Genetic and molecular functional characterization of variants within TNFSF13B, a positional candidate preeclampsia susceptibility gene on 13q

Extracellular vesicles alter trophoblast function in pregnancies complicated by COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and resulting coronavirus disease (COVID-19) causes placental dysfunction, which increases the risk of adverse pregnancy outcomes. While abnormal placental pathology resulting from COVID-19 is common, direct infection of the placenta is rare. This suggests that pathophysiology associated with maternal COVID-19, rather than direct placental infection, is responsible for placental dysfunction and alteration of the placental transcriptome. We hypothesized that maternal circulating extracellular vesicles (EVs), altered by COVID-19 during pregnancy, contribute to placental dysfunction. To examine this hypothesis, we characterized maternal circulating EVs from pregnancies complicated by COVID-19 and tested their effects on trophoblast cell physiology in vitro . We found that the gestational timing of COVID-19 is a major determinant of circulating EV function and cargo. In vitro trophoblast exposure to EVs isolated from patients with an active infection at the time of delivery, but not EVs isolated from Controls, altered key trophoblast functions including hormone production and invasion. Thus, circulating EVs from participants with an active infection, both symptomatic and asymptomatic cases, can disrupt vital trophoblast functions. EV cargo differed between participants with COVID-19 and Controls, which may contribute to the disruption of the placental transcriptome and morphology. Our findings show that COVID-19 can have effects throughout pregnancy on circulating EVs and circulating EVs are likely to participate in placental dysfunction induced by COVID-19.

Type I interferon alters invasive extravillous trophoblast function

Inappropriate type I interferon (IFN) signaling during embryo implantation and placentation is linked to poor pregnancy outcomes. Here, we evaluated the consequence of elevated type I IFN exposure on implantation using a biomimetic model of human implantation in an organ-on-a-chip device. We found that type I IFN reduced extravillous trophoblast (EVT) invasion capacity. Analyzing single-cell transcriptomes, we uncovered that IFN truncated endovascular EVT emergence in the implantation-on-a-chip device by stunting EVT epithelial-to-mesenchymal transition. Disruptions to the epithelial-to-mesenchymal transition is associated with the pathogenesis of preeclampsia, a life-threatening hypertensive disorder of pregnancy. Strikingly, unwarranted IFN stimulation induced genes associated with increased preeclampsia risk and a preeclamptic gene-like signature in EVTs. These dysregulated EVT phenotypes ultimately reduced EVT-mediated endothelial cell vascular remodeling in the implantation-on-a-chip device. Overall, our work indicates IFN signaling can alter EVT epithelial-to-mesenchymal transition progression which results in diminished EVT-mediated spiral artery remodeling and a preeclampsia gene signature upon sustained stimulation. Our work implicates unwarranted type I IFN as a maternal disturbance that can result in abnormal EVT function that could trigger preeclampsia.

BAFF and APRIL counterregulate susceptibility to inflammation-induced preterm birth

Clinical evidence points to a function for B cell-activating factor (BAFF) in pregnancy. However, direct roles for BAFF-axis members in pregnancy have not been examined. Here, via utility of genetically modified mice, we report that BAFF promotes inflammatory responsiveness and increases susceptibility to inflammation-induced preterm birth (PTB). In contrast, we show that the closely related A proliferation-inducing ligand (APRIL) decreases inflammatory responsiveness and susceptibility to PTB. Known BAFF-axis receptors serve a redundant function in signaling BAFF/APRIL presence in pregnancy. Treatment with anti-BAFF/APRIL monoclonal antibodies or BAFF/APRIL recombinant proteins is sufficient to manipulate susceptibility to PTB. Notably, macrophages at the maternal-fetal interface produce BAFF, while BAFF and APRIL presence divergently shape macrophage gene expression and inflammatory function. Overall, our findings demonstrate that BAFF and APRIL play divergent inflammatory roles in pregnancy and provide therapeutic targets for mitigating risk of inflammation-induced PTB.

Protein and functional isoform levels and genetic variants of the BAFF and APRIL pathway components in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is the prototype of an autoimmune disease. Belimumab, a monoclonal antibody targets BAFF, is the only biologic approved for SLE and active lupus nephritis. BAFF is a cytokine with a key-regulatory role in the B cell homeostasis, which acts by binding to three receptors: BAFF-R, TACI and BCMA. TACI and BCMA also bind APRIL. Many studies reported elevated soluble BAFF and APRIL levels in the sera of SLE patients, but other questions about the role of this system in the disease remain open. The study aimed to investigate the utility of the cytokine levels in serum and urine as biomarkers, the role of non-functional isoforms, and the association of gene variants with the disease. This case–control study includes a cohort (women, 18–60 years old) of 100 patients (48% with nephritis) and 100 healthy controls. We used ELISA assays to measure the cytokine concentrations in serum (sBAFF and sAPRIL) and urine (uBAFF and uAPRIL); TaqMan Gene Expression Assays to quantify the relative mRNA expression of ΔBAFF, βAPRIL, and εAPRIL, and next-generation sequencing to genotype the cytokine (TNFSF13 and TNFSF13B) and receptor (TNFRSF13B, TNFRSF17 and TNFRSF13C) genes. The statistical tests used were: Kruskal–Wallis (qualitative variables), the Spearman Rho coefficient (correlations), the Chi-square and SKAT (association of common and rare genetic variants, respectively). As expected, sBAFF and sAPRIL levels were higher in patients than in controls (p ≤ 0.001) but found differences between patient subgroups. sBAFF and sAPRIL significantly correlated only in patients with nephritis (r_s = 0.67, p ≤ 0.001) and βAPRIL levels were lower in patients with nephritis (p = 0.04), and ΔBAFF levels were lower in patients with dsDNA antibodies (p = 0.04). Rare variants of TNFSF13 and TNFRSF13B and TNFSF13 p.Gly67Arg and TNFRSF13B p.Val220Ala were associated with SLE. Our study supports differences among SLE patient subgroups with diverse clinical features in the BAFF/APRIL pathway. In addition, it suggests the involvement of genetic variants in the susceptibility to the disease.

Delineating differential regulatory signatures of the human transcriptome in the choriodecidua and myometrium at term labor

Preterm deliveries remain the leading cause of neonatal morbidity and mortality. Current therapies target only myometrial contractions and are largely ineffective. As labor involves multiple coordinated events across maternal and fetal tissues, identifying fundamental regulatory pathways of normal term labor is vital to understanding successful parturition and consequently labor pathologies. We aimed to identify transcriptomic signatures of human normal term labor of two tissues: in the fetal-facing choriodecidua and the maternal myometrium. Microarray transcriptomic data from choriodecidua and myometrium following term labor were analyzed for functional hierarchical networks, using Cytoscape 2.8.3. Hierarchically high candidates were analyzed for their regulatory casual relationships using Ingenuity Pathway Analysis. Selected master regulators were then chemically inhibited and effects on downstream targets were assessed using real-time quantitative PCR (RT-qPCR). Unbiased network analysis identified upstream molecular components in choriodecidua including vimentin, TLR4, and TNFSF13B. In the myometrium, candidates included metallothionein 2 (MT2A), TLR2, and RELB. These master regulators had significant differential gene expression during labor, hierarchically high centrality in community cluster networks, interactions amongst the labor gene set, and strong causal relationships with multiple downstream effects. In vitro experiments highlighted MT2A as an effective regulator of labor-associated genes. We have identified unique potential regulators of the term labor transcriptome in uterine tissues using a robust sequence of unbiased mathematical and literature-based in silico analyses. These findings encourage further investigation into the efficacy of predicted master regulators in blocking multiple pathways of labor processes across maternal and fetal tissues, and their potential as therapeutic approaches.

Association of ERAP2 gene variants with risk of pre-eclampsia among Iranian women

OBJECTIVES

To determine the association between ERAP2 rs2549782 and rs17408150 polymorphisms and pre-eclampsia among Iranian women.

METHODS

A retrospective case-control study comparing 319 women with pre-eclampsia and 291 normotensive pregnant Iranian women between January and August 2016. Pre-eclampsia was diagnosed by the International Society for the Study of Hypertension in Pregnancy's criteria. Demographic data were collected by oral interview. Genotyping was done by allele-specific PCR. Data were analyzed using SPSS v. 16.

RESULTS

The frequency of the rs2549782TT genotype was 31.0% and 27.5% among cases and controls, respectively (P=0.006). There was no difference in the frequency of the T allele between groups (P>0.05). Regarding the rs17408150 polymorphism, a high portion of women with pre-eclampsia was homozygous for the AA genotype (P<0.001). The frequency of the A allele was 32.5% and 25.05% among cases and controls, respectively (P=0.004). The combined haplotype of the rs2549782A and rs17408150G alleles was associated with increased risk of pre-eclampsia (P=0.031).

CONCLUSION

ERAP2 gene polymorphisms were associated with the risk of pre-eclampsia in an Iranian population. The results provide further evidence of the role of ERAP2 in the pathophysiology of this disease.

Non-additive effects of ACVR2A in preeclampsia in a Philippine population

BACKGROUND

Multiple interrelated pathways contribute to the pathogenesis of preeclampsia, and variants in susceptibility genes may play a role among Filipinos, an ethnically distinct group with high prevalence of the disease. The objective of this study was to examine the association between variants in maternal candidate genes and the development of preeclampsia in a Philippine population.

METHODS

A case-control study involving 29 single nucleotide polymorphisms (SNPs) in 21 candidate genes was conducted in 150 patients with preeclampsia (cases) and 175 women with uncomplicated normal pregnancies (controls). Genotyping for the GRK4 and DRD1 gene variants was carried out using the TaqMan Assay, and all other variants were assayed using the Sequenom MassARRAY Iplex Platform. PLINK was used for SNP association testing. Multilocus association analysis was performed using multifactor dimensionality reduction (MDR) analysis.

RESULTS

Among the clinical factors, older age (P <  1 × 10-4), higher BMI (P <  1 × 10-4), having a new partner (P = 0.006), and increased time interval from previous pregnancy (P = 0.018) associated with preeclampsia. The MDR algorithm identified the genetic variant ACVR2A rs1014064 as interacting with age and BMI in association with preeclampsia among Filipino women.

CONCLUSIONS

The MDR algorithm identified an interaction between age, BMI and ACVR2A rs1014064, indicating that context among genetic variants and demographic/clinical factors may be crucial to understanding the pathogenesis of preeclampsia among Filipino women.

A tag SNP in syncytin-2 3-UTR significantly correlates with the risk of severe preeclampsia

BACKGROUND

Preeclampsia is a disease that frequently complicates pregnancy and poses a serious threat to maternal and fetal health. The causes and pathogenic mechanisms of preeclampsia are poorly defined. Genetic predisposition could be an important etiological factor. Previous studies have demonstrated that syncytin-1 and syncytin-2, encoded by the genes ERVWE1 and ERVFRDE-1, are involved in the pathogenesis of preeclampsia.

METHODS

In this study, we applied multiplex PCR and MALDI-TOF MS techniques to analyze six selected tag SNPs of ERVWE1 and ERVFRDE-1 in 120 preeclampsia patients and 181 normal controls.

RESULTS

One SNP polymorphism (rs9393931) with the recessive TT genotype located in the 3-UTR of ERVFRDE-1 gene was found to be significantly associated with an increased risk of preeclampsia (OR (95% CI) = 2.05 (1.27-3.32); p = 2.8 × 10^-3). No significant correlation of this polymorphism with the clinical severity of preeclampsia, e.g. the extent of hypertension, was detected between carrier and non-carrier patients.

CONCLUSIONS

These results suggested that genetic predisposition in ERVFRDE-1 may be associated with an increased risk of preeclampsia. This polymorphism is possibly involved in the regulation of syncytin-2 expression in preeclamptic placenta.

Genetic Approaches in Preeclampsia

Preeclampsia (PE) is a serious hypertensive disorder that affects up to 8% of all pregnancies annually. An established risk factor for PE is family history, clearly demonstrating an underlying genetic component to the disorder. To date, numerous genetic studies, using both the candidate gene and genome-wide approach, have been undertaken to tease out the genetic basis of PE and understand its origins. Such studies have identified some promising candidate genes such as STOX1 and ACVR2A. Nevertheless, researchers face ongoing challenges of replicating these genetic associations in different populations and performing the functional validation of identified genetic variants to determine their causality in the disorder. This chapter will review the genetic approaches used in the study of PE, discuss their limitations and possible confounders, and describe current strategies.

Rare Variants in NOD1 Associated with Carotid Bifurcation Intima-Media Thickness in Dominican Republic Families

Cardiovascular disorders including ischemic stroke (IS) and myocardial infarction (MI) are heritable; however, few replicated loci have been identified. One strategy to identify loci influencing these complex disorders is to study subclinical phenotypes, such as carotid bifurcation intima-media thickness (bIMT). We have previously shown bIMT to be heritable and found evidence for linkage and association with common variants on chromosome 7p for bIMT. In this study, we aimed to characterize contributions of rare variants (RVs) in 7p to bIMT. To achieve this aim, we sequenced the 1 LOD unit down region on 7p in nine extended families from the Dominican Republic (DR) with strong evidence for linkage to bIMT. We then performed the family-based sequence kernel association test (famSKAT) on genes within the 7p region. Analyses were restricted to single nucleotide variants (SNVs) with population based minor allele frequency (MAF) <5%. We first analyzed all exonic RVs and then the subset of only non-synonymous RVs. There were 68 genes in our analyses. Nucleotide-binding oligomerization domain (NOD1) was the most significantly associated gene when analyzing exonic RVs (famSKAT p = 9.2x10^-4; number of SNVs = 14). We achieved suggestive replication of NOD1 in an independent sample of twelve extended families from the DR (p = 0.055). Our study provides suggestive statistical evidence for a role of rare variants in NOD1 in bIMT. Studies in mice have shown Nod1 to play a role in heart function and atherosclerosis, providing biologic plausibility for a role in bIMT thus making NOD1 an excellent bIMT candidate.

Integrative transcriptome analysis reveals dysregulation of canonical cancer molecular pathways in placenta leading to preeclampsia

We previously suggested links between specific XPD mutations in the fetal genome and the risk of placental maldevelopment and preeclampsia, possibly due to impairment of Transcription Factor (TF)IIH-mediated functions in placenta. To identify the underlying mechanisms, we conducted the current integrative analysis of several relevant transcriptome data sources. Our meta-analysis revealed downregulation of TFIIH subunits in preeclamptic placentas. Our overall integrative analysis suggested that, in the presence of hypoxia and oxidative stress, EGFR signaling deficiency, which can be caused by TFIIH impairment as well as by other mechanisms, results in ATF3 upregulation, inducing mediators of clinical symptoms of preeclampsia such as FLT1 and ENG. EGFR- and ATF3-dependent pathways play prominent roles in cancer development. We propose that dysregulation of these canonical cancer molecular pathways occurs in preeclampsia and delineate the relevance of TFIIH, providing etiologic clues which could eventually translate into a therapeutic approach.

Increased decidual mRNA expression levels of candidate maternal pre-eclampsia susceptibility genes are associated with clinical severity

INTRODUCTION

Pre-eclampsia (PE) has a familial association, with daughters of women who had PE during pregnancy having more than twice the risk of developing PE themselves. Through genome-wide linkage and genetic association studies in PE-affected families and large population samples, we previously identified the following as positional candidate maternal susceptibility genes for PE; ACVR1, INHA, INHBB, ERAP1, ERAP2, LNPEP, COL4A1 and COL4A2. The aims of this study were to determine mRNA expression levels of previously identified candidate maternal pre-eclampsia susceptibility genes from normotensive and severe PE (SPE) pregnancies and correlate mRNA expression levels with the clinical severity of SPE.

METHODS

Third trimester decidual tissues were collected from both normotensive (n = 21) and SPE pregnancies (n = 24) and mRNA expression levels were determined by real-time PCR. Gene expression was then correlated with several parameters of clinical severity in SPE. Statistical significance was determined by Mann-Whitney U test and Spearman's Correlation.

RESULTS

The data demonstrate significantly increased decidual mRNA expression levels of ACVR1, INHBB, ERAP1, ERAP2, LNPEP, COL4A1 and COL4A2 in SPE (p < 0.05). Increased mRNA expression levels of several genes - INHA, INHBB, COL4A1 and COL4A2 were correlated with earlier onset of PE and earlier delivery of the fetus (p < 0.05).

CONCLUSION

These results suggest altered expression of maternal susceptibility genes may play roles in PE development and the course of disease severity.

The BAFF/APRIL system: emerging functions beyond B cell biology and autoimmunity

The BAFF system plays a key role in the development of autoimmunity, especially in systemic lupus erythematosus (SLE). This often leads to the assumption that BAFF is mostly a B cell factor with a specific role in autoimmunity. Focus on BAFF and autoimmunity, driven by pharmaceutical successes with the recent approval of a novel targeted therapy Belimumab, has relegated other potential roles of BAFF to the background. Far from being SLE-specific, the BAFF system has a much broader relevance in infection, cancer and allergy. In this review, we provide the latest views on additional roles of the BAFF system in health and diseases, as well as an update on BAFF and autoimmunity, with particular focus on current clinical trials.

Genome-wide association scan identifies a risk locus for preeclampsia on 2q14, near the inhibin, beta B gene

Elucidating the genetic architecture of preeclampsia is a major goal in obstetric medicine. We have performed a genome-wide association study (GWAS) for preeclampsia in unrelated Australian individuals of Caucasian ancestry using the Illumina OmniExpress-12 BeadChip to successfully genotype 648,175 SNPs in 538 preeclampsia cases and 540 normal pregnancy controls. Two SNP associations (rs7579169, p = 3.58×10⁻⁷, OR = 1.57; rs12711941, p = 4.26×10⁻⁷, OR = 1.56) satisfied our genome-wide significance threshold (modified Bonferroni p<5.11×10⁻⁷). These SNPs reside in an intergenic region less than 15 kb downstream from the 3′ terminus of the Inhibin, beta B (INHBB) gene on 2q14.2. They are in linkage disequilibrium (LD) with each other (r² = 0.92), but not (r²<0.80) with any other genotyped SNP ±250 kb. DNA re-sequencing in and around the INHBB structural gene identified an additional 25 variants. Of the 21 variants that we successfully genotyped back in the case-control cohort the most significant association observed was for a third intergenic SNP (rs7576192, p = 1.48×10⁻⁷, OR = 1.59) in strong LD with the two significant GWAS SNPs (r²>0.92). We attempted to provide evidence of a putative regulatory role for these SNPs using bioinformatic analyses and found that they all reside within regions of low sequence conservation and/or low complexity, suggesting functional importance is low. We also explored the mRNA expression in decidua of genes ±500 kb of INHBB and found a nominally significant correlation between a transcript encoded by the EPB41L5 gene, ∼250 kb centromeric to INHBB, and preeclampsia (p = 0.03). We were unable to replicate the associations shown by the significant GWAS SNPs in case-control cohorts from Norway and Finland, leading us to conclude that it is more likely that these SNPs are in LD with as yet unidentified causal variant(s).

Pathogenesis of preeclampsia: the genetic component

Preeclampsia (PE) is one of the main causes of maternal and fetal morbidity and mortality in the world, causing nearly 40% of births delivered before 35 weeks of gestation. PE begins with inadequate trophoblast invasion early in pregnancy, which produces an increase in oxidative stress contributing to the development of systemic endothelial dysfunction in the later phases of the disease, leading to the characteristic clinical manifestation of PE. Numerous methods have been used to predict the onset of PE with different degrees of efficiency. These methods have used fetal/placental and maternal markers in different stages of pregnancy. From an epidemiological point of view, many studies have shown that PE is a disease with a strong familiar predisposition, which also varies according to geographical, socioeconomic, and racial features, and this information can be used in the prediction process. Large amounts of research have shown a genetic association with a multifactorial polygenic inheritance in the development of this disease. Many biological candidate genes and polymorphisms have been examined in their relation with PE. We will discuss the most important of them, grouped by the different pathogenic mechanisms involved in PE.