Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The number of patients with spinocerebellar degeneration (SCD) has recently exceeds 20,000 in Japan. Among them, sporadic form is the most common form (67.2%). Among the hereditary forms of SCD, autosomal dominant (AD) form comprises 27.0%, while autosomal recessive (AR) form is rare (1.8%). Because of the rare occurrence of AR-SCD, the molecular genetic studies have been difficult to conduct. Recent progresses in molecular genetics, however, have enabled identification of causative genes for the majority of AR-SCD. Although Friedreich's ataxia is the most representative form of AR-SCD, patients with molecular diagnosis of Friedreich's ataxia have not been described in the Japanese population. Among the various forms of AR-SCD, early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH) seems to be the most common form in the Japanese population. Aprataxin, the causative gene for EAOH, has been suggested to play a role in the single strand DNA break repair. Interestingly, abnormalities in DNA break repair processes have been implicated in several forms of AR-SCD including AOA2, SCAN1 and ataxia telangiectasia. In this group of AR-SCD, cerebellar atrophy is more marked compared to that observed in Friedreich's ataxia. Taken together, abnormalities in DNA break repair processes may play an essential role in cerebellar degeneration in this group of AR-SCD.
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PMID:[Clinical features and molecular genetics of autosomal recessive spinocerebellar degenerations]. 1565 Dec 91

Autosomal recessive cerebellar ataxias (ARCAs) are a phenotypically and genetically heterogeneous group of diseases. Recently, a subgroup of ARCA associated with oculomotor apraxia (AOA) has been delineated. It includes at least four distinct genetic entities: ataxia-telangiectasia, ataxia-telangiectasia-like disorder, and ataxia with oculomotor apraxia type 1 (AOA1) and type 2 (AOA2). The phenotypes share several similarities, and the responsible genes, ATM, MRE11, APTX, and SETX, respectively, are all implicated in DNA break repair. As in many other DNA repair deficiencies, neurodegeneration is a hallmark of these diseases. Recently, the genes for two new autosomal recessive cerebellar ataxias with oculomotor apraxia, AOA1 and AOA2, were identified. Here, we report the phenotypic characteristics, genetic characteristics, and the recent advances concerning AOA1 and AOA2.
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PMID:New autosomal recessive cerebellar ataxias with oculomotor apraxia. 1613 25

A subgroup of autosomal recessive cerebellar ataxias (ARCAs) associated with oculomotor apraxia (OMA) and other variable features has been reported. Ataxia-oculomotor apraxia types 1 and 2 (AOA1 and AOA2) belong to this subgroup and have been described in adults with early onset cerebellar ataxia. AOA1 is associated with oculomotor apraxia, severe sensorimotor neuropathy, choreiform movements, cognitive impairment, and cerebellar atrophy at an early age. We describe a male child with AOA1 who is homozygous for the G837A (W279X) mutation in the APTX gene. He presented at the age of 3 years 6 months with some atypical features including absence of OMA, chorea, and cerebellar atrophy. These manifestations, in addition to peripheral neuropathy, appeared at 8 years of age. We highlight the importance of considering the diagnosis of AOA1 in children with early-onset cerebellar ataxia, once other well-known disorders such as Friedreich's ataxia and ataxia-telangiectasia have been excluded.
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PMID:Atypical presentation of ataxia-oculomotor apraxia type 1. 1670 Sep 49

Autosomal recessive cerebellar ataxias (ARCA) are a heterogeneous group of rare neurological disorders involving both central and peripheral nervous system, and in some case other systems and organs, and characterized by degeneration or abnormal development of cerebellum and spinal cord, autosomal recessive inheritance and, in most cases, early onset occurring before the age of 20 years. This group encompasses a large number of rare diseases, the most frequent in Caucasian population being Friedreich ataxia (estimated prevalence 2-4/100,000), ataxia-telangiectasia (1-2.5/100,000) and early onset cerebellar ataxia with retained tendon reflexes (1/100,000). Other forms ARCA are much less common. Based on clinicogenetic criteria, five main types ARCA can be distinguished: congenital ataxias (developmental disorder), ataxias associated with metabolic disorders, ataxias with a DNA repair defect, degenerative ataxias, and ataxia associated with other features. These diseases are due to mutations in specific genes, some of which have been identified, such as frataxin in Friedreich ataxia, alpha-tocopherol transfer protein in ataxia with vitamin E deficiency (AVED), aprataxin in ataxia with oculomotor apraxia (AOA1), and senataxin in ataxia with oculomotor apraxia (AOA2). Clinical diagnosis is confirmed by ancillary tests such as neuroimaging (magnetic resonance imaging, scanning), electrophysiological examination, and mutation analysis when the causative gene is identified. Correct clinical and genetic diagnosis is important for appropriate genetic counseling and prognosis and, in some instances, pharmacological treatment. Due to autosomal recessive inheritance, previous familial history of affected individuals is unlikely. For most ARCA there is no specific drug treatment except for coenzyme Q10 deficiency and abetalipoproteinemia.
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PMID:Autosomal recessive cerebellar ataxias. 1711 70

A defective response to DNA damage is observed in several human autosomal recessive ataxias with oculomotor apraxia, including ataxia-telangiectasia. We report that senataxin, defective in ataxia oculomotor apraxia (AOA) type 2, is a nuclear protein involved in the DNA damage response. AOA2 cells are sensitive to H2O2, camptothecin, and mitomycin C, but not to ionizing radiation, and sensitivity was rescued with full-length SETX cDNA. AOA2 cells exhibited constitutive oxidative DNA damage and enhanced chromosomal instability in response to H2O2. Rejoining of H2O2-induced DNA double-strand breaks (DSBs) was significantly reduced in AOA2 cells compared to controls, and there was no evidence for a defect in DNA single-strand break repair. This defect in DSB repair was corrected by full-length SETX cDNA. These results provide evidence that an additional member of the autosomal recessive AOA is also characterized by a defective response to DNA damage, which may contribute to the neurodegeneration seen in this syndrome.
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PMID:Senataxin, defective in ataxia oculomotor apraxia type 2, is involved in the defense against oxidative DNA damage. 1756 89

Autosomal recessive cerebellar ataxias are a phenotypically and genetically heterogeneous group of diseases. Major forms can be distinguished on the basis of clinical signs, age of onset, biochemical parameters or genotypes. To develop rational diagnostic strategies, phenotypic information, e.g., age of onset combined with population-specific disease frequencies could be highly favourable. We tested this hypothesis for single candidate loci and mutations in North European ataxia patients with juvenile and early adult onset. While we could prove that Friedreich ataxia (FRDA) is frequent in Germany, only few patients with ataxia-oculomotor apraxia type 1 (AOA1) and type 2 (AOA2) were diagnosed. The frequency of the mitochondrial recessive ataxia syndrome (MIRAS) and the infantile onset spinocerebellar ataxia (IOSCA) in this population remains unknown since no case with the common mutation of the corresponding gene was detected.
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PMID:Investigation of recessive ataxia loci in patients with young age of onset. 1805 31

Ataxia with oculomotor apraxia (AOA) type 2 (AOA2 MIM 606002) is a recessive subtype of AOA characterized by cerebellar atrophy, oculomotor apraxia, early loss of reflexes, and peripheral neuropathy. Various mutations either in homozygous or compound heterozygous condition were so far identified in the associated gene SETX (MIM 608465). SETX encodes a large protein called senataxin with a DNA-RNA helicase domain and a putative N-terminus protein interaction domain. Here, we report the identification of two novel homozygous mutations in SETX gene, c.340_342delCTT (p.L114Del) and c.1669C > T (p.R557X), in two AOA2 families. The characterization of the mutant lymphoblastoid cell lines for sensitivity to oxidative DNA-damaging agents indicates that the p.L114Del deletion confers an increased sensitivity to H2O2, camptothecin, and mitomycin C, previously found to induce death in lymphoblasts harbouring other SETX mutations; the cells carrying the nonsense mutation display instead values within the normal range. Further analysis of a neuronal cell model SKNBE, transfected with the mutant senataxin proteins, reveals increased sensitivity also to staurosporine and excitotoxicity associated with the p.L114Del mutant only. We also demonstrate that the sensitizing effect of p.L114Del on apoptosis can be reversed by senataxin silencing. The ability of a single amino acid deletion to sensitize cells to death by different agents, compared to the lack of effect of a whole protein deletion, seems to exclude a protective role played by the native protein while suggesting that a specific mutation confers to the protein the ability to enhance the toxic effect of various cell damaging agents.
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PMID:Characterization of two novel SETX mutations in AOA2 patients reveals aspects of the pathophysiological role of senataxin. 1959 98

Spinocerebellar ataxia autosomal recessive 1 (SCAR1/AOA2) is clinically characterized by an early-onset progressive cerebellar ataxia with axonal neuropathy, ocular motor apraxia, and elevation of serum alpha-fetoprotein level. The disorder is caused by mutations in senataxin (SETX) gene. Here, we report a Japanese SCAR1/AOA2 family with a homozygous nonsense mutation (p.Q1441X) of SETX that was identified by exome sequencing. The family was previously reported as early-onset ataxia of undetermined cause. The present study emphasized the role of whole exome-sequence analysis to establish the molecular diagnosis of neurodegenerative disease presenting with diverse clinical presentations.
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PMID:Exome analysis reveals a Japanese family with spinocerebellar ataxia, autosomal recessive 1. 2378 67

Senataxin (SETX) is an RNA/DNA helicase implicated in transcription termination and the DNA damage response and is mutated in two distinct neurological disorders: AOA2 (ataxia oculomotor apraxia 2) and ALS4 (amyotrophic lateral sclerosis 4). Here we provide evidence that Rrp45, a subunit of the exosome, associates with SETX in a manner dependent on SETX sumoylation. We show that the interaction and SETX sumoylation are disrupted by SETX mutations associated with AOA2 but not ALS4. Furthermore, Rrp45 colocalizes with SETX in distinct foci upon induction of transcription-related DNA damage. Our results thus provide evidence for a SUMO-dependent interaction between SETX and the exosome, disrupted in AOA2, that targets the exosome to sites of DNA damage.
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PMID:A SUMO-dependent interaction between Senataxin and the exosome, disrupted in the neurodegenerative disease AOA2, targets the exosome to sites of transcription-induced DNA damage. 2410 44

Interest in senataxin biology began in 2004 when mutations were first identified in what was then a novel protein. Dominantly inherited mutations were documented in rare juvenile-onset, motor neuron disease pedigrees in a familial form of amyotrophic lateral sclerosis (ALS4), while recessive mutations were found to cause a severe early-onset ataxia with oculomotor apraxia (AOA2) that is actually the second most common recessive ataxia after Freidreich's ataxia. From earlier studies of sen1p, the yeast ortholog of senataxin, a range of important RNA processing functions have been attributed to this protein. Like sen1p, senataxin contains a helicase domain to interact with RNA and an amino-terminal domain for critical protein interactions. Senataxin also joins a group of important proteins responsible for maintaining RNA transcriptome homeostasis, including FUS, TDP-43, and SMN that can all cause familial forms of motor neuron disease (MND). Independent of this association, senataxin is gaining attention for its role in maintaining genomic stability. Senataxin has been shown to resolve R-Loop structures, which form when nascent RNA hybridizes to DNA, displacing the non-transcribed strand. But in cycling cells, senataxin is also found at nuclear foci during the S/G2 cell-cycle phase, and may function at sites of specific collision between components of the replisome and transcription machinery. Which of these important processes is most critical to prevent neurodegeneration remains unknown, but our evolving understanding of these processes will be crucial not only for understanding senataxin's role in neurological disease, but also in a number of fundamentally important cellular functions.
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PMID:Unwinding the role of senataxin in neurodegeneration. 2572 27


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