339 resultados para Friedreich ataxia
Resumo:
“Naturally occurring cancers in pet dogs and humans share many features, including histological appearance, tumour genetics, molecular targets, biological behaviour and response to conventional therapies. Studying dogs with cancer is likely to provide a valuable perspective that is distinct from that generated by the study of human or rodent cancers alone. The value of this opportunity has been increasingly recognized in the field of cancer research for the identification of cancer-associated genes, the study of environmental risk factors, understanding tumour biology and progression, and, perhaps most importantly, the evaluation and development of novel cancer therapeutics”.(Paoloni and Khanna, 2008) In last years, the author has investigated some molecular features of cancer in dogs. The Thesis is articulated in two main sections. In section 1, the preliminary results of a research project aimed at investigating the role of somatic mutations of Ataxia-Telangiectasia mutated (ATM) gene in predisposing to cancer in boxer dogs, are presented. The canine boxer breed may be considered an unique opportunity to disclose the role of ATM somatic mutation since boxer dogs are known to be dramatically susceptible to cancer and since they may be considered a closed gene pool. Furthermore, dogs share with human the some environment. Overall, the abovementioned features could be considered extremely useful for our purposes. In the section 2, the results of our studies aimed at setting up accurate and sensitive molecular assays for diagnosing and assessing minimal residual disease in lymphoproliferative disorders of dogs, are presented. The results of those molecular assay may be directly translated in the field of Veterinary practice as well as the may be used to improve our objective evaluation of new investigational drugs effectiveness in canine cancer trials.
Resumo:
Friedreich’s Ataxia (FRDA) is a neurodegenerative disorder caused by a deficiency of the protein frataxin and characterized by oxidative stress. The first aim of my research project was to analyze the effects of tocotrienol in FRDA patients. Patients received for 2 months a low dose of tocotrienol. A number of biochemical parameters related to oxidative stress were studied. We consistently showed that taking for 2 months a low dose of tocotrienol led to the decrease of oxidative stress indexes in FRDA patients. Also, this study provides a suitable model to investigate the efficacy of natural compounds to counteract the oxidative stress in FRDA. Furthermore, we investigated whether the tocotrienol was able to modulate the expression of the frataxin isoforms (FXN-1, FXN -2, FXN-3) in FRDA patients. We demonstrated that tocotrienol leads to a specific and significant increase of FXN-3 expression. As no structural and functional details were available for FNX-2 and FXN-3, 3D-models were built. FXN-1, the canonical isoform, was then docked on the human iron-sulphur complex and functional interactions were computed; when FXN-1 was replaced by FXN-2 or FNX-3, we found that the interactions were maintained, thus suggesting a possible biological role for both isoforms. The second aim of my research project was to investigate the role of a single nucleotide polymorphism (SNP) in the protein Sirtuin 6 in FRDA patients. In fact, it was known that those who harbour a SNP (Asn46/Ser46) in the gene enconding Sirt6 show a better outcome those individuals who are homozygous for the Asn 46 allele. We found that fibroblasts and iPSC-derived neurons from FRDA patients harboring the SNP (Asn46/Ser46) have a reduced amount of Sirt6 protein compared to cells from individuals who are homozygous for the prevalent Asn allele. Our studies provide new information on the role of Sirtuins in FRDA pathogenesis.
Resumo:
Die Ursache der neurodegenerativen Erkrankung Spinozerebelläre Ataxie Typ 2 (SCA2) ist eine expandierte Polyglutamin-Domäne im humanen ATXN2-Gen von normalerweise 22 auf über 31 CAGs. Von der Degeneration sind vorwiegend die zerebellären Purkinje Neuronen betroffen, in denen zunehmend zytoplasmatische Aggregate sichtbar werden. Auch wenn die genaue Funktion von ATXN2 und die zugrunde liegenden molekularen Mechanismen noch immer ungeklärt sind, werden ein toxischer Funktionsgewinn sowie der Verlust der normalen Proteinfunktion als mögliche Ursachen diskutiert.rnUm ein wirklichkeitsgetreues Tiermodell für die SCA2 zu haben, wurde eine knock-in Maus generiert, deren einzelnes CAG im Atxn2-Gen durch 42 CAGs ersetzt wurde. Dieses Mausmodell ist durch eine stabile Vererbung der Expansion charakterisiert. Weiterhin zeigt sie ein verringertes Körpergewicht sowie eine spät beginnende motorische Inkoordination, was dem Krankheitsbild von SCA2 entspricht. rnIm Weiteren konnte gezeigt werden, dass, obwohl die Atxn2 mRNA-Spiegel in Großhirn und Kleinhirn erhöht waren, die Menge an löslichem ATXN2 im Laufe der Zeit abnahm und dies mit einem Auftreten an unlöslichem ATXN2 korrelierte. Dieser im Kleinhirn progressive Prozess resultierte schließlich in zytoplasmatischen Aggregaten innerhalb der Purkinje Neuronen alter Mäuse. Der Verlust an löslichem ATXN2 könnte Effekte erklären, die auf einen partiellen Funktionsverlust von ATXN2 zurückzuführen sind, wobei die Aggregatbildung einen toxischen Funktionsgewinn wiederspiegeln könnte. Neben ATXN2 wurde auch sein Interaktor PABPC1 zunehmend unlöslich. Während dies im Großhirn eine Erhöhung der PABPC1 mRNA- und löslichen Proteinspiegel zur Folge hatte, konnte keine kompensatorische Veränderung seiner mRNA und zudem eine Verminderung an löslichem PABPC1 im Kleinhirn beobachtet werden. Auch PABPC1 wurde in Aggregate sequestriert. Diese Unterschiede zwischen Großhirn und Kleinhirn könnten zu der spezifischen Vulnerabilität des Kleinhirns beitragen.rnUm die Folgen auf mRNA-Prozessierung zu untersuchen, wurde ein Transkriptomprofil im mittleren sowie fortgeschrittenen Alter der Mäuse erstellt. Hierbei war eine erhöhte Expression von Fbxw8 im Kleinhirn alter Mäuse auffällig. Als Komponente eines Ubiquitin-E3-Ligase-Komplexes, hilft FBXW8 in der Degradierung von Zielproteinen und könnte somit die Toxizität des expandieren ATXN2 verringern. rnZur näheren Beschreibung der physiologischen Funktion von ATXN2, konnte in ATXN2-knock-out Mäusen gezeigt werden, dass das Fehlen von ATXN2 zu einer reduzierten globalen Proteinsyntheserate führte und somit eine Rolle als Translationsaktivator möglich erscheint. Kompensatorisch wurde eine erhöhte S6-Phosphorylierung gemessen.
Resumo:
Episodic ataxia type 1 is a neuronal channelopathy caused by mutations in the KCNA1 gene encoding the fast K(+) channel subunit K(v)1.1. Episodic ataxia type 1 presents with brief episodes of cerebellar dysfunction and persistent neuromyotonia and is associated with an increased incidence of epilepsy. In myelinated peripheral nerve, K(v)1.1 is highly expressed in the juxtaparanodal axon, where potassium channels limit the depolarizing afterpotential and the effects of depolarizing currents. Axonal excitability studies were performed on patients with genetically confirmed episodic ataxia type 1 to characterize the effects of K(v)1.1 dysfunction on motor axons in vivo. The median nerve was stimulated at the wrist and compound muscle action potentials were recorded from abductor pollicis brevis. Threshold tracking techniques were used to record strength-duration time constant, threshold electrotonus, current/threshold relationship and the recovery cycle. Recordings from 20 patients from eight kindreds with different KCNA1 point mutations were compared with those from 30 normal controls. All 20 patients had a history of episodic ataxia and 19 had neuromyotonia. All patients had similar, distinctive abnormalities: superexcitability was on average 100% higher in the patients than in controls (P < 0.00001) and, in threshold electrotonus, the increase in excitability due to a depolarizing current (20% of threshold) was 31% higher (P < 0.00001). Using these two parameters, the patients with episodic ataxia type 1 and controls could be clearly separated into two non-overlapping groups. Differences between the different KCNA1 mutations were not statistically significant. Studies of nerve excitability can identify K(v)1.1 dysfunction in patients with episodic ataxia type 1. The simple 15 min test may be useful in diagnosis, since it can differentiate patients with episodic ataxia type 1 from normal controls with high sensitivity and specificity.
Resumo:
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a childhood-onset neurological disease resulting from mutations in the SACS gene encoding sacsin, a 4,579-aa protein of unknown function. Originally identified as a founder disease in Québec, ARSACS is now recognized worldwide. Prominent features include pyramidal spasticity and cerebellar ataxia, but the underlying pathology and pathophysiological mechanisms are unknown. We have generated an animal model for ARSACS, sacsin knockout mice, that display age-dependent neurodegeneration of cerebellar Purkinje cells. To explore the pathophysiological basis for this observation, we examined the cell biological properties of sacsin. We show that sacsin localizes to mitochondria in non-neuronal cells and primary neurons and that it interacts with dynamin-related protein 1, which participates in mitochondrial fission. Fibroblasts from ARSACS patients show a hyperfused mitochondrial network, consistent with defects in mitochondrial fission. Sacsin knockdown leads to an overly interconnected and functionally impaired mitochondrial network, and mitochondria accumulate in the soma and proximal dendrites of sacsin knockdown neurons. Disruption of mitochondrial transport into dendrites has been shown to lead to abnormal dendritic morphology, and we observe striking alterations in the organization of dendritic fields in the cerebellum of knockout mice that precedes Purkinje cell death. Our data identifies mitochondrial dysfunction/mislocalization as the likely cellular basis for ARSACS and indicates a role for sacsin in regulation of mitochondrial dynamics.
Resumo:
The cause of porcine congenital progressive ataxia and spastic paresis (CPA) is unknown. This severe neuropathy manifests shortly after birth and is lethal. The disease is inherited as a single autosomal recessive allele, designated cpa. In a previous study, we demonstrated close linkage of cpa to microsatellite SW902 on porcine chromosome 3 (SSC3), which corresponds syntenically to human chromosome 2. This latter chromosome contains ion channel genes (Ca(2+), K(+) and Na(+)), a cholinergic receptor gene and the spastin (SPG4) gene, which cause human epilepsy and ataxia when mutated. We mapped porcine CACNB4, KCNJ3, SCN2A and CHRNA1 to SSC15 and SPG4 to SSC3 with the INRA-Minnesota porcine radiation hybrid panel (IMpRH) and we sequenced the entire open reading frames of CACNB4 and SPG4 without finding any differences between healthy and affected piglets. An anti-epileptic drug treatment with ethosuximide did not change the severity of the disease, and pigs with CPA did not exhibit the corticospinal tract axonal degeneration found in humans suffering from hereditary spastic paraplegia, which is associated with mutations in SPG4. For all these reasons, the hypothesis that CACNB4, CHRNA1, KCNJ3, SCN2A or SPG4 are identical with the CPA gene was rejected.
Resumo:
A 20-year old Swiss Warmblood mare was referred to the Swiss Institute of Equine Medicine with a history of poor performance, coughing and ataxia and hindlimb weakness which progressed to recumbency. Lung auscultation revealed pronounced wheezing, blood work showed signs of chronic inflammation and increased bone turnover and thoracic ultrasound indicated patchy pulmonary consolidation. Cerebrospinal fluid revealed only mild, unspecific changes allowing exclusion of meningoencephalomyelitis and clinically relevant bleeding. Despite medical treatment and support in a sling the mare did not improve and was euthanized. Necropsy revealed a poorly demarcated, non-encapsulated and invasively growing mass dorsally in the musculature at the level of the forth cervical vertebra (C4) infiltrating the vertebral body and the spinal canal at the level of C1–C2. Multiple nodular, firm masses were present in all lobes of the lung and appeared to be mainly located in vessels. Histologically the masses were composed of spindle cells with marked anisocytosis, anisocaryosis, a high mitotic activity and showed invasive growth. These neoplastic cells stained positive for CD31, an endothelial cell marker, which confirmed diagnosis of a hemangiosarcoma. Definite ante mortem diagnosis of hemangiosarcoma, which is rare in horses, is challenging. Besides the vertebral localization, disseminated, locally invasive and cutaneous forms of hemangiosarcoma exist and can be either acquired or congenital. Prognosis for equine hemangiosarcoma and response to treatment are usually poor and progression of clinical signs is rapid. Vertebral hemangiosarcoma is an uncommon cause of spinal ataxia in horses.
Resumo:
Friedreich’s ataxia (FRDA) is caused by the transcriptional silencing of the frataxin (FXN) gene. FRDA patients have expansion of GAA repeats in intron 1 of the FXN gene in both alleles. A number of studies demonstrated that specific histone deacetylase inhibitors (HDACi) affect either histone modifications at the FXN gene or FXN expression in FRDA cells, indicating that the hyperexpanded GAA repeat may facilitate heterochromatin formation. However, the correlation between chromatin structure and transcription at the FXN gene is currently limited due to a lack of more detailed analysis. Therefore, I analyzed the effects of the hyperexpanded GAA repeats on transcription status and chromatin structure using lymphoid cell lines derived from FRDA patients. Using chromatin immunoprecipitation and quantitative PCR, I observed significant changes in the landscape of histone modifications in the vicinity of the GAA tract in FRDA cells relative to control cells. Similar epigenetic changes were observed in GFP reporter construct containing 560 GAA repeats. Further, I detected similar levels of FXN pre-mRNA at a region upstream of hyperexpanded GAA repeats in FRDA and control cells, indicating similar efficiency of transcription initiation in FRDA cells. I also showed that histone modifications associated with hyperexpanded GAA repeats are independent of transcription progression using the GFP reporter system. My data strongly support evidence that FXN deficiency in FRDA patients is consequence of defective transition from initiation to elongation of FXN transcription due to heterochromatin-like structures formed in the proximity of the hyperexpanded GAAs.
Resumo:
Spinocerebellar Ataxia type 7 (SCA7) is a neurodegenerative disease caused by expansion of a CAG repeat encoding a polyglutamine tract in ATXN7, a component of the SAGA histone acetyltransferase (HAT) complex. Previous studies provided conflicting evidence regarding the effects of polyQ-ATXN7 on the activity of Gcn5, the HAT catalytic subunit of SAGA. Here I showed that reducing Gcn5 expression accelerates both cerebellar and retinal degeneration in a mouse model of SCA7. Deletion of Gcn5 in Purkinje cells in mice expressing wild type Atxn7, however, causes only mild ataxia and does not lead to the early lethality observed in SCA7 mice. Reduced Gcn5 expression strongly enhances retinopathy in SCA7 mice, but does not affect the transcriptional targets of Atxn7, as expression of these genes is not further altered by Gcn5 depletion. These findings demonstrate that loss of Gcn5 functions can contribute to the time of onset and severity of SCA7 phenotypes, but suggest that non-transcriptional functions of SAGA may play a role in neurodegeneration in this disease.
Resumo:
Ataxia telangiectasia (A-T) is a rare, progressive, multisystem disease that has a large number of complex and diverse manifestations which vary with age. Patients with A-T die prematurely with the leading causes of death being respiratory diseases and cancer. Respiratory manifestations include immune dysfunction leading to recurrent upper and lower respiratory infections; aspiration resulting from dysfunctional swallowing due to neurodegenerative deficits; inefficient cough; and interstitial lung disease/pulmonary fibrosis. Malnutrition is a significant comorbidity. The increased radiosensitivity and increased risk of cancer should be borne in mind when requesting radiological investigations. Aggressive proactive monitoring and treatment of these various aspects of lung disease under multidisciplinary expertise in the experience of national multidisciplinary clinics internationally forms the basis of this statement on the management of lung disease in A-T. Neurological management is outwith the scope of this document.
Resumo:
The KARP-1 (Ku86 Autoantigen Related Protein-1) gene, which is expressed from the human Ku86 autoantigen locus, appears to play a role in mammalian DNA double-strand break repair as a regulator of the DNA-dependent protein kinase complex. Here we demonstrate that KARP-1 gene expression is significantly up-regulated following exposure of cells to DNA damage. KARP-1 mRNA induction was completely dependent on the ataxia telangiectasia and p53 gene products, consistent with the presence of a p53 binding site within the second intron of the KARP-1 locus. These observations link ataxia telangiectasia, p53, and KARP-1 in a common pathway.
Evolution of the Friedreich’s ataxia trinucleotide repeat expansion: Founder effect and premutations
Resumo:
Friedreich’s ataxia, the most frequent inherited ataxia, is caused, in the vast majority of cases, by large GAA repeat expansions in the first intron of the frataxin gene. The normal sequence corresponds to a moderately polymorphic trinucleotide repeat with bimodal size distribution. Small normal alleles have approximately eight to nine repeats whereas a more heterogeneous mode of large normal alleles ranges from 16 to 34 GAA. The latter class accounts for ≈17% of normal alleles. To identify the origin of the expansion mutation, we analyzed linkage disequilibrium between expansion mutations or normal alleles and a haplotype of five polymorphic markers within or close to the frataxin gene; 51% of the expansions were associated with a single haplotype, and the other expansions were associated with haplotypes that could be related to the major one by mutation at a polymorphic marker or by ancient recombination. Of interest, the major haplotype associated with expansion is also the major haplotype associated with the larger alleles in the normal size range and was almost never found associated with the smaller normal alleles. The results indicate that most if not all large normal alleles derive from a single founder chromosome and that they represent a reservoir for larger expansion events, possibly through “premutation” intermediates. Indeed, we found two such alleles (42 and 60 GAA) that underwent cataclysmic expansion to pathological range in a single generation. This stepwise evolution to large trinucleotide expansions already was suggested for myotonic dystrophy and fragile X syndrome and may relate to a common mutational mechanism, despite sequence motif differences.