Extracellular ADP augments microglial inflammasome and NF-κB activation via the P2Y12 receptor.

The NLRP3 inflammasome is a molecular complex that translates signals from pathogens and tissue damage into inflammatory responses, and plays crucial roles in numerous neurological diseases. Activation of the NLRP3 inflammasome leads to caspase-1 dependent cleavage of pro-IL-1ß to form mature IL-1ß. By acting on the P2X7 purinergic receptor, extracellular ATP is one of the major stimuli that activates the NLRP3 inflammasome. Although microglia express multiple purinergic receptors, their roles in inflammasome-mediated inflammation are largely unknown. We studied the role of the P2Y12 receptor, a metabotropic P2Y receptor enriched in microglia, on inflammation in vitro. Inhibition of the microglial P2Y12 receptor by PSB0739 or siRNA knockdown suppressed IL-1ß release. P2Y12 receptor-deficient microglia displayed markedly attenuated IL-1ß mRNA expression and release. P2Y12 receptor blockade also suppressed IL-6 production. Both IL-1ß and IL-6 responses were augmented by extracellular ADP or ADP-ßS and were abrogated by PSB0739. Mechanistically, ADP-ßS potentiated NF-κB activation. In addition, ADP altered mitochondrial membrane potential in combination with ATP and increased the number of caspase-1 positive cells through the P2Y12 receptor. These results elucidate a novel inflammatory mechanism by which extracellular ADP acts on the P2Y12 receptor to activate NF-κB and the NLRP3 inflammasome to enhance microglial inflammation.

Long-Term Evaluation of Low-Dose Betamethasone for Ataxia Telangiectasia.

BACKGROUND: Ataxia telangiectasia is an autosomal recessive disorder characterized by cerebellar ataxia, telangiectases, immune defects, and a predisposition to malignancy. Quality of life is severely impaired by neurological symptoms. However, curative options for the neurological symptoms are limited. Recent studies have demonstrated short-term improvement in neurological symptoms with betamethasone therapy. However, the long-term and adverse effects of betamethasone are unclear. The aim of this study was to evaluate the long-term effects, benefits, and adverse effects of low-dose betamethasone in ataxia telangiectasia. METHODS: Six patients with ataxia telangiectasia received betamethasone at 0.02 mg/kg/day for two years. After cessation of betamethasone, the patients were observed for two additional years. Neurological assessments were performed, and adverse effects were monitored every three months throughout the four-year study period. RESULTS: Transient improvement of neurological symptom was observed in five of the six patients. However, after two years betamethasone treatment, only one of the six patients showed a slight improvement in the neurological score, one patient showed no change, and the neurological scores of the remaining four patients deteriorated. After the cessation of betamethasone treatment, neurological symptoms worsened in all patients. As an adverse effect of betamethasone, transient adrenal dysfunction was observed in all cases. CONCLUSIONS: Although these findings are in agreement with previous studies suggesting that short-term betamethasone treatment transiently benefits patients with ataxia telangiectasia, the long-term benefits and risks should be carefully considered.

A novel splicing mutation in SLC9A6 in a boy with Christianson syndrome.

A loss of function mutation in SLC9A6 (Xq26.3) is responsible for Christianson syndrome in males. We identified a novel splicing mutation (NM_006359.2:c.1141-8C>A) of SLC9A6 in a seven-year-old boy with microcephaly, severe developmental delay, and intractable epilepsy. Functional analysis found multiple aberrant transcripts, none of which maintained the canonical open reading frame. Computer prediction tools, however, failed to detect all of the aberrant transcripts.

Infantile-onset spinocerebellar ataxia type 5 associated with a novel SPTBN2 mutation: A case report.

BACKGROUND: Spinocerebellar ataxia type 5 (SCA5), a dominant spinocerebellar ataxia is caused by spectrin beta nonerythrocytic 2 gene (SPTBN2) mutation. It typically consists of a slow progressive cerebellar ataxia with an onset principally in adulthood. Here, we report on the first Japanese patient with infantile-onset SCA5 associated with a novel heterozygous SPTBN2 mutation. CASE REPORT: The patient, a 6-year-old girl, developed delayed motor development and unsteady arm movement during infancy. She also showed gaze-evoked nystagmus, saccadic eye pursuit, dysarthria, dysmetria, intention tremor and mild intellectual disability. Brain MRI revealed moderate cerebellar atrophy and mild pontine atrophy. Comprehensive target capture sequencing to identify the causative gene identified a novel missense mutation in SPTBN2 (c.1309C

Genetic analysis of undiagnosed ataxia-telangiectasia-like disorders.

OBJECTIVES: Defects in DNA damage responses or repair mechanisms cause numerous rare inherited diseases, referred to as "DNA-repair defects" or "DNA damage deficiency", characterized by neurodegeneration, immunodeficiency, and/or cancer predisposition. Early accurate diagnosis is important for informing appropriate clinical management; however, diagnosis is frequently challenging and can be delayed, due to phenotypic heterogeneity. Comprehensive genomic analysis could overcome this disadvantage. The objectives of this study were to determine the prevalence of ataxia-telangiectasia (A-T) and A-T-like DNA-repair defects in Japan and to determine the utility of comprehensive genetic testing of presumptively diagnosed patients in facilitating early diagnosis. METHODS: A nationwide survey of diseases presumably caused by DNA-repair defects, including A-T, was performed. Additionally, comprehensive next-generation sequencing (NGS) analysis, targeting known disease-causing genes, was conducted. RESULTS: Sixty-three patients with A-T or other diseases with characteristics of DNA-repair defects were identified. Thirty-four patients were genetically or clinically definitively diagnosed with A-T (n = 22) or other DNA-repair defects (n = 12). Genetic analysis of 17 presumptively diagnosed patients revealed one case of ataxia with oculomotor apraxia type 1 (AOA1); one ataxia with oculomotor apraxia type 2 (AOA2); two types of autosomal dominant spinocerebellar ataxia (SCA5, SCA29); two CACNA1A-related ataxias; one microcephaly with or without chorioretinopathy, lymphedema, or mental retardation (MCLMR); and one autosomal dominant KIF1A-related disorder with intellectual deficit, cerebellar atrophy, spastic paraparesis, and optic nerve atrophy. The diagnostic yield was 58.8%. CONCLUSION: Comprehensive genetic analysis of targeted known disease-causing genes by NGS is a powerful diagnostic tool for subjects with indistinguishable neurological phenotypes resembling DNA-repair defects.

Targeting the enhanced ER stress response in Marinesco-Sjögren syndrome.

BACKGROUND AND OBJECTIVE: Marinesco-Sjögren syndrome (MSS) is an autosomal recessive infantile-onset disorder characterized by cataracts, cerebellar ataxia, and progressive myopathy caused by mutation of SIL1. In mice, a defect in SIL1 causes endoplasmic reticulum (ER) chaperone dysfunction, leading to unfolded protein accumulation and increased ER stress. However, ER stress and the unfolded protein response (UPR) have not been investigated in MSS patient-derived cells. METHODS: Lymphoblastoid cell lines (LCLs) were established from four MSS patients. Spontaneous and tunicamycin-induced ER stress and the UPR were investigated in MSS-LCLs. Expression of UPR markers was analyzed by western blotting. ER stress-induced apoptosis was analyzed by flow cytometry. The cytoprotective effects of ER stress modulators were also examined. RESULTS: MSS-LCLs exhibited increased spontaneous ER stress and were highly susceptible to ER stress-induced apoptosis. The inositol-requiring protein 1α (IRE1α)-X-box-binding protein 1 (XBP1) pathway was mainly upregulated in MSS-LCLs. Tauroursodeoxycholic acid (TUDCA) attenuated ER stress-induced apoptosis. CONCLUSION: MSS patient-derived cells exhibit increased ER stress, an activated UPR, and susceptibility to ER stress-induced death. TUDCA reduces ER stress-induced death of MSS patient-derived cells. The potential of TUDCA as a therapeutic agent for MSS could be explored further in preclinical studies.

ATM Regulates Adipocyte Differentiation and Contributes to Glucose Homeostasis.

Ataxia-telangiectasia (A-T) patients occasionally develop diabetes mellitus. However, only limited attempts have been made to gain insight into the molecular mechanism of diabetes mellitus development in A-T patients. We found that Atm-/- mice were insulin resistant and possessed less subcutaneous adipose tissue as well as a lower level of serum adiponectin than Atm+/+ mice. Furthermore, in vitro studies revealed impaired adipocyte differentiation in Atm-/- cells caused by the lack of induction of C/EBPα and PPARγ, crucial transcription factors involved in adipocyte differentiation. Interestingly, ATM was activated by stimuli that induced differentiation, and the binding of ATM to C/EBPß and p300 was involved in the transcriptional regulation of C/EBPα and adipocyte differentiation. Thus, our study sheds light on the poorly understood role of ATM in the pathogenesis of glucose intolerance in A-T patients and provides insight into the role of ATM in glucose metabolism.

Myoclonic axial jerks for diagnosing atypical evolution of ataxia telangiectasia.

BACKGROUND: Ataxia telangiectasia (A-T) is a common inherited cause of early childhood-onset ataxia, distinguished by progressive cerebellum malfunction, capillary vessel extension, and immunodeficiency. The diagnosis of A-T is sometimes difficult to establish in patients with atypical clinical evolution. CASE REPORT: We experienced a pediatric 12-years-old female patient, who was finally diagnosed with classic A-T, demonstrating progressive dystonic-myoclonic axial jerks with ataxia as a predominant clinical feature. Oculocutaneous telangiectasias and immune status were unremarkable. Her myoclonic jerks were spontaneous or stimulus-sensitive, and partially ameliorated by levodopa treatment, but the ataxia was slowly progressive. A laboratory examination showed moderate atrophy of the vermis and cerebellum on brain magnetic resonance imaging, elevated serum alpha fetoprotein (AFP) levels, and total absence of A-T mutated (ATM) protein activity. We subsequently confirmed compound heterozygous truncating mutations of the ATM gene in this patient. CONCLUSION: Our findings highlight the importance of recognizing dystonic-myoclonic jerks as one of the extrapyramidal signs of classic A-T. Measurement of AFP levels should be considered in patients with unexplained myoclonic jerk movements with ataxia in whom definitive diagnoses are not identified. Physicians should be aware that there are cases where typical findings of A-T may not be fulfilled.

Whole-exome sequence analysis of ataxia telangiectasia-like phenotype.

A number of diseases exhibit neurodegeneration with/without additional symptoms such as immunodeficiency, increased cancer risk, and microcephalus. Ataxia telangiectasia and Nijmegen breakage syndrome, for example, develop as a result of mutations in genes involved in the DNA damage response. However, such diseases can be difficult to diagnose as they are only rarely encountered by physicians. To overcome this challenge, nine patients with symptoms that resemble those of ataxia telangiectasia, including neurodegeneration, hypogammaglobulinemia, telangiectasia, and/or elevated serum α-fetoprotein, were subjected to whole-exome sequencing (WES) to identify the causative mutations. Molecular diagnosis was achieved in two patients: one displayed CD40 ligand (CD40LG) deficiency, while a second showed a homozygous SIL1 mutation, which has been linked to Marinesco-Sjögren syndrome (MSS). Typical features of CD40LG deficiency and MSS are distinct from the symptoms usually seen in ataxia telangiectasia. These dissociations between phenotype and genotype make it difficult to achieve molecular diagnosis of orphan diseases. Whole-exome sequencing analyses will assist in the molecular diagnosis of such cases and allow the identification of genotypes that would not be expected from the phenotype.