FGL1 as a modulator of plasma D-dimer levels: exome-wide marker analysis of plasma tPA, PAI-1 and D-dimer.

BACKGROUND Use of targeted exome-arrays with common, rare variants and functionally enriched variation has led to discovery of new genes contributing to population variation in risk factors. Plasminogen activator-inhibitor 1 (PAI-1), tissue plasminogen activator (tPA), and the plasma product D-dimer are important components of the fibrinolytic system. There have been few large-scale genome-wide or exome-wide studies of PAI-1, tPA and D-dimer. OBJECTIVES We sought to discover new genetic loci contributing to variation in these traits using an exome-array approach. METHODS Cohort level analyses and fixed effects meta-analyses of PAI-1 (n = 15,603), tPA (n = 6,876) and D-dimer (n = 19,306) from 12 cohorts of European ancestry with diverse study design were conducted, including single-variant analyses and gene-based burden testing. RESULTS Five variants located in NME7, FGL1 and the fibrinogen locus, all associated with D-dimer levels, achieved genome-wide significance (P < 5 × 10-8 ). Replication was sought for these 5 variants, as well as 45 well-imputed variants with P < 1 × 10-4 in the discovery using an independent cohort. Replication was observed for 3 out of the 5 significant associations, including a novel and uncommon (0.013 allele frequency) coding variant p.Trp256Leu in FGL1 (Fibrinogen-Like-1) with increased plasma D-dimer levels. Additionally, a candidate-gene approach revealed a suggestive association for a coding variant (rs143202684-C) in SERPINB2, and suggestive associations with consistent effect in the replication analysis include an intronic variant (rs11057830-A) in SCARB1 associated with increased D-dimer levels. CONCLUSION This work provides new evidence for a role of FGL1 in hemostasis.