Sequence-specific RNA binding by a Nova KH domain: implications for paraneoplastic disease and the fragile X syndrome.
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The structure of a Nova protein K homology (KH) domain recognizing single-stranded RNA has been determined at 2.4 A resolution. Mammalian Nova antigens (1 and 2) constitute an important family of regulators of RNA metabolism in neurons, first identified using sera from cancer patients with the autoimmune disorder paraneoplastic opsoclonus-myoclonus ataxia (POMA). The structure of the third KH domain (KH3) of Nova-2 bound to a stem loop RNA resembles a molecular vise, with 5'-Ura-Cyt-Ade-Cyt-3' pinioned between an invariant Gly-X-X-Gly motif and the variable loop. Tetranucleotide recognition is supported by an aliphatic alpha helix/beta sheet RNA-binding platform, which mimics 5'-Ura-Gua-3' by making Watson-Crick-like hydrogen bonds with 5'-Cyt-Ade-3'. Sequence conservation suggests that fragile X mental retardation results from perturbation of RNA binding by the FMR1 protein. (+info)
RNA-binding analyses of HuC and HuD with the VEGF and c-myc 3'-untranslated regions using a novel ELISA-based assay.
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Human members of the ELAV family, referred to as ELAV-like proteins (ELPs), include HuC, HuD, Hel-N1 and HuR. These proteins bind to AU-rich elements in the 3'-untranslated regions (3'-UTRs) of many growth-related mRNAs, including c-myc and VEGF, and may participate in regulating the stability of these transcripts. Here, I have developed an enzyme-linked immunosorbent assay (ELISA) which can rapidly assess the RNA-protein-binding properties of ELPs. With this assay, I demonstrate that HuC and HuD bind to the VEGF 3'-UTR regulatory segment (VRS) and to the c- myc 3'-UTR in a specific and concentration-dependent pattern, with both proteins showing a greater affinity for the VRS. Further analysis of the VRS indicated that the binding affinity was greater for the 3'-end where the majority of AU motifs reside. Binding to the VRS could be competed by both proteins as well as a poly(U) ribohomopolymer. The binding could not be competed by other ribohomopolymers or serum from patients with high titer anti-HuD antibodies. In summary, this assay provides a rapid analysis of ELP-RNA binding which can be utilized for further characterization of RNA-binding properties and for identification of competitor molecules for in vivo functional analysis of ELPs. (+info)
Paraneoplastic limbic encephalitis: neurological symptoms, immunological findings and tumour association in 50 patients.
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Paraneoplastic limbic encephalitis (PLE) is a rare disorder characterized by personality changes, irritability, depression, seizures, memory loss and sometimes dementia. The diagnosis is difficult because clinical markers are often lacking, and symptoms usually precede the diagnosis of cancer or mimic other complications. The frequency of antineuronal antibodies in patients with PLE has not been investigated. We examined the neurological symptoms and the causal tumours in 50 patients with PLE to determine the utility of paraneoplastic antibodies and other tests. The diagnosis of PLE required neuropathological examination or the presence of the four following criteria: (i) a compatible clinical picture; (ii) an interval of <4 years between the development of neurological symptoms and tumour diagnosis; (iii) exclusion of other neuro-oncological complications; and (iv) at least one of the following: CSF with inflammatory changes but negative cytology; MRI demonstrating temporal lobe abnormalities; EEG showing epileptic activity in the temporal lobes. Of 1047 patients with neurological symptoms, whose sera or CSF were examined for paraneoplastic antibodies, 79 had the presumptive diagnosis of limbic encephalitis, dementia, cognitive dysfunction, or confusion. Fifty of these patients fulfilled our criteria for PLE. Pathological confirmation was obtained in 12 patients. The commonly associated neoplasms were of the lung (50%), testis (20%) and breast (8%). Neurological symptoms preceded the cancer diagnosis in 60% of patients (by a median of 3.5 months). Twenty-five of 44 (57%) patients with MRI studies had signal abnormalities in the limbic system. Thirty (60%) patients had antineuronal antibodies (18 anti-Hu, 10 anti-Ta, 2 anti-Ma), and 20 were antibody-negative or had uncharacterized antibodies (n = 4). The combination of symptoms, MRI findings and paraneoplastic antibodies established the diagnosis of PLE in 78% of the patients. Patients with anti-Hu antibodies usually had small-cell lung cancer (94%), multifocal neurological symptoms (78%) and a poor neurological outcome. Patients with anti-Ta (also called anti-Ma2) antibodies were young men with testicular tumours (100%), frequent hypothalamic involvement (70%) and a poor neurological outcome. In the group of patients without anti-Hu or anti-Ta antibodies, the tumour distribution was diverse, with cancer of the lung the most common (36%); 57% had positive MRI. Fifteen of 34 (44%) patients with a median follow-up of 8 months showed neurological improvement. Treatment of the tumour appeared to have more effect on the neurological outcome than the use of immune modulation. Improvement was observed in 38% of anti-Hu patients, 30% of anti-Ta patients and 64% of patients without these antibodies. (+info)
Autoantibodies to ganglionic acetylcholine receptors in autoimmune autonomic neuropathies.
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BACKGROUND: Idiopathic autonomic neuropathy is a severe, subacute disorder with a presumed autoimmune basis. It is indistinguishable from the subacute autonomic neuropathy that may accompany lung cancer or other tumors. Autoantibodies specific for nicotinic acetylcholine receptors in the autonomic ganglia are potentially pathogenic and may serve as serologic markers of various forms of autoimmune autonomic neuropathy. METHODS: We tested serum from 157 patients with a variety of types of dysautonomia. Immunoprecipitation assays with iodine-125-labeled epibatidine and solubilized human neuroblastoma acetylcholine receptors were used to detect autoantibodies that bound to or blocked ganglionic receptors. RESULTS: Ganglionic-receptor-binding antibodies were found in 19 of 46 patients with idiopathic or paraneoplastic autonomic neuropathy (41 percent), in 6 of 67 patients with postural tachycardia syndrome, idiopathic gastrointestinal dysmotility, or diabetic autonomic neuropathy (9 percent), and in none of 44 patients with other autonomic disorders. High levels of the binding antibodies correlated with more severe autonomic dysfunction (including the presence of tonic pupils). Levels of these antibodies decreased in patients who had clinical improvement. All seven patients with ganglionic-receptor-blocking antibodies had ganglionic-receptor-binding antibodies and had idiopathic or paraneoplastic autonomic neuropathy. CONCLUSIONS: Seropositivity for antibodies that bind to or block ganglionic acetylcholine receptors identifies patients with various forms of autoimmune autonomic neuropathy and distinguishes these disorders from other types of dysautonomia. The positive correlation between high levels of ganglionic-receptor antibodies and the severity of autonomic dysfunction suggests that the antibodies have a pathogenic role in these types of neuropathy. (+info)
Clinical outcome in adult onset idiopathic or paraneoplastic opsoclonus-myoclonus.
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We analysed a series of 24 adult patients with idiopathic (10 cases) and paraneoplastic (14 cases) opsoclonus-myoclonus syndrome (OMS) to ascertain possible differences in clinical course and response to immunotherapies between both groups. Associated tumours were small-cell lung cancer (SCLC) (nine patients), non-SCLC (one patient), breast carcinoma (two patients), gastric adenocarcinoma (one patient) and kidney carcinoma (one patient). Patients with paraneoplastic OMS were older [median age: 66 years versus 40 years (P = 0.006) of those with idiopathic OMS] and had a higher frequency of encephalopathy (64% versus 10%; P = 0.02). Serum from 10/10 idiopathic and 12/14 paraneoplastic OMS patients showed no specific immunoreactivity on rat or human brainstem or cerebellum, lacked specific antineuronal antibodies (Hu, Yo, Ri, Tr, glutamic acid decarboxylase, amphiphysin or CV2) and did not contain antibodies to voltage-gated calcium channels. The two paraneoplastic exceptions were a patient with SCLC, whose serum contained both anti-Hu and anti-amphiphysin antibodies and a patient with breast cancer who had serum anti-Ri antibodies. The clinical course of idiopathic OMS was monophasic except in two elderly women who had relapses of the opsoclonus and mild residual ataxia. Most idiopathic OMS patients made a good recovery, but residual gait ataxia tended to persist in older patients. Immunotherapy (mainly intravenous immunoglobulins or corticosteroids) seemed to accelerate recovery. Paraneoplastic OMS had a more severe clinical course, despite treatment with intravenous immunoglobulins or corticosteroids, and was the cause of death in five patients whose tumours were not treated. By contrast the eight patients whose tumours were treated showed a complete or partial neurological recovery. We conclude that idiopathic OMS occurs in younger patients, the clinical evolution is more benign and the effect of immunotherapy appears more effective than in paraneoplastic OMS. In patients aged 50 years and older with OMS who develop encephalopathy, early diagnosis and treatment of a probable underlying tumour, usually SCLC, is indicated to increase the chances of neurological recovery. At present, there are no immunological markers to identify the adult patients with paraneoplastic OMS. (+info)
Paraneoplastic brain stem encephalitis in a woman with anti-Ma2 antibody.
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A woman developed brain stem encephalopathy in association with serum anti-Ma2 antibodies and left upper lobe lung mass. T2 weighted MRI of the brain showed abnormalities involving the pons, left middle and superior cerebellar peduncles, and bilateral basal ganglia. Immunohistochemical analysis for serum antineuronal antibodies was confounded by the presence of a non-neuronal specific antinuclear antibody. Immunoblot studies showed the presence of anti-Ma2 antibodies. A premortem tissue diagnosis of the lung mass could not be established despite two CT guided needle biopsies, and the patient died as a result of rapid neurological deterioration. The necropsy showed that the lung lesion was an adenocarcinoma which expressed Ma2 immunoreactive protein. Neuropathological findings included prominent perivascular inflammatory infiltrates, glial nodules, and neuronophagia involving the brain stem, basal ganglia, hippocampus and the dentate nucleus of the cerebellum. Ma2 is an autoantigen previously identified in patients with germ cell tumours of the testis and paraneoplastic brain stem and limbic encephalitis. Our patient's clinical and immunopathological findings indicate that this disorder can affect women with lung adenocarcinoma, and that the encephalitic changes predominate in those regions of the brain known to express high concentrations of Ma proteins. (+info)
Neurological manifestations of enterovirus 71 infection in children during an outbreak of hand, foot, and mouth disease in Western Australia.
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Enterovirus 71 (EV71) causes epidemics of hand, foot, and mouth disease associated with neurological complications in young children. We report an outbreak of EV71-associated neurological disease that occurred from February through September 1999 in Perth, Western Australia. Fourteen children with culture-proven, EV71-induced neurological disease were identified. Nine patients (64%) developed severe neurological disease; 4 of these patients developed long-term neurological sequelae. Neurological syndromes included aseptic meningitis, Guillain-Barre syndrome, acute transverse myelitis, acute cerebellar ataxia, opso-myoclonus syndrome, benign intracranial hypertension, and a febrile convulsion. Clinical and magnetic resonance imaging data indicated that immunopathology was a major factor in the pathogenesis of neurological disease in this outbreak. This finding is in contrast to reports of previous EV71 epidemics, in which virus-induced damage to gray matter was the most frequent cause of neurological disease. (+info)
Anti-Hu-associated paraneoplastic encephalomyelitis: analysis of 200 patients.
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We reviewed 200 patients with paraneoplastic encephalomyelitis (PEM) and anti-Hu antibodies to show possible clinical differences with respect to previous series, and to identify patient, tumour and treatment-related characteristics associated with neurological disability and survival. The median age of the 200 patients was 63 years (range 28-82 years) and 75% were men. The predominant neurological syndromes were sensory neuropathy (54%), cerebellar ataxia (10%), limbic encephalitis (9%) and multifocal involvement (11%). Sensorimotor neuropathies with predominant motor involvement were observed in only 4% of the patients. Pathological or X-ray evidence of a tumour was obtained in 167 patients (83%) and was a small-cell lung cancer (SCLC) in 74% of those with histological diagnosis. Coexistence of extrathoracic tumours with SCLC was rare (0.5%). Positive Hu immunoreactivity was observed in the extrathoracic tumours of six out of seven patients in whom autopsy or long-term follow-up ruled out a coexisting SCLC. PEM preceded the diagnosis of the tumour in 71% of patients (mean delay +/- SD 6.5 +/- 7.0 months; range 0.1-47 months). In the 24 patients in whom the tumour diagnosis was the initial event, PEM predicted the progression or relapse of the tumour in 87% of them. No tumour was found in 33 patients, including four who had a post-mortem study and four with >5 years of follow-up. In a logistic regression analysis, treatment of the tumour, associated or not with immunotherapy, was an independent predictor of improvement/stabilization of PEM [odds ratio 4.56; 95% confidence interval (CI) 1.62-12.86]. Cox multivariate analysis indicated that the variables independently associated with mortality were: age >60 years [relative risk (RR) 1.49; 95% CI 1.05-2.12], Rankin score at diagnosis >3 (RR 1.60; 95% CI 1.12-2.28), more than one area of the nervous system affected (RR 1.61; 95% CI 1.08-2.40), and absence of treatment (RR 2.56; 95% CI 1.76-3.71). We conclude that, unlike previous series, the majority of our patients were male, and there was a low occurrence of predominantly motor neuropathies and extrathoracic tumours coexisting with SCLC. When the diagnosed extrathoracic tumour expresses Hu antigens, further tests to rule out a coexisting SCLC are probably unnecessary. Finally, the predictors of mortality and PEM evolution found in the study may be important in the design of future therapeutic protocols, and emphasize the importance of early diagnosis and treatment of the underlying tumour. (+info)