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 newly recognized ataxia-ocular apraxia 1 (AOA1; MIM 208920) is the most frequent cause of autosomal recessive ataxia in Japan and is second only to Friedreich ataxia in Portugal. It shares several neurological features with ataxia-telangiectasia, including early onset ataxia, oculomotor apraxia and cerebellar atrophy, but does not share its extraneurological features (immune deficiency, chromosomal instability and hypersensitivity to X-rays). AOA1 is also characterized by axonal motor neuropathy and the later decrease of serum albumin levels and elevation of total cholesterol. We have identified the gene causing AOA1 and the major Portuguese and Japanese mutations. This gene encodes a new, ubiquitously expressed protein that we named aprataxin. This protein is composed of three domains that share distant homology with the amino-terminal domain of polynucleotide kinase 3'- phosphatase (PNKP), with histidine-triad (HIT) proteins and with DNA-binding C2H2 zinc-finger proteins, respectively. PNKP is involved in DNA single-strand break repair (SSBR) following exposure to ionizing radiation and reactive oxygen species. Fragile-HIT proteins (FHIT) cleave diadenosine tetraphosphate, which is potentially produced during activation of the SSBR complex. The results suggest that aprataxin is a nuclear protein with a role in DNA repair reminiscent of the function of the protein defective in ataxia-telangiectasia, but that would cause a phenotype restricted to neurological signs when mutant.
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PMID:The gene mutated in ataxia-ocular apraxia 1 encodes the new HIT/Zn-finger protein aprataxin. 1158

Maintenance of genome stability is essential for keeping cellular homeostasis. The DNA damage response is a central component in maintaining genome integrity. Among of the most cytotoxic DNA lesions are double strand breaks (DSBs) caused by ionizing radiation or radiomimetic chemicals. ATM is missing or inactivated in patients with ataxia-telangiectasia. Ataxia-telangiectasia patients display a pleiotropic phenotype and suffer primarily from progressive ataxia caused by degeneration of cerebellar Purkinje and granule neurons. Additional features are immunodeficiency, genomic instability, radiation sensitivity, and cancer predisposition. Disruption of the mouse Atm locus creates a murine model of ataxia-telangiectasia that exhibits most of the clinical features of the human disease but very mild neuronal abnormality. The ATM protein is a multifunctional protein kinase, which serves as a master regulator of cellular responses to DSBs. There is growing evidence that ATM may be involved in addition to the DSB response in other processes that maintain processes in cellular homeostasis. For example, mounting evidence points to increased oxidative stress in the absence of ATM. Here we report that the AP-1 pathway is constantly active in the brains of Atm-deficient mice not treated with DNA damaging agents. A canonical activation (increased phosphorylation of mitogen-activated protein kinase kinase-4, c-Jun N-terminal kinase, and c-Jun) of the AP-1 pathway was found in Atm-deficient cerebra, whereas induction of the AP-1 pathway in Atm-deficient cerebella is likely to mediate elevated expression of c-Fos and c-Jun. Although Atm(+/+) mice are capable of responding to ionizing radiation by activating stress responses such as the AP-1 pathway, Atm-deficient mice display higher basal AP-1 activity but gradually lose their ability to activate AP-1 DNA-binding activity in response to ionizing radiation. Our results further demonstrate that inactivation of the ATM gene results in a state of constant stress.
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PMID:Contribution of the Atm protein to maintaining cellular homeostasis evidenced by continuous activation of the AP-1 pathway in Atm-deficient brains. 1249 86

We describe MRI of the brain in 19 patients with ataxia-telangiectasia (AT) and correlate the appearances with the degree of neurologic deficit. We examined 10 male and nine female patients; 17 were aged between 2 and 12 years (mean 8 years) but a woman and her brother were 35 and 38 years old, and had a variant of AT. Ataxia was the first recognized sign of the disease in every patient. We detected the following patterns of cerebellar atrophy: in the youngest patient, aged 2 years, the study was normal; in the five next youngest patients 3-7 years of age, the lateral cerebellum and superior vermis showed the earliest changes of atrophy; and all but one of the other patients had moderate to marked diffuse atrophy of vermis and cerebellar hemispheres. There were 12 patients aged 9 years and above; one, who was normal, was 9 years old. The five patients who at the time of examination were unable to walk all had diffuse atrophy involving both vermis and cerebellar hemispheres.
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PMID:Ataxia-telangiectasia: the pattern of cerebellar atrophy on MRI. 1274 Jul 24

Much progress has been made in the early diagnosis of ataxia-telangiectasia since the gene was cloned in 1995, A clinical diagnosis can now be confirmed by radiosensitivity testing (colony survival assay), immunoblotting, and mutation detection. The diagnostic value of serum alpha-fetoprotein levels and radiosensitivity has been reevaluated using patients with diagnoses based on the presence of mutations in the ATM gene and the absence of ATM protein in nuclear extracts. Little progress has been made in treating the progressive ataxia.
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PMID:Ataxia-telangiectasia: diagnosis and treatment. 1465 5

The pleiotropic nature of the clinical phenotypes of patients with ataxia-telangiectasia (A-T)--which encompass cerebellar degeneration (leading to ataxia), gonadal atrophy, and cancer predisposition--suggests multiple functions of the gene responsible for the disease. The ataxia-telangiectasia mutated gene product (ATM), whose loss of function is responsible for ataxia-telangiectasia, is a protein kinase that interacts with several substrates and is implicated in mitogenic signal transduction, chromosome condensation, meiotic recombination, cell-cycle control and telomere maintenance. This review focuses on the critical roles that ATM appears to play in cell-cycle checkpoints, DNA repair, telomere metabolism and oxidative stress, indicating how defects in these processes might lead to ataxia-telangiectasia.
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PMID:A multifaceted role for ATM in genome maintenance. 1498 98

Ataxia-oculomotor apraxia (AOA1) is a neurological disorder with symptoms that overlap those of ataxia-telangiectasia, a syndrome characterized by abnormal responses to double-strand DNA breaks and genome instability. The gene mutated in AOA1, APTX, is predicted to code for a protein called aprataxin that contains domains of homology with proteins involved in DNA damage signalling and repair. We demonstrate that aprataxin is a nuclear protein, present in both the nucleoplasm and the nucleolus. Mutations in the APTX gene destabilize the aprataxin protein, and fusion constructs of enhanced green fluorescent protein and aprataxin, representing deletions of putative functional domains, generate highly unstable products. Cells from AOA1 patients are characterized by enhanced sensitivity to agents that cause single-strand breaks in DNA but there is no evidence for a gross defect in single-strand break repair. Sensitivity to hydrogen peroxide and the resulting genome instability are corrected by transfection with full-length aprataxin cDNA. We also demonstrate that aprataxin interacts with the repair proteins XRCC1, PARP-1 and p53 and that it co-localizes with XRCC1 along charged particle tracks on chromatin. These results demonstrate that aprataxin influences the cellular response to genotoxic stress very likely by its capacity to interact with a number of proteins involved in DNA repair.
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PMID:Aprataxin, a novel protein that protects against genotoxic stress. 1504 83

Ataxia-oculomotor apraxia 1 (AOA1) is an autosomal recessive neurodegenerative disease that is reminiscent of ataxia-telangiectasia (A-T). AOA1 is caused by mutations in the gene encoding aprataxin, a protein whose physiological function is currently unknown. We report here that, in contrast to A-T, AOA1 cell lines exhibit neither radioresistant DNA synthesis nor a reduced ability to phosphorylate downstream targets of ATM following DNA damage, suggesting that AOA1 lacks the cell cycle checkpoint defects that are characteristic of A-T. In addition, AOA1 primary fibroblasts exhibit only mild sensitivity to ionising radiation, hydrogen peroxide, and methyl methanesulphonate (MMS). Strikingly, however, aprataxin physically interacts in vitro and in vivo with the DNA strand break repair proteins XRCC1 and XRCC4. Aprataxin possesses a divergent forkhead associated (FHA) domain that closely resembles the FHA domain present in polynucleotide kinase, and appears to mediate the interactions with CK2-phosphorylated XRCC1 and XRCC4 through this domain. Aprataxin is therefore physically associated with both the DNA single-strand and double-strand break repair machinery, raising the possibility that AOA1 is a novel DNA damage response-defective disease.
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PMID:The ataxia-oculomotor apraxia 1 gene product has a role distinct from ATM and interacts with the DNA strand break repair proteins XRCC1 and XRCC4. 1538 Jan 5

Nijmegen breakage syndrome (NBS), ataxia telangiectasia and ataxia telangiectasia-like disorder (ATLD) show overlapping phenotypes such as growth retardation, microcephaly, cerebellar developmental defects and ataxia. However, the molecular pathogenesis of these neurological defects remains elusive. Here we show that inactivation of the Nbn gene (also known as Nbs1) in mouse neural tissues results in a combination of the neurological anomalies characteristic of NBS, ataxia telangiectasia and ATLD, including microcephaly, growth retardation, cerebellar defects and ataxia. Loss of Nbn causes proliferation arrest of granule cell progenitors and apoptosis of postmitotic neurons in the cerebellum. Furthermore, Nbn-deficient neuroprogenitors show proliferation defects (but not increased apoptosis) and contain more chromosomal breaks, which are accompanied by ataxia telangiectasia mutated protein (ATM)-mediated p53 activation. Notably, depletion of p53 substantially rescues the neurological defects of Nbn mutant mice. This study gives insight into the physiological function of NBS1 (the Nbn gene product) and the function of the DNA damage response in the neurological anomalies of NBS, ataxia telangiectasia and ATLD.
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PMID:An essential function for NBS1 in the prevention of ataxia and cerebellar defects. 1587 49

We report four patients with ataxia-telangiectasia syndrome that presented varied neurologic evolution. Three patients initially presented neurologic alterations of slow progression, evolving to late immunocompromised conditions. The fourth patient presented, from symptom onset, immune and neurologic debilitation, that were both severe and of fast progression. The chronological sequence of the most commonly observed immunocompromised conditions were in our patients, in ascending order, IgA deficiency, IgG2 deficiency and the neutrophil phagocytosis stage and common variable immunodeficiency. The first two reports are of sisters in whom the diagnosis was done between the ages of three and six years, having ocular apraxia, cerebellar ataxia and telangiectasia. Slow progression of neurologic debilitation was observed, without presentation of intermittent infections. The patients began presenting accentuated immunocompromised conditions at the ages of 14 and 17 years, dying at the ages of 16 and 20 years, respectively, due to severe infections that were resistant to treatment. The diagnosis of the third case was established when the patient was two years old, presenting ataxia and telangiectasia. Syndrome progression was slow, presenting at the age of eight years more accentuated neurologic disorders and IgA deficiency. The fourth case presented significant neurologic compromise at the age of five, simultaneous to IgA and IgG2 deficiency, and repeating pneumonias and sinusitis. At this time, intravenous gammaglobulin reposition was done. The neurologic and immune disorders progressed rapidly, and at the age of eight presented the inability to walk. At this time inversion of the CD4/CD8 ration was verified through laboratory tests.
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PMID:Different clinical and laboratory evolutions in ataxia-telangiectasia syndrome: report of four cases. 1604 57

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


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