The maternal 14 bp Ins/Del polymorphism inHLA-Gis not associated with preeclampsia risk

Human leukocyte antigen-G 14 bp insertion/deletion polymorphism contributes to preeclampsia risk in Asian population: A systematic review and meta‑analysis

Preeclampsia remains enigmatic and responsible for vast maternal and fetal morbidity and mortality worldwide. Our objective was to assess the strength of the effect of the 14 bp deletion/insertion polymorphism in exon 8 of the 3'UTR region of the human leukocyte antigen-G (HLA-G) gene on preeclampsia risk across different populations. A systematic review by a meta-analysis was performed to summarize the scattered epidemiologic evidence, which remains inconclusive and controversial. A systematic literature search according to the PRISMA guidelines was conducted to screen relevant publications. Odds ratio and corresponding 95% confidence interval were estimated to measure the magnitude of the association between this polymorphism and preeclampsia onset. Thirty studies comprising 9402 subjects were eligible. Pooled estimates suggested that both fetal and paternal insertion variants were significantly associated with increased odds of this disease. Nevertheless, the presence of the 14 bp insertion sequence in mothers does not seem to increase the risk of preeclampsia. Moreover, the results of subgroup analysis suggested that the fetal, maternal, and paternal polymorphism has a significant deleterious impact on the preeclampsia risk in the Asian population. In addition, the significant association between the paternal polymorphism and preeclampsia in primigravida was observed in the pooled estimation with a small sample size. By summarizing the amount of significant evidence, our study nominated this polymorphism as a potential biomarker for early risk stratification for Asians. Further large-scale validation is needed to establish fully solid and conclusive evidence for the impact of the insertion polymorphism on preeclampsia risk.

Association between maternal single-nucleotide polymorphisms in HLA-G gene and risk of preeclampsia

AIM

To determine the relationship between the maternal single-nucleotide polymorphisms (SNPs) in human leukocyte antigen G (HLA-G) gene and preeclampsia (PE), so as to provide guidance for the early risk prediction of PE.

METHODS

From October 2017 to October 2019, a total of 99 pregnant women were enrolled in this cross-sectional study. The PE group included 51 pregnant women with severe PE, and the control group included 48 pregnant women with normal delivery during the same period. DNA was extracted and the SNPs in HLA-G gene of the two groups were sequenced. Maternal SNPs in HLA-G gene affecting the occurrence of the PE were determined.

RESULTS

In this study, patients with PE had increased gravidity (p = .002), increased BMI before delivery (p = .004), reduced neonatal weight (p < .001), reduced gestational weeks (p < .001), reduced placental weight (p < .001), and increased proportion of cesarean section (p < .001). There were significant differences in SNPs at locus 29794467, 29796376, and 29799440 between the two groups (p < .05). In locus 29799440, patients with genotype CC had a lower risk of PE than patients with genotype TT (p = .047), with an odds ratio (OR) of 0.347(95%CI: 0.031, 3.881). And there was no significant difference in the risk of PE between patients with genotype CT, and those with genotype TT (p = .090) (OR = 2.344 95%CI: 0.187, 29.344).

CONCLUSION

There is an association between a SNP in locus 29799440 of the HLA-G gene and susceptibility of PE in Han Chinese pregnant women, and the risk of PE increases with genotype CT/TT in pregnant women.

Analysis of HLA-G long-read genomic sequences in mother-offspring pairs with preeclampsia

Preeclampsia is a pregnancy-induced disorder that is characterized by hypertension and is a leading cause of perinatal and maternal–fetal morbidity and mortality. HLA-G is thought to play important roles in maternal–fetal immune tolerance, and the associations between HLA-G gene polymorphisms and the onset of pregnancy-related diseases have been explored extensively. Because contiguous genomic sequencing is difficult, the association between the HLA-G genotype and preeclampsia onset is controversial. In this study, genomic sequences of the HLA-G region (5.2 kb) from 31 pairs of mother–offspring genomic DNA samples (18 pairs from normal pregnancies/births and 13 from preeclampsia births) were obtained by single-molecule real-time sequencing using the PacBio RS II platform. The HLA-G alleles identified in our cohort matched seven known HLA-G alleles, but we also identified two new HLA-G alleles at the fourth-field resolution and compared them with nucleotide sequences from a public database that consisted of coding sequences that cover the 3.1-kb HLA-G gene span. Intriguingly, a potential association between preeclampsia onset and the poly T stretch within the downstream region of the HLA-G*01:01:01:01 allele was found. Our study suggests that long-read sequencing of HLA-G will provide clues for characterizing HLA-G variants that are involved in the pathophysiology of preeclampsia.

HLA-G: Function, polymorphisms and pathology

HLA-G immune modulatory genes and molecules are presently being studied by a widespread number of research groups. In the present study, we do not aim to be exhaustive since the number of manuscripts published every year is overwhelming. Instead, our aim is pointing out facts about HLA-G function, polymorphism and pathology that have been confirmed by several different researchers, together with exposing aspects that may have been overlooked or not sufficiently remarked in this productive field of study. On the other hand, we question whether performing mainly studies on HLA-G and disease associations is going to give a clear answer in the future, since 40 years of study of classical HLA molecules association with disease has still given no definite answer on this issue.

HLA-G Polymorphisms Associated with HIV Infection and Preeclampsia in South Africans of African Ancestry

OBJECTIVES

HLA-G, part of the major histocompatibility complex (MHC), is associated with the risk of developing preeclampsia (PE). In this study, we determined the contribution of specific HLA-G polymorphisms on the risk of developing preeclampsia in HIV-infected and uninfected South Africans of African ancestry.

METHODS

One hundred and ninety-three women of African ancestry were enrolled (74 HIV-uninfected normotensive, 60 HIV-infected normotensive, 34 HIV-uninfected, and 25 HIV-infected preeclamptics). Sanger sequencing of the untranslated region was performed to genotype six SNPs, i.e., 14 bp Ins/Del of rs66554220, rs1710, rs1063320, rs1610696, rs9380142, and rs1707).

RESULTS

For rs66554220, we have the following results: (a) based on pregnancy type-the Ins/Ins and Del/Ins genotype frequency was higher in preeclampsia (PE) compared to normotensive pregnancies (Ins/Ins vs. Del/Ins, P = 0.02∗: OR (95%CI) = 13.44 (0.7222-249.9); Del/Del vs. Del/Ins, P = 0.03∗: OR (95%CI) = 2.95 (1.10-7.920)); (b) based on HIV status-the Ins/Ins showed both genotypic and allelic association with HIV infection. HIV-infected PE has higher Ins/Ins genotypic and allelic frequencies compared to HIV-uninfected PE (Ins/Ins vs. Del/Ins, P = 0.005∗∗: OR (95%CI) = 21.32 (1.71-4.17); Ins, P = 0.005∗∗; OR (95%IC) = 21.32 (1.71-4.17)). For rs1707, we have the following results: (a) based on pregnancy type-there were CT genotypic frequencies in PE, more especially LOPE compared to normotensive pregnancies (TT vs. CT, P = 0.0092∗∗: OR (95%CI) = 5.(1.39 - 25.64)), and no allelic association was noted; (b) based on HIV status-CT was higher in HIV-infected LOPE compared to uninfected LOPE (TT vs. TC, P = 0.0006∗∗∗: OR (95%CI) = 40.00 (2.89 - 555.1)). For rs1710 and rs1063320, no significant differences in the genotype and allele frequencies were noted based on pregnancy type and HIV status. For rs9380142, we have the following results: (a) based on pregnancy type-no significant differences were noted between normotensive compared to PE pregnancies; (b) based on HIV status-AA genotypes occurred more in the HIV-infected PE group (AA vs. GG, P = 0.02∗: OR (95%CI) = 13.97 (0.73 - 269.4)), while A allelic frequency occurred more in HIV-infected PE, especially LOPE compared to uninfected groups (A vs. G, P = 0.0003∗∗∗: OR (95%CI) = 10.72 (2.380 - 48.32); P = 0.02∗: OR (95%CI) = 9.00 (1.07 - 75.74)). For rs1610696, we have the following results: (a) based on pregnancy type-genotypic and allelic frequencies of CC were higher in PE compared to normotensive pregnancies (CC vs. GG, P = 0.0003∗∗∗: OR (95%CI) = 31.87 (1.861 - 545.9); C, P = 0.0001∗∗∗: OR (95%IC) = 21.91 (2.84 - 169.0)); (b) based on HIV status-GG frequencies were higher in the HIV-infected PE more especially LOPE groups (GG vs. GC, P = 0.02∗: OR (95%CI) = 16.87 (0.81 - 352.1); GG vs. CC, P = 0.0001∗∗∗: OR (95%CI) = 159.5 (13.10 - 1942)).

CONCLUSION

Selected HLA-G 14 bp polymorphisms (Ins/Ins) and genotypic and allelic differences in rs9380142, rs1610696, and rs1707 are associated with the pathogenesis of preeclampsia in HIV-infected South African women of African ancestry. More genetic studies evaluating the association between preeclampsia and HIV infection are needed to improve diagnosis and antenatal care.

Molecular Analysis of HLA-G in Women with High-Risk Pregnancy and Their Partners with Regard to Possible Complications

The understanding of the molecular and biochemical characteristics of the human leukocyte antigen-G (HLA-G) is important because of the diverse influence of this antigen’s polymorphisms on the course of a pregnancy. The aim of our study was to assess how the variation of the HLA-G allele and the HLA-G 14-bp ins/del polymorphism influence predisposition to a complicated pregnancy. The clinical material consisted of parental pairs with complicated pregnancies (210 women; 190 men). The control group included parental pairs without complications during pregnancy (89 women; 86 men). The study involved isolation of genome DNA from peripheral blood leukocytes, sequencing, and analysis of the 14-bp ins/del polymorphism in the 3′-untranslated region (3′-UTR) of the HLA-G gene based on polymerase chain reaction (PCR). The most common HLA-G allele in the group of women with complicated pregnancies was the HLA-G 10101 allele. There were no statistically significant differences in the frequencies of the 14-bp ins/del polymorphism in the 3′UTR of the HLA-G gene between the groups. Our results suggest that the risk of complications in pregnancy is influenced by the HLA-G 10101, HLA-G 10108, and HLA-G 10106 alleles and is not influenced by the 14-bp ins/del polymorphism in the 3′UTR of the HLA-G gene.

Genetic Variants in Preeclampsia: Lessons From Studies in Latin-American Populations

Placental vascularization is a tightly regulated physiological process in which the maternal immune system plays a fundamental role. Vascularization of the maternal-placental interface involves a wide range of mechanisms primarily orchestrated by the fetal extravillous trophoblast and maternal immune cells. In a healthy pregnancy, an immune cross-talk between the mother and fetal cells results in the secretion of immunomodulatory mediators, apoptosis of specific cells, cellular differentiation/proliferation, angiogenesis, and vasculogenesis, altogether favoring a suitable microenvironment for the developing embryo. In the context of vasculopathy underlying common pregnancy disorders, it is believed that inefficient invasion of extravillous trophoblast cells in the endometrium leads to a poor placental blood supply, which, in turn, leads to decreased secretion of angiogenic factors, hypoxia, and inflammation commonly associated with preterm delivery, intrauterine growth restriction, and preeclampsia. In this review, we will focus on studies published by Latin American research groups, providing an extensive review of the role of genetic variants from candidate genes involved in a broad spectrum of biological processes underlying the pathophysiology of preeclampsia. In addition, we will discuss how these studies contribute to fill gaps in the current understanding of preeclampsia. Finally, we discuss some trending topics from important fields associated with pregnancy vascular disorders (e.g., epigenetics, transplantation biology, and non-coding RNAs) and underscore their possible implications in the pathophysiology of preeclampsia. As a result, these efforts are expected to give an overview of the extent of scientific research produced in Latin America and encourage multicentric collaborations by highlighted regional research groups involved in preeclampsia investigation.