Genome‐Wide Analysis of Genetic Determinants Of
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Journal of Thrombosis and Haemostasis, 16: 2024–2034 DOI: 10.1111/jth.14258 ORIGINAL ARTICLE Genome-wide analysis of genetic determinants of circulating factor VII-activating protease (FSAP) activity M. OLSSON,* T. M. STANNE,* A. PEDERSEN,* E. LORENTZEN,† E. KARA,‡ A. MARTINEZ-PALACIAN,‡ N. P. RØNNOW SAND,§ A. F. JACOBSEN,¶ P. M. SANDSET,** € J. J. SIDELMANN,†† G. ENGSTROM , ‡‡ O. MELANDER,‡‡ S. M. KANSE‡ and C . J E R N * *Department of Pathology and Genetics, Institute of Biomedicine, The Sahlgrenska Academy at University of Gothenburg; †Bioinformatics Core Facility, University of Gothenburg, Gothenburg, Sweden; ‡Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway; §Department of Cardiology, Hospital of South West Denmark, Esbjerg and Department of Regional Health Research, Faculty of Health Science, University of Southern Denmark, Esbjerg, Denmark; ¶Department of Obstetrics, Oslo University Hospital and University of Oslo; **Department of Hematology, Oslo University Hospital and University of Oslo, Oslo, Norway; ††Unit for Thrombosis Research, Department of Regional Health Research, Faculty of Health Science, University of Southern Denmark, Esbjerg, Denmark; and ‡‡Department of Clinical Sciences, Malmo,€ Lund University, Lund, Sweden To cite this article: Olsson M, Stanne TM, Pedersen A, Lorentzen E, Kara E, Martinez-Palacian A, Rønnow Sand NP, Jacobsen AF, Sandset PM, Sidelmann JJ, Engstrom€ G, Melander O, Kanse SM, Jern C. Genome-wide analysis of genetic determinants of circulating factor VII-activating protease (FSAP) activity. J Thromb Haemost 2018; 16: 2024–34. study (GWAS) on plasma FSAP activity amongst 3230 Essentials Swedish subjects. Directly genotyped rare variants were also analyzed with gene-based tests. Using GWAS, we • Knowledge of genetic regulators of plasma factor VII confirmed the strong association between the Marburg-I activating protease (FSAP) levels is limited. variant and FSAP activity. HABP2 was also significant • We performed a genome-wide analysis of variants influ- in the gene-based analysis, and remained significant encing FSAP activity in Scandinavian cohorts. after exclusion of Marburg-I carriers. This was attribu- • We replicated an association for Marburg-1 and identi- table to a rare HABP2 stop variant (rs41292628). Carri- fied an association for a HABP2 stop variant. ers of this stop variant showed a similar reduction in • We identified a novel locus near ADCY2 as a potential FSAP activity as Marburg-I carriers, and this finding additional regulator of FSAP activity. was replicated. A secondary genome-wide significant locus was identified at a 5p15 locus (rs35510613), and Summary. Background: Factor VII-activating protease this finding requires future replication. This common (FSAP) has roles in both coagulation and fibrinolysis. variant is located upstream of ADCY2, which encodes Recent data indicate its involvement in several other a protein catalyzing the formation of cAMP. Results processes, such as vascular remodeling and inflamma- and Conclusions: This study verified the Marburg-I vari- tion. Plasma FSAP activity is highly variable among ant to be a strong regulator of FSAP activity, and healthy individuals and, apart from the low-frequency identified an HABP2 stop variant with a similar impact missense variant Marburg-I (rs7080536) in the FSAP- on FSAP activity. A novel locus near ADCY2 was encoding gene HABP2, determinants of this variation identified as a potential additional regulator of FSAP are unclear. Objectives: To identify novel genetic vari- activity. ants within and outside of the HABP2 locus that influ- ence circulating FSAP activity. Patients/Methods: We Keywords: blood coagulation factors; epidemiology; performed an exploratory genome-wide association genetic variation; hemostasis; plasma. Correspondence: Maja Olsson, Institute of Biomedicine, the Sahlgrenska Academy at University of Gothenburg, Box 445, SE-405 30 Gothenburg, Sweden Introduction Tel.: +46 31 343 4805 Factor VII-activating protease (FSAP) is a plasma ser- E-mail: [email protected] ine protease targeting various substrates. FSAP is Received: 8 February 2018 mainly produced by the liver, and is present in the cir- Manuscript handled by: W. Ruf culation as an inactive proenzyme. Activation is trig- Final decision: P. H. Reitsma, 26 July 2018 gered by histones released from apoptotic or necrotic © 2018 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and Haemostasis. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Genome-wide analysis of circulating FSAP activity 2025 cells [1]. The protein was initially separately shown to Methods be involved in fibrinolysis, as an activator of single- chain pro-urokinase, and as an activator of FVII [2–4]. Study design More recently, FVII was recognized as a poor FSAP substrate [5,6], and tissue factor pathway inhibitor This study included 3230 participants from the Malmo€ (TFPI) was identified as a novel substrate. In line with Diet and Cancer (MDC) study and the Sahlgrenska this, impaired FSAP modulation of TFPI levels was Academy Study on Ischemic Stroke (SAHLSIS). suggested as an explanation for the defective thrombus The MDC study is a population-based prospective study formation observed in mice made deficient for FSAP that has been described in detail elsewhere [37]. In brief, all (FSAPÀ/À) [7]. Other studies have shown that FSAP men and women living in the Malmo€ area in southern Swe- has a role not only in vascular compartments [8–10], den and born in 1923–1950 were invited to participate. The but also in liver fibrosis [11,12], inflammation [13–16], participation rate was 41% [38]. The present study is based and cancer [17,18]. In vivo experiments in wild-type and on the MDC Cardiovascular Cohort, which randomly FSAPÀ/À mice support a role for FSAP in vascular selected participant from the MDC study [39]. We included remodeling, liver fibrosis, neointima formation, and subjects without both prevalent (i.e. at baseline) and inci- arteriogenesis [11,19–21]. dent cardiovascular disease (CVD) with biobanked plasma Epidemiological studies have shown that circulating available for FSAP activity measurements (n = 2030). FSAP activity is increased in women as compared with The SAHLSIS is a case–control study for which FSAP men, and is further enhanced by pregnancy or the use activity has been reported [27]. In brief, 600 patients with of oral contraceptives [22–24]. FSAP activity is also ischemic stroke at ages 18–69 years were consecutively increased in subjects with deep vein thrombosis [25] recruited at stroke units in western Sweden [40]. Controls or with coronary heart disease [26] as compared with (n = 600) were selected from population-based health sur- controls. We have found that traditional vascular risk veys or registers to match the cases with regard to age, sex, factors explain very little of the variation in plasma and geographical region [40]. Only control subjects without FSAP activity, i.e. < 10% in healthy individuals [27]. a history of CVD or signs of ischemic heart disease on elec- We have also reported on increased FSAP activity in trocardiogram were included [41]. ischemic stroke cases as compared with controls [27]. Sample sizes and baseline characteristics for the two Furthermore, a region near the FSAP-encoding gene studies are summarized in Table 1. The studies were hyaluronan-binding protein 2 (HABP2) was recently approved by the ethics committee at the respective univer- identified as being associated with young-onset stroke sities. All participants or their next of kin gave informed [28]. consent. An early study of interindividual plasma levels of FSAP in healthy subjects discovered individuals with FSAP activity measurement markedly reduced FSAP activity that was not related to antigen levels [23]. Low levels of FSAP activity were Venous blood samples were collected in tubes containing found to be associated with the minor allele of the 10% by volume of 0.13 mol LÀ1 sodium citrate. Aliquots so-called Marburg-I (MI) single-nucleotide polymor- of plasma were stored at À 80 °C. For the prospective phism (SNP) (rs7080536), which introduces an amino MDC study, blood samples were drawn during the baseline acid change, Gly534Glu (NP_004123.1), in the FSAP examinations in 1991–1996. For the SAHLSIS, blood sam- protein [29]. The MI-SNP has been associated with sev- pling was performed in 1998–2003; at enrollment for con- eral disease processes, such as carotid stenosis [30], trols, and at 3-month follow-up for cases [27,40]. Plasma stroke [31], and liver fibrosis [12]. Associations between levels of FSAP activity were measured with an immunocap- the MI-SNP and venous thrombosis have also been ture activity test, as previously described [23,27]. These reported [32,33], but inconsistent results do exist measurements were performed in 2010 and 2014 for the [25,34–36]. SAHLSIS and the MDC study, respectively. The interassay To our knowledge, only three studies have searched for and intra-assay coefficients of variation (CVs) for FSAP genetic variants associated with FSAP activity, and these activity were 14.7% and 4.7%, respectively, in the SAHL- studies were restricted to variants within HABP2 SIS, as reported in [27], and the interassay CV was 8.2% in [16,27,29]. We hypothesized that there are additional the MDC study. FSAP activity values followed a normal genetic variants that contribute to the variation in circu- distribution, and were not transformed for analysis. lating FSAP activity. Hence, we set out to test this hypothesis by conducting the first genome-wide associa- Genotyping, imputation, and quality control (QC) tion study (GWAS) of this quantitative trait. We used a genotyping platform that is enriched with exome content, DNA was extracted from whole blood, and genotyping and searched for both common and rare genetic variants was performed with either the HumanOmniExpress Exome associated with FSAP activity.