Circulating Cell-Free DNA Promotes Inflammation in Patients with Dermatomyositis with Anti-NXP2 Antibodies via the cGAS/STING Pathway.

OBJECTIVES: Dermatomyositis (DM) is a rare type I interferon (IFN-I)-driven autoimmune disease, and anti-nuclear matrix protein 2 (NXP2) antibody is related to severe muscle disease and poor prognosis. Circulating cell-free DNA (ccf-DNA), including ccf-mitochondrial DNA and ccf-nuclear DNA, activates cGAS/STING pathway to induce IFN-I production in autoimmune diseases. We investigated whether serum-derived ccf-DNA played a pathogenic role on skeletal muscle in anti-NXP2 antibody-positive DM. METHODS: Serum ccf-DNA levels were measured, and correlations between ccf-DNA and clinicopathological indicators were performed. RNA sequencing, immunofluorescence, western blotting and RT-qPCR were performed on skeletal muscle samples. The serum-induced expression of p-STING in C2C12 cells was assessed in vitro. RESULTS: We found that increased ccf-DNA levels were positively correlated with MYOACT scores in anti-NXP2 antibody-positive DM. RNA sequencing and immunofluorescence results revealed that the cytosolic DNA-sensing pathway was upregulated and that increased cytosolic dsDNA was colocalised with cGAS in skeletal muscle in anti-NXP2 antibody-positive DM. Western blot analysis revealed activation of the cGAS/STING pathway in patients with perifascicular atrophy (PFA) but not in patients without PFA. RT-qPCR showed increased IFN-I scores in both patients with PFA and patients without PFA. Sera from patients with PFA increased p-STING expression in C2C12 cells, and DNase I treatment and STING inhibitor efficiently inhibited p-STING expression, respectively. CONCLUSIONS: Increased ccf-DNA levels may be potential biomarkers for monitoring disease activity in anti-NXP2 antibody-positive DM. Activation of the cGAS/STING pathway is associated with PFA. Our findings identify the pathogenic role of ccf-DNA on skeletal muscle via the cGAS/STING pathway.

Combining salivary α-synuclein seeding activity and miRNA-29a to distinguish Parkinson's disease and multiple system atrophy.

INTRODUCTION: The differential diagnosis of early Parkinson's disease (PD) by a single biomarker is still challenging due to its symptomatic overlap with other neurological diseases. Increasing evidences support the use of saliva biomarkers of neurodegeneration, including microRNAs and α-synuclein (α-syn) seeding activity, to diagnose patients with idiopathic PD and multiple system atrophy (MSA). Our previous study confirmed the salivary microRNA-29a-3p (miRNA-29a-3p) and α-syn seeding activity could differentiate PD and MSA from healthy control subjects (HCs) and patients with essential tremor (ET). METHODS: We set up α-syn real-time quaking induced conversion seed amplification assay (α-syn RT-QuIC SAA) in 203 participants from the Peking University First Hospital with PD (n = 101), MSA (n = 32), ET (n = 17) and healthy control subjects (HCs, n = 53). We also determined miRNA-29a-3p in saliva by real time quantitative PCR (RT-qPCR) and, in 155 participants (36HCs, 80PD, 22MSA, 17ET). RESULTS: Sensitivity of RT-QuIC seed amplification assay (SAA) for PD was 70.30 %, for MSA was 56.25 % and specificity for healthy controls was 92.45 %. The expression level of saliva miRNA-29a-3p was significantly decreased in patients with PD (p < 0.001) and MSA (p < 0.0001), and allowed differentiation with HCs (PD vs. HCs, AUC 0.69; MSA vs. HCs, AUC 0.95). Sensitivity of salivary miRNA-29a-3p for PD and MSA were 70.00 % and 95.45 %, respectively, and specificity for PD and MSA were 77.23 % and 80.56 %, respectively. By combining the salivary α-syn RT-QuIC SAA with miRNA-29a-3p, sensitivity for PD vs. HCs increasing to 75.00 %, while sensitivity for MSA vs. HCs increasing to 90.00 %. Specificity was 91.67 % for PD and 88.89 % for MSA after combining assessment of salivary α-syn RT-QuIC SAA. Salivary α-syn RT-QuIC SAA yielded 100.00 % sensitivity and 79.21 % specificity for PD vs. ET, and 100.00 % sensitivity and 65.63 % specificity for MSA vs. ET. Salivary miRNA-29a-3p provied 88.24 % sensitivity and 48.75 % specificity for PD vs. ET and 86.36 % sensitivity and 88.24 % specificity for MSA vs. ET. The combined assessment of saliva markers provided a better diagnostic value for ET vs. synucleinopathies (ET vs. PD: 88.24 % sensitivity and 81.25 % specificity; ET vs. MSA: 94.12 % sensitivity and 90.00 % specificity) than RT-QuIC SAA alone, or miRNA-29a-3p alone. The combination of lag phase and miRNA-29a-3p could add higher specificity (85.71 %) which increased approximately 40 percent (specificity: miRNA-29a-3p 47.50 %, lag phase 48.98 %) for discriminating PD from MSA. However, the sensitivity of combining these two methods was 61.11 %, which was lower than lag phase alone (89.66 %) or miRNA-29a-3p alone (95.45 %). CONCLUSIONS: This study confirmed that saliva, a non-invasive biofluid in synucleinopathies possessed potential diagnostic power between PD, MSA, ET and normal controls. We show the combined value of saliva miRNA-29a-3p and saliva α-syn RT-QuIC SAA in the diagnosis and differential diagnosis of Parkinsonism.

Clinical and pathological characteristics of OPDM4 patients in advanced disease.

INTRODUCTION/AIMS: Oculopharyngodistal myopathy type 4 (OPDM4) arises from a CGG repeat expansion in the 5' UTR of the RILPL1 gene. Reported cases of OPDM4 have been limited. The aim of this study was to investigate the clinical and myopathological characteristics of OPDM4 patients with advanced disease. METHODS: We assessed a total of 8 affected and 12 unaffected individuals in an OPDM4 family with autosomal dominant inheritance. Muscle biopsy tissue from the proband underwent histological, enzyme histochemical, and immunohistochemical stains, and electron microscopy analysis. Whole exome sequencing and repeat primer PCR (RP-PCR) were conducted to investigate underlying variants. RESULTS: OPDM4 patients displayed a progressive disease course. Most experienced lower limb weakness and diminished walking ability in their 20s and 30s, followed by ptosis, ophthalmoplegia, swallowing difficulties, and dysarthria in their 30s to 50s, By their 50s to 70s, they became non-ambulatory. Muscle magnetic resonance imaging (MRI) of the proband in advanced disease revealed severe fatty infiltration of pelvic girdle and lower limb muscles. Biopsied muscle tissue exhibited advanced changes typified by adipose connective tissue replacement and the presence of multiple eosinophilic and p62-positive intranuclear inclusions. Immunopositivity for the intranuclear inclusions was observed with anti-glycine antibody and laboratory-made polyA-R1 antibody. RP-PCR unveiled an abnormal CGG repeat expansion in the 5' UTR of the RILPL1 gene. DISCUSSION: The clinical and radiological features in this family broaden the phenotypic spectrum of OPDM4. The presence of intranuclear inclusions in the proliferative adipose connective tissues of muscle biopsy specimens holds diagnostic significance for OPDM4 in advanced disease.

The relationship between ischemic penumbra progression and the oxygen content of cortex microcirculation in acute ischemic stroke.

The precise oxygen content thresholds of ischemic deep parenchymal (OCIDP) and that in cortical microcirculation (OCCM), which leads to ischemic penumbra converting into the infarcted core, remain uncertain. This study employed an invasive fiber-optic oxygen meter and a newly developed oxygen-responsive probe called RuA3-Cy5-rtPA (RC-rtPA) based on recombinant tissue-type plasminogen activator (rtPA) to examine the oxygen content thresholds. A mouse model of middle cerebral artery occlusion was generated and animals were randomly divided into a sham, 24-h reperfusion after 3-h ischemia (IR 3-h), and IR 6-h groups, all of which were sacrificed following reperfusion. Stroke severity was evaluated based on the infarction area, neurological symptoms, microcirculation perfusion, and microemboli in microcirculation. OCIDP was characterized based on its extent and distribution, whereas OCCM was measured using RC-rtPA. During ischemia, stroke severity escalation manifested as increasing infarction area, severe neurologic symptoms, and poorer microcirculation perfusion with more microthrombi depositions. OCIDP presented rapid decline following artery occlusion along with a gradual increase in the hypoxic area. Within 3 â€‹h following ischemia induction, the ischemic tissue that experienced hypoxia could be rescued, and this reversibility would disappear after 6 â€‹h. Within 6 â€‹h, OCCM continued to decrease. A significant decrease in oxygen content in cortical venules and cortical parenchyma was observed. These findings assist in establishing the extent of the ischemic penumbra at the microcirculation level and offer a foundation for assessing the ischemic penumbra that could respond positively to reperfusion therapy beyond the typical time window.

Multiomics analysis reveals serine catabolism as a potential therapeutic target for MELAS.

Mitochondrial disease is a devastating genetic disorder, with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and m.3243A>G being the most common phenotype and genotype, respectively. The treatment for MELAS patients is still less effective. Here, we performed transcriptomic and proteomic analysis in muscle tissue of MELAS patients, and discovered that the expression of molecules involved in serine catabolism were significantly upregulated, and serine hydroxymethyltransferase 2 (SHMT2) increased significantly in both the mRNA and protein levels. The SHMT2 protein level was also increased in myoblasts with m.3243A>G mutation, which was transdifferentiated from patients derived fibroblasts, accompanying with the decreased nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) ratio and cell viability. After treating with SHMT2 inhibitor (SHIN1), the NAD+/NADH ratio and cell viability in MELAS myoblasts increased significantly. Taken together, our study indicates that enhanced serine catabolism plays an important role in the pathogenesis of MELAS and that SHIN1 can be a potential small molecule for the treatment of this disease.

A novel deep intronic variant introduce dystrophin pseudoexon in Becker muscular dystrophy: A case report.

Most pathogenic DMD variants are detectable and interpretable by standard genetic testing for dystrophinopthies. However, approximately 1∼3% of dystrophinopthies patients still do not have a detectable DMD variant after standard genetic testing, most likely due to structural chromosome rearrangements and/or deep intronic pseudoexon-activating variants. Here, we report on a boy with a suspected diagnosis of Becker muscular dystrophy (BMD) who remained without a detectable DMD variant after exonic DNA-based standard genetic testing. Dystrophin mRNA studies and genomic Sanger sequencing were performed in the boy, followed by in silico splicing analyses. We successfully detected a novel deep intronic disease-causing variant in the DMD gene (c.2380 + 3317A > T), which consequently resulting in a new dystrophin pseudoexon activation through the enhancement of a cryptic donor splice site. The patient was therefore genetically diagnosed with BMD. Our case report further emphasizes the significant role of disease-causing splicing variants within deep intronic regions in genetically undiagnosed dystrophinopathies.

Encephalitis-like episodes with cortical edema and enhancement in patients with neuronal intranuclear inclusion disease.

OBJECTIVES: Neuronal intranuclear inclusion disease (NIID) exhibited significant clinical heterogeneities. However, the clinical features, radiographic changes, and prognosis of patients with encephalitis-like NIID have yet to be systematically elucidated. METHODS: Clinical data including medical history, physical examination, and laboratory examinations were collected and analyzed. Skin and sural nerve biopsies were conducted on the patient. Repeat-primed PCR (RP-PCR) and fluorescence amplicon length PCR (AL-PCR) were used to detect the expansion of CGG repeat. We also reviewed the clinical and genetic data of NIID patients with cortical enhancement. RESULTS: A 54-year-old woman presented with encephalitis-like NIID, characterized by severe headache and agitative psychiatric symptoms. The brain MRI showed cortical swelling in the temporo-occipital lobes and significant enhancement of the cortical surface and dura, but without hyperintensities along the corticomedullary junction on diffusion-weighted image (DWI). A biopsy of the sural nerve revealed a demyelinating pathological change. The intranuclear inclusions were detected in nerve and skin tissues using the p62 antibody and electron microscopy. RP-PCR and AL-PCR unveiled the pathogenic expansion of CGG repeats in the NOTCH2NLC gene. A review of the literature indicated that nine out of the 16 patients with cortical lesions and linear enhancement exhibited encephalitis-like NIID. CONCLUSION: This study indicated that patients with encephalitis-like NIID typically exhibited headache and excitatory psychiatric symptoms, often accompanied by cortical edema and enhancement of posterior lobes, and responded well to glucocorticoid treatment. Furthermore, some patients may not exhibit hyperintensities along the corticomedullary junction on DWI, potentially leading to misdiagnosis.

Novel TUBA4A variant causes congenital myopathy with focal myofibrillar disorganisation.

BACKGROUND: Congenital myopathies are a clinical, histopathological and genetic heterogeneous group of inherited muscle disorders that are defined on peculiar architectural abnormalities in the muscle fibres. Although there have been at least 33 different genetic causes of the disease, a significant percentage of congenital myopathies remain genetically unresolved. The present study aimed to report a novel TUBA4A variant in two unrelated Chinese patients with sporadic congenital myopathy. METHODS: A comprehensive strategy combining laser capture microdissection, proteomics and whole-exome sequencing was performed to identify the candidate genes. In addition, the available clinical data, myopathological changes, the findings of electrophysiological examinations and thigh muscle MRIs were also reviewed. A cellular model was established to assess the pathogenicity of the TUBA4A variant. RESULTS: We identified a recurrent novel heterozygous de novo c.679C>T (p.L227F) variant in the TUBA4A (NM_006000), encoding tubulin alpha-4A, in two unrelated patients with clinicopathologically diagnosed sporadic congenital myopathy. The prominent myopathological changes in both patients were muscle fibres with focal myofibrillar disorganisation and rimmed vacuoles. Immunofluorescence showed ubiquitin-positive TUBA4A protein aggregates in the muscle fibres with rimmed vacuoles. Overexpression of the L227F mutant TUBA4A resulted in cytoplasmic aggregates which colocalised with ubiquitin in cellular model. CONCLUSION: Our findings expanded the phenotypic and genetic manifestations of TUBA4A as well as tubulinopathies, and added a new type of congenital myopathy to be taken into consideration in the differential diagnosis.

A new pseudoexon activation due to ultrarare branch point formation in Duchenne muscular dystrophy.

Deep-intronic variants that create or enhance a splice site are increasingly reported as a significant cause of monogenic diseases. However, deep-intronic variants that activate pseudoexons by affecting a branch point are extremely rare in monogenic diseases. Here, we describe a novel deep-intronic DMD variant that created a branch point in a Duchenne muscular dystrophy (DMD) patient. A 7.0-year-old boy was enrolled because he was suspected of DMD based on his clinical, muscle imaging, and pathological features. Routine genetic testing did not discover a pathogenic DMD variant. We then performed muscle-derived dystrophin mRNA analysis and detected an aberrant pseudoexon-containing transcript. Further genomic Sanger sequencing and bioinformatic analyses revealed a novel deep-intronic splicing variant in DMD (NM_004006.2:c.5325+1759G>T), which created a new branch point sequence and thus activated a new dystrophin pseudoexon (NM_004006.2:r.5325_5326ins5325+1779_5325+1855). Our study highlights the significant role of branch point alterations in the pathogenesis of monogenic diseases.

Pathologic changes in neuronal intranuclear inclusion disease are linked to aberrant FUS interaction under hyperosmotic stress.

CGG repeat expansion in NOTCH2NLC is the genetic cause of neuronal intranuclear inclusion disease (NIID). Previous studies indicated that the CGG repeats can be translated into polyglycine protein (N2CpolyG) which was toxic to neurons by forming intranuclear inclusions (IIs). However, little is known about the factors governing polyG IIs formation as well as its molecular pathogenesis. Considering that neurogenetic disorders usually involve interactions between genetic and environmental stresses, we investigated the effect of stress on the formation of IIs. Our results revealed that under hyperosmotic stress, N2CpolyG translocated from the cytoplasm to the nucleus and formed IIs in SH-SY5Y cells, recapitulating the pathological hallmark of NIID patients. Furthermore, N2CpolyG interacted/ co-localized with an RNA-binding protein FUS in the IIs of cellular model and NIID patient tissues, thereby disrupting stress granule formation in cytoplasm under hyperosmotic stress. Consequently, dysregulated expression of microRNAs was found both in NIID patients and cellular model, which could be restored by FUS overexpression in cultured cells. Overall, our findings indicate a mechanism of stress-induced pathological changes as well as neuronal damage, and a potential strategy for the treatment of NIID.

A novel biomarker of fibrofatty replacement in dystrophinopathies identified by integrating transcriptome, magnetic resonance imaging, and pathology data.

BACKGROUND: We aimed to analyse genome-wide transcriptome differences between Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) patients and identify biomarkers that correlate well with muscle magnetic resonance imaging (MRI) and histological fibrofatty replacement in both patients, which have not been reported. METHODS: One hundred and one male patients with dystrophinopathies (55 DMD and 46 BMD) were enrolled. Muscle-derived genome-wide RNA-sequencing was performed in 31 DMD patients, 29 BMD patients, and 11 normal controls. Fibrofatty replacement was scored on muscle MRI and histological levels in all patients. A unique pipeline, single-sample gene set enrichment analysis combined with Spearman's rank correlations (ssGSEA-Cor) was developed to identify the most correlated gene signature for fibrofatty replacement. Quantitative real-time PCR (qRT-PCR) analysis, western blot analysis, and single-nucleus RNA-sequencing (snRNA-seq) were performed in the remaining patients to validate the most correlated gene signature. RESULTS: Comparative transcriptomic analysis revealed that 31 DMD muscles were characterized by a significant increase of inflammation/immune response and extracellular matrix remodelling compared with 29 BMD muscles (P < 0.05). The ssGSEA-Cor pipeline revealed that the gene set of CDKN2A and CDKN2B was the most correlated gene signature for fibrofatty replacement (histological rs  = 0.744, P < 0.001; MRI rs  = 0.718, P < 0.001). Muscle qRT-PCR confirmed that CDKN2A mRNA expression in both 15 DMD (median = 25.007, P < 0.001) and 12 BMD (median = 5.654, P < 0.001) patients were significantly higher than that in controls (median = 1.101), while no significant difference in CDKN2B mRNA expression was found among DMD, BMD, and control groups. In the 27 patients, muscle CDKN2A mRNA expression respectively correlated with muscle MRI (rs  = 0.883, P < 0.001) and histological fibrofatty replacement (rs  = 0.804, P < 0.001) and disease duration (rs  = 0.645, P < 0.001) and North Star Ambulatory Assessment total scores (rs  = -0.698, P < 0.001). Muscle western blot analysis confirmed that both four DMD (median = 2.958, P < 0.05) and four BMD (median = 1.959, P < 0.01) patients had a significantly higher level of CDKN2A protein expression than controls (median = 1.068). The snRNA-seq analysis of two DMD muscles revealed that CDKN2A was mainly expressed in fibro-adipogenic progenitors, satellite cells, and myoblasts. CONCLUSIONS: We identify CDKN2A expression as a novel biomarker of fibrofatty replacement, which might be a new target for antifibrotic therapy in dystrophinopathies.