GDF15: Anotação funcional de SNPs não codificantes, validação funcional de sequência candidata a acentuadora, e estudo do seu potencial papel como biomarcador da Pré-eclâmpsia

Abstract

GDF15 is stress-induced cytokine and a potential biomarker of cardiovascular diseases and preeclampsia (PE). Single nucleotide polymorphisms (SNPs) can explain a significant portion of variability in circulating GDF15 levels, including several non-coding SNPs. In Chapter 1, we identified candidate enhancer regions in silico using data from the Encyclopedia of DNA Elements (ENCODE) and tools for assigning cis-regulatory elements. We then perform functional annotation of SNPs located in these regions and identified in GWAS for GDF15 levels and locus associated with expression quantitative trait loci (eQTLs) by the Genotype-Tissue Expression (GTEx). In order to better understand the functional role of SNP rs888663 and its nearby region as a candidate regulatory sequence, in Chapter 2 we accessed publicly available data from ENCODE and GeneHancer. We identified an enhancer candidate region upstream the GDF15 locus, containing the rs888663 (G>T) and using a dual luciferase reporter assay with vectors containing either the reference (G) or the alternative (T) alleles, we found that the T allele presents an enhancer activity when compared to the G allele and the negative control. Meta-analysis of genome-wide association studies (GWAS) found SNPs in GDF15 locus associated with GDF15 levels, including rs888663 and rs1059369. However, no previous study has tested the hypothesis that GDF15 SNPs affect GDF15 levels in hypertensive disorders of pregnancy. In Chapter 3, we examine the effects of these SNPs and their haplotypes on GDF15 levels in healthy pregnant women (HP, n = 233), patients with gestational hypertension (GH, n = 197) and PE (n = 188). HP women showed higher plasma levels of GDF15 than patients with PE and GH (P<0.01). We found no association of alleles and genotypes of rs888663 (G>T) and rs1059369 (T>A) SNPs and their haplotypes with susceptibility to PE and/or GH. However, patients with PE and GH carrying the TT genotype for the GDF15 SNP rs1059369 (T>A) and the ‘T, T’ haplotype showed lower plasma GDF15 levels than HP women carrying the same genotype and haplotype. Our novel findings suggest that GDF15 genotypes and haplotypes affect circulating GDF15 levels in hypertensive disorders of pregnancy.