NLRP genes and their role in preeclampsia and multi-locus imprinting disorders

Multi-locus imprinting disturbance (MLID): interim joint statement for clinical and molecular diagnosis

BACKGROUND

Imprinting disorders are rare diseases resulting from altered expression of imprinted genes, which exhibit parent-of-origin-specific expression patterns regulated through differential DNA methylation. A subgroup of patients with imprinting disorders have DNA methylation changes at multiple imprinted loci, a condition referred to as multi-locus imprinting disturbance (MLID). MLID is recognised in most but not all imprinting disorders and is also found in individuals with atypical clinical features; the presence of MLID often alters the management or prognosis of the affected person. Some cases of MLID are caused by trans-acting genetic variants, frequently not in the patients but their mothers, which have counselling implications. There is currently no consensus on the definition of MLID, clinical indications prompting testing, molecular procedures and methods for epigenetic and genetic diagnosis, recommendations for laboratory reporting, considerations for counselling, and implications for prognosis and management. The purpose of this study is thus to cover this unmet need.

METHODS

A comprehensive literature search was conducted resulting in identification of more than 100 articles which formed the basis of discussions by two working groups focusing on clinical diagnosis (n = 12 members) and molecular testing (n = 19 members). Following eight months of preparations and regular online discussions, the experts from 11 countries compiled the preliminary documentation and determined the questions to be addressed during a face-to-face meeting which was held with the attendance of the experts together with four representatives of patient advocacy organisations.

RESULTS

In light of available evidence and expert consensus, we formulated 16 propositions and 8 recommendations as interim guidance for the clinical and molecular diagnosis of MLID.

CONCLUSIONS

MLID is a molecular designation, and for patients with MLID and atypical phenotypes, we propose the alternative term multi-locus imprinting syndrome. Due to the intrinsic variability of MLID, the guidelines underscore the importance of involving experts from various fields to ensure a confident approach to diagnosis, counselling, and care. The authors advocate for global, collaborative efforts in both basic and translational research to tackle numerous crucial questions that currently lack answers, and suggest reconvening within the next 3-5 years to evaluate the research advancements and update this guidance as needed.

The Placental Function Beyond Pregnancy: Insights from Latin America

Currently, more than 100,000 papers had been published studying the placenta in both physiological and pathological contexts. However, relevant health conditions affecting placental function, mostly found in low-income countries, should be evaluated deeper. This review will raise some - of what we think necessary - points of discussion regarding challenging topics not fully understood, including the paternal versus maternal contribution on placental genes imprinting, placenta-brain communication, and some environmental conditions affecting the placenta. The discussions are parts of an international effort to fulfil some gaps observed in this area, and Latin-American research groups currently evaluate that.

Inflammasome activation in preeclampsia and intrauterine growth restriction

PROBLEM

Preeclampsia (PE) and intrauterine growth restriction (IUGR) are leading causes of perinatal complications, affecting 8%-10% of all pregnancies. Inflammasomes are suspected to be one of the mechanisms that lead to the process of term and preterm labors. This study evaluated the inflammasome-dependent inflammation processes in placental tissue of women with PE and IUGR.

METHODS OF STUDY

In this prospective cohort study, 14 women with PE, 15 with placental-related IUGR and 19 with normal pregnancy (NP) were recruited during admission for delivery. Maternal blood was obtained prior to delivery and neonatal cord blood and placental tissue were obtained after delivery.

RESULTS

NLRP7 and PYCARD protein expression were higher in placental PE and IUGR samples versus NP samples. Immunostaining revealed that NLRP7 and PYCARD were upregulated in PE and IUGR placental syncytiotrophoblast, stroma and endothelial cells. PYCARD serum levels were significantly higher in women with PE and IUGR. No significant changes were observed in neonatal cord blood.

CONCLUSIONS

NLRP7 and PYCARD are key inflammatory proteins that are significantly elevated in PE and IUGR. Better understanding their significance may enable them to become markers of prediction or progression of PE and IUGR.

Protein Network Analysis of Whole Exome Sequencing of Severe Preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy, which complicates up to 15% of US deliveries. It is an idiopathic disorder associated with several different phenotypes. We sought to determine if the genetic architecture of preeclampsia can be described by clusters of patients with variants in genes in shared protein interaction networks. We performed a case-control study using whole exome sequencing on early onset preeclamptic mothers with severe clinical features and control mothers with uncomplicated pregnancies between 2016 and 2020. A total of 143 patients were enrolled, 61 women with early onset preeclampsia with severe features based on ACOG criteria, and 82 control women at term, matched for race and ethnicity. A network analysis and visualization tool, Proteinarium, was used to confirm there are clusters of patients with shared gene networks associated with severe preeclampsia. The majority of the sequenced patients appear in two significant clusters. We identified one case dominant and one control dominant cluster. Thirteen genes were unique to the case dominated cluster. Among these genes, LAMB2, PTK2, RAC1, QSOX1, FN1, and VCAM1 have known associations with the pathogenic mechanisms of preeclampsia. Using bioinformatic analysis, we were able to identify subsets of patients with shared protein interaction networks, thus confirming our hypothesis about the genetic architecture of preeclampsia.

Pathophysiological Implication of Pattern Recognition Receptors in Fetal Membranes Rupture: RAGE and NLRP Inflammasome

Preterm prelabor ruptures of fetal membranes (pPROM) are a pregnancy complication responsible for 30% of all preterm births. This pathology currently appears more as a consequence of early and uncontrolled process runaway activation, which is usually implicated in the physiologic rupture at term: inflammation. This phenomenon can be septic but also sterile. In this latter case, the inflammation depends on some specific molecules called “alarmins” or “damage-associated molecular patterns” (DAMPs) that are recognized by pattern recognition receptors (PRRs), leading to a microbial-free inflammatory response. Recent data clarify how this activation works and which receptor translates this inflammatory signaling into fetal membranes (FM) to manage a successful rupture after 37 weeks of gestation. In this context, this review focused on two PRRs: the receptor for advanced glycation end-products (RAGE) and the NLRP7 inflammasome.

Comprehensive analysis of gene expression and DNA methylation for preeclampsia progression

BACKGROUND

The purpose of our study is to identify novel preeclampsia (PE)-related methylation genes and uncover the molecular mechanism of PE.

METHODS

All the datasets of gene expression and DNA methylation datasets for PE and normal samples were obtained from the Gene Expression Omnibus database. We first identified the differentially expressed genes (DEGs) and differential methylation genes (DMGs) between PE and normal samples followed by the functional enrichment analysis. Comprehensive analysis of DEGs and DMGs was also conducted for the identification of valuable PE-related biomarkers. The methylation validation was also performed with MassARRAY.

RESULTS

Three DNA methylation and three gene expression datasets were incorporated. We obtained 1754 DEGs and 99 DMGs in PE samples with the thresholds of p value <0.05, |Δbeta| > 0.1, and p value <0.05, respectively. Functional analysis of DEGs obtained cell adhesion molecules and leukocyte transendothelial migration. Besides, several valuable biomarkers of PE, including OCA2, CDK2AP1, and ADAM12, were identified through the integrated analysis of gene expression and DNA methylation datasets. Four methylation sites (cg03449867, cg09084244, cg09247979, and cg24194674) were validated, among which cg03449867 and cg09084244 were found to be hypermethylated and the related genes of OCA2 and CDK2AP1 were downregulated in PE compared with normal samples simultaneously. cg24194674 was hypomethylated and its correlated gene ADAM12 was upregulated in PE compared with normal samples simultaneously.

CONCLUSION

Our study should be helpful for the development of potential biomarkers and therapeutic targets for PE.

Gene-based analyses of the maternal genome implicate maternal effect genes as risk factors for conotruncal heart defects

Congenital heart defects (CHDs) affect approximately 1% of newborns. Epidemiological studies have identified several genetically-mediated maternal phenotypes (e.g., pregestational diabetes, chronic hypertension) that are associated with the risk of CHDs in offspring. However, the role of the maternal genome in determining CHD risk has not been defined. We present findings from gene-level, genome-wide studies that link CHDs to maternal effect genes as well as to maternal genes related to hypertension and proteostasis. Maternal effect genes, which provide the mRNAs and proteins in the oocyte that guide early embryonic development before zygotic gene activation, have not previously been implicated in CHD risk. Our findings support a role for and suggest new pathways by which the maternal genome may contribute to the development of CHDs in offspring.

Exploring the Molecular Aetiology of Preeclampsia by Massive Parallel Sequencing of DNA

PURPOSE OF REVIEW

This manuscript aims to review (for the first time) studies describing NGS sequencing of preeclampsia (PE) women's DNA.

RECENT FINDINGS

Describing markers for the early detection of PE is an essential task because, although associated molecular dysfunction begins early on during pregnancy, the disease's clinical signs usually appear late in pregnancy. Although several biochemical biomarkers have been proposed, their use in clinical environments is still limited, thereby encouraging research into PE's genetic origin. Hundreds of genes involved in numerous implantation- and placentation-related biological processes may be coherent candidates for PE aetiology. Next-generation sequencing (NGS) offers new technical possibilities for PE studying, as it enables large genomic regions to be analysed at affordable cost. This technique has facilitated the description of genes contributing to the molecular origin of a significant amount of monogenic and complex diseases. Regarding PE, NGS of DNA has been used in familial and isolated cases, thereby enabling new genes potentially related to the phenotype to be proposed. For a better understanding of NGS, technical aspects, applications and limitations are presented initially. Thereafter, NGS studies of DNA in familial and non-familial cases are described, including pitfalls and positive findings. The information given here should enable scientists and clinicians to analyse and design new studies permitting the identification of novel clinically useful molecular PE markers.

NLRP7 Is Involved in the Differentiation of the Decidual Macrophages

Macrophage polarization, regulated appropriately, may play important roles in successful pregnancy. In the face of the vital roles of decidua macrophages in pregnancy, it is insufficient to recognize the trigger of macrophage differentiation and polarization. We aimed to explore the link between the NLRP7 gene and macrophage polarization in human deciduas. Here, we enrolled the endometrial tissues from eight pregnant women in the first trimester. We found that NLRP7 was abundant in endometrial tissues and that NLRP7 was expressed in decidual macrophages of the first-trimester pregnancy. NLRP7 was predominately expressed in the decidual M2 macrophages, as compared with the M1 macrophages. Furthermore, our results suggest that NLRP7 is associated with decidual macrophage differentiation. NLRP7 over-expression suppresses the expression of M1 markers and enhances the expression of the M2 markers. Considering that NLRP7 relates to decidualization and macrophage differentiation, we propose that NLRP7 is a primate-specific multitasking gene to maintain endometrial hemostasis and reproductive success. This finding may pave the way for therapies of pathological pregnancies.

Interleukin-23 receptor (IL-23R) gene polymorphisms and haplotypes associated with the risk of preeclampsia: evidence from cross-sectional and in silico studies

PURPOSE

Pre-eclampsia is a relatively common pregnancy disorder. Serum concentrations of certain pro-inflammatory molecules and cytokines like interleukin-23 may affect the pathogenesis of pre-eclampsia. The interleukin-23 receptor (IL-23R) gene plays an important role in the progression of inflammatory and autoimmune diseases and IL-23 polymorphisms might influence the susceptibility of pre-eclampsia. The aim of the recent study was to establish the association between IL-23R gene polymorphisms and the susceptibility for developing of pre-eclampsia.

METHODS

One hundred and fifty-eight pregnant patients with pre-eclampsia and 153 controls were genotyped using RFLP-PCR and AS-PCR. Also, an in silico analysis was performed to predict possible effects of these variations on IL-23R mRNA and protein structures.

RESULTS

The frequency of the AG genotype of rs11209026 is related to a higher risk of pre-eclampsia. The mutant C and A allele in rs10889677 and rs11209026 SNPs, respectively, are correlated with the risk of pre-eclampsia and they are more frequent in severe late onset PE. We found higher frequency of the haplotype CG in patients with pre-eclampsia in comparison to healthy controls, as well as, the CG haplotype frequency significantly increased the risk of PE in severe, early onset, and late onset sub-groups. The results of computational analysis predicted rs11209026 and rs10889677 SNPs as functional variations, which can influence IL-23R mRNA and protein.

CONCLUSIONS

The results of present study show positive association between polymorphisms in the IL-23R gene and pre-eclampsia. Therefore, the presence of IL-23R rs11209026, rs10889677 polymorphism might be markers for the genetic susceptibility to pre-eclampsia.

Search for cis-acting factors and maternal effect variants in Silver-Russell patients with ICR1 hypomethylation and their mothers

Silver-Russell syndrome is an imprinting disorder characterized by severe intrauterine and postnatal growth retardation. The majority of patients show loss of methylation (LOM) of the H19/IGF2 IG-DMR (ICR1) in 11p15.5. In ~10% of these patients aberrant methylation of additional imprinted loci on other chromosomes than 11 can be observed (multilocus imprinting defect - MLID). Recently, genomic variations in the ICR1 have been associated with disturbed methylation of the ICR1. In addition, variants in factors contributing to the life cycle of imprinting are discussed to cause aberrant imprinting, including MLID. These variants can either be identified in the patients with imprinting disorders themselves or in their mothers. We performed comprehensive studies to elucidate the role of both cis-acting variants in 11p15.5 as well as of maternal effect variants in the etiology of ICR1 LOM. Whereas copy number analysis and next generation sequencing in the ICR1 did not provide any evidence for a variant, search for maternal effect variants in 21 mothers of patients with ICR1 LOM identified two carriers of NLRP5 variants. By considering our results as well as those from the literature, we conclude that the causes for epimutations are heterogeneous. MLID might be regarded as an own etiological subgroup, associated with maternal effect variants in NLRP and functionally related genes. In addition, these variants might also contribute to LOM of single imprinted loci. Furthermore, genomic variants in the patients themselves might result in aberrant methylation patterns and need further investigation.