Genome-wide significant genes implicated by Hypertension-GWAS based TWAS analysis
We integrated the eQTL matrix of GTEx aorta and GWAS summary statistics of UK Biobank (https://www.ukbiobank.ac.uk/) [22] traits “Hypertension (Self-reported)”, “High blood pressure”, “Systolic blood pressure, automated reading”, and “Diastolic blood pressure, automated reading” through used the FUSION-based TWAS analysis [21]. At the canonically genome-wide significant level (TWAS P-value < 5.0 × 10-8), we observed 28 genes for “Hypertension (Self-reported)” (Supplementary Table S1), 28 genes for “High blood pressure” (Supplementary Table S2), 39 genes for “Systolic blood pressure, automated reading” (Supplementary Table S3), and 45 genes for “Diastolic blood pressure, automated reading” (Supplementary Table S4). Among these genes, 32 genes were overlapped by at least two GWAS, representing the most significant and robust genes that are regulated by hypertension-risk loci and function in aorta (Table 1). To explore whether these predicted genes were truly involved in aortic dissection, we investigated their expression changes in aorta from dissection patients. Eight (NOV, OPRL1, ERI1, HAUS8, UBE2D3, SPATA33, DCAF16, ARHGAP42) out of these cross-validated 32 genes were differentially expressed in aorta of patients with marginal significance (GSE52093, Table 1).
Suggestively significant genes cross-validated by four hypertension-related GWASs
In addition to the genome-wide significant hits, genes showing suggestively significant TWAS P-values in all four GWASs might also be relevant in aorta. We then extended the gene list with a nominally significant threshold of TWAS-P-value < 0.01 (Supplementary Table 1). There were 113 such cross validated genes with a TWAS P-value < 0.01 in all the four GWASs “Hypertension (Self-reported)” (n = 385), “High blood pressure” (n = 381), “Systolic blood pressure, automated reading” (n = 402), and “Diastolic blood pressure, automated reading” (n = 423) (Figure 2). These 113 suggestively significant genes might be hypertension-risk-loci regulated genes that contribute to aortic dissection and were subjected to differential expression analysis. 19 genes were differentially (P-value < 0.05) expressed in aorta of patients in GSE52093, including four genome-wide significant genes mentioned above. This added 15 additional targets (ALDH2, AGTRAP, SF3B3, CTSW, SPNS1, CCNT2, PRADC1, ACADVL, TUFM, SLC26A1, TPD52L2, MRAS, SMOC1, OIP5-AS1, and TOP3A) in the effect gene list (Table 1). These 23 genes were genetically-regulated and were differentially expressed in aorta of patients, thus acting as the underlying effect genes for aortic dissection in at-risk individuals with hypertension.
Detection of genetically dysregulated aortic gene DCAF16 in blood of dissection patients
We then asked whether the dysregulated genes in aorta could be observed in blood of patients with thoracic aortic aneurysm [25], which usually leads to aortic dissection [26-29]. In the gene expression dataset GSE9106 which contains 36 cases and 25 controls [25], we found that three (OPRL1, HAUS8, DCAF16) out of the 23 effect genes were significantly altered in blood of patients compared with controls. However, the directions of differential expression of OPRL1 and HAUS8 were opposite between aorta (GSE52093) and blood (GSE9106). DCAF16 was the only hit that shows consistent decrease in both aorta and blood (P = 0.00948 in the training set, 36 cases and 25 controls) of patients (Figure 3). Notably, expression change of DCAF16 was well-validated by the testing set (P = 0.0002 in 22 cases and 11 controls) of GSE9106.