Genetic Medicine, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.
Vanderbilt Genetics Institute, Nashville, TN, 37232, USA.
BMC Genomics. 2023 Feb 16;24(1):75. doi: 10.1186/s12864-023-09179-7.
BACKGROUND: Exfoliation syndrome (XFS) is an age-related systemic disorder characterized by excessive production and progressive accumulation of abnormal extracellular material, with pathognomonic ocular manifestations. It is the most common cause of secondary glaucoma, resulting in widespread global blindness. The largest global meta-analysis of XFS in 123,457 multi-ethnic individuals from 24 countries identified seven loci with the strongest association signal in chr15q22-25 region near LOXL1. Expression analysis have so far correlated coding and a few non-coding variants in the region with LOXL1 expression levels, but functional effects of these variants is unclear. We hypothesize that analysis of the contribution of the genetically determined component of gene expression to XFS risk can provide a powerful method to elucidate potential roles of additional genes and clarify biology that underlie XFS. RESULTS: Transcriptomic Wide Association Studies (TWAS) using PrediXcan models trained in 48 GTEx tissues leveraging on results from the multi-ethnic and European ancestry GWAS were performed. To eliminate the possibility of false-positive results due to Linkage Disequilibrium (LD) contamination, we i) performed PrediXcan analysis in reduced models removing variants in LD with LOXL1 missense variants associated with XFS, and variants in LOXL1 models in both multiethnic and European ancestry individuals, ii) conducted conditional analysis of the significant signals in European ancestry individuals, and iii) filtered signals based on correlated gene expression, LD and shared eQTLs, iv) conducted expression validation analysis in human iris tissues. We observed twenty-eight genes in chr15q22-25 region that showed statistically significant associations, which were whittled down to ten genes after statistical validations. In experimental analysis, mRNA transcript levels for ARID3B, CD276, LOXL1, NEO1, SCAMP2, and UBL7 were significantly decreased in iris tissues from XFS patients compared to control samples. TWAS genes for XFS were significantly enriched for genes associated with inflammatory conditions. We also observed a higher incidence of XFS comorbidity with inflammatory and connective tissue diseases. CONCLUSION: Our results implicate a role for connective tissues and inflammation pathways in the etiology of XFS. Targeting the inflammatory pathway may be a potential therapeutic option to reduce progression in XFS.
背景:剥脱综合征(XFS)是一种与年龄相关的系统性疾病,其特征是异常细胞外物质的过度产生和逐渐积累,并伴有特征性的眼部表现。它是继发性青光眼最常见的原因,导致广泛的全球失明。在来自 24 个国家的 123457 名多民族个体的最大全球 XFS 元分析中,在 chr15q22-25 区域附近的 LOXL1 发现了与最强关联信号相关的七个基因座。表达分析迄今为止将该区域的编码和少数非编码变体与 LOXL1 的表达水平相关联,但这些变体的功能影响尚不清楚。我们假设分析基因表达的遗传决定成分对 XFS 风险的贡献,可以为阐明潜在的其他基因作用和阐明 XFS 基础生物学提供一种强大的方法。
结果:使用在 48 个 GTEx 组织中利用多民族和欧洲血统 GWAS 结果训练的 PrediXcan 模型进行了转录组广泛关联研究(TWAS)。为了消除由于连锁不平衡(LD)污染而导致假阳性结果的可能性,我们 i)在去除与 XFS 相关的 LOXL1 错义变体和 LOXL1 模型中的变体的简化模型中进行了 PrediXcan 分析,多民族和欧洲血统个体,ii)对欧洲血统个体中的显著信号进行条件分析,iii)基于相关基因表达、LD 和共享 eQTL 对信号进行过滤,iv)在人虹膜组织中进行表达验证分析。我们在 chr15q22-25 区域观察到 28 个基因显示出统计学上显著的关联,在经过统计学验证后,这些基因被简化为 10 个基因。在实验分析中,与对照样本相比,XFS 患者的虹膜组织中 ARID3B、CD276、LOXL1、NEO1、SCAMP2 和 UBL7 的 mRNA 转录水平显着降低。XFS 的 TWAS 基因显着富集与炎症状态相关的基因。我们还观察到 XFS 与炎症和结缔组织疾病的合并症发病率较高。
结论:我们的结果表明,结缔组织和炎症途径在 XFS 的发病机制中起作用。靶向炎症途径可能是减少 XFS 进展的潜在治疗选择。
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