Mitochondrial DNA Leakage and cGas/STING Pathway in Microglia: Crosstalk Between Neuroinflammation and Neurodegeneration.

Neurodegenerative diseases, characterized by abnormal deposition of misfolded proteins, often present with progressive loss of neurons. Chronic neuroinflammation is a striking hallmark of neurodegeneration. Microglia, as the primary immune cells in the brain, is the main type of cells that participate in the formation of inflammatory microenvironment. Cytoplasmic free mitochondrial DNA (mtDNA), a common component of damage-associated molecular patterns (DAMPs), can activate the cGas/stimulator of interferon genes (STING) signalling, which subsequently produces type I interferon and proinflammatory cytokines. There are various sources of free mtDNA in microglial cytoplasm, but mitochondrial oxidative stress accumulation plays the vital role. The upregulation of cGas/STING pathway in microglia contributes to the abnormal and persistent microglial activation, accompanied by excessive secretion of neurotoxic inflammatory mediators such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), which exacerbates the damage of neurons and promotes the development of neurodegeneration. Currently, novel therapeutic approaches need to be found to delay the progression of neurodegenerative disorders, and regulation of the cGas/STING signaling in microglia may be a potential target.

"Hot Cross Bun" Sign in a Patient with Glutamic Acid Decarboxylase 65-KDa Isoform Associated Cerebellar Ataxia: Case Report and Review of the Literature.

The "hot cross bun" sign (HCBs) is a cruciform hyperintensity on T2-weighted imaging within the pons initially found in patients diagnosed as multiple system atrophy. However, recent findings have broadened the disease spectrum presented with HCBs. Here is a case report at an academic medical center. Cerebral magnetic resonance imaging (MRI), electroneuromyography, serum, and CSF analysis were performed. Literature is comprehensively reviewed. We investigated a woman presented with blurred speech and cerebellar ataxia. Her MRI showed the vertical line of HCBs 2 weeks after disease onset and gradually enhanced, presenting as an intact HCBs in a year. Glutamic acid decarboxylase 65-kDa isoform (GAD65) antibody IgG was detected in serum and CSF. The patient was diagnosed as GAD65 associated cerebellar ataxia and treated with corticosteroid and rituximab. We found 6 previously reported autoimmune cerebellar ataxia patients with HCBs. Anti-KLHL-11, anti-Homer-3, anti-Ri, and anti-Amphiphysin were associated. All patients had cerebellar ataxia with other neurological symptoms. Five patients were diagnosed with tumor. First-line immunotherapy including corticosteroid, intravenous immunoglobulin, and plasma exchange for most patients was unsatisfied. This case highlights the importance of considering GAD65 IgG evaluation in patients with progressive cerebellar syndrome and HCBs. Early diagnosis and therapy are challenging but imperative. Further studies are required in regard to therapeutic management.

Favorable Outcomes in a Case of Non-paraneoplastic DNER Ataxia Treated with Immunotherapy.

Anti-DNER antibody is associated with paraneoplastic cerebellar degeneration (PCD) and Hodgkin's disease (HD). However, recent studies reported cases absence of HD and that non-tumor anti-DNER antibody-associated ataxia was not well characterized. We present a case of acute cerebellar ataxia and nystagmus with detected anti-DNER antibody. Brain magnetic resonance imaging (MRI) showed cerebellar atrophy. High titer of anti-DNER antibody was detected in CSF and serum. Positron emission tomography (PET) scanning was unremarkable at a 10-month follow up. The patient improved significantly after immunosuppressive therapy with intravenous steroids, immunoglobulin followed by rituximab. Our study suggest that the presence of such anti-neuronal antibodies might not come along with malignancy and that early onset non-tumor patients are more likely to have a better outcome after immunotherapy. Early diagnosis and timely immunosuppressive therapy may prove beneficial for these patients.

Neuronal intranuclear inclusion disease mimicking progressive supranuclear palsy.

BACKGROUND: Given the variable nature of clinical manifestations, neuronal intranuclear inclusion disease (NIID) is regarded as a heterogeneous disease which is challenging to diagnose early. To the present, progressive supranuclear palsy (PSP)-like symptoms have never been listed in the performance of NIID. CASE PRESENTATION: A 58-year-old man presented with progressive Parkinsonism and postural instability for 3 years. Initially, he was considered as probable PSP due to vertical supranuclear gaze palsy, postural instability, and hummingbird sign. No high-intensity signal on diffusion-weighted imaging (DWI) was revealed. Eventually, the diagnosis was revised to NIID by Notch 2 N-terminal like C (NOTCH2NLC) GGC repeat expansions and skin biopsy showing intranuclear eosinophilic inclusions in the vesicles and ductal epithelial cells of sweat glands. CONCLUSION: Even if the typical high-intensity along the corticomedullary junction (CMJ) on DWI is lacking, clinicians should be alert to the possibility of NIID when PSP-like symptoms develop. This case report offers new features of NIID and expands its clinical spectrum.

A heterozygous deletion of PDGFB gene causes paroxysmal kinesigenic dyskinesia with primary familial brain calcification.

BACKGROUND: Primary familial brain calcification (PFBC) is a neurodegenerative disease characterized with calcium deposition in multiple brain regions. Mutations in PDGFB have been discovered in sporadic and familial PFBC cases. While several known variants displayed loss-of function, no complete deletion of platelet-derived growth factor B (PDGFB) has been reported. METHODS: For the diagnostic purpose, brain computerized tomography or magnetic resonance imaging scanning and whole-genome sequencing were performed on the proband and family members in the pedigree. RESULTS: We identified a heterozygous PDGFB complete deletion in a Chinese pedigree. The proband presented with paroxysmal kinesigenic dyskinesia (PKD), a rare symptom in PFBC. The proband's mother carrying the same mutation was asymptomatic. CONCLUSIONS: For the first time, we reported a PFBC with a heterozygous deletion of PDGFB, and provided evidence of haploinsufficiency in the pathogenesis of PFBC.

Deficiency in WDFY4 reduces the number of CD8+ T cells via reactive oxygen species-induced apoptosis.

WDFY4 (WD repeat and FYVE domain-containing 4) is a susceptibility gene involved in several autoimmune diseases and plays an important role in the immune system. However, it is not clear how WDFY4 affects T cells. We have generated a Wdfy4-knockout mouse and found that selective deficiency of Wdfy4 in T cells led to a reduction in the number of CD8+ T cells in the periphery, thus promoting tumor growth when mice were challenged with a transplantable tumor. Moreover, conditional ablation of Wdfy4 in T cells enhanced the apoptosis of CD8+ T cells and increased the intracellular levels of reactive oxygen species accompanied by the upregulation of Nox2. Mechanistically, the decrease in the CD8+ T-cell numbers in Wdfy4-knockout mice was associated with activation of the p53 pathway and inhibition of the extracellular signal-regulated kinase pathway. In addition, WDFY4 participated in cell proliferation. In conclusion, our results elucidate the biological role of WDFY4 in apoptosis and establish a link between WDFY4 and T cells.

A SMOC2 variant inhibits BMP signaling by competitively binding to BMPR1B and causes growth plate defects.

Endochondral ossification is the major process of long bone formation, and chondrogenesis is the final step of this process. Several studies have indicated that bone morphogenetic proteins (BMPs) are required for chondrogenesis and regulate multiple growth plate features. Abnormal BMP pathways lead to growth plate defects, resulting in osteochondrodysplasia. The SPARC-related modular calcium binding 2 (SMOC2) gene encodes an extracellular protein that is considered to be an antagonist of BMP signaling. In this study, we generated a mouse model by knocking-in the SMOC2 mutation (c.1076 T > G), which showed short-limbed dwarfism, reduced, disorganized, and hypocellular proliferative zones and expanded hypertrophic zones in tibial growth plates. To determine the underlying pathophysiological mechanism of SMOC2 mutation, we used knock-in mice to investigate the interaction between SMOC2 and the BMP-SMAD1/5/9 signaling pathway in vivo and in vitro. Eventually, we found that mutant SMOC2 could not bind to COL9A1 and HSPG. Furthermore, mutant SMOC2 inhibited BMP signaling by competitively binding to BMPR1B, which lead to defects in growth plates and short-limbed dwarfism in knock-in mice.

A De Novo Frameshift Mutation in TNFAIP3 Impairs A20 Deubiquitination Function to Cause Neuropsychiatric Systemic Lupus Erythematosus.

PURPOSE: Genome-wide association study of systemic lupus erythematosus (SLE) revealed tumor necrosis factor alpha-induced protein 3 (TNFAIP3, A20) as a susceptibility gene. Here, we report a de novo mutation in TNFAIP3 in a Chinese patient with neuropsychiatric SLE (NPSLE). METHODS: Whole exome sequencing was performed for the patient and healthy members from the family. Suspected pathogenic variants were further analyzed and co-segregation was confirmed by Sanger sequencing. Real-time PCR and western blot were performed with peripheral blood mononuclear cells (PBMCs) and patient-derived T cells. Transfected HEK293T cells, human umbilical vein endothelial cells, normal human astrocytes, and microglia were used for in vitro studies. RESULTS: A de novo frameshift mutation in TNFAIP3 was found in the NPSLE patient. Western blot analysis showed activated NF-κB and mitogen-activated protein kinase pathways. Real-time PCR revealed elevated expression of pro-inflammatory cytokines. On immunoprecipitation assay, the mutant A20 altered the K63-linked ubiquitin level of TRAF6 via its ubiquitin-editing function. CONCLUSIONS: The mutant A20 may play a role in weakening the tight junction of the blood-brain barrier to cause neurologic symptoms. We report a rare variant of TNFAIP3 in a patient with NPSLE and reveal its autoimmune disease-causing mechanism in both peripheral tissues and the central nervous system.

Cervical Spinal Involvement in a Chinese Pedigree With Pontine Autosomal Dominant Microangiopathy and Leukoencephalopathy Caused by a 3' Untranslated Region Mutation of COL4A1 Gene.

Background and Purpose- Pontine autosomal dominant microangiopathy and leukoencephalopathy, a recently defined subtype of cerebral small vessel disease, is associated with mutations in COL4A1 (collagen type IV alpha 1 chain) 3' untranslated region. We here describe a pontine autosomal dominant microangiopathy and leukoencephalopathy pedigree with COL4A1 mutation presenting both pontine and cervical spinal cord involvement. Methods- For the diagnostic purpose, brain and spinal magnetic resonance imaging scanning, skin biopsy, and whole-exome sequencing were performed on the patients in the pedigree. Suspected pathogenic variants were further confirmed by cosegregation analysis using Sanger sequencing in the family members. Results- We identified a mutation located at the binding site of miR-29 (microRNA-29) in 3' untranslated region of COL4A1(c.*32G>A). The pontine autosomal dominant microangiopathy and leukoencephalopathy patients in this pedigree carried this variant, whereas other healthy family members but one did not. Magnetic resonance imaging showed lesions in the pons, white matter, and cervical spinal cord. Skin biopsy revealed thickened basal lamina in vessels. Conclusions- For the first time, we reported cervical spinal involvement in pontine autosomal dominant microangiopathy and leukoencephalopathy and expanded the clinical spectrum of this disease.

WDFY4 Is Involved in Symptoms of Systemic Lupus Erythematosus by Modulating B Cell Fate via Noncanonical Autophagy.

Genome-wide association studies have recently illuminated that WDFY4 is genetically associated with systemic lupus erythematosus (SLE) susceptibility in various ethnic groups. Despite strong genetic evidence suggesting a role of WDFY4 in SLE pathogenesis, its functional relevance is largely unknown. In this study, we generated Wdfy4 B lymphocyte conditional knockout (Wdfy4-CKO) mice and found that loss of Wdfy4 led to a decrease in number of total B cells and several subpopulations of B cells in the periphery and a defect in the transition from the pro- to pre-B cell stage in bone marrow. Also, Wdfy4-CKO mice showed impaired Ab responses as compared with controls when challenged with Ag. SLE phenotypes were effectively alleviated in Wdfy4-CKO mice, with significantly diminished pristane-elicited production of autoantibodies and glomerulonephritis. Genetic silencing of WDFY4 in B cells increased lipidation of LC3 independent of p62 and Beclin1, which are essential proteins of canonical autophagy. Our in vivo and in vitro data suggest that WDFY4 facilitates noncanonical autophagic activity. Our findings provide a novel functional link underlying the mechanism of SLE in which WDFY4 influences B cell fate via noncanonical autophagy.

Whole-Genome Linkage Analysis with Whole-Exome Sequencing Identifies a Novel Frameshift Variant in NEFH in a Chinese Family with Charcot-Marie-Tooth 2: A Novel Variant in NEFH for Charcot-Marie-Tooth 2.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is the most common neurodegenerative disorder of the peripheral nervous system. More than 50 genes/loci were found associated with the disease. We found a family with autosomal-dominant CMT2. OBJECTIVE: To reveal the pathogenic gene of the family and further investigate the function of the variant. METHODS: DNA underwent whole-genome linkage analysis for all family members and whole-exome sequencing for 2 affected members. Neurofilament light polypeptide and wild-type or mutant neurofilament heavy polypeptide (NEFH) were co-transfected into SW13 (vim-) cells. The nefh-knockdown zebrafish model was produced by using morpholino antisense oligonucleotides. RESULTS: We identified a novel insertion variant (c.3057insG) in NEFH in the family. The variant led to the loss of a stop codon and an extended 41 amino acids in the protein. Immunofluorescence results revealed that mutant NEFH disrupted the neurofilament network and induced aggregation of NEFH protein. Knockdown of nefh in zebrafish caused a slightly or severely curled tail. The motor ability of nefh-knockdown embryos was impaired or even absent, and the embryos showed developmental defects of axons in motor neurons. The abnormal phenotype and axonal developmental defects could be rescued by injection of human wild-type but not human mutant NEFH mRNA. CONCLUSIONS: We identified a novel stop loss variant in NEFH that is likely pathogenic for CMT2, and the results provide further evidence for the role of an aberrant assembly of neurofilament in CMT.

Caspase-1 inhibitor ameliorates experimental autoimmune myasthenia gravis by innate dendric cell IL-1-IL-17 pathway.

BACKGROUND: IL-1ß has been shown to play a pivotal role in autoimmunity. Cysteinyl aspartate-specific proteinase-1 (caspase-1) inhibitor may be an important drug target for autoimmune diseases. However, the effects of caspase-1 inhibitor on myasthenia gravis (MG) remain undefined. METHODS: To investigate the effects of caspase-1 inhibitor on experimental autoimmune myasthenia gravis (EAMG), an animal model of MG, caspase-1 inhibitor was administered to Lewis rats immunized with region 97-116 of the rat AChR α subunit (R97-116 peptide) in complete Freund's adjuvant. The immunophenotypical characterization by flow cytometry and the levels of autoantibody by ELISA were carried out to evaluate the neuroprotective effect of caspase-1 inhibitor. RESULTS: We found that caspase-1 inhibitor improved EAMG clinical symptom, which was associated with decreased IL-17 production by CD4+ T cells and γδ T cells, lower affinity of anti-R97-116 peptide IgG. Caspase-1 inhibitor decreased expression of CD80, CD86, and MHC class II on DCs, as well as intracellular IL-1ß production from DCs. In addition, caspase-1 inhibitor treatment inhibited R97-116 peptide-specific cell proliferation and decreased follicular helper T cells relating to EAMG development. CONCLUSIONS: Our results suggest that caspase-1 inhibitor ameliorates experimental autoimmune myasthenia gravis by innate DC IL-1-IL-17 pathway and provides new evidence that caspase-1 is an important drug target in the treatment of MG and other autoimmune diseases.