Pre-eclampsia TAC-seq

The etiology of preeclampsia, a hypertensive disorder of human pregnancy, remains unknown. We addressed fetal sex selection and the suggestive role of fetal HLA-G and related genes, regulating maternal immune responses, in preeclampsia pathogenesis. We assessed birth sex ratios, weights, and seasonality of preeclampsia among 1.79 million births in Finland. We studied haplotypes of HLA-G 3’ untranslated region (UTR), regulating HLA-G expression, in 1000 Genomes series and in a preeclampsia cohort (n=1249). We quantified placental (n=163) mRNA expression of 136 genes, studied HLA-G and IFNα protein expression by immunohistochemistry, and measured maternal and fetal circulating IFNα levels by ELISA. Population-level data showed loss of male fetuses as a characteristic of preeclampsia. As a potential contributor to immune-mediated loss, we found balancing selection at HLA-G 3’UTR modulating sex ratio, and association of HLA-G 3’UTR haplotypes with placental HLA-G expression. HLA-G and its receptors were downregulated in preeclampsia placentas, and surprisingly, interferon alpha-1 (IFNA1) was highly upregulated. IFNA1 and HLA-G distinguished preeclampsia better than placental FLT1 expression. Fetal but not maternal circulating IFNα, produced by trophoblasts, showed association with maternal hypertension and fetal growth restriction. We uncover the link between placental HLA-G expression and human birth sex ratio. We propose that preeclampsia shares, through reduced HLA-G mediated immunotolerance, the mechanism needed to fight placental viral infections and malaria in evolution. IFNα upregulation in preeclampsia placenta, together with its known actions upstream of inflammatory genes, encourages testing IFNα inhibitors and especially the pregnancy-approved antimalarial hydroxichloroquine in treatment of preeclampsia. 163 samples in total in 5 libraries (SATU1, SATU2, SATU3, SATU4, SATU5). 169 targets in total including 162 biomarker genes (136 remaining after QC) and 7 ERCC RNA Spike-In controls.