archives@tulane.edu / 1 / Angela Crist

Orientador: Carmen Sílvia Bertuzzo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-23T04:59:08Z (GMT). No. of bitstreams: 1 Assis_AngelaMariade_D.pdf: 2409399 bytes, checksum: 620279a2d72b5132a10f7af956d4bebf (MD5) Previous issue date: 2007 / Resumo: A Telangiectasia Hemorrágica Hereditária (THH) é uma desordem autossômica dominante caracterizada por epistaxe recorrente, telangiectases mucocutânea, hemorragia gastrointestinal, e malformação arteriovenosa pulmonar (PAVM), cerebral e hepática. A prevalência da doença é de 1/5000 e a mortalidade relatada da doença entre pacientes jovens quando comparado com aqueles com mais de 60 anos é de 36%. Dois genes da superfamília de receptores para TGF-? têm sido relacionados com THH, o gene da endoglina e o gene da activina (activin receptor-like-kinase). Estes genes são altamente expressos em células endoteliais e outros tecidos altamente vascularizados como pulmão e placenta. Mutações no gene da endoglina causam a THH tipo 1 que é caracterizada pela alta incidência de malformação arteriovenosa pulmonar sintomática (PAVMs). Mutações no gene da activina levam a THH tipo 2 caracterizada por epistaxe recorrente e malformação arteriovenosa gastrointestinal. Foi objetivo deste trabalho realizar uma triagem de mutações na região codificadora dos genes ALK-1 e endoglina em doze pacientes portadores de THH atendidos no Hemocentro da Unicamp. A abordagem metodológica incluiu a amplificação dos exóns dos genes da activina e endoglina seguida pela técnica de PCR/CSGE, clonagem e sequenciamento. Dos doze pacientes estudados, sete apresentaram alguma alteração molecular, destes três pacientes apresentaram uma deleção de um nucleotídeo T na posição 913 no exon 7, um paciente apresentou uma inserção de um nucleotídeo G na posição 204-205 no exon 3 e três pacientes apresentavam uma mutação misense nos exons 7 e 8 na posição 976 e 1204 respectivamente. Nossos resultados mostraram que a THH tipo 1 e tipo 2 são raras no Brasil e todas as mutações citadas na tabela IV e Figura 10 são novas, somente a mutação ocorrida no exon 8 foi previamente descrita na literatura / Abstract: Background: Hereditary hemorrhagic telangiectasia in humans, also known as HHT or Osler-Rendu-Weber syndrome, is an autosomal dominant vascular disorder characterizes by recurrent epistaxis, mucocutaneous telangiectases, gastrointestinal, pulmonary, cerebral and hepatic arteriovenous malformations (HAVM). The prevalence of the illness is of 1/5000 and the reported mortality of the illness among young patients when compared with those with more than 60 years is 36%. Two genes of the receptors superfamily for TGF-? have been related with THH, the gene of the endoglin (ENG) in the chromosome 9q33-34 and the gene of the activin (receptor-like-kinase 1 ALK-1), in the chromosome 12q11q14. These genes are highly express in endothelial cells and other tissue highly vascularized as lung and placenta. Mutations in the gene of the endoglin cause the HHT type 1 which is characterized by the high incidence of symptomatic pulmonary arteriovenous malformation (PAVM). Mutations in the activin gene cause HHT were described among patients in whom the linking with HHT in the chromosome 9q33 or mutation in the endoglin gene was excluded. It was the objective of this work to carry through a selection of mutations in the coding region of gene ALK-1 and endoglin in 12 patients carrying HHT whose are treated in the Blood Center at Unicamp. Methods: Twelve patients were analyzed. Diagnosis of HHT was carried out by means of clinical history of recurrent bleeding, heredity studies, and the presence of multiple telangiectases lesions. PCR products with consistent abnormal migration patterns were cloned into the SureCloneTM ligation kit vector system and sequenced using the DYEnamic TM ET dye terminator cycle sequencing Kit, and analyzed by the MegaBace 1000 DNA automated analyzer. A panel of 252 chromosomes from unrelated individuals without the disease was used to evaluate the frequency of each mutation in the general population. Results: In six patients three novel mutations were identified in the coding sequence of the ALK-1 gene in their families, which demonstrated clinical manifestations of HHT type 2. These mutations included an insertion a deletion of single base pairs in éxons 3 (c.204-205insG) and 7 (c.913del T), as well as missense mutations in éxons 7 (c.976A>G) and 8 (c.1204G>A) of the ALK-1 gene. The mutations identified in éxons 7 and 8 affect the kinase domain and the mutation identified in éxon 3 affect the extracellular domain. These data indicate that loss-of-function mutations in a single allele of the ALK1 locus are sufficient to contribute to defects in maintaining endothelial integrity. Conclusion: We suggest the high rate of mutation detection and the small size of the ALK-1 gene make genomic sequencing a viable diagnostic test for HHT2. This was the only research about this subject made in Brazil so far / Doutorado / Genetica Animal e Evolução / Doutora em Genética e Biologia Molecular

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a rare genetic blood disorder that leads to abnormal bleeding due to absent capillaries and multiple abnormal blood vessels known as arteriovenous malformations. A feature of HHT is high-output heart failure due to multiple arteriovenous malformations. High-output heart failure can lead to recurrent epistaxis Kiesselbach area syndrome (REKAS), further exacerbating heart failure through increased blood loss and resultant anemia. We report a patient with HHT who presented with high-output heart failure contributing to REKAS. In patients with REKAS, we propose if anemia is present, REKAS can be avoided by correcting the anemia by increasing the hemoglobin level to greater than 9 to 10 g/dL. This decreases hyperdynamic circulation and reduces pressure in the blood vessels of the nose.

La télangiectasie hémorragique héréditaire (HHT) est une maladie rare (1/10.000). Son incidence est plus élevée (pouvant atteindre 1/1000) dans certaines zones géographiques dont la région Poitou-Charentes. Cette maladie autosomique dominante est causée par des mutations d'un des trois gènes identifiés ENG, ACVRL1 et SMAD4 codant pour des protéines de la voie BMP spécifiquement exprimés dans les cellules endothéliales. Le nombre croissant de mutations détectées chez les patients et l'expressivité variable de certaines mutations nous a ammené à déterminer les conséquences de mutations afin d'établir une corrélation génotype/phénotype. Cette corrélation est importante pour le conseil génétique et évidemment le diagnostic prénatal. Dans ce contexte, nous avons étudié aux niveaux cellulaire et moléculaire les effets de plusieurs mutations. L'effet délétère de ces mutations sur la protéine et/ou l'épissage de l'ARN a été évalué. Nous avons montré que sur les 23 mutations d'ACVRL1 : 1) 18 mutations faux-sens affectent la fonctionnalité de la protéine en réponse à BMP9 et 3 mutations sont de simples polymorphismes, 2) la mutation exonique c.733A>G (p.Ile245Val) affecte l'épissage de l'exon 6, 3) La mutation c.1048+5G>A de l'intron 7 en dehors du site consensus induit un épissage aberrant de l'exon 7. En ce qui concerne l'ENG, nous avons analysé 4 mutations et nous avons montré que la mutation c.1088G>A (p.Cys363Tyr) a un impact sur l'activité du récepteur et que les mutations c.1134G>A (p.Ala378Ala) et c.1060C>T (p.Leu364Leu) altèrent l'épissage de l'exon 8. Ce travail montre l'importance de l'étude approfondie de toute nouvelle mutation par des études in silico, in vitro et in cellulo à différents niveaux cellulaires. Des études in vivo ultérieures peuvent compléter et appuyer la stratégie expérimentale que nous avons suivie. / Hereditary hemorrhagic telangiectasia (HHT) is a rare disease (1/10.000). Its incidence is higher in certain geographic areas including the Poitou-Charentes region (1/1000). This autosomal dominant disease is caused by mutations in one of three identified genes ENG, ACVRL1 and SMAD4 encoding BMP pathway proteins specially expressed in endothelial cells. The increasing number of mutations detected in patients and the variable expressivity of certain mutations has taken us to determine the consequences of mutations to establish a genotype/phenotype correlation. This correlation is important for genetic counseling and obviously for prenatal diagnosis. In this context, we investigated the effects of several mutations at the cellular and molecular levels. The deleterious impact of these mutations on the protein and/or RNA splicing was evaluated. We have shown that for the 23 mutations of ACVRL1: 1) 18 missense mutations affect the functionality of the protein in response to BMP9 and 3 are polymorphisms, 2) exonic mutation c.733A>G (p. Ile245Val) affects the splicing of the exon 6, 3) mutation c.1048+5G>A in intron 7 off the consensus site induces an aberrant splicing of exon 7. Concerning the ENG, we analyzed 4 mutations and we showed that the mutation c.1088G> A (p.Cys363Tyr) has an impact on the activity of the receptor and that the mutations c.1134G> A (p.Ala378Ala) and c.1060C> T (p.Leu364Leu) inhibit the splicing of exon 8. This work shows the importance of the comprehensive study of any new mutation by in silico, in vitro and in cellulo studies at different cellular levels. The in vivo studies can further complement and support the experimental strategy that we followed.