5566409 IMPACT OF GENETIC VARIATIONS ON THROMBOTIC RISK OF SICKLE CELL DISEASE IN SAUDI PATIENTS

Abstract

Introduction: Sickle cell disease (SCD) patients are at higher risk of developing venous thromboembolism (VTE) in comparison to healthy individuals (1). The prevalence of VTE in SCD patients is 8.4-11.3% in the Saudi population (2-3), whereas rates are extremely lower in healthy people (0.1 %). This might be attributed to several risk factors, in particular genetic predisposition. Certain mutations, rs6025 (G1691A) in Factor V Leiden (FVL), rs1799963 (G20210A) in Prothrombin (PRT, FII), and rs1801133 (C677T) in Methylenetetrahydrofolate Reductase (MTHFR) are associated with hypercoagulability status involved in various thrombophilic conditions (4). Thus, we aimed to assess the impact of genetic mutations on VTE development in SCD patients. Method: 350 SCD Saudi adult patients (65 cases with a history of VTE and 285 SCD controls without VTE) were genotyped using 10x Affymetrix Axiom Array which includes 812,820 markers for Genome-Wide Association Study (GWAS). PLINK software version 1.07 was used to analyse GWAS data. Genotyping statistical differences between cases and controls were assessed using Fisher’s exact test. Calculations of means and standard deviations were performed to assess matching of the age factor using SPSS 27.0 program and the differences were measured using the 2-independent samples t-test. Institutional Review Board (IRB) approval (ref RC19-083-R) was obtained from King Abdullah International Medical Research Centre, King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard – Health Affairs, Riyadh, Saudi Arabia. Results: Matching was confirmed for age and sex between cases and controls. No significant differences seen in genotypes of FVL (rs6025), PRT (rs1799963), and MTHFR (rs1801133) between the cases and control groups (P=0.34, 1.0, and 0.87, respectively). GWAS analysis has identified 6 association signals at threshold of P<5×10-8, rs139341092 is an indel variant located at chromosome (chr) 20, rs76076035 an intron variant at chr 9, and four variants (three intronic (rs35390334 and rs331532 in strong linkage disequilibrium (LD), and rs372091) and one exonic (rs317777 in OLFM5P) at chr 11. Eight polymorphisms with a significance P-value <5×10-7 were detected; two of them are functional variants (rs73395847, a splice acceptor variant in C11orf40 gene at chr 11 and rs6554634, a transcription factor binding site variant at chr 5). Moreover, 53 variants with an association significance (P-value) <5×10-6 were discovered, 14 of them have known clinical significance. Two of them are missense variants (rs7933549 in OR51V1 at chr 11 and rs111681839 in CEP131 at chr 17), whereas the remaining variants (n=12) are regulatory variants; five of them (rs2071348, rs73402629, and rs73402631 are in LD, in addition to rs2213170 and rs2213169) located at chr 11 and the other seven located at chr 6 (rs145017319), chr 8 (rs16904858 and rs77365846), chr 9 (rs2289658 in NTRK2), chr 16 (rs142329036), chr 20 (rs139719409), and chr 21 (rs73189215). Two of the detected intron variants located at chr 11 (rs1455957 and rs11035718) were found to be in strong LD with a missense variant (rs2472530) in OR52A5 gene at chr 11 too. Conclusion: This study showed no impact of FVL, PRT, and MTHFR on VTE induced in Saudi patients with SCD. However, significant GWAS novel associations, at levels of P<5×10-8 to P<5×10-6, between VTE in SCD with 67 variants were identified which need further replication studies to be confirmed.