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X Chromosome Inactivation in Systemic Lupus Erythematosus
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Introdução: O lúpus eritematoso sistémico (LES) é uma doença imuno-mediada com elevada morbilidade e mortalidade. A prevalência nas mulheres (XX) é muito superior à dos homens (XY) e aumenta na síndrome do triplo X (XXX) e de Klinefelter (XXY) e diminui na de Turner (XO). Há, assim, uma associação entre o número de cromossomas X e o risco de lúpus. Em cada célula da mulher um dos cromossomas X é silenciado aleatoriamente para igualar a informação genética entre os sexos. A Inativação do Cromossoma X (ICX) é regulada por um RNA não codificante: o XIST. A inativação preferencial de um dos cromossomas X, a desregulação da expressão do XIST e a produção de anticorpos contra o XIST e as proteínas às quais se liga podem estar envolvidos na patogénese do LES. Objetivos: Estudar a ICX no LES.
Métodos: Estudo de doentes com LES (critérios ACR/EULAR 2019) e controlos saudáveis. Isolamento de monócitos e linfócitos B e T (CD4+ e CD8+) por FACS. Quantificação do XIST por PCR quantitativo. Análise da inativação do cromossoma X pelo método HUMARA e pyrosequencing.
Resultados: 1) Os doentes com LES tinham uma elevação dos níveis de XIST em comparação com os controlos saudáveis. Esta diferença é estatisticamente significativa para os linfócitos B (p=0.0092) e os linfócitos T CD4+ (p=0.0077). 2) A expressão de XIST estava significativamente aumentada em monócitos de doentes com LN ativo versus LN inativo (p=0.0140). 3) Pelo método HUMARA, a distorção do ICX (≥70%) ocorreu mais frequentemente no LES (linfócitos T CD4+: 38% dos doentes com LES vs 15% dos controlos; linfócitos B: 29% dos doentes com LES vs 11% dos controlos). Utilizando o pyrosequencing em linfócitos B, ICX foi aleatória em todos os controlos, tendo sido encontrada uma inativação preferencial em 27% dos doentes com LES com o SNP XIST rs16 e em 11% com o SNP XIST rs18.
Discussão: Os resultados evidenciam o potencial envolvimento da ICX na patogénese do LES.
Introduction: Systemic lupus erythematosus (SLE) is an immune-mediated disease with high morbidity and mortality. The prevalence of SLE in women (XX) is much higher than in men (XY) and increases in triple X syndrome (XXX) and Klinefelter syndrome (XXY) and decreases in Turner syndrome (XO). There is, therefore, an association between the number of X chromosomes and the risk of lupus in each female cell, one of the X chromosomes is randomly silenced to equalize the genetic information in the X chromosome between the sexes. X chromosome inactivation (XCI) is regulated by XIST, a long non-coding RNA. Preferential inactivation of one of the X chromosomes, XIST expression deregulation, and the production of autoantibodies against the XIST ribonucleoprotein complex may be involved in SLE pathogenesis. Objectives: To study XCI in SLE. Methods: Study of patients with SLE (2019 ACR/EULAR criteria) and healthy controls. Isolation of monocytes and B and T lymphocytes (CD4+ and CD8+) by FACS. Quantification of XIST by quantitative PCR. Analysis of the preferential inactivation of one of the X chromosomes by HUMARA and pyrosequencing. Results: 1) XIST was over-expressed in SLE patients compared to healthy controls. This difference was statistically significant for B lymphocytes (p=0.0092) and CD4+ T lymphocytes (p=0.0077). 2) XIST expression was significantly increased in monocytes of patients with active vs inactive LN (p=0.0140). 3) By the HUMARA method, skewing XCI (≥70%) was more common in SLE (CD4+ T lymphocytes: 38%of SLE patients vs 15% of controls; B lymphocytes: 29% of SLE patients vs 11% of controls). Using the pyrosequencing method in B lymphocytes, the controls were all randomly inactivated, and preferential inactivation was found in 27% of SLE patients with the SNP XIST rs16 and 11% with the SNP XIST rs18. Discussion: These results highlight the potential involvement of XCI in the pathogenesis of SLE.
Introduction: Systemic lupus erythematosus (SLE) is an immune-mediated disease with high morbidity and mortality. The prevalence of SLE in women (XX) is much higher than in men (XY) and increases in triple X syndrome (XXX) and Klinefelter syndrome (XXY) and decreases in Turner syndrome (XO). There is, therefore, an association between the number of X chromosomes and the risk of lupus in each female cell, one of the X chromosomes is randomly silenced to equalize the genetic information in the X chromosome between the sexes. X chromosome inactivation (XCI) is regulated by XIST, a long non-coding RNA. Preferential inactivation of one of the X chromosomes, XIST expression deregulation, and the production of autoantibodies against the XIST ribonucleoprotein complex may be involved in SLE pathogenesis. Objectives: To study XCI in SLE. Methods: Study of patients with SLE (2019 ACR/EULAR criteria) and healthy controls. Isolation of monocytes and B and T lymphocytes (CD4+ and CD8+) by FACS. Quantification of XIST by quantitative PCR. Analysis of the preferential inactivation of one of the X chromosomes by HUMARA and pyrosequencing. Results: 1) XIST was over-expressed in SLE patients compared to healthy controls. This difference was statistically significant for B lymphocytes (p=0.0092) and CD4+ T lymphocytes (p=0.0077). 2) XIST expression was significantly increased in monocytes of patients with active vs inactive LN (p=0.0140). 3) By the HUMARA method, skewing XCI (≥70%) was more common in SLE (CD4+ T lymphocytes: 38%of SLE patients vs 15% of controls; B lymphocytes: 29% of SLE patients vs 11% of controls). Using the pyrosequencing method in B lymphocytes, the controls were all randomly inactivated, and preferential inactivation was found in 27% of SLE patients with the SNP XIST rs16 and 11% with the SNP XIST rs18. Discussion: These results highlight the potential involvement of XCI in the pathogenesis of SLE.
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Systemic Lupus Erythematosus X chromosome inactivation XIST Skewing of XCI