgartigimod can be considered for the treatment of patients with generalized MG who do not achieve minimal manifestations, with a broad flexibility of patient selection and treatment schedules.

YKL-40 is implicated in inflammation and tissue repair, but no reports have investigated its involvement in myositis in polymyositis (PM) and dermatomyositis (DM). Therefore, we aimed to investigate the relationship between YKL-40 and PM/DM. We retrospectively enrolled 35 patients diagnosed with PM/DM along with 26 healthy controls (HCs). Both PM and DM were diagnosed according to Bohan and Peter's criteria. Serum YKL-40 levels were measured, age-corrected to YKL-40 percentile values, and compared to HCs. Patients with myositis without interstitial lung disease were also enrolled and compared to HCs. Immunofluorescence staining was performed to identify YKL-40-positive inflammatory cells in muscle biopsy samples from two patients each with PM and DM. Age-corrected serum YKL-40 levels were significantly higher in patients with PM/DM compared to HCs with and without lung disease; however, these levels decreased significantly after treatment. Immunohistochemical analysis showed infiltration of YKL-40-positive inflammatory cells into the intramuscular sheath and perimuscular membrane. Immunofluorescence staining showed CD68 expression in YKL-40-positive inflammatory cells, suggesting that these cells were macrophages. To the best of our knowledge, this is the first study to demonstrate that YKL-40-positive macrophages are present in PM and DM, indicating that YKL-40 may be involved in PM/DM.

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.

Objective In this study, we report the case of a 24-year-old man with intellectual disability and childhood-onset seizures. This patient had newly identified biallelic variants in the laminin subunit gamma 3 (LAMC3) gene with unreported cortical malformation. Methods Exome sequencing. Results Genetic analyses revealed new biallelic variants in the LAMC3 gene. An MRI examination of the brain revealed cortical malformations predominantly in the temporal lobes and mildly in the occipital, frontal, and parietal lobes. In addition, our patient also exhibited mild midline malformation in the ventral pons, which is unique to LAMC3 variants. Discussion Patients with LAMC3 variants have been reported to exhibit cortical malformation predominantly in the occipital lobes, but this patient exhibited cortical malformation predominantly in the temporal lobes and mildly in the occipital, frontal, and parietal lobes. In addition, this patient also exhibited mild midline malformation in the ventral pons. These unique findings cast new light on the role of LAMC3 in brain development.

Purpose The word “fixel” refers to the specific fiber population within each voxel, and fixel-based analysis (FBA) is a recently developed technique that facilitates fiber tract-specific statistical analysis. The aim of the paper is to apply FBA to detect impaired fibers for corticobasal syndrome (CBS) especially in regions that contain multiple crossed fibers. Methods FBA was performed in cohorts of participants clinically diagnosed with CBS (n = 10) and Parkinson’s disease (n = 15) or in healthy controls (n = 9). The parameters of the diffusion weighted image were echo time, 83 ms; time, 8123.6 ms; flip angle, 90°; section thickness, 2 mm; b = 1000 s/mm²; and 32 axes. Diffusion tensor analysis was conducted using tract-based spatial statistics (TBSS), and white matter volume was estimated via voxel-based morphometry. Results A comparison of PD or HC to CBS revealed a significant difference in the dentatorubrothalamic tract of the brainstem in FBA in addition to the affected regions in voxel-based morphometry and TBSS (family-wise error-corrected p < 0.05). Reduction of the white matter fibers crossing the brainstem could not be detected via microstructural changes identified using TBSS, but it was detected using FBA. Conclusion FBA has some advantages in determining the distribution of corticobasal syndrome lesions.

Myotonic dystrophy (dystrophia myotonica, DM) is caused by expanded CTG/CCTG microsatellite repeats, leading to multi-systemic symptoms in skeletal muscle, heart, gastrointestinal, endocrine, and central nervous systems (CNS), among others. For some patients, CNS issues can be as debilitating or more so than muscle symptoms; they include hypersomnolence, executive dysfunction, white matter atrophy, and neurofibrillary tangles. Although transcriptomes from DM type 1 (DM1) skeletal muscle have provided useful insights into pathomechanisms and biomarkers, limited studies of transcriptomes have been performed in the CNS. To elucidate underlying causes of CNS dysfunction in patients, we have generated and analyzed RNA-seq transcriptomes from the frontal cortex of 21 DM1 patients, 4 DM type 2 (DM2) patients, and 8 unaffected controls. One hundred and thirty high confidence splicing changes were identified, most occurring exclusively in the CNS and not in skeletal muscle or heart. Mis-spliced exons were found in neurotransmitter receptors, ion channels, and synaptic scaffolds, and we identified an alternative exon in GRIP1 that modulates association with kinesins. Splicing changes exhibited a gradient of severity correlating with CTG repeat length, as measured by optical mapping of individual DNA molecules. All individuals studied, including those with modest splicing defects, showed extreme somatic mosaicism, with a subset of alleles having >1000 CTGs. Analyses of gene expression changes showed up-regulation of genes transcribed in microglia and endothelial cells, suggesting neuroinflammation, and downregulation of genes transcribed in neurons. Gene expression of RNAs encoding proteins detectable in cerebrospinal fluid were also found to correlate with mis-splicing, with implications for CNS biomarkers of disease severity. These findings provide a framework for future mechanistic and therapeutic studies of CNS issues in DM.