Variants underlying sex bias in Systemic Lupus Erythematosus

摘要 系统性红斑狼疮(SLE)是一种自身免疫性疾病，对女性的比例为9：1。 SLE中的性别偏见反映了男性和女性之间的荷尔蒙和性染色体差异。这 提案的重点是识别和从功能上建立X染色体上的遗传变异 导致系统性红斑狼疮的性别偏见。利用全基因组研究狼疮遗传结构的最新进展 关联研究已经确定了13个与系统性红斑狼疮相关的X连锁基因的变异。然而， 这些基因座上的致病变异仍不清楚。这些Gwas基因座可能导致SLE中的女性偏见，如果 它们影响基因对X染色体失活(XCI)的反应，XCI是一种早期发育过程， 表观遗传学沉默大多数女性的X-连锁基因，以维持与男性的剂量相等。 虽然XCI在雌性的X上抑制大多数基因，但一些基因逃脱了XCI并在两个X上都表达 活动和非活动X。20%的人类X基因的XCI状态是可变的，并从XCI的子集中逃脱 X，但在其他雌性身上是沉默的。我们最近的数据表明，在变量上逃脱XCI的基因的遗传性 充斥着性别偏见的疾病，包括系统性红斑狼疮。我们假设X上的因果变量 染色体在SLE中的异常失活X表达。这项提案的目标是确定 这些因果变异并直接评估他们对XCI的反应。为了解决这一假设，我们在 目的1对X染色体上的致病变异进行精细定位，鉴定致病基因。将结果与 EQTL和功能基因组注释将进一步细化基因座并将其与因果基因联系起来。关联效果将 在男性和女性之间进行比较，以进一步区分那些可能受到X失活影响的人。在AIM 2我们将从功能上评估定位到Xq28的变异体对XCI和B细胞表达的改变的基因反应。 我们将进行多重报告基因分析，作为对具有调节作用的功能变异的初步筛选 潜力。我们还将建立一个新的系统，通过编辑茎来对X染色体变异进行功能评估 将被分化为B细胞并接受XCI的细胞。我们预计实验结果将是 首先，提供相关变异和X染色体失活之间的关键功能联系， 这将对理解SLE和狼疮生物学的机制产生深远的影响。

ABSTRACT Systemic Lupus Erythematosus (SLE) is an autoimmune disorder that is heavily biased 9:1 towards females. Sex bias in SLE reflects both hormonal and sex chromosome differences between men and women. This proposal focuses on identifying and functionally establishing genetic variants on the X chromosome that contribute to SLE sex bias. Current efforts to understand the genetic architecture of lupus using genome-wide association studies (GWAS) have identified variants at 13 X-linked genes that are associated with SLE. However, causative variants at these loci remain unknown. These GWAS loci may contribute to female bias in SLE if they influence how genes respond to X chromosome inactivation (XCI), the early developmental process that epigenetically silences most X-linked genes in females in order to maintain dosage equivalence with males. Although XCI represses most genes on one X in females, some genes escape XCI and are expressed from both active and inactive Xs. XCI states for >20% of human X genes are variable, and escape XCI from a subset of Xs, but are silenced in other females. Our recent data indicate that heritability at genes that variably escape XCI is enriched in sex-biased disorders including SLE. We hypothesize that causal variants on the X chromosome underlie aberrant inactive X expression in SLE. The objective of this proposal is to identify these causal variants and directly evaluate their response to XCI. To address this hypothesis, we propose in Aim 1 to fine map causal variants on the X chromosome and identify causal genes. Integration of results with eQTL and functional genome annotation will further refine loci and link to causal genes. Association effects will be compared between males and females to further differentiate those likely influenced by X inactivation. In Aim 2 we will functionally evaluate variants mapping to Xq28 for altered gene response to XCI and B cell expression. We will perform multiplex reporter gene assays as an initial screen for functional variants with regulatory potential. We will also establish a novel system to functionally evaluate X chromosome variants by editing stem cells that will be differentiated to B cells and undergo XCI. We expect that results from experiments will be the first to provide a critical functional link between associated variants and X chromosome inactivation, and as such will have a profound impact on understanding mechanisms of SLE and lupus biology.