Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative syndrome of unknown etiology that most commonly affects people in middle and high age. The hallmark of ALS is a progressive and simultaneous loss of upper and lower motor neurons in the central nervous system that leads to a progressive muscle atrophy, paralysis and death usually by respiratory failure. ALS is not a pure motor neuronal syndrome; it extends beyond the motor system and affects extramotor areas of the brain as well. The majority of the patients suffer from a sporadic ALS disease (SALS) while in at least ten percent the disease appears in a familial form (FALS). Mutations in the gene encoding the antioxidant enzyme superoxide dismutase-1 (SOD1) are the most common cause of FALS. More than 165 SOD1 mutations have been described, and these confer the enzyme a cytotoxic gain of function. Evidence suggests that the toxicity results from structural instability which makes the mutated enzyme prone to misfold and form aggregates in the spinal cord and brain motor neurons. Recent studies indicate that the wild-type human SOD1 protein (wt-hSOD1) has the propensity to develop neurotoxic features. The aim of the present study was to investigate if wt-hSOD1 is involved in the pathogenesis of SALS and FALS patients lacking SOD1 mutations and to evaluate the neurotoxic effect of misfolded wt-hSOD1 protein in vivo by generating a transgenic wt-hSOD1 mice model. We produced specific SOD1-peptide-generated antibodies that could discriminate between the misfolded and native form of the enzyme and optimized a staining protocol for detection of misfolded wt-hSOD1 by immunohistochemistry and confocal microscopy of brain and spinal cord tissue. We discovered that aggregates of misfolded wt-hSOD1 were constitutively present in the cytoplasm of motor neurons in all investigated SALS patients and in FALS patients lacking SOD1 gene mutations. Interestingly, the misfolded wt-hSOD1 aggregates were also found in some motor neuron nuclei and in the nuclei of the surrounding glial cells, mainly astrocytes but also microglia and oligodendrocytes, indicating that misfolded wt-hSOD1 protein aggregates may exert intranuclear toxicity. We compared our findings to FALS with SOD1 mutations by investigating brain and spinal cord tissue from patients homozygous for the D90A SOD1 mutation, a common SOD1 mutation that encodes a stable SOD1 protein with a wild-type-like enzyme activity. We observed a similar morphology with a profound loss of motor neurons and aggregates of misfolded SOD1 in the remaining motor neuron. Interestingly, we found gliosis and microvacuolar degeneration in the superficial lamina of the frontal and temporal lobe, indicating a possible frontotemporal lobar dementia in addition to the ALS disorder. Our morphological and biochemical findings were tested in vivo by generating homozygous transgenic mice that over expressed wt-hSOD1. These mice developed a fatal ALS-like disease, mimicking the one seen in mice expressing mutated hSOD1. The wt-hSOD1 mice showed a slower weight gain compared to non-transgenic mice and developed a progressive ALS-like hind-leg paresis. Aggregates of misfolded wt-hSOD1 were found in the brain and spinal cord neurons similar to those in humans accompanied by a loss of 41 % of motor neurons compared to non-transgenic litter mates. In conclusion, we found misfolded wt-hSOD1 aggregates in the cytoplasm and nuclei of motor neurons and glial cells in all patients suffering from ALS syndrome. Notable is the fact that misfolded wt-hSOD1 aggregates were also detected in FALS patients lacking SOD1 mutations indicating a role for SOD1 even when other genetic mutations are present. The neurotoxicity of misfolded wt-hSOD1 protein was confirmed in vivo by wt-hSOD1 transgenic mice that developed a fatal ALS-like disease. Taken together, our results support the notion that misfolded wt-hSOD1 could be generally involved and play a decisive role in the pathogenesis of all forms of ALS.

Made available in DSpace on 2016-08-10T10:38:40Z (GMT). No. of bitstreams: 1 ALEANDRO GERALDO ALVES.pdf: 687501 bytes, checksum: 815caf3ef15e76a3ef410c769760c097 (MD5) Previous issue date: 2011-08-11 / Amyotrophic lateral sclerosis (ALS) is a multifactorial disease that affects motor neurons. In most cases, the disease is sporadic, however, 5 to 10% of patients have a familial history (FALS). Among patients with FALS, 12 to 23% present with mutations in the SOD1 gene. Objectives: To present a systematic review about the mutations described in SOD1 gene in patients with FALS. Methods: The databases used in this study included PubMed, ISI Web of Science and Cochrane Library Virtual Health. After reading the abstracts, 71 articles were selected and systematically reviewed on this study. Results: The largest number of publications was found in 1997, and Japan was the country with the majority of published studies on the subject, with 23 articles. The majority of the mutations were described in éxons four and five of SOD1 gene, and A4V, I113T, I144F, D90A and L38V were the most commonly mutation described. More than 156 mutations in the SOD1 gene have been cataloged in patients with ALS-F and these data are deposited in ALS GENETICS ONLINE DATABASE, a database that contains specific information on mutations associated with amyotrophic lateral sclerosis. However, the articles reviewed in this study described 103 mutations. Conclusions: Several mutations in the SOD1 gene have been described in patients with ALS-F, however, the relationship between such mutations and the pathogenesis of ALS-F remains unclear, as well as the relationship between mutations and disease progression. Further studies are necessary in order to better explain such relationship. / A esclerose amiotrófica lateral (EAL) é uma doença multifatorial que afeta os neurônios motores. Na maioria dos casos, a doença é esporádica, entretanto, 5 a 10% dos pacientes apresentam história familiar (EAL-F). Dentre os pacientes com EAL-F, 12 a 23% apresentam mutações no gene SOD1. O objetivo deste trabalho foi realizar uma revisão sistemática acerca das mutações descritas no gene SOD1 em pacientes com EAL-F. As bases de dados consultadas incluíram Pubmed, ISI Web of Science e Cochrane Biblioteca Virtual em Saúde. Após a revisão dos resumos, 71 artigos foram selecionados descrevendo mutações no gene SOD1 em pacientes com EAL-F. O ano que apresentou o maior número de publicações foi 1997 e o Japão foi o país que mais publicou sobre o assunto, aparecendo em 23 artigos. O maior número de mutações foi descrito nos éxons 4 e 5 do gene SOD1 e as mutações A4V, I113T, I144F, D90A e L38V foram as mais comumente citadas. Até o momento 156 mutações no gene SOD1 já foram catalogadas em pacientes com EAL-F e esses dados encontram-se depositados no ALS ONLINE GENETICS DATABASE, um banco de dados que contém informações específicas sobre mutações associadas à esclerose amiotrófica lateral. Entretanto, os artigos revisados neste estudo descrevem 103 destas mutações. As causas relacionadas às mutações no gene SOD1 permanecem incertas, assim como a relação entre tais mutações e a evolução da doença, portanto, muito ainda deve ser estudado acerca desse tema.