Reversal of Epigenetic Silencing of the G-Globin Gene

描述（由申请人提供）： 胎儿血红蛋白可以改善镰状细胞病的临床严重程度的发现产生了相当大的兴趣，在成年生活中沉默的γ-珠蛋白基因的重新激活作为一种潜在的治疗方法，在这种疾病的患者。对遗传性疾病的分子基础的深入研究，其特征是胎儿血红蛋白在成年后持续产生，但尚未转化为有效的治疗方法。相比之下，对γ-珠蛋白基因发育沉默中的表观遗传修饰（例如DNA甲基化和组蛋白乙酰化）的研究刺激了许多治疗剂的开发，这些治疗剂可以诱导胎儿血红蛋白并改善镰状细胞病的严重程度。在过去的8年里，我们一直在进行丁酸盐和羟基脲在镰状细胞病中的临床试验。 在这些研究的过程中，我们进行了一些重要的，有时是意想不到的临床观察，提出了关于这些药物诱导胎儿血红蛋白的机制的新问题。本申请的主要目的是研究β-珠蛋白基因簇的表观遗传状态在γ-珠蛋白基因的可变沉默中以及在丁酸盐和羟基脲对胎儿血红蛋白的再活化中的潜在作用。具体目标是：1）比较具有可变沉默的患者的γ-珠蛋白基因簇中的组蛋白乙酰化和DNA甲基化的状态2）研究丁酸盐和羟基脲对β-珠蛋白基因簇中组蛋白乙酰化和DNA甲基化的影响; 3）研究组蛋白乙酰化和DNA甲基化在丁酸抗性中的潜在作用以及用羟基脲预处理逆转这种抗性的作用; 4）研究组蛋白去乙酰化酶的丁酸盐和非丁酸盐抑制剂诱导γ-珠蛋白基因表达的遗传性; 5）研究丁酸盐和其他组蛋白去乙酰化酶抑制剂对γ-珠蛋白mRNA翻译效率的影响。我们相信这些研究将为γ-珠蛋白基因沉默的正常机制和药物治疗的逆转提供重要的线索。

DESCRIPTION (provided by applicant): The discovery that fetal hemoglobin can ameliorate the clinical severity of sickle cell disease generated considerable interest in the reactivation of the silenced gamma-globin genes in adult life as a potential therapeutic approach in patients with this disease. Intensive investigation of the molecular bases of the genetic disorders that are characterized by the persistence of fetal hemoglobin production in adult life has not translated into effective therapies. In contrast, the study of epigenetic modifications (e.g. DNA methylation and histone acetylation) in the developmental silencing of the gamma-globin genes spurred the development of a number of therapeutic agents that can induce fetal hemoglobin and ameliorate the severity of sickle cell disease. For the past 8 years, we have been conducting clinical trials of butyrate and hydroxyurea in sickle cell disease. In the course of these studies, we made a number of important and at times unexpected clinical observations that raised new questions about the mechanism(s) of induction of fetal hemoglobin by these agents. The major aim of this application is to study the potential role of the epigenetic state of the beta-globin gene cluster in the variable silencing of the gamma-globin genes and in the reactivation of fetal hemoglobin by butyrate and hydroxyurea. The specific aims are to: 1) Compare the state of histone acetylation and DNA methylation in the gamma-globin gene cluster of patients with variable silencing (i.e. either complete or partial silencing) of the beta-globin genes; 2) Investigate the effects of butyrate and hydroxyurea on histone acetylation and DNA methylation in the beta-globin gene cluster; 3) Investigate the potential roles of histone acetylation and DNA methylation in butyrate resistance and the reversal of this resistance by pre-treatment with hydroxyurea; 4) Investigate the heritability of the induction of gamma-globin gene expression by butyrate and nonbutyrate inhibitors of histone deacetylases; 5) Investigate the effects of butyrate and other inhibitors of histone deacetylase on the translational efficiency of gamma-globin mRNA. We believe these studies will shed important light on the normal mechanisms of silencing of the gamma-globin genes and their reversal by pharmacological therapies.