Orientador: Carmen Sílvia Bertuzzo

Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia

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...

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...

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