xiv, 78 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Myotonic Dystrophy (DM) is a genetic disorder with multisystemic symptoms that is caused by expression (as RNA) of expanded repeats of CTG or CCTG in the genome. It is hypothesized that the protein MBNL1 (M[barbelow]uscleb[barbelow]lin[barbelow]d-l[barbelow]ike-1) is sequestered to the expanded CUG or CCUG RNAs. MBNL1 regulates the alternative splicing of a variety of pre-mRNAs and its mis-localization results in mis-splicing of a subset of pre-mRNAs that are linked to the symptoms found in DM patients. I initially demonstrated that MBNL1 can bind short structured CUG and CCUG repeats with high affinity and specificity in vitro . Next, I was able to determine and articulate the first structure of a binding site of MBNL1 in an endogenous pre-mRNA that it regulates. I found that MBNL1 binds a stem-loop in the cardiac troponin T (cTNT) pre-mRNA. The stem-loop contains two mismatches and resembles both CUG and CCUG repeats. I determined that MBNL1 regulated exon 5 by directly competing with the essential splicing factor U2AF65 for binding upstream of exon 5. When U2AF65 is prevented from binding, factors in the spliceosome can no longer be recruited and the following exon is skipped. Furthermore, I found that MBNL1 and U2AF65 compete by binding mutually exclusive RNA structures. I also characterized a potential therapeutic approach for DM. Current data suggest that if MBNL1 is released from sequestration, disease symptoms may be alleviated. Using a targeted screen of small molecules known to bind structured nucleic acids, I identified the small molecule pentamidine as a compound that disrupted MBNL1 binding to CUG repeats in vitro . I showed in cell culture that pentamidine was able to reverse the mis-splicing of two pre-mRNAs affected in DM. Pentamidine also significantly reduced the formation of RNA foci in tissue culture cells, which are characteristic of DM. MBNL1 was released from the foci in the treated cells. Furthermore, pentamidine partially rescued splicing defects of two pre-mRNAs in mice expressing expanded CUG repeats. This dissertation includes three previously published co-authored publications. / Committee in charge: Kenneth Prehoda, Chairperson, Chemistry; J. Andrew Berglund, Advisor, Chemistry; Victoria DeRose, Member, Chemistry; Peter von Hippel, Member, Chemistry; Alice Barkan, Outside Member, Biology

INTRODUÇÃO: A disfagia orofaríngea e os distúrbios de motilidade esofágica são considerados as mais importantes causas de pneumonia aspirativa em pacientes com distrofia miotônica. O objetivo deste estudo foi avaliar as características clínicas da motricidade orofacial e a deglutição de indivíduos com distrofia miotônica (DM1), utilizando um protocolo clínico padronizado e eletromiografia de superfície (EMGs). MÉTODO: Os participantes foram divididos em dois grupos: G1-composto por 20 adultos com DM1; G2-composto por 20 voluntários saudáveis, os participantes foram pareados por idade e gênero com G1 para a análise estatística. Foi realizada a avaliação das estruturas e funções orofaciais, utilizando um protocolo clínico padronizado, e mensurada a atividade mioelétrica da deglutição por meio da EMGs, com eletrodos localizados em quatro grupos musculares: (1) orbicular da boca, (2) masseter, (3) musculatura suprahioidea e (4) extrínseca da laringe. A atividade mioelétrica foi medida durante o repouso muscular e durante a deglutição de saliva e de 16,5ml e 20ml de água. Os traçados da EMGs foram avaliados durante o inicio (onset), pico e o término (offset), dos evento da deglutição. A análise estatística incluiu a ANOVA de duplo fator para intragrupos e intergrupos e o teste de Bonferroni para correções de comparações múltiplas. RESULTADOS: Pacientes com DM1 apresentaram déficits em posição, postura e mobilidade dos órgãos miofuncionais orofaciais, e nas funções de mastigação e deglutição. Além disso, os resultados da EMGs para diferentes tarefas de deglutição indicaram maior atividade muscular do orbicular da boca e maior duração da ativação muscular para os músculos: orbicular da boca, masseter e extrínseco de laringe. Não foi observado aumento significativo na amplitude da EMGs, nos pacientes com DM1, quando comparado aos resultados obtidos no teste de deglutição normal com o teste de estresse. CONCLUSÕES: A maior duração da deglutição na EMGs no grupo DM1, possivelmente está relacionada a miotonia e/ou incoordenação dos músculos envolvidos no processo da deglutição ou pode estar relacionado a uma adaptação fisiológica para uma deglutição segura. A identificação precoce dos distúrbios da deglutição permite reabilitação precoce oral, o que poderia diminuir o risco de pneumonia por aspiração nesta população. / INTRODUCTION: Oropharyngeal dysphagia and oesophageal motility disorders were found to be the most important reasons causing aspiration pneumonia in patients with myotonic dystrophy. The purpose of this report was to evaluate clinical characteristics of the oral motor movements and swallowing of individuals with myotonic dystrophy type 1 (DM1), using a standardized clinical protocol and surface electromyography (sEMG). METHOD: Participants were 40 individuals divided in two groups: G1- composed by 20 adults with DM1; G2- composed by 20 healthy volunteers paired by age and gender to individuals in G1. Participants of all groups underwent clinical assessment of the orofacial structures and functions using a standardized clinical protocol. The myoelectric activity of swallowing was measured using sEMG. Four muscle groups were examined: (1) the orbicularis oris superior and inferior; (2) the masseter; (3) the submental muscle group; and (4) the laryngeal strap muscles. Muscle activity was measured during rest, during dry swallows and during the swallowing of 16.5ml and 20ml of water. Surface EMG traces were evaluated for onset, peak and offset of activity during swallow events. The statistical analysis included the one-way ANOVA with two factors for within and between group comparisons and the Bonferroni correction for multiple comparisons. RESULTS: Patients with DM1 presented deficits in posture, position and mobility of the oral motor organs, as well as compromised mastication and deglutition. Moreover, sEMG results for different swallowing tasks indicated higher muscle activity for the orbicularis oris and longer durations of muscle activation for the orbicularis oris, masseter and laryngeal strap muscles. When considering within group comparisons, DM1 patients did not present a significant increase of sEMG amplitude during the stress test in comparison with the normal swallow test. CONCLUSION: Compared to healthy individuals, patients with DM1 presented longer times to pass a bolus from the oral cavity to the esophagus. The larger duration of sEMG in the DM1 group is possibly related to myotonia and/or incoordination of the muscles involved in the swallowing process or could reflect a physiological adaptation for safe swallowing. Early identification of swallowing disorders enables early oral rehabilitation, which in turn could decrease the risk of aspiration pneumonia in this population.

Over the past decade several converging lines of evidence have highlighted the importance of post-transcriptional events in skeletal muscle. This level of regulation is controlled by multi-functional RNA-binding proteins and trans-acting factors. In fact, several RNA-binding proteins are implicated in neuromuscular disorders including myotonic dystrophy type I, spinal muscular atrophy and amyotrophic lateral sclerosis. Therefore, it is necessary to examine the impact of RNA-binding proteins during skeletal muscle development and plasticity in order to understand the consequences linked to their misregulation in disease. Here, we focused on the RNA-binding protein Staufen1, which assumes multiple roles in both skeletal muscle and neurons. We previously demonstrated that Staufen1 is regulated during myogenic differentiation and that its expression is increased in denervated and in myotonic dystrophy type I skeletal muscles. The increased expression of Staufen1 initially appeared beneficial for DM1 since further elevating Staufen1 levels rescued key hallmarks of the disease. However, based on the multi-functional nature of Staufen1, we hypothesized that Staufen1 acts as a disease modifier in DM1. To test this, we investigated the roles of Staufen1 in skeletal muscle biology and their implications for disease. Our data demonstrated that Staufen1 is required during the early stages of muscle development, however its expression must remain low in postnatal skeletal muscle. Interestingly, the overexpression of Staufen1 impaired myogenesis through the regulation of c-myc translation. Since the function of c-myc in oncogenesis is well described, we investigated the role of Staufen1 in cancer biology. In particular, we determined novel functions of Staufen1 in rhabdomyosarcoma tumorigenesis, thus providing the first direct evidence for Staufen1’s involvement in cancer. Moreover, based on Staufen1’s role in myogenic differentiation and in myotonic dystrophy type I, we generated muscle-specific transgenic mice to examine the impact of sustained Staufen1 expression in postnatal skeletal muscle. Staufen1 transgenic mice developed a myopathy characterized by histological and functional abnormalities via atrogene induction and the regulation of PTEN mRNAs. In parallel, we further investigated Staufen1-regulated alternative splicing and our data demonstrated that Staufen1 regulates multiple alternative splicing events in normal and myotonic dystrophy type I skeletal muscles, both beneficial and detrimental for the pathology. Collectively, these findings uncover several novel functions of Staufen1 in skeletal muscle biology and highlight Staufen1’s role as a disease modifier in DM1.

Orientadores: Anamarli Nucci, Marcondes Cavalcante França Junior / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-27T03:57:08Z (GMT). No. of bitstreams: 1 Mendonca_HelenaRezendeSilva_D.pdf: 2329027 bytes, checksum: 0f0b498b853a5b5821670460c3bfdca0 (MD5) Previous issue date: 2015 / Resumo: Objetivo. O estudo propôs-se a caracterizar as alterações neuropsicológicas, encefálicas e da bioquímica cerebral em pacientes com Distrofia Miotônica tipo 1 (DM1) e correlacionar as anormalidades encontradas aos parâmetros clínicos. Métodos: Estudo descritivo em 13 pacientes com diagnóstico clínico, laboratorial e genético de DM1, comparados a 14 controles saudáveis com correção para gênero, idade e escolaridade. Avaliações realizadas: 1) clínica e neurológica com ênfase na quantificação da força muscular.(MRC) e escala MIRS (motor impairment ranting scale). 2) cognitiva pelo Mini Exame do Estado Mental. 3) do humor pelo questionário de depressão de Beck. 4) psicométrica pela escala de inteligência de Wechsler para adultos (WAIS III). 5) neuropsicológica compreendendo os testes: dominância manual; atenção e memória operacional por dígitos direto e inverso e Stroop incongruente; percepção visuoespacial; fluência verbal semântica; nomeação de Boston; praxia construtiva visuoespacial por cubo de Kohs; aprendizado auditivo-verbal de Rey; memória visuoespacial 10/36. As imagens cerebrais por ressonância magnética foram obtidas em aparelho de 2 Tesla, com aplicação da: a) Morfometria baseada em voxels (VBM) para substância cinzenta e branca. b) Espectroscopia de single voxel nas áreas frontal, temporoparietal e occipital, sendo considerados os valores relativos de N-acetilaspartato (NAA), creatina total (creatina mais fosfocreatina), colina e glutamato mais glutamina. Análise estatística não paramétrica foi aplicada aos dados cognitivos e de espectroscopia e teste-t com duas amostras independentes para dados de VBM. Resultados e Conclusões. Nos pacientes (6 DM1-juvenil e 7 DM1-clássico) com moderada a grave afecção muscular (MIRS 3 a 5), o desempenho psicométrico pelo WAIS III foi pior na escala verbal. Encontrou-se significativo acometimento da praxia com cubos de Kohs e com o teste Stroop incongruente, não correlacionado ao desempenho motor, nos pacientes. Não houve diferença significativa nos demais testes entre DM1 e controles. No VBM houve redução de substância cinzenta nos pacientes em regiões: 1) frontais com predomínio à direita: giro frontal inferior, porções orbicular, triangular e opercular; giro pré-central, giro frontal inferior e medial; 2) lobo límbico: giro para-hipocampal direito e giro cingulado bilateral (anterior e médio à esquerda e posterior à direita); 3) lobo temporal esquerdo (giros médio e superior). Atrofia da substância branca ocorreu no corpo caloso posterior, giro frontal medial e polo temporal medial à direita e uncus bilateral. Na espectroscopia não houve diferença na concentração relativa de metabólitos, mas a concentração de NAA temporoparital se correlacionou com o pior desempenho no teste de Stroop e com a atrofia da substância cinzenta temporal à esquerda. No total, as alterações córtico-subcorticais identificadas no estudo mostraram relação com as redes neurofuncionais referentes às alterações neuropsicológicas construtiva visuoespacial e processo inibitório executivo, sugerindo que redes neuronais de integração fronto-temporo-límbicas, sobretudo a rede fronto-límbica, implicada na integração de componentes visuais e tomada de decisão envolvendo inibição, possam estar envolvidas na gênese das disfunções encefálicas deste grupo de pacientes DM1 / Abstract: Objective. The study aimed to characterize the neuropsychological, encephalic and biochemical disorders in patients with Myotonic Dystrophy Type 1 (DM1) patients and correlate abnormalities findings with clinical parameters. Methods. A descriptive study in 13 patients with clinical, biochemical and genetic diagnosis of DM1, compared to 14 healthy controls with correction for gender, age and education. Evaluations conducted: 1) clinical and neurological evaluation with emphasis on quantification of muscle strength (MRC) and MIRS scale (motor impairment ranting scale). 2) cognitive assessment by the Mini-Mental State Examination ¿ MMSE. 3) Evaluation by Beck depression inventory. 4) the psychometric evaluation by Wechsler Intelligence Scale for Adults, third edition - WAIS III. 5) neuropsychological evaluation comprising the tests: handedness dominance; attention and working memory by span digits forward and reverse and incongruent version Stroop test; visuospatial perception; semantic verbal fluency; Boston naming test; constructive visuospatial praxis by Kohs¿ bloks; Rey auditory-verbal learning test; visuospatial memory 10/36.test. 6) Brain magnetic resonance images (MRI) evaluation by 2 Tesla scanner by. a) Voxel based morphometry (VBM) to gray and white matter. b) single voxel spectroscopy in the frontal, temporoparietal and occipital areas, being considered the relative values of metabolites: N-acetyl aspartate (NAA), total creatine (creatine plus phosphocreatine), choline and glutamate plus glutamine. Non-parametric statistical analysis was applied to cognitive and spectroscopy data and t-test with two independent samples to VBM data. Results and Conclusions. In patients (6 DM1-juvenile and 7 classical-DM1) with moderate to severe muscular disorder (MIRS 3-5), the psychometric performance by WAIS III was worse on the verbal scale. It was found significant impairment of constructive visuospatial praxis with Kohs¿ bloks and the incongruent Stroop test, not correlated to motor performance in patients. There was no significant difference in the other tests between DM1 and controls. VBM results: gray matter atrophy in patients in the regions: 1) frontal predominantly right: inferior frontal gyrus, orbicularis, triangular and opercular areas; pre-central gyrus, inferior and medial frontal gyrus; 2) limbic lobe: right parahippocampal gyrus and bilateral cingulate gyrus (anterior and middle to left and posterior to right); 3) left temporal lobe: middle and superior temporal gyri. Atrophy of the white matter occurred in the posterior corpus callosum, medial frontal gyrus and medial temporal pole to right and bilateral uncus. In spectroscopy there was no difference in the relative concentration of metabolites, but temporoparietal NAA was correlated with poorer performance on the Stroop test and the atrophy of the left temporal gray matter. In total, the cortico-subcortical changes identified in the study showed a relationship with the neurofunctional networks related to neuropsychological visuospatial constructive and executive inhibitory process disorders, suggesting that neuronal networks of fronto-temporo-limbic integration, particularly the frontal-limbic network, involved in integration of visual components and decision making involving inhibition, may be involved in the genesis of brain dysfunction in this group of DM1 patients / Doutorado / Neurologia / Doutora em Ciências Médicas

Myotonic dystrophy type 1 (DM1) is the most common form of adult muscular dystrophy (1:8000) and is caused by an abnormal expansion of CTG repeats in the 3’ untranslated region of the dystrophia myotonica protein kinase (DMPK) gene. The expanded repeats of the DMPK mRNA forms hairpin structures which sequester RNA-binding proteins (RBP) in intranuclear foci, such as the splicing regulator muscleblind-like 1 (MBNL1), which results in aberrant splicing of several mRNAs and underlie, at least in part, DM1 pathogenesis. It has been previously shown that disaggregating these RNA foci repletes free and thus functional MBNL1, rescuing DM1 spliceopathy and alleviating associated signs and symptoms such as myotonia. Importantly, the direct upregulation of MBNL1 has comparable beneficial outcomes. The focus of this thesis was to develop novel and practical therapeutic avenues for DM1 by employing high-throughput screening technology to identify key pathways and small molecule candidates which reduce CUG foci in patient cells, and ultimately correct DM1 spliceopathy and associated signs in vivo. First, a high-throughput kinome screen using an siRNA library targeting 692 kinase subunits identified PACT, HIPK4, and PKA2β as candidates for reducing CUG foci in patient fibroblasts. Knockdown of each gene resulted in a partial reduction in CUG foci, but ultimately did not correct aberrant splicing of insulin receptor (IR) or sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA1), two genes which are typically misspliced in DM1. A second set of screens focused on testing small molecules, several of which are FDA-approved for clinical use, in an effort to expedite drug discovery. One approach was to data-mine from a previously completed chemical screen, which used system-wide RNA sequencing to establish drug-gene interactions in mouse neuronal cultures treated with blood brain barrier-penetrant drugs, and specifically look for compounds which downregulate DMPK mRNA or upregulate MBNL mRNA (MBNL1 and MBNL2). No compounds were found to downregulate DMPK mRNA. However, several compounds upregulated MBNL mRNAs; the activity of one of these, nilotinib, was validated in human DM1 fibroblasts and converted myoblasts, mediating a small correction in SERCA1 spliceopathy. Administration of nilotinib to unaffected mice did not result in in vivo MBNL gene upregulation in mouse skeletal muscle, as was seen in vitro. Further testing of nilotinib in DM1 in vivo models is required. A final set of chemical screens in patient myoblasts using an FDA-approved drug library and a chemogenomic drug library identified several HDAC inhibitors which reduced foci and rescued SERCA1 spliceopathy in vitro in DM1 differentiated myoblasts. Of these, vorinostat (SAHA) was further tested in a mouse model of DM1 (HSALR), proving safe and effective in correcting aberrant muscle pathology as well as splicing defects of RYR1, SERCA1, and CLCN1. Functional validation, such as myotonia, remains to be completed, but given the strong evidence for CUG foci reduction and splicing correction, vorinostat has emerged as a promising novel candidate for DM1 therapy.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20788号 / 医博第4288号 / 新制||医||1025(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 髙橋 良輔, 教授 高橋 淳, 教授 山下 潤 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant and progressive neuromuscular disorder caused by the CTG trinucleotide repeat expansion in the 3’ untranslated region of the DMPK gene. Clinical manifestations include extensive atrophy of skeletal muscle (SkM) concomitant with muscle weakness, that develops in a distal to proximal fashion. Central to muscle plasticity is the satellite cell (SC), a muscle specific stem cell that, upon activation, facilitates muscle repair and regeneration. To date, SCs have yet to be elucidated in DM1; therefore, the aim of the present study was to extensively characterize the PAX7+ SC population, along with other indices of muscle quality in SkM. DM1 patients (6 women, 5 men) performed stationary cycling 3 times per week for 12wks, with biopsies taken from the Vastus lateralis pre- (PRE) and post-endurance exercise intervention (POST). Age-matched, healthy controls (CTRL) were used for comparison of baseline measures. Type 1 and 2 myofiber-specific PAX7+ cells were significantly greater in DM1 patients (PRE), in comparison to CTRL (2.24- and 1.84-fold, respectively), with type 2 SC content further increasing following training (p<0.05). In addition, protein expression of myogenic regulatory factors PAX7 and myogenin were significantly higher in DM1 compared to CTRL, with no training effects observed. Both immunohistochemical and immunoblotting analysis showed that activated MYOD+/PAX7+ cells did not significantly differ in DM1 vs. CTRL. FISH- IF analysis of CUG repeats show that 30% of SCs in DM1 were positive for these inclusions. Muscle capillarization was significantly lower in type 2 fibers in DM1 vs CTRL, which was fully rescued with training (p<0.05). At baseline, DM1 muscle showed the presence of de novo and fat infiltrated fibres, as well as fibrosis, that were relatively non-existent in the CTRL. In vitro results show patient-derived myoblasts exhibit a proliferation defect. Furthermore, myoblasts showed impairments in both glycolysis and mitochondrial respiration, with the latter being completely normalized to CTRL in myotubes. Our novel findings display an increased, albeit non-functional, SC pool in DM1 SkM indicated by disturbances in the myogenic program and overall poor muscle quality. We show that both SCs and SkM remain responsive to exercise training, suggesting therapeutic potential. We also suggest that mitochondrial dysfunction may underpin these impairments in the myogenic program. / Thesis / Master of Science (MSc) / Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults worldwide affecting 1:8000 individuals, with certain areas in northeastern Quebec having a higher prevalence of 1:600 individuals. DM1 is caused by an autosomal dominant genetic mutation that leads to muscle weakness, respiratory insufficiency, cataracts and cardiac conduction block, ultimately resulting in poor quality of life and shortened lifespan. Preliminary evidence suggests that the maintenance of muscle health can greatly improve quality of life and life-span of these individuals, making an in-depth research focus on this therapeutic intervention extremely important. Optimal muscle health is maintained by the functionality of muscle stem cells, that aid in muscle repair and facilitate adaptations in muscle following exercise interventions. These cells are shown to be dys- or non-functional in various muscular dystrophies which coincide with the observation of poor muscle health. Therefore, the aim of this study was to examine the number and functionality of muscle stem cells, and physiological factors of muscle health in DM1. In addition, we also aimed to explore whether exercise has therapeutic potential to alleviate poor muscle quality in DM1. In general, we found that DM1 patients have a higher proportion of muscle stem cells; however, they are inherently dysfunctional but did respond to exercise. Consistent with the latter observation, we found poor muscle quality metrics in DM1 patients, with aerobic training leading to improvements in muscle health. Altogether, our results provide in-depth analysis that underscores muscle dysfunction observed in DM1 and the benefits of exercise interventions.

No description available.

京都大学 / 新制・論文博士 / 博士(医科学) / 乙第13611号 / 論医科博第12号 / 新制||医科||11(附属図書館) / 九州大学大学院薬学府創薬科学専攻 / (主査)教授 井上 治久, 教授 松田 秀一, 教授 萩原 正敏 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM