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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Branchpoints as potential targets of exon-skipping therapies for genetic disorders / ブランチポイントは遺伝性疾患に対するエクソンスキッピング療法の有望な標的である

Ohara, Hiroaki 23 January 2024 (has links)
京都大学 / 新制・課程博士 / 博士(医学) / 甲第24996号 / 医博第5030号 / 新制||医||1069(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 齊藤 博英, 教授 滝田 順子, 教授 小川 誠司 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM
42

Preclinical and clinical characterization of lung cancers with Exon 19 insertion

Shaffer, William Wood Lee 08 March 2024 (has links)
The epidermal growth factor receptor (EGFR)-K745_E746insIPVAIK and others with rare PVAI amino-acid insertions are exon 19 insertion mutations (<1% of all EGFR mutations), which, at the structural modeling level, resemble EGFR tyrosine kinase inhibitor (TKI)-sensitizing mutants. An important unmet clinical need is the characterization of therapeutic windows of rare exon 19 PVAI amino-acid insertions to available EGFR TKIs. A limited number of preclinical and clinical reports have studied the response of these mutants to all classes of approved EGFR TKIs. We used models of EGFR-K745_E746insIPVAIK and more typical EGFR mutations (exon 19 deletion, L858R, L861Q, G719S, A763_Y764insFQEA, other exon 20 insertion mutations) to probe representative 1st (erlotinib), 2nd (afatinib), 3rd generation (osimertinib), and EGFR exon 20 active (mobocertinib) TKIs. We used human lung-cancer derived cell lines and transduced Ba/F3 cells to measure the treatment efficacy. We also compiled outcomes of EGFR exon 19 insertion mutated lung cancers−from our institution plus the literature−treated with EGFR TKIs. Cells driven by EGFR-K745_E746insIPVAIK had sensitivity to all classes of EGFR TKIs when compared to cells driven by EGFR-wild type in proliferation assays and at the protein level. However, the therapeutic window (calculated in preclinical models as the logarithm of the 50% inhibitory concentration of EGFR mutation compared to wild-type EGFR) of EGFR-K745_E746insIPVAIK driven cells was most akin to those of cells driven by EGFR-L861Q, EGFR-G719S and EGFR- A763_Y764insFQEA than the more sensitive patterns seen with cells driven by an EGFR exon 19 deletion or EGFR-L858R. The majority of patients with lung cancers harboring EGFR- K745_E746insIPVAIK and other mutations with rare PVAI amino-acid insertions responded to clinically available EGFR TKIs (including icotinib, gefitinib, erlotinib, afatinib and osimertinib), with heterogeneous periods of progression-free survival. This is the largest preclinical/clinical report to highlight that EGFR- K745_E746insIPVAIK and other mutations with rare exon 19 PVAI amino-acid insertions are sensitive to clinically available TKIs; in a pattern that mostly resembles the outcomes of models with EGFR-L861Q, EGFR-G719S and EGFR-A763_Y764insFQEA mutations. These findings are consistent with the proposed mechanism of activation of mutant EGFR by alteration of the proposed hydrophobic core. These data may help with the off-label selection of EGFR TKIs and clinical expectations of outcomes when targeted therapy is deployed for these rare EGFR mutated lung cancers. / 2026-03-08T00:00:00Z
43

Recherche des mécanismes impliqués dans les dérégulations de l'épissage alternatif à l'origine de la progéria et étude du rôle de l'étape d'épissage dans les changements globaux d'expression des gènes en réaction au choc thermique / Search of the mechanisms involved in alternative splicing misregulations resulting in progeria and study of the role of the splicing step in global changes of gene expression in response to thermic stress

Vautrot, Valentin 12 December 2013 (has links)
Le syndrome de Hutchinson-Gilford, ou progéria, est une pathologie génétique rare qui se caractérise par des symptômes assimilés à un vieillissement prématuré. Les mutations à l'origine de la progéria affectent le gène LMNA, codant la lamine A, qui joue un rôle majeur dans la formation, la maintenance et la résistance du noyau. Ces mutations activent l'utilisation de sites 5' alternatif ou cryptique d'épissage présents dans l'exon 11 du pré-ARNm LMNA en amont du site normalement utilisé. Nous avons révélé un effet des mutations sur la structure secondaire de l'ARN aux alentours des mutations, qui permet l'augmentation de l'utilisation des sites d'épissage mutants. De plus, nous avons montré l'implication de plusieurs protéines SR (SRSF1, SRSF5 et SRSF6) dans la régulation de l'utilisation des différents sites d'épissage. D'autre part, il a déjà été observé que les noyaux des cellules des patients atteints de progéria contiennent des granules de stress, les nSB, situés dans les régions péricentromériques des chromosomes et contenant des ARN dits satellite III et des facteurs d'épissage. Des nSB similaires sont formés dans les cellules saines suite à divers stress, comme le stress thermique. Il est possible que ces nSB séquestrent ces facteurs d'épissage afin de réguler le profil d'épissage alternatif des cellules pendant la régénération après un stress. Nous avons purifié les protéines associées aux ARN satellite III in vitro afin de trouver de nouveaux composants des nSB et analysé, par emploi de puces jonction-exon, le transcriptome de cellules soumises à un choc thermique, pour mieux comprendre à terme comment la formation des nSB peut affecter l'épissage alternatif / The Hutchinson-Gilford syndrome, also called progeria, is a rare genetic disease, characterized by symptoms that can be assimilated to accelerated natural ageing. Mutations that cause progeria affect the LMNA gene, which codes the lamin A that plays a major role in the shaping, maintenance and resistance of the nucleus. These mutations lead to the activation of alternative or cryptic 5' splice sites located within the exon 11 of LMNA pre-mRNA upstream from the normal 5' splice site. Our work revealed an effect of the mutations on the 2D RNA structure of the splice sites, which contributes to the increased use of the mutant sites. On top of it, we showed the impact of several SR proteins, (SRSF1, SRSF5 and SRSF6) on the regulation of the use of the exon 11 5' splice sites. On the other hand, it was previously observed that cells from progeria patients contain nuclear stress bodies (nSB), located in chromosomal pericentromeric regions and containing satellite III RNAs and several splicing regulatory proteins. Similar bodies are formed in healthy cells submitted to various stresses such as heat shock. A work hypothesis is that those nSBs sequester splicing factors in order to regulate the global alternative splicing profile in cells during the recovery period after stress. We purified proteins associated with satellite III RNAs in vitro, to find new components of the nSBs, and analyzed the transcriptome of cells subjected to heat shock using exon junction microarrays, in order to eventually understand how nSB formation can affect alternative splicing
44

Histonmodifieringar och alternativ splicing / Histone modifications and alternative splicing

Berggren, Jenny January 2011 (has links)
Alternativ splicing av pre-mRNA ger upphov till proteindiversitet. Histonmodifieringar kopplas till den alternativa splicingens reglering genom adaptorsystem som overfor den epigenetiska informationen direkt till splicingfaktorerna. De cis- agerande RNA- elementen pa exoner och introner med tillhorande trans- reglerande splicingfaktorer paverkas darfor direkt av specifika histonmodifieringar. En sammankopplande integrerad modell over en rad DNA- baserade processer foreslas. Denna komplexa modell ger en bild av interaktioner och paverkan mellan dessa delar. Kromatin remodellering kravs for bildandet av eukromatin. Nukleosomers placering vid exonrika regioner med specifika modifieringsmonster pekar ut exonerna samt mojliggor inbindning av RNA polymeras II som med sin CTD doman rekryterar bade splicing- och modifieringsfaktorer. Transkriptionshastigheten paverkas av nukleosomplaceringen vilket i sin tur paverkar rekrytering av spliceosomens komponenter, andra trans- agerande regulatorer och aven pre-mRNA sekvensens sekundarstruktur. Kromatin- adaptorkomplex laser av specifika histonmodifieringar och overfor informationen till splicingapparaten. Detta skapar mojlighet till den viktiga cell- och vavnadsspecifika alternativa splicingens reglering. I den integrerade modellen blir komplexiteten tydligare dar alla dessa processer interagerar med varandra och de cis- regulatoriska sekvenserna pa premRNA transkriptet. / Alternative splicing of pre-mRNA generates protein diversity. Histone modifications are connected to the regulation of alternative splicing through adaptor systems that transfers the epigenetic information directly to the splicing factors. The cis- acting RNA elements on the exons and introns together with the trans- regulating splicing factors are therefore directly affected of specific histone modifications. An integrated model over several DNA process mechanisms is suggested. This complex model explains the interactions of the different parts and how they affect each other. Chromatin remodelers are required to obtain euchromatin. Nucleosome positioning at exon rich regions with a specific modification pattern point out where the exons are, and this enable the RNA polymerase II to find and bind to the DNA. It’s CTD domain recruits both splicing- and modifications factors. The transcription rate is also affected of the nucleosome positioning and that in turn affects the recruitment of the components of the spliceosomen, other trans- acting regulators and even the formation of the secondary structure of the pre-mRNA transcript. Chromatin- adaptor complex reads specific histone modifications and transfers this information to the splicing apparatus. All this creates the possibility to regulate important cell- and tissue specific alternative splicing patterns. The integrated model makes the complex processes more clearer when all these integrates with each other and the cis- acting regulating elements on the pre-mRNA transcript.
45

Avaliação das características demográficas, clínicas e polimorfismo genético como fatores de risco para o prolapso pélvico em mulheres brasileiras / Collagen type 3 alpha 1 polymorphism as a risk factor for genital prolapse

Martins, Karina de Falco [UNIFESP] 26 May 2010 (has links) (PDF)
Made available in DSpace on 2015-07-22T20:49:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-26. Added 1 bitstream(s) on 2015-08-11T03:26:03Z : No. of bitstreams: 1 Publico-12542.pdf: 1298581 bytes, checksum: c93d3b1854a9178225ef23685647d105 (MD5) / Objetivo: verificar a possível associação entre a presença do polimorfismo no exon 31 do gene do COL3A1 e a ocorrência de prolapso genital em uma amostra da população brasileira. Casuística e Métodos: estudo caso controle envolvendo 316 pacientes estadiadas para prolapso genital, utilizando-se o sistema de quantificação de prolapso dos órgãos pélvicos (POP-Q), padronizado pela Sociedade Internacional de Continência (ICS). O grupo caso foi constituído por 107 pacientes nos estádios III e IV e o grupo controle por 209 mulheres nos estádios 0 e I. Aplicouse a estas pacientes a anamnese dirigida, com o objetivo de avaliar a presença ou não dos principais fatores de risco para prolapso genital (história obstétrica, idade da menopausa, história familiar, tosse crônica e constipação intestinal). Foi realizada, ainda, coleta de 5 ml de sangue periférico para extração do DNA leucocitário. O fragmento a ser estudado (exon 31 do gene do COL3A1) foi amplificado por meio de reação de polimerase em cadeia (PCR). Para a comparação das variáveis qualitativas foi utilizado o teste de Qui-quadrado (X2). Para as variáveis quantitativas foi optado pelo teste de Mann-Whitney U, já que estas variáveis não tiveram padrão de distribuição normal na população. Para o cálculo do valor de odds ratio e Intervalos de Confiança foi utilizada Regressão Logística Binária. O valor de significância estatística estabelecido foi de 5%, ou p<0,05 e o intervalo de confiança foi de 95% (95% IC). Os indivíduos homozigotos mutados e heterozigotos foram analisados e englobados em um só grupo e comparados com os homozigotos selvagens para a alteração genética pesquisada. Toda a análise estatística foi realizada com o software Statistical Package for Social Sciences, version 14.0. Resultados: Com relação às variáveis quantitativas, foram observadas diferenças significativas para todas (p<0,05), com exceção da idade da menopausa. Já na análise das variáveis qualitativas, observamos que só houve diferença significante para as mulheres que apresentavam história familiar de prolapso genital. Não houve diferença estatisticamente significante quanto à presença do polimorfismo em questão em ambos os grupos estudados, considerando que os genótipos em estudo encontravam-se em Equilíbrio de Hardy-Weinberg. Conclusão: a presença de polimorfismo no exon 31 da cadeia alfa 1 do gene do colágeno tipo III não é fator de risco para prolapso genital na amostra da população brasileira estudada. / Objective: To verify the possible association between the presence of the polymorphism in exon 31 of COL3A1 gene and the occurrence of genital prolapse in a sample of the population. Methods: case-control study involving 316 patients staged for pelvic organ prolapse, using the system for quantification of pelvic organ prolapse (POP-Q), standardized by the International Continence Society (ICS). The case group consisted of 107 patients with stage III and IV and the control group of 209 women at stages 0 and I. Was applied to these patients anamnesis, in order to assess the presence or absence of major risk factors for genital prolapse (obstetric history, age at menopause, family history, chronic cough and constipation). There was also, collecting 5 ml of peripheral blood leukocyte DNA extraction. The fragment to be studied (exon 31 of COL3A1 gene) was amplified by the polymerase chain reaction (PCR). To compare the qualitative variables we used the chi square (X2). For quantitative variables was chosen by the Mann - Whitney U, as these variables had normal distribution pattern in the population. For the calculation of odds ratios and confidence intervals was used binary logistic regression. The value of statistical significance was set at 5% or p <0.05 and confidence interval was 95% (95% CI). The homozygous and heterozygous mutant were analyzed and grouped into one group and compared with the homozygous wild for the gene studied. All statistical analysis was performed with the Statistical Package for Social Sciences, version 14.0. Results: With respect to quantitative variables, significant differences were observed for all (p <0.05), except for age of menopause. In the analysis of qualitative variables, we found that only significant difference for women who had a family history of prolapse. There was no statistically significant difference regarding the presence of the polymorphism in question in both groups, whereas the genotypes studied were in Hardy-Weinberg. Conclusion: The presence of a polymorphism in exon 31 of alpha chain 1 gene of collagen type 3 is not a risk factor for pelvic organ prolapse in the Brazilian population studied. / TEDE / BV UNIFESP: Teses e dissertações
46

RNA-based therapies for dysferlinopathies / Utilisation d'acide ribonucléique pour le traitement des dysferlinopathies

Philippi, Susanne 25 September 2014 (has links)
L’épissage en cis des précurseurs d’ARN messager (pre-ARNm) est une stratégie intéressante afin de réparer des gènes dont la régulation transcriptionnelle est déterminante pour la fonction de la protéine. Les mutations touchant le gène dysferline (DYSF) sont liées au développement de dystrophies musculaires: la dystrophie musculaire des ceintures de type 2B et la myopathie distale de Miyoshi. Une stratégie à modifier l’épissage en cis des pre-ARNm du gène DYSF est le procédé SMaRT (pour spliceosome-mediated mRNA trans-splicing), une technique de réparation de l'ARN messager au moyen d'un complexe de trans-épissage appelé PTM (pour pre-mRNA trans-splicing molecule). Le procédé SMaRT utilisant le complexe PTM permet le remplacement d’importantes portions de pre-ARNm tout en préservant l’intégrité totale du transcrit. Dans un soucis d’obtenir un trans-epissage efficace, seuls les introns codant pour les pre-ARNm de DYSF présentant de forts signaux d’épissage répartis de façon disparate ainsi que des tailles très différentes furent ciblées par les PTMs dans des myoblasts humains ne possédant pas de dysferlin. Le trans-épissage de deux introns ciblés du gène DYSF engendra une formation correcte de la protéine dysferlin dans des mutants DYSF-/- de souris. Les niveaux de protéine fonctionnelle furent toutefois modérés, mais similaires aux taux de récupération obtenus par des stratégies précédentes de trans-épissage ciblant d’autres gènes. Néanmoins, parmi les introns ciblés avec succès dans cette étude et dans des essais précédents, des critères concordants ont pu être identifiés afin de faciliter le choix des introns à cibler pour de futures stratégies de trans-épissage. / RNA-based therapy is an approach to cure genetic disorders with no intervention into endogenous spatiotemporal gene regulation. I established two approaches for the dysferlin gene, (i) spliceosome-mediated pre-mRNA trans-splicing (SmaRT) and (ii) exon-skipping, in order to rescue dysferlin mutations leading to Limb Girdle Muscular Dystrophy 2B and Miyoshi Myopathy. SmaRT permits the correction of numerous mutations of a gene by a single pre-mRNA trans-splicing molecule (PTM) by exchanging multiple exons of a gene for a healthy mRNA sequence. The PTM binds to intronic sequence and competes with the endogenous pre-mRNA for the binding of the spliceosome. I designed PTMs to exchange the 3’ part of the dysferlin messenger and determined two functioning PTMs bytransduction of human myoblasts and intramuscular injection in wild-type and DYSF-/- mice and could show dysferlin protein rescue in DYSF-/- mice.By exon-skipping exons carrying mutations can be excised from pre-mRNA in masking exon or intron internal sequences defining the exon in the splicing process. I employed antisense oligonucleotides (AONs) of tricyclo-DNA in order to excise dysferlin exon 32. It was shown to be particularly feasible for systemic application, making it suitable for diseases affecting different compartments of skeletal muscle and other organs. The dysferlin exon 32 has been shown to be dispensable for known functions of the dysferlin protein. I designed tc-DNA AONs leading to efficient skipping in patient myoblasts and in wild-type mice following intramuscular injection. I am collaborating to investigate effects of exon 32 skipping in an Exon-32-STOP mouse model.
47

Genetic Risk Factors in Parkinson’s Disease

Daniel Buchanan Unknown Date (has links)
Background: Parkinson’s disease (PD) is a complex disease with a multi-factorial aetiology, comprising both genetic and environmental risk factors. The disease pathology is progressive and neurodegenerative where dopaminergic nerve cell death occurs predominantly in the substantia nigra pars compacta (SNpc) with the subsequent loss of the dopamine neurotransmitter in the basal ganglia. The most significant risk factors for PD include an advancing age and a family history of the disease, while environmental and lifestyle risk factors such as pesticide exposure and smoking are widely accepted as risk altering exposures. Currently up to 10% of PD is attributed to Mendelian inherited PD at one of 13 PARK loci in 9 genes. The pursuit of common susceptibility alleles for idiopathic PD has proven challenging with only a few loci reproducibility associated with an altered risk. The aim of this thesis is to study, using a candidate gene case-control design, the potential role of genetic variants in PD. The APOE candidate gene was hypothesized to modify the risk of PD as it is a proven modifier of Alzheimer’s disease (AD). The common pathological finding in PD of elevated levels of iron within the SNpc is proposed to increase the oxidative state of the nerve cells and predispose the dopaminergic neurons to apoptosis. Therefore, susceptibility alleles within the candidate genes that regulate iron metabolism and homeostasis are hypothesized to alter iron metabolism and predispose to iron-induced neurodegeneration in PD. Missense variants and common “tagging” SNPs with the HFE, Transferrin and Transferrin Receptor genes are investigated extensively in this thesis. Finally, autosomal recessively inherited PD can result from mutations in the parkin gene at the PARK2 locus. The final hypothesis explored in this thesis suggests that non-deleterious missense variants in the parkin gene modify the risk for developing sporadic PD. Further genetic variation in the parkin gene such as exon rearrangements is a frequently reported mutation where heterozygosity for these rearrangements may increase the risk of PD. Heterozygous deletions or duplications of exons in the parkin gene provide technical challenges for their detection. In this thesis a novel assay for the detection of these mutations is investigated. Methods: Genotyping was performed using PCR-RFLP for genetic variants in the APOE (E2 and E4 alleles), HFE (C282Y, H63D and S65C), Transferrin receptor (TfR; S142G), Transferrin (Tfn; P570S and G258S), IREB2 genes (L159V) and the parkin gene (S167N, R366W and V380L) in a cohort of 425 PD cases and 387 controls recruited from throughout Queensland, Australia. A tagged SNP high-throughput genotyping approach was then employed to try to replicate single SNP associations in 6 iron-related genes using a cohort of 1034 PD cases and 774 controls. These genetic variants were analysed for direct association with PD risk, age of onset effects as well as potential gene x gene (GxG) and gene x environment (GxE) interactions. Additionally, a quantitative PCR assay was developed to detect heterozygous deletions and duplications within the parkin gene and utilised to screen 43 YOPD cases for these mutations. Results: The initial study of the HFE C282Y variant revealed a significant protective association with PD in the two independent cohorts studied. Further study did not reveal significant associations with PD for the other HFE variants or missense variants within the Tfn and TfR genes. When analysed for GxE interactions, the C282Y, P589S and G277S variants showed evidence for an increased risk of PD in synergy with pesticide and herbicide exposure. Carriers of the risk variant and with toxin exposure were at two-fold increased risk of PD, although the number of individuals in this category was small. A further investigation of the role of common genetic polymorphisms in iron genes revealed only one of the 20 SNPs genotyped using high-throughput multiplex methods, remained significantly associated with PD after correction for age and sex. The rs198855 SNP is downstream of the HFE gene and further implicates a role for HFE in PD. The APOE E4 allele demonstrated modifying effects for the age of PD onset, restricted to the female cases. Analysis of the parkin missense variants also demonstrated a modifying effect on the age of PD onset in carriers of the S167N variant, with putative interactions between the APOE E4 allele, a family history of PD and toxin exposure that further reduced the age of onset. Twenty individuals of the 43 YOPD cases screened demonstrated heterozygous parkin exon rearrangements using the novel qPCR method. Conclusions: Non-synonymous variants within iron-related genes or the parkin gene putatively interact with herbicide and pesticide exposure to increase the risk of PD or modify the phenotype, highlighting the need for future studies to address the multi-factorial aetiology of PD in their study design and analysis. This thesis provides evidence for the association between genetic variation within the HFE locus and PD and for the APOE E4 allele as a modifier of PD.
48

Early pathogenesis of Duchenne muscular dystrophy modelled in patient-derived human induced pluripotent stem cells. / デュシェンヌ型筋ジストロフィー患者由来iPS細胞を用いた初期病態再現

Shoji, Emi 23 July 2015 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19229号 / 医博第4028号 / 新制||医||1011(附属図書館) / 32228 / 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 妻木 範行, 教授 井上 治久 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM
49

Transcriptional regulation of the human alcohol dehydrogenases and alcoholism

Pochareddy, Sirisha 09 March 2011 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Alcohol dehydrogenase (ADH) genes encode proteins that metabolize ethanol to acetaldehyde. Humans have seven ADH genes in a cluster. The hypothesis of this study was that by controlling the levels of ADH enzymes, cis-regulatory regions could affect the risk for alcoholism. The goal was thus to identify distal regulatory regions of ADHs. To achieve this, sequence conservation across 220 kb of the ADH cluster was examined. An enhancer (4E) was identified upstream of ADH4. In HepG2 human hepatoma cells, 4E increased the activity of an ADH4 basal promoter by 50-fold. 4E was cell specific, as no enhancer activity was detected in a human lung cell line, H1299. The enhancer activity was located in a 565 bp region (4E3). Four FOXA and one HNF-1A protein binding sites were shown to be functional in the 4E3 region. To test if this region could affect the risk for alcoholism, the effect of variations in 4E3 on enhancer activity was tested. Two variations had a significant effect on enhancer activity, decreasing the activity to 0.6-fold. A third variation had a small but significant effect. The effect of variations in the ADH1B proximal promoter was also tested. At SNP rs1229982, the C allele had 30% lower activity than the A allele. In addition to studying the regulatory regions of ADH genes, the effects of alcohol on liver-derived cells (HepG2) were also explored. Liver is the primary site of alcohol metabolism, and is highly vulnerable to injuries due to chronic alcohol abuse. To identify the effects of long term ethanol exposure on global gene expression and alternative splicing, HepG2 cells were cultured in 75 mM ethanol for nine days. Global gene expression changes and alternative splicing were measured using Affymetrix GeneChip® Human Exon 1.0 ST Arrays. At the level of gene expression, genes involved in stress response pathways, metabolic pathways (including carbohydrate and lipid metabolism) and chromatin regulation were affected. Alcohol effects were also observed on alternative transcript isoforms of some genes.
50

Etude de séquences cis-régulatrices d'épissage dans le gène DMD : rôle dans la régulation des pseudoexons et intérêt pour le saut d'exon thérapeutique. / Splicing cis-regulatory sequences in the DMD gene : role in pseudoexons regulation and interest for the therapeutic exon skipping strategy.

Messaoud Khelifi, Mouna 16 December 2010 (has links)
L'épissage des ARN pré-messagers est une étape essentielle pour l'expression des gènes chez les eucaryotes supérieurs. La reconnaissance des exons par la machinerie d'épissage est réalisée grâce à différents éléments cis-régulateurs incluant les séquences consensus d'épissage et les séquences auxiliaires activatrices ou inhibitrices d'épissage. Le pré-ARNm représente une nouvelle cible thérapeutique pour le traitement des maladies génétiques. L'approche du saut d'exon thérapeutique, destinée à restaurer l'expression d'une protéine totalement ou partiellement fonctionnelle en interférant avec le processus d'épissage, suscite un grand intérêt notamment pour la dystrophie musculaire de Duchenne où la modification du transcrit permettrait d'obtenir une forme modérée de la maladie, la Dystrophie musculaire de Becker. Des oligonucléotides antisens sont utilisés pour masquer les signaux d'épissage de reconnaissance d'un exon par le spliceosome, et induire son excision (ou saut) du transcrit mature. La détermination de la meilleure séquence cible des AONs est une difficulté majeure de cette approche. Pour le gène DMD, nous avons pu établir grâce à des analyses bioinformatiques et statistiques combinées avec des tests fonctionnels utilisant des minigènes rapporteurs d'épissage, que le ciblage de motifs exoniques qui fixent le facteur d'épissage SF2/ASF permettait d'obtenir la meilleure efficacité des AONs. Par ailleurs, nous avons exploré la régulation de l'épissage des pseudoexons dans le gène DMD, et notamment les mécanismes conduisant à l'inclusion de ces séquences introniques dans le transcrit mature en condition pathologique. L'étude de deux cas exceptionnels d'activation de pseudoexons associée à des remaniements introniques rares (double délétion, inversion) élargit le spectre des mutations à l'origine de ces défauts d'épissage, et illustre le rôle encore mal connu des remaniements introniques en pathologie humaine. / Splicing of pre-messenger RNAs to mature transcripts is a crucial step in eukaryotic gene expression. The recognition of exon by the splicing machinery involves different cis-regulatory elements, including the splice site motifs and auxiliary sequences, which can act by stimulating or repressing splicing. The pre-mRNA represents a new therapeutic target for the treatment of genetic diseases. Notably, the exon skipping strategy is currently one of the most promising therapeutic approaches for the Duchenne muscular dystrophy. It intends to restore the expression of a partially functional protein by interfering with the splicing process, and converts the severe DMD phenotype into the moderate form of the disease, Becker muscular Dystrophy (BMD). Antisense oligonucleotides are used to mask the splicing signals involved in exon recognition by the spliceosome to induce its skipping from the mature transcript and restore an open reading frame. The determination of the best target sequence of the AONs is one of the major hurdles to overcome. For the DMD gene, a bioinformatic and statistical analysis combined with minigenes studies allowed us to establish that targeting binding sites for the splicing factor SF2/ASF maximizes the AONs efficiency. In a second part of this work, we investigated the splicing regulation of pseudoexons in the DMD gene, in particular the mechanisms leading to the inclusion of these intronic sequences in the mature transcript in pathological conditions. The study of two exceptional cases of pseudoexons activation associated with rare intronic rearrangements (double-deletions, inversion) expands the spectrum of missplicing mutations, and demonstrates the potential role of pure intronic rearrangements in human pathology.

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