A role for endogenous retroelements in Aicardi-Goutieres Syndrome

 描述(由申请人提供)：内源性逆转录因子在艾卡迪-古蒂埃综合征中的作用艾卡迪-古蒂埃综合征(AGS)是一种严重的孟德尔炎症性疾病，尤其影响大脑，经常导致儿童死亡。该病的特点是进行性脑病、精神运动减退和皮肤损害，以及脑脊液和血清中I型干扰素水平的增加，以及 诱导外周血中可检测到的干扰素刺激基因。已在TREX1、RNASE H 2A、RNASE H 2B、RN E E H 2C、SAMHD1、ADAR1和IFIH1 7个基因上发现了致病突变，但其相关表型的严重程度有所不同。这些基因的蛋白产物参与RNA代谢或信号转导，也与抑制感染逆转录病毒和/或内源性反转录转座子有关。这项研究是基于这样一种假设，即AGS相关基因的功能缺失会改变逆转录转座子RNA或其反转录的cDNA的正常代谢，从而引发干扰素反应和AGS。反转录转座子是一种可移动的DNA元件，它通过使用RNA中间体的“复制和粘贴”机制来复制自己。内源性逆转录病毒(HERV)占人类基因组的8%。虽然还没有发现能够复制的HERV，但正在进行的HERV表达与几种疾病有关，包括多发性硬化症、肌萎缩侧索硬化症和自身免疫性风湿病。LINE1(L1)反转录转座子占据了人类DNA的17%，尽管人们认为只有大约100个仍然能够在任何个体中进行反转录转座子。L1反转录转座子还导致了100多万个非自主Alu反转录转座子和数千个加工假基因的插入。这种细胞进化出了限制逆转座的防御，这种防御在某些体细胞类型中偶尔会放松，特别是人脑中的神经细胞。我们预测AGS患者逆转录元件表达的松弛。使用RNA分析、免疫细胞化学和逆转录酶活性的功能分析，我们将检查AGS患者的脑组织、血液、血清和衍生细胞系，以确定在疾病状态下逆转录元件RNA或蛋白质的表达是否升高。我们将使用高通量测序方案确定AGS患者组织中的从头L1和Alu插入数量是否增加。L1表达是否可以诱导干扰素反应的问题将通过携带可诱导的L1转基因的小鼠模型来解决。最后，我们将开发ELISA法来确定AGS患者的血清中是否含有针对逆转录元件蛋白的自身抗体。这项研究应该会为一种毁灭性的儿童疾病提供新的线索，并为未来的治疗策略提供建议。此外，还将对细胞的内在免疫系统和内源性逆转录因子之间的相互作用获得新的见解。

 DESCRIPTION (provided by applicant): A role for endogenous retroelements in Aicardi-Goutières syndrome Aicardi-Goutières syndrome (AGS) is a severe Mendelian inflammatory disorder that affects particularly the brain and frequently causes death in childhood. The disease is characterized by progressive encephalopathy, psychomotor regression, and lesions of the skin, together with increased levels of Type I interferon in the cerebrospinal fluid and serum, and induction of interferon-stimulated genes detectable in peripheral blood. Causative mutations have been identified in seven genes, TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR1 and IFIH1, with variation in the severity of their associated phenotypes. The protein products of these genes are involved in RNA metabolism or signaling, and have also been linked with suppression of infecting retroviruses and/or endogenous retrotransposons. This study is based on the hypothesis that functional loss of an AGS-associated gene alters the normal metabolism of retrotransposon RNA or its reverse-transcribed cDNA, triggering an interferon response and AGS. Retrotransposons are mobile DNA elements that duplicate themselves by a "copy and paste" mechanism using an RNA intermediate. Endogenous retroviruses (HERVs) comprise 8% of the human genome. Although no HERVs capable of replication have been identified, ongoing HERV expression has been implicated in several disease conditions, including multiple sclerosis, amyotrophic lateral sclerosis, and autoimmune rheumatic disease. LINE1 (L1) retrotransposons occupy 17% of human DNA, although it is believed that only about 100 remain competent for retrotransposition in any individual. L1 retrotransposition has also been responsible for the insertion of over a million non-autonomous Alu retrotransposons and thousands of processed pseudogenes. The cell has evolved defenses restricting retrotransposition, which are occasionally relaxed in certain somatic cell types, notably neuronal cells in the human brain. We predict relaxation of retroelement expression in AGS patients. Using RNA analyses, immunocytochemistry, and functional assays for reverse transcriptase activity, we will examine brain tissue, blood, sera, and derived cell lines from AGS patients to ascertain if retroelement RNA or protein expression is elevated in the disease state. We will determine if de novo L1 and Alu insertion numbers are increased in tissues of AGS patients using high-throughput sequencing protocols. The question of whether L1 expression can induce an interferon response will be addressed using a mouse model harboring an inducible L1 transgene. Finally, we will develop ELISA assays to ascertain if sera from AGS patients contain autoantibodies directed against retroelement proteins. This research should shed new light on a devastating childhood disease and suggest future strategies for treatment. Furthermore, new insights into the interaction of the intrinsic immune system of the cell and endogenous retroelements will be gained.