GWAS of Retinal Vessel Tortuosity Identifies 173 Novel Loci Revealing Genes and Pathways Associated with Vascular Pathomechanics and Cardiometabolic Diseases

Background Fundus images allow for non-invasive assessment of the retinal vasculature whose features provide important information on health. Blood vessel tortuosity is a morphological feature associated with many diseases including hypertension. Methods We analyzed 116 639 fundus images of suitable quality from 63 662 participants from three cohorts, namely the UK Biobank (n = 62 751), SKIPOGH (n = 397), and OphtalmoLaus (n = 512). We used a fully automated image processing pipeline to annotate vessels and a deep learning algorithm to determine the vessel type, characterizing these subjects in terms of their median retinal vessel tortuosity specific to arteries and to veins. Tortuosity was measured by the distance factor (the length of a vessel segment over its chord length), as well as measures that integrate over vessel curvature. Using these measures as traits, we performed the largest genome-wide association study (GWAS) of vessel tortuosity to date. We assessed gene set enrichment using the novel high-precision statistical method PascalX . Results Higher tortuosity was significantly associated with higher incidence of angina, myocardial infarction, stroke, deep vein thrombosis, and hypertension. We identified 175 significantly associated genetic loci in the UK Biobank; 173 of these were novel and 4 replicated in our second, much smaller, meta-cohort. We estimated heritability at ∼25% using linkage disequilibrium score regression. Vessel type specific GWAS revealed 114 loci for arteries and 63 for veins. Genes with significant association signals included COL4A2, ACTN4, LGALS4, LGALS7, LGALS7B, TNS1, MAP4K1, EIF3K, CAPN12, ECH1, and SYNPO2. These tortuosity genes were overexpressed in arteries and heart muscle and linked to pathways related to the structural properties of the vasculature. We demonstrated that tortuosity loci served pleiotropic functions as cardiometabolic disease variants and risk factors. Concordantly, Mendelian randomization revealed causal effects between tortuosity, BMI and LDL. Conclusions Several alleles associated with retinal vessel tortuosity point to a common genetic architecture of this trait with cardiovascular diseases and metabolic syndrome. Our results shed new light on the genetics of vascular diseases and their pathomechanisms and highlight how GWASs and heritability can be used to improve phenotype extraction from high-dimensional data, such as images. What is new? What are the clinical implications? ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the Swiss National Science Foundation (#FN 310030_152724/1 to SB) and by the Swiss Personalized Health Network (2018DRI13 to Thomas J. Wolfensberger). The SKIPOGH study was also supported by the Swiss National Science Foundation (#FN 33CM30-124087 to MB). The OphtalmoLaus study was supported by the Claire et Selma Kattenburg Foundation. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Cohort name: SKIPOGH. -Full name of Ethics Committee / Institutional Review Board (IRB) for the cohort: Ethics Committee of the Universities of Bern, Geneva, and Lausanne, Switzerland. -Decision made by ethical oversight body: approved / waived: approved Cohort name: CoLaus. -Full name of Ethics Committee / Institutional Review Board (IRB) for the cohort: Ethics Committee of the Universities of Lausanne, Lausanne, Switzerland. -Decision made by ethical oversight body: approved / waived: approved Cohort name and Ethics Committee: UK Biobank - Decision made by ethical oversight body: approved / waived: approved, project 43805. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The data are made available by the UK Biobank Consortium. * BMI : body mass index BRB : blood-retina barrier CAD : coronary artery disease CVD : cardiovascular diseases DBP : diastolic blood pressure DF : distance factor DVT : deep vein thrombosis EC : endothelial cells GO : gene ontology GWAS : genome-wide association study LD : linkage disequilibrium LDL : low-density lipoprotein SBP : systolic blood pressure SMC : smooth muscle cell SNP : single nucleotide polymorphism VEGF : vascular endothelial growth factor