For more than a decade, studies focused on RNA interference (RNAi) pathway as a pivotal gene regulatory mechanism. RNAi components are attracting considerable interest due to the recent evidence demonstrating that they play a role not only in post-transcriptional regulation but also in transcriptional level. The involvement of RNAi components in heterochromatin formation and RNA Pol II processivity and alternative splicing in different organisms has been shown. Dicer protein, a highly conserved protein among kingdoms, is one of the main effectors in this pathway. There is a considerable amount of literature on Dicer’s role in the cytoplasm; however, there is still vast ambiguity concerning nuclear Dicer. More recent evidence reveals the existence of Dicer1 variants that are differentially expressed in some cancer cells. Our experiments set out to investigate one of these variants that we hypothesise is responsible for the nuclear function. We undertook genomic and biochemical approaches applied to HAP 1 cells as a model system to characterise Dicer1-s, taking advantage of a custom-made antibody in our research group. Here, as anticipated, our experiments proved that Dicer1-s is enriched in the nuclear compartment compared to full-length Dicer1, indicating that it might be a putative contributor to nuclear gene regulation activity. Unfortunately, it was not possible to establish a mutant cell line to investigate the significant nuclear function of Dicer1-s, due to the need for further optimisation of the methods used. Exploitation of previously optimised gene knock-out tools might accelerate shedding light on protein, DNA, and RNA partners, disclosing the exact nuclear mechanisms that might exhibit similar activity.

Les tumeurs malignes rares de l'ovaire représentent moins de 8% des tumeurs ovariennes de l'adulte. Il s'agit essentiellement des tumeurs germinales de l'ovaire et des tumeurs du stroma et des cordons sexuels de l'ovaire (tumeurs de la granulosa et tumeurs de Sertoli-Leydig). En 2002, du fait de l'extrême rareté de ces tumeurs, un site internet français (www.ovaire-rare.org) a été créé dans le but d'informer les patientes, de créer un forum de discussion, d'actualiser les informations scientifiques, d'inclure les données cliniques et biologiques des patientes et de collecter les blocs de tumeurs. Ce travail coopératif a pour but de standardiser la gestion des tumeurs ovariennes non épithéliales, et d'accumuler les données cliniques et biologiques. Cet observatoire nous a permis de regrouper plus de 200 tumeurs sur lequel repose notre travail. Des mutations des gènes FOXL2 et DICER1 ont été récemment décrites respectivement dans les tumeurs de la granulosa et les tumeurs de Sertoli-Leydig. Nous avons montré l'importance de la recherche de ces mutations pour le diagnostic et le pronostic de ces tumeurs. Nous avons également élaboré un nouvel arbre décisionnel, incluant ces nouveaux outils, et qui a permis de corriger plus de 20% des diagnostics initiaux. Au niveau moléculaire, nous avons analysé l'impact de la mutation C134W de FOXL2 sur le développement des tumeurs de la granulosa. De façon très intéressante, nous montrons une expression préférentielle de la protéine anti-apoptotique Bfl-1 (famille Bcl-2) dans les cellules exprimant FOXL2 sous sa forme mutée. L'expression de Bfl-1 est induite dans les lignées surexprimant la forme mutée de FOXL2 et confère aux cellules une résistance au stress apoptotique. De même, l'inhibition de l'expression de Bfl-1 restaure la sensibilité à l'apoptose induite par des stress apoptotiques. L'ensemble de nos résultats montre que Bfl-1 est une cible transcriptionnelle de FOXL2 et qu'il constitue une cible thérapeutique très intéressante pour ces tumeurs. En conclusion, nos travaux ont permis d'améliorer nos connaissances sur les tumeurs rares de l'ovaire, en terme de pronostic et de diagnostic, mais aussi d'entrevoir de nouvelles stratégies thérapeutiques / Rare malignant ovarian tumors represent less than 8% of ovarian tumors in adults. It is essentially germ cell tumors of the ovary and stromal tumors and sex cord ovarian (granulosa cell tumors and Sertoli-Leydig cell tumors). In 2002, due to the extreme rarity of these tumors, a French website (www.ovaire-rare.org) was created to inform patients, create a discussion forum, update scientific information, to include clinical and laboratory data of patients and collect blocks of tumors. This collaborative work has the purpose to standardize the management of nonepithelial ovarian tumors, and accumulating clinical and laboratory data. The observatory has allowed us to consolidate more than 200 tumors on which our work is based. Mutations of FOXL2 and DICER1genes have recently been described respectively in the granulosa cell tumors and Sertoli-Leydig tumor. We have shown the importance of research of these mutations for the diagnosis and prognosis of these tumors. We also developed a new decision tree, including these new tools, and has corrected more than 20% of initial diagnoses. At the molecular level, we analyzed the impact of the FOXL2 C134W mutation on the development of granulosa cell tumors. Very interestingly, we show preferential expression of anti-apoptotic protein Bfl-1 (Bcl-2A1) in cells expressing FOXL2 mutated form. Bfl-1 expression is induced in the lines overexpressing the mutated FOXL2 and confers resistance to apoptotic cells form stress. Similarly, inhibition of expression Bfl-1 restores sensitivity to apoptosis induced by the apoptotic stress. All of our results show that Bfl-1 is a transcriptional target of FOXL2 and it is a very interesting therapeutic target for these tumors. In conclusion, our work has improved our knowledge about rare ovarian tumors in terms of prognosis and diagnosis, but also opens up new therapeutic strategies

Les syndromes myélodysplasiques (SMD) sont dus à une atteinte oligoclonale de la cellule souche hématopoïétique aboutissant à une dysplasie des lignées myéloïdes, des cytopénies sanguines et une évolution fréquente vers la leucémie aiguë. De nombreuses mutations décrites dans des gènes contrôlant la régulation épigénétique sont responsables de la genèse des SMD. Mais des travaux récents montrent également que des anomalies du microenvironnement médullaire, notamment des cellules stromales mésenchymateuses (CSM), peuvent induire et propager un SMD suggérant l’idée d’une communication intercellulaire étroite entre la niche et les cellules hématopoïétiques. L’invalidation du gène Dicer1 (RNASE de type III impliquée dans le processing des microARN) dans les progéniteurs ostéoblastiques murins induit un véritable SMD avec dysmyélopoïèse.Nous avons confirmé la sous-expression de Dicer1 dans les CSM SMD à partir de prélèvements primaires de moelle totale et dans les CSM en expansion. La sous-expression de Dicer1 s’accompagne d’une dérégulation du profil des microARN au sein de CSM SMD mise en évidence par étude transcriptomique des CSM SMD vs CSM témoins. Nous avons découvert une possible cible thérapeutique : le miR-486-5p que nous avons retrouvé constamment surexprimé dans les CSM SMD. Un des moyens pour les CSM d’influer sur les cellules souches hématopoïétiques peut se faire par la sécrétion de vésicules extracellulaires (EVs). Ces EVs sont hétérogènes et peuvent être définies par leur taille. Nous nous sommes plus particulièrement intéressés aux petites vésicules extracellulaires (sEVs) contenant la fraction exosomale qui est connue comme pouvant transporter des microARN, mARN et des protéines entre les cellules. Nous avons retrouvé ce miR-486-5p transporté comme cargo dans les sEVs sécrétées des CSM, des CSM vers les CD34+. De plus, nous montrons dans un modèle de co-incubation (sEVs avec CD34+ de sujets sains), que sur le plan fonctionnel, les sEVs provenant de CSM SMD induisent plus d’apoptose, plus de stress oxydatif ainsi que plus de dommage à l’ADN.Par ailleurs, la surcharge martiale observée chez les patients SMD est également responsable d’un stress oxydatif. Le déférasirox (DFX), un chélaleur de fer, a montré dans le cadre d’études rétrospectives une amélioration de l’érythropoïèse chez des patients SMD. Grâce à un modèle de différenciation érythroïde avec surcharge martiale, nous avons montré que de faibles doses de DFX induisent une meilleure prolifération des progéniteurs érythroïdes (moins d’apoptose et plus de cellules en cycle) via une activation de NF-κB. Cette activation est due à une diminution du niveau de dérivés réactifs de l’oxygène (ROS) en rapport avec une diminution du fer labile et est contrôlée de manière très fine par le niveau de ROS.Enfin, nous avons utilisé les propriétés du microenvironnement médullaire pour établir un modèle murin de SMD humain. En effet, la relative incapacité des cellules souches myélodysplasiques humaines de greffer et de reconstituer une hématopoïèse pathologique dans des souris immunodéprimées suggère que ces cellules souches SMD doivent avoir besoin d’un support extrinsèque du microenvironnement. Nous avons réalisé un modèle de souris humanisées en co-injectant des CSM et des CD34+ en intratibial. Une prise de greffe a été observée chez toutes les souris injectées et avons pu étudier l’évolution clonale au fil des générations dans les différentes sous-populations de progéniteurs myéloïdes (common myeloid progenitors (CMP), granulocyte macrophage progenitors (GMP) and megakaryocyte–erythroid progenitor (MEP)). Notre modèle est stable au cours des générations avec persistance du clone fondateur initial.En conclusion, ce travail confirme le rôle prépondérant du microenvironnement médullaire dans la genèse et la physiopathologie des syndromes myélodysplasiques et ouvre la voie à de nouvelles possibilités thérapeutiques. / Myelodysplastic syndromes (MDS) are hematopoietic stem cell (HSC) oligoclonal diseases leading to dysplasia, blood cytopenia and evolution to acute leukemia. Numerous mutations in genes involved in epigenetic regulation are responsible of MDS genesis. But recently, studies show that medullar microenvironment, particularly mesenchymal stromal cells (MSC), could induces and propagates a truly MDS suggesting a narrow communication between HSC and this niche. Dicer1’s (type III RNAse implicating in microRNA processing) invalidation in murine osteoblastic progenitors induces a MDS with sign of dysplasia.In this work, we have confirmed the under expression of Dicer1 in MDS mesenchymal stromal cells from total bone marrow and cultured MSC. Dicer1 down regulation leads to a deregulation of miRNome profile in MDS MSC highlighted by transcriptomic approaches. We found a potential therapeutic target: miR-486-5p which is constantly overexpressed in MDS MSC. Extracellular vesicles (EVs) could be a possible way for MSC to influence HSC fates. Those EVs are heterogeneous are could be characterized by their sight. We mainly focused on small EVs (sEVs) containing the exosomal fraction known to be able to carry miRNA, mRNA and proteins. We found that miR-486-5p is carry from MSC to the HSC. Transcriptomic analyses of HD HSC overexpressing miR-486-5p are ongoing. Moreover, in a co-incubation model (sEVs and healthy donor (HD) HSC), sEVs coming from MDS MSC induced apoptosis, oxidative stress and DNA damages.Moreover, iron overload seen in MDS patients is also able to induce DNA damages and oxidative stress. Deferasirox (DFX), an iron chelator, has shown an erythropoiesis improvement in MDS patients. Using an erythroid differentiation model with iron overload, we have observed that low dose of DFX induce a better proliferation of erythroid progenitors (less apoptosis and more cycling cells) due to NF-κB activation. This activation is due to a decrease of reactive oxygen species level in relation to a decrease of the labile iron pool.Finally, we have used medullar microenvironment properties to establish a murine model of MDS. Indeed, MDS HSC incapacity to reconstitute a pathological hematopoiesis in immunocompromised mice suggests that MDS HSC need an extrinsic support from the microenvironment. We have engineered a MDS patient derived xenograft (PDX) model by intra-tibial co-injection CD34+ cells with MSC. All mice engrafted et we have follow the clonal evolution over mice generation in the different subset of myeloid progenitors. (common myeloid progenitors (CMP), granulocyte macrophage progenitors (GMP) and megakaryocyte–erythroid progenitor (MEP)). Our model is stable over generations with persistence of the initial founding clone.In conclusion, this work confirms the preponderant role of the medullary microenvironment in the genesis and physiopathology of myelodysplastic syndromes and opens the way to new therapeutic possibilities.

Cystic nephromas are rare, multiloculated cysts on the kidneys that occur mostly in early childhood. They are considered to be on the same spectrum as cystic partially differentiated nephroblastomas (CPDN) and Wilm’s tumors (WT). They are mostly benign, however, when cystic nephroma is associated with DICER1 mutation, the patient is predisposed to other, more aggressive tumors. DICER1 mutations are not seen in CPDN or WT, so molecular evaluation can help differentiate between them if the histology is unclear. The DICER1 gene is on chromosome 14 and it functions to make microRNA that attaches to mRNA and represses protein synthesis. Mutations of this gene predispose patients to neoplasms on various organs such as the lung, kidneys, ovaries, and thyroid. The data in this case report was gathered via direct patient care and patient chart review. An 18-month-old previously healthy female was hospitalized for a newly diagnosed abdominal mass found on palpation during a well child evaluation. The ultrasound revealed a 9 cm cystic mass on the left kidney and the patient was subsequently sent to St. Jude Children’s Research Hospital. Further evaluation via CT scan has shown a large left renal mass that invaded the ureter and bladder, as well as enlarged lymph nodes in the left suprarenal space and a single 3mm right pulmonary nodule. At this time, cystic Wilm’s tumor was considered and the patient underwent a left radical ureteronephrectomy with lymph node sampling. Cytology report of the pelvic fluid had some inflammatory cells, but no tumor cells were seen in the sample. All of the sampled lymph nodes were also negative for tumor cells. The histological analysis of the mass revealed multiple cystic cavities separated by septa. No blastemal elements (WT1 immunostain was negative) or distinct solid areas were identified, which made the diagnosis of cystic Wilm’s tumor unlikely. The diagnosis of cystic nephroma (CN) vs cystic partially differentiated nephroblastoma (CPDN) is determined histologically by looking at the components of the septa – which, in this case, due to a marked inflammatory infiltrate expending the septa, made the morphology be more congruent with CPDN. Molecular testing of the tumoral tissue identified two DICER1 mutations (DICER1 frameshift mutation and DICER1 D1709E). Patient was subsequently diagnosed with Cystic Nephroma Stage I and further surveillance will be continued to monitor for more neoplasms associated with this mutation. This case highlights a rare disorder that predisposes patients to multiple neoplasms. Histology may not always be sufficient in determining the diagnosis, especially in differentiating CN from CPDN. Molecular evaluation may be helpful for the initial diagnosis and in order to provide adequate genetic counseling. Clinicians should be aware of DICER1 syndrome so they can adequately survey the at-risk patients for a range of benign and malignant neoplasms.

No description available.

A cardiomiopatia Chagásica Crônica (CCC) é a principal complicação decorrente da infecção pelo protozoário hemoflagelado Trypanosoma cruzi (T. cruzi). Trata-se de uma cardiomiopatia dilatada, caracterizada por um intenso infiltrado inflamatório, fibrose, dilatação das câmaras cardíacas, hipertrofia de cardiomiócitos e anormalidades de condução. Sua fisiopatologia é complexa e ainda não se consegue explicar porque apenas 30% dos pacientes infectados desenvolvem essa complicação. Nesse contexto, nosso laboratório descreveu pela primeira vez uma redução na expressão de microRNAs (miRNAs) enriquecidos em músculo (myomiRs) no miocárdio de pacientes com CCC. Sabendo-se que disfunções na biogênese de miRNAs em modelos animais levam ao desenvolvimento de cardiomiopatia do tipo dilatada com redução da expressão de myomiRs, hipotetizou-se que a CCC em humanos estaria associada a um prejuízo na biogênese de miRNAs no miocárdio. Dessa forma, amostras de ventrículo esquerdo de miocárdio de pacientes com CCC (n=16) e controles não-cardiomiopatas (n=6) foram utilizadas para avaliar: 1) a expressão gênica e proteica da maquinaria da biogênese de miRNAs (Drosha, Exportina-5, RAN, Dicer1, TRBP, PACT e Argonauta2), por qPCR e western blotting, respectivamente; 2) a expressão do transcrito primário (pri-miRNA), precursor (pré-miRNA) e miRNA maduro de myomiRs (miR-1, -133a, -133b, -208a, -208b, e -499); 3) o perfil de miRNAs diferencialmente expressos em CCC utilizando qPCR array; e 4) a interação dos miRNAs diferencialmente expressos com disfunções características da CCC (fibrose, miocardite, arritmia e hipertrofia) por meio de análises de bioinformática. Nossos resultados apontam para uma não-alteração nas etapas nucleares da biogênese de miRNAs (transcrição, edição e transporte), já que não foram encontradas alterações na expressão de pri- e pré-miRNAs de myomiRs, bem como dos componentes protéicos da biogênese, Drosha, Exportina-5 e RAN. Entretanto, observou-se uma disfunção na segunda etapa de edição da biogênese, citoplasmática, caracterizada por uma redução de 2/3 nos níveis protéicos de Dicer1, a qual não foi acompanhada por uma redução na expressão de seu RNA mensageiro. Evidenciou-se ainda, uma redução na expressão de 97,5% dos miRNAs maduros diferencialmente expressos no miocárdio de pacientes com CCC, incluindo myomiRs. As análises in silico revelaram haver participação dos miRNAs diferencialmente expressos em disfunções associadas a CCC, com destaque para a fibrose miocárdica, nodo central da rede. Experimentos adicionais preliminares sugeriram o acúmulo de adutos de 4-hidroxi-2-nonenal, decorrente do estresse oxidativo e de uma menor atividade da enzima aldeído desidrogenase 2, como uma possível causa para as alterações encontradas. Este é o primeiro estudo a caracterizar a biogênese de microRNAs em uma cardiomiopatia. Além disso, demonstrou-se que uma redução global do perfil dos miRNAs maduros diferencialmente expressos, decorrente uma disfunção na enzima Dicer1, está associada a eventos patológicos característicos da CCC. Estes mecanismos apresentam relevância biológica e terapêutica, podendo ser possivelmente compartilhados com cardiomiopatias de outras etiologias / Chronic Chagas disease cardiomyopathy (CCC) is the most severe complication of the infection by the haemoflagellate protozoan Trypanosoma cruzi. This dilated cardiomyopathy is characterized by an intense inflammatory infiltrate, fibrosis, dilation of cardiac chambers, cardiomyocyte hypertrophy and conduction abnormalities. Its pathophysiology is complex and why only 30% of patients experience this complication remains an open question. In this regard, our laboratory described for the first time a reduction in the expression of muscle-enriched microRNAs (myomiRs) in human CCC myocardium. Knowing that biogenesis dysfunction and myomiR reduced expression have been associated to the development of dilated cardiomyopathy in animal models, we hypothesized that an impairment of myocardial microRNA biogenesis would be associated to CCC. Hence, left ventricle tissue samples from CCC patients (16) and non-cardiomyopathy donors (6) were used to analyze: 1) mRNA and protein expression, by qPCR and western blotting, of canonical microRNA biogenesis machinery (Drosha, Exportin-5, RAN, Dicer1, TRBP, PACT, AGO2); 2) primary transcript (pri-miR), precursor (pre-miR) and mature microRNA expression of myomiRs (miR-1, -133a, -133b, -208a, -208b, e -499); 3) mature microRNA profile using qPCR array; and 4) the interaction between differentially expressed mature microRNAs and hallmark CCC dysfunctions (fibrosis, myocarditis, hypertrophy and arrhythmia) using bioinformatics tools. Our results point to a non-dysfunction of biogenesis nuclear steps (transcription, editing and transport), since expression of pri-, pre-microRNAs, Drosha, Exportin-5 and Ran are similar between CCC patients and controls. However, we observed an alteration in the cytoplasmic editing step, characterized by a 2/3 reduction in Dicer1 protein levels. In addition, a major downregulation of differentially expressed mature microRNAs (97,5%) was noticed. In silico analysis revealed an association between differentially expressed microRNAs and CCC hallmarks, particularly fibrosis, a central node in the network. Additional preliminary data suggest 4-hydroxi-2-nonenal myocardial accumulation, resulting from oxidative stress and aldehyde dehydrogenase 2 lower activity, as a possible cause for the alterations here described. This is the first study to conduct a comprehensive analysis of microRNA biogenesis machinery in a cardiomyopathy. Moreover, we have shown a major reduction in the expression of mature microRNAs, due to lower Dicer1 protein levels, to be associated to CCC hallmark dysfunctions. These mechanisms are biologically and therapeutically relevant, and may be shared with cardiomyopathies from different etiologies

A cardiomiopatia Chagásica Crônica (CCC) é a principal complicação decorrente da infecção pelo protozoário hemoflagelado Trypanosoma cruzi (T. cruzi). Trata-se de uma cardiomiopatia dilatada, caracterizada por um intenso infiltrado inflamatório, fibrose, dilatação das câmaras cardíacas, hipertrofia de cardiomiócitos e anormalidades de condução. Sua fisiopatologia é complexa e ainda não se consegue explicar porque apenas 30% dos pacientes infectados desenvolvem essa complicação. Nesse contexto, nosso laboratório descreveu pela primeira vez uma redução na expressão de microRNAs (miRNAs) enriquecidos em músculo (myomiRs) no miocárdio de pacientes com CCC. Sabendo-se que disfunções na biogênese de miRNAs em modelos animais levam ao desenvolvimento de cardiomiopatia do tipo dilatada com redução da expressão de myomiRs, hipotetizou-se que a CCC em humanos estaria associada a um prejuízo na biogênese de miRNAs no miocárdio. Dessa forma, amostras de ventrículo esquerdo de miocárdio de pacientes com CCC (n=16) e controles não-cardiomiopatas (n=6) foram utilizadas para avaliar: 1) a expressão gênica e proteica da maquinaria da biogênese de miRNAs (Drosha, Exportina-5, RAN, Dicer1, TRBP, PACT e Argonauta2), por qPCR e western blotting, respectivamente; 2) a expressão do transcrito primário (pri-miRNA), precursor (pré-miRNA) e miRNA maduro de myomiRs (miR-1, -133a, -133b, -208a, -208b, e -499); 3) o perfil de miRNAs diferencialmente expressos em CCC utilizando qPCR array; e 4) a interação dos miRNAs diferencialmente expressos com disfunções características da CCC (fibrose, miocardite, arritmia e hipertrofia) por meio de análises de bioinformática. Nossos resultados apontam para uma não-alteração nas etapas nucleares da biogênese de miRNAs (transcrição, edição e transporte), já que não foram encontradas alterações na expressão de pri- e pré-miRNAs de myomiRs, bem como dos componentes protéicos da biogênese, Drosha, Exportina-5 e RAN. Entretanto, observou-se uma disfunção na segunda etapa de edição da biogênese, citoplasmática, caracterizada por uma redução de 2/3 nos níveis protéicos de Dicer1, a qual não foi acompanhada por uma redução na expressão de seu RNA mensageiro. Evidenciou-se ainda, uma redução na expressão de 97,5% dos miRNAs maduros diferencialmente expressos no miocárdio de pacientes com CCC, incluindo myomiRs. As análises in silico revelaram haver participação dos miRNAs diferencialmente expressos em disfunções associadas a CCC, com destaque para a fibrose miocárdica, nodo central da rede. Experimentos adicionais preliminares sugeriram o acúmulo de adutos de 4-hidroxi-2-nonenal, decorrente do estresse oxidativo e de uma menor atividade da enzima aldeído desidrogenase 2, como uma possível causa para as alterações encontradas. Este é o primeiro estudo a caracterizar a biogênese de microRNAs em uma cardiomiopatia. Além disso, demonstrou-se que uma redução global do perfil dos miRNAs maduros diferencialmente expressos, decorrente uma disfunção na enzima Dicer1, está associada a eventos patológicos característicos da CCC. Estes mecanismos apresentam relevância biológica e terapêutica, podendo ser possivelmente compartilhados com cardiomiopatias de outras etiologias / Chronic Chagas disease cardiomyopathy (CCC) is the most severe complication of the infection by the haemoflagellate protozoan Trypanosoma cruzi. This dilated cardiomyopathy is characterized by an intense inflammatory infiltrate, fibrosis, dilation of cardiac chambers, cardiomyocyte hypertrophy and conduction abnormalities. Its pathophysiology is complex and why only 30% of patients experience this complication remains an open question. In this regard, our laboratory described for the first time a reduction in the expression of muscle-enriched microRNAs (myomiRs) in human CCC myocardium. Knowing that biogenesis dysfunction and myomiR reduced expression have been associated to the development of dilated cardiomyopathy in animal models, we hypothesized that an impairment of myocardial microRNA biogenesis would be associated to CCC. Hence, left ventricle tissue samples from CCC patients (16) and non-cardiomyopathy donors (6) were used to analyze: 1) mRNA and protein expression, by qPCR and western blotting, of canonical microRNA biogenesis machinery (Drosha, Exportin-5, RAN, Dicer1, TRBP, PACT, AGO2); 2) primary transcript (pri-miR), precursor (pre-miR) and mature microRNA expression of myomiRs (miR-1, -133a, -133b, -208a, -208b, e -499); 3) mature microRNA profile using qPCR array; and 4) the interaction between differentially expressed mature microRNAs and hallmark CCC dysfunctions (fibrosis, myocarditis, hypertrophy and arrhythmia) using bioinformatics tools. Our results point to a non-dysfunction of biogenesis nuclear steps (transcription, editing and transport), since expression of pri-, pre-microRNAs, Drosha, Exportin-5 and Ran are similar between CCC patients and controls. However, we observed an alteration in the cytoplasmic editing step, characterized by a 2/3 reduction in Dicer1 protein levels. In addition, a major downregulation of differentially expressed mature microRNAs (97,5%) was noticed. In silico analysis revealed an association between differentially expressed microRNAs and CCC hallmarks, particularly fibrosis, a central node in the network. Additional preliminary data suggest 4-hydroxi-2-nonenal myocardial accumulation, resulting from oxidative stress and aldehyde dehydrogenase 2 lower activity, as a possible cause for the alterations here described. This is the first study to conduct a comprehensive analysis of microRNA biogenesis machinery in a cardiomyopathy. Moreover, we have shown a major reduction in the expression of mature microRNAs, due to lower Dicer1 protein levels, to be associated to CCC hallmark dysfunctions. These mechanisms are biologically and therapeutically relevant, and may be shared with cardiomyopathies from different etiologies