A genetic association study of maternal and fetal candidate genes that predispose to preterm prelabor rupture of membranes (PROM)

Abstract

Objective: We sought to determine whether maternal/fetal single-nucleotide polymorphisms (SNPs) in candidate genes are associated with preterm prelabor rupture of membranes (pPROM).

Study design: A case-control study was conducted in patients with pPROM (225 mothers and 155 fetuses) and 599 mothers and 628 fetuses with a normal pregnancy; 190 candidate genes and 775 SNPs were studied. Single locus/haplotype association analyses were performed; false discovery rate was used to correct for multiple testing (q* = 0.15).

Results: First, a SNP in tissue inhibitor of metalloproteinase 2 in mothers was significantly associated with pPROM (odds ratio, 2.12; 95% confidence interval, 1.47-3.07; P = .000068), and this association remained significant after correction for multiple comparisons. Second, haplotypes for Alpha 3 type IV collagen isoform precursor in the mother were associated with pPROM (global P = .003). Third, multilocus analysis identified a 3-locus model, which included maternal SNPs in collagen type I alpha 2, defensin alpha 5 gene, and endothelin 1.

Conclusion: DNA variants in a maternal gene involved in extracellular matrix metabolism doubled the risk of pPROM.

Figure 1. Haploview plots of genes identified in analyses of haplotype tests of association in maternal samples

LD plots were generated in Haploview and are presented for: A) COL4A3 cases r²; and B) COL4A3 controls r². Within each triangle is presented the pairwise correlation coefficient (r²) LD plots white, (r² = 0), shades of grey, (0 < r² < 1), black, (r² = 1).

Figure 2. MDR results for maternal-fetal analyses

MDR model for a three-way interaction involving maternal SNPs rs4610776 (DEFA5) and rs5359 (EDN1) and rs1800248 (COL1A2). Each panel represents a three locus genotype; the genotype for each SNP is labeled on the figure. Each large square (3 × 3 box) represents a different genotype for rs4610776 (AA on left, AT in the middle, and TT on the right). Within each square, each row of cells delineates rs1800248 genotypes (top CC, middle CT and bottom TT) and each column the rs35369 genotypes. Therefore, each small cell describes a single and unique three locus genotype. Within each cell are two bars that represent the number of cases with this genotype (left hand bar) and number of controls (right hand bar). Each multilocus cell is denoted as “high risk” (dark gray) or “low risk” (light gray) for spontaneous preterm labor/delivery with intact membranes. Empty cells are shown in white. Risk status is determined by the ratio of cases to controls adjusted by the number of cases and controls studied. The testing average balanced accuracy is 60% (p-value = 0.047) with a cross-validation consistency of 10 out of 10.

Figure 3. Connection map for the first ranked network generated by IPA from maternal focus gene input

The biomarkers passing the p < 0.05 significance threshold (focus molecules, depicted as pink or red) were entered into the IPA software for an unsupervised functional analysis to discern regulatory networks involving these molecules. The asterisk indicates that there was more than one SNP probe for the gene tested and the most significant value was placed into the analysis. Solid lines show direct interaction (binding/physical contact); dashed line, indirect interaction supported by the literature but possibly involving one or more intermediate molecules that have not been investigated definitively. Molecular interactions involving only binding are connected with a solid line (no arrowhead) since directionality cannot be inferred.

Figure 4. Connection map for the first ranked network generated by IPA from fetal focus gene input

The biomarkers passing the p < 0.05 significance threshold (focus molecules, depicted as pink or red) were entered into the IPA software for an unsupervised functional analysis to discern regulatory networks involving these molecules. The asterisk indicates that there was more than one SNP probe for the gene tested and the most significant value was placed into the analysis. Solid lines show direct interaction (binding/physical contact); dashed line, indirect interaction supported by the literature but possibly involving one or more intermediate molecules that have not been investigated definitively. Molecular interactions involving only binding are connected with a solid line (no arrowhead) since directionality cannot be inferred.