Avaliação do padrão de inativação do cromossomo X e sua possível relação com a manifestação clínica de mulheres heterozigotas para a Doença de Fabry
Data
2014
Autores
Müller, Karen Barbosa 
Orientadores
D'Almeida, Vânia
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Introdução: A Doenca de Fabry (DF) e uma doenca de deposito lisossomico de heranca ligada ao cromossomo X, causada pela defiCiência da enzima alfa-galactosidase A. Esta defiCiência enzimatica, que provoca um acumulo de glicoesfingolipideos nao metabolizados, resulta em um quadro progressivo de sintomas com acometimento principalmente cardiaco, renal e cerebrovascular. Mulheres heterozigotas para a DF apresentam muitas vezes quadros tao graves quanto aqueles apresentados pelos homens hemizigotos, e os motivos que levam a esta manifestacao clinica ainda sao incertos. Dentre os mecanismos propostos esta o desequilibrio na inativacao do cromossomo X (ICX), mas os estudos que ja realizaram esta investigacao ainda nao mostram um consenso. A fim de tentar aprofundar a investigacao sobre os mecanismos moleculares que resultam na sintomatologia apresentada pelas mulheres com DF, este estudo visou a investigar o padrao de ICX em portadoras de DF do Brasil e correlacionar este fenomeno com dados referentes a sintomatologia, idade e mutacao causadora da DF. Metodos: Apos extracao do DNA de sangue periferico o padrao de ICX foi avaliado atraves de ensaio HUMARA, tecnica baseada na avaliacao do padrao de metilacao do gene receptor de androgeno (AR) para estimar a proporcao de ICX. As informacoes clinicas e demograficas das voluntarias com DF foram obtidas a partir de consulta ao banco de dados Fabry Registry. Resultados: Das 23 mulheres heterozigotas para DF avaliadas, uma foi identificada como homozigota para o gene AR. Das 22 restantes, seis apresentaram ICX randomica e 16 apresentavam algum grau de desequilibrio de ICX (72,7%), sendo sete com desequilibrio leve (65:35 ate 80:20) e nove com desequilibrio elevado (acima de 80:20). Destas 16 amostras com algum grau de desequilibrio de ICX, 10 delas (62,5%) tinham o alelo mutado do gene alfa-galactosidase A (GLA) preferencialmente inativado. Nao foi observada associacao entre a gravidade do sintoma apresentado e a proporcao de ICX (2(0,05; 2)=1,31; p=0,519) nem entre o tipo de mutacao para a DF e a proporcao de ICX (2(0,05; 4)=5,12; p=0,276). Foi identificada a ocorrencia de recombinacao genica em entre os genes AR e GLA em 4 das 23 mulheres com DF e este fenomeno nao e citado nos trabalhos que avaliam ICX na DF. Conclusao: o presente estudo reforca a ideia de que um desequilibrio no padrao de ICX tem um papel no mecanismo da doenca, mesmo que este nao seja o unico fator que contribui para o surgimento dos sintomas nas eterozigotas para DF
Fabry disease (Habekost et al.) is an Xlinked lysosomal storage disorder caused by enzyme alphagalactosidase A deficiency. This deficiency leads to accumulation of glucosphingolipds and, as consequence, to progressive symptoms, especially in cardiac, cerebrovascular and renal systems. Females heterozygous for FD show symptoms as severe as those observed in hemizygous patients, and the reasons that lead to this clinical panorama are still uncertain. Among the proposed mechanisms is skewed X chromosome inactivation (ICX), but studies that have carried out this investigation have not shown a consensus. In attempt to further investigate the molecular mechanisms that result in symptomatic female of FD, this study aimed to investigate the ICX pattern in women with FD in Brazil and correlate this phenomenon with symptoms, age and the disease causing mutation of FD. After extraction of DNA from peripheral blood, ICX pattern was assessed through HUMARA assay. Clinical, biochemical and molecular data were obtained from Fabry Registry database. Of 23 women heterozygous for FD evaluated, 1 was identified as homozygous for AR gene. Of the remaining 22, 6 showed random ICX and 16 showed skewed ICX (72.7%), in which 7 showed moderate skewed ICX (65:35 to 80:20) and 9 high skewed ICX (above 80:20). 62.5% of the samples with some degree of skewed ICX had the mutated GLA inactivated. There was no association between symptoms severity and ICX pattern (2(0,05, 2)=1,31; p=0,519) or between FD mutation and ICX pattern (2(0,05, 4)=5,12; p=0,276). The occurrence of crossing over between AR and GLA genes was identified in 4 of 23 women with FD and this phenomenon is not reported in previous studies. This study reinforces the idea that skewed in ICX pattern has a role in the disease mechanism, even though this is not the only factor contributing to the appearance of symptoms in female heterozygote for FD.
Fabry disease (Habekost et al.) is an Xlinked lysosomal storage disorder caused by enzyme alphagalactosidase A deficiency. This deficiency leads to accumulation of glucosphingolipds and, as consequence, to progressive symptoms, especially in cardiac, cerebrovascular and renal systems. Females heterozygous for FD show symptoms as severe as those observed in hemizygous patients, and the reasons that lead to this clinical panorama are still uncertain. Among the proposed mechanisms is skewed X chromosome inactivation (ICX), but studies that have carried out this investigation have not shown a consensus. In attempt to further investigate the molecular mechanisms that result in symptomatic female of FD, this study aimed to investigate the ICX pattern in women with FD in Brazil and correlate this phenomenon with symptoms, age and the disease causing mutation of FD. After extraction of DNA from peripheral blood, ICX pattern was assessed through HUMARA assay. Clinical, biochemical and molecular data were obtained from Fabry Registry database. Of 23 women heterozygous for FD evaluated, 1 was identified as homozygous for AR gene. Of the remaining 22, 6 showed random ICX and 16 showed skewed ICX (72.7%), in which 7 showed moderate skewed ICX (65:35 to 80:20) and 9 high skewed ICX (above 80:20). 62.5% of the samples with some degree of skewed ICX had the mutated GLA inactivated. There was no association between symptoms severity and ICX pattern (2(0,05, 2)=1,31; p=0,519) or between FD mutation and ICX pattern (2(0,05, 4)=5,12; p=0,276). The occurrence of crossing over between AR and GLA genes was identified in 4 of 23 women with FD and this phenomenon is not reported in previous studies. This study reinforces the idea that skewed in ICX pattern has a role in the disease mechanism, even though this is not the only factor contributing to the appearance of symptoms in female heterozygote for FD.
Descrição
Citação
MULLER, Karen Barbosa. avaliação do padrão de inativação do cromossomo x e sua possível relação com a manifestação clínica de mulheres heterozigotas para a Doença de Fabry. 2014. 112 f. Tese (Doutorado em Ciências) - Escola Paulista de Medicina, Universidade Federal de São Paulo. São Paulo, 2014.