Identification of causal genes and cellular pathways for idiopathic achalasia on the basis of genome-wide association studies (GWAS)

特发性贲门失弛缓症是一种原发性食道运动障碍。它的特征是食管开胃，下食管括约肌（LES）由于肌丛中抑制性神经元的丧失而不能放松。虽然这种神经元变性的病理生理主要是未知的，但自身免疫过程似乎涉及具有遗传易感性的个体。在病因水平上，失弛缓症是多因素的，涉及各种风险基因变异和环境因素的累积效应。最近，我们使用Illumina免疫芯片在贲门失弛弛症病例对照样本中进行了首次系统的关联研究，该芯片在基因组区域中含有bb0 190 K单核苷酸多态性（snp），这些snp先前显示与各种自身免疫性疾病相关。这表明，在HLA-DQ受体的细胞质尾部插入8个氨基酸是导致失弛缓症的最大风险（Gockel et al. (2014) Nat Genet 46: 901-904）。此外，HLA-DQ受体胞外区域的两个氨基酸替换独立地赋予失弛缓症风险。此外，我们已经证明，与南欧人相比，北方人在HLA-DQ受体中插入8个氨基酸的情况不太常见（Becker等人（2016）Eur J Hum Genet 24: 1228-1231）。这种地理空间上的南北梯度表明，特发性失弛缓症的患病率可能因人群而异。该项目的目的是全面鉴定进一步的遗传风险变异特发性失弛缓症。为此，一项全基因组关联研究（GWAS）将在5000名欧洲患者和6346名种族匹配的对照中进行。将通过计算机功能研究跟踪已确定的风险变异，以确定其细胞功能并确定与疾病相关的生物学途径。为了阐明失弛缓症的生物学基础，确定的风险变异和途径为未来的功能研究提供了重要的先决条件。此外，失弛缓症的GWAS数据将与其他自身免疫性疾病的GWAS数据联合分析。此外，基因型-表型（GxP）研究将使用贲门失弛缓症GWAS数据和详细收集的患者表型数据进行。这些数据将有助于估计贲门失弛缓症与其他自身免疫性疾病之间的遗传相关性，以及识别贲门失弛缓症的生物学亚型。申请的项目不会以GWAS结束。通过我们自己的工作并与其他科学家合作，将对识别出的风险变异进行功能分析，这将有助于阐明失弛缓症的病理生理。

Idiopathic achalasia represents a primary motility disorder of the esophagus. It is characterized by esophageal aperistalsis and a failure of the lower esophageal sphincter (LES) to relax due to a loss of inhibitory neurons in the myenteric plexus. Although the pathophysiology of this neuronal degeneration is mainly unknown, autoimmune processes seem to be involved in individuals with a genetic susceptibility. On the etiology level, achalasia is multifactorial and involves a combination of the cumulative effect of variants in various risk genes and environmental factors. Recently, we have conducted the first systematic association studies in case control samples with achalasia using the Illumina ImmunoChip that contains > 190 K single nucleotide polymorphisms (SNPs) in genomic regions that previously showed association to various autoimmune diseases. This revealed that an 8-amino-acid insertion in the cytoplasmic tail of the HLA-DQ receptor confers the strongest risk for achalasia (Gockel et al. (2014) Nat Genet 46: 901-904). Furthermore, two amino acid substitutions in the extracellular domain of the HLA-DQ receptor independently confer achalasia risk. In addition, we have shown that the 8-amino-acid insertion in the HLA-DQ receptor is less common in Northern compared to Southern Europeans (Becker et al. (2016) Eur J Hum Genet 24: 1228-1231). This geospatial north-south gradient implies that the prevalence of idiopathic achalasia may differ among populations. The aim of this project is the comprehensive identification of further genetic risk variants for idiopathic achalasia. For this purpose, a genome-wide association study (GWAS) will be carried out using 5,000 European patients as well as 6,346 ethnically matched controls. Identified risk variants will be followed up by in silico functional studies in order to determine their cellular function and to identify disease relevant biological pathways. The identified risk variants and pathways represent important prerequisites for future functional studies in order to elucidate the biological basis of achalasia. In addition, the achalasia GWAS data will be analyzed jointly using GWAS data for other autoimmune diseases. Furthermore, genotype-phenotype (GxP) studies will be carried out using the achalasia GWAS data and detailed collected phenotypic data from patients. These data will allow to estimate the genetic correlation between achalasia and other autoimmune disorders as well as the identification of biologically based subtypes of achalasia. The applied project does not end with the GWAS. By our own work and in cooperation with other scientist, the identified risk variants will be functionally analyzed, which will help to elucidate the pathophysiology of achalasia.