柴田 頌太

Neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disease characterized by eosinophilic hyaline intranuclear inclusions in the neurons, glial cells, and other somatic cells. Although CGG repeat expansions in NOTCH2NLC have been identified in most East Asian patients with NIID, the pathophysiology of NIID remains unclear. Ubiquitin- and p62-positive intranuclear inclusions are the pathological hallmark of NIID. Targeted immunostaining studies have identified several other proteins present in these inclusions. However, the global molecular changes within nuclei with these inclusions remained unclear. Herein, we analyzed the proteomic profile of nuclei with p62-positive inclusions in a NIID patient with CGG repeat expansion in NOTCH2NLC to discover candidate proteins involved in the NIID pathophysiology. We used fluorescence-activated cell sorting and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify each protein identified in the nuclei with p62-positive inclusions. The distribution of increased proteins was confirmed via immunofluorescence in autopsy brain samples from three patients with genetically confirmed NIID. Overall, 526 proteins were identified, of which 243 were consistently quantified using MS. A 1.4-fold increase was consistently observed for 20 proteins in nuclei with p62-positive inclusions compared to those without. Fifteen proteins identified with medium or high confidence in the LC-MS/MS analysis were further evaluated. Gene ontology enrichment analysis showed enrichment of several terms, including poly(A) RNA binding, nucleosomal DNA binding, and protein binding. Immunofluorescence studies confirmed that the fluorescent intensities of increased RNA-binding proteins identified by proteomic analysis, namely hnRNP A2/B1, hnRNP A3, and hnRNP C1/C2, were higher in the nuclei with p62-positive inclusions than in those without, which were not confined to the intranuclear inclusions. We identified several increased proteins in nuclei with p62-positive inclusions. Although larger studies are needed to validate our results, these proteomic data may form the basis for understanding the pathophysiology of NIID.

Background and Objectives: CSF tau phosphorylated at threonine 181 (p-tau181) is a widely used biomarker for Alzheimer’s disease (AD) and has recently been regarded to reflect amyloid-beta and/or p-tau deposition in the AD brain. Neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disease characterized by intranuclear inclusions in neurons, glial cells, and other somatic cells. Symptoms include dementia, neuropathy, and others. CSF biomarkers were not reported. The objective of this study was to investigate whether CSF biomarkers including p-tau181 are altered in patients with NIID. Methods: This was a retrospective observational study. CSF concentrations of p-tau181, total tau, amyloid-beta 1-42 (Aβ42), monoamine metabolites homovanillic acid (HVA), and 5-hydroxyindole acetic acid (5-HIAA) were compared between 12 patients with NIID, 120 patients with Alzheimer’s clinical syndrome biologically confirmed based on CSF biomarker profiles, and patients clinically diagnosed with other neurocognitive disorders (dementia with Lewy bodies [DLB], 24; frontotemporal dementia [FTD], 13; progressive supranuclear palsy [PSP], 21; and corticobasal syndrome [CBS], 13). Amyloid PET using Pittsburgh compound B (PiB) was performed in six NIID patients. Results: The mean age of patients with NIID, AD, DLB, FTD, PSP, and CBS were 71.3, 74.6, 76.8, 70.2, 75.5, and 71.9 years old, respectively. CSF p-tau181 was significantly higher in NIID (72.7 ± 24.8 pg/mL) compared to DLB, PSP, and CBS and was comparable between NIID and AD. CSF p-tau181 was above the cutoff value (50.0 pg/mL) in 11 of 12 NIID patients (91.7%). Within these patients, only two patients showed decreased CSF Aβ42, and these patients showed negative or mild local accumulation in PiB PET, respectively. PiB PET scans were negative in the remaining 4 patients tested. The proportion of patients with increased CSF p-tau181 and normal Aβ42 (A−T+) was significantly higher in NIID (75%) compared to DLB, PSP, and CBS (4.2%, 4.8%, and 7.7%, respectively). CSF HVA and 5-HIAA concentrations were significantly higher in patients with NIID compared to disease controls. Discussion: CSF p-tau181 was increased in patients with NIID without amyloid accumulation. Although the deposition of p-tau has not been reported in NIID brains, molecular mechanism of tau phosphorylation or secretion of p-tau may be altered in NIID.

症例は25歳女性で、発熱、頭痛、めまい、左半身のしびれをきたし、当院に救急搬送された。20歳時に両側感音難聴を発症し、他院で突発性難聴と診断された。その後、右補聴器を使用していたが、難聴が進行したため24歳時に人工内耳植込術を施行され、術後経過は良好であった。若年発症で血管支配域に一致しない頭部CT低吸収域があり、脳卒中様発作を考え、低身長、両側感音難聴があることを併せてMELASを疑い加療を開始した。エダラボンを開始したが意識レベルの低下をきたし、第5病日に経鼻胃管を挿入し、L-アルギニン、タウリン、ユビデカレノン、レボカルニチンの4剤の経管投与を開始した。第10病日に撮影した頭部CT検査で後頭葉への低吸収域の拡大を確認し、浮腫の軽減効果を期待してグリセリンを投与、左半側空間無視、着衣失行は残存するが自立歩行可能となり、第41病日に自宅退院した。

Purpose: To report the ocular characteristics of neuronal intranuclear inclusion disease (NIID)-related retinopathy with expansion of the CGG repeats in the NOTCH2NLC gene. Methods: Seven patients from six families (aged 66-81 years) diagnosed with adult-onset NIID were studied. Ophthalmologic examinations, including the best-corrected visual acuity (BCVA), Goldmann perimetry, fundus photography, fundus autofluorescence (FAF) imaging, optical coherence tomography (OCT), and full-field electroretinography (ERGs), were performed. The expansion of the CGG repeats in the NOTCH2NLC gene was determined. Results: All patients had an expansion of the CGG repeats (length approximately from 330-520 bp) in the NOTCH2NLC gene. The most common symptoms of the five symptomatic cases were reduced BCVA and night blindness. The other two cases did not have any ocular symptoms. The decimal BCVA varied from 0.15 to 1.2. Goldmann perimetry was constricted in all four cases tested; physiological blind spot was enlarged in two of the cases. The FAF images showed an absence of autofluorescence (AF) around the optic disc in all cases and also showed mild hypo-AF or extinguished AF in the midperiphery. In all cases, the OCT images showed an absence of the ellipsoid zone of the photoreceptors in the peripapillary region, and hyperreflective dots were also present between the retinal ganglion cell layer and outer nuclear layer. The macular region was involved in the late stage of the retinopathy. The full-field ERGs showed rod-cone dysfunction. Conclusions: Patients with adult-onset NIID with CGG repeats expansions in the NOTCH2NLC gene had similar ophthalmologic features, including rod-cone dysfunction with progressive retinal degeneration in the peripapillary and midperipheral regions. The primary site is most likely the photoreceptors. Because the ocular symptoms are often overlooked due to dementia and occasionally precede the onset of dementia, detailed ophthalmological examinations are important for the early diagnosis of NIID-related retinopathy.

Two ethnic Chinese men with clinico-radiologic features of Fragile X-associated tremor-ataxia syndrome (FXTAS) were found on genetic testing to have neuronal intranuclear inclusion disease (NIID), highlighting that NIID should be considered in the differential diagnosis of FXTAS. NIID may also be much more common than FXTAS in certain Asian populations.

Noncoding repeat expansions cause various neuromuscular diseases, including myotonic dystrophies, fragile X tremor/ataxia syndrome, some spinocerebellar ataxias, amyotrophic lateral sclerosis and benign adult familial myoclonic epilepsies. Inspired by the striking similarities in the clinical and neuroimaging findings between neuronal intranuclear inclusion disease (NIID) and fragile X tremor/ataxia syndrome caused by noncoding CGG repeat expansions in FMR1, we directly searched for repeat expansion mutations and identified noncoding CGG repeat expansions in NBPF19 (NOTCH2NLC) as the causative mutations for NIID. Further prompted by the similarities in the clinical and neuroimaging findings with NIID, we identified similar noncoding CGG repeat expansions in two other diseases: oculopharyngeal myopathy with leukoencephalopathy and oculopharyngodistal myopathy, in LOC642361/NUTM2B-AS1 and LRP12, respectively. These findings expand our knowledge of the clinical spectra of diseases caused by expansions of the same repeat motif, and further highlight how directly searching for expanded repeats can help identify mutations underlying diseases.

Epilepsy is a common neurological disorder, and mutations in genes encoding ion channels or neurotransmitter receptors are frequent causes of monogenic forms of epilepsy. Here we show that abnormal expansions of TTTCA and TTTTA repeats in intron 4 of SAMD12 cause benign adult familial myoclonic epilepsy (BAFME). Single-molecule, real-time sequencing of BAC clones and nanopore sequencing of genomic DNA identified two repeat configurations in SAMD12. Intriguingly, in two families with a clinical diagnosis of BAFME in which no repeat expansions in SAMD12 were observed, we identified similar expansions of TTTCA and TTTTA repeats in introns of TNRC6A and RAPGEF2, indicating that expansions of the same repeat motifs are involved in the pathogenesis of BAFME regardless of the genes in which the expanded repeats are located. This discovery that expansions of noncoding repeats lead to neuronal dysfunction responsible for myoclonic tremor and epilepsy extends the understanding of diseases with such repeat expansion.