Analysis of the S810L Point Mutation of the Mineralocorticoid Receptor in Patients with Pregnancy‐Induced Hypertension

The role of the renin-angiotensin-aldosterone system in preeclampsia: genetic polymorphisms and microRNA

The compensatory alterations in the rennin-angiotensin-aldosterone system (RAAS) contribute to the salt-water balance and sufficient placental perfusion for the subsequent well-being of the mother and fetus during normal pregnancy and is characterized by an increase in almost all the components of RAAS. Preeclampsia, however, breaks homeostasis and leads to a disturbance of this delicate equilibrium in RAAS both for circulation and the uteroplacental unit. Despite being a major cause for maternal and neonatal morbidity and mortality, the pathogenesis of preeclampsia remains elusive, where RAAS has been long considered to be involved. Epidemiological studies have indicated that preeclampsia is a multifactorial disease with a strong familial predisposition regardless of variations in ethnic, socioeconomic, and geographic features. The heritable allelic variations, especially the genetic polymorphisms in RAAS, could be the foundation for the genetics of preeclampsia and hence are related to the development of preeclampsia. Furthermore, at a posttranscriptional level, miRNA can interact with the targeted site within the 3'-UTR of the RAAS gene and thereby might participate in the regulation of RAAS and the pathology of preeclampsia. In this review, we discuss the recent achievements of genetic polymorphisms, as well as the interactions between maternal and fetal genotypes, and miRNA posttranscriptional regulation associated with RAAS in preeclampsia. The results are controversial but utterly inspiring and attractive in terms of potential prognostic significance. Although many studies suggest positive associations with genetic mutations and increased risk for preeclampsia, more meticulously designed large-scale investigations are needed to avoid the interference from different variations.

Genetics talks to epigenetics? The interplay between sequence variants and chromatin structure

Transcription is regulated by two major mechanisms. On the one hand, changes in DNA sequence are responsible for genetic gene regulation. On the other hand, chromatin structure regulates gene activity at the epigenetic level. Given the fundamental participation of these mechanisms in transcriptional regulation of virtually any gene, they are likely to co-regulate a significant proportion of the genome. The simple concept behind this idea is that a mutation may have a significant impact on local chromatin structure by modifying DNA methylation patterns or histone type recruitment. Yet, the relevance of these interactions is poorly understood. Elucidating how genetic and epigenetic mechanisms co-participate in regulating transcription may assist in some of the unresolved cases of genetic variant-phenotype association. One example is loci that have biologically predictable functions but genotypes that fail to correlate with phenotype, particularly disease outcome. Conversely, a crosstalk between genetics and epigenetics may provide a mechanistic explanation for cases in which a convincing association between phenotype and a genetic variant has been established, but the latter does not lie in a promoter or protein coding sequence. Here, we review recently published data in the field and discuss their implications for genetic variant-phenotype association studies.

Relationship of aldosterone synthase gene (C-344T) and mineralocorticoid receptor (S810L) polymorphisms with gestational hypertension

The extent of genetic influence in the aetiology of gestational hypertension has not been completely determined. The aim of this study was to analyse the relationship between aldosterone levels and the -344T/C polymorphism of the aldosterone synthase gene (CYP11B2) and to investigate the frequency of the S810L mutation of mineralocorticoid receptor (MR) in gestational hypertension. One hundred women with pregnancy-induced hypertension and 100 with normal pregnancy were studied to measure serum aldosterone and progesterone levels and for the genotypification of the -344T/C polymorphism of CYP11B2 gene and the S810L mutation of MR by RFLP-PCR and SSP, respectively. Serum aldosterone levels were reduced (<0.000001) and serum progesterone levels increased (<0.000001) in gestational hypertensive women as compared with normal pregnant women. The -344T/C of CYP11B2 genotypic frequencies were similar in the hypertensive and normotensive pregnant women. The 810L-mutated allele of MR was found in 12% of the hypertensive and 9.4% of the normotensive pregnant women. In contrast to the observations made in preeclampsia, the genotype of -344T/C of CYP11B2 was neither related with gestational hypertension nor with aldosterone levels at delivery. The frequency of the S810L mutation was similar in the hypertensive and normotensive women but higher than observed in other reports.

High aldosterone-to-renin variants of CYP11B2 and pregnancy outcome

BACKGROUND

Increased aldosterone concentrations and volume expansion of normal pregnancies are hallmarks of normal pregnancies and blunted in pre-eclampsia. Accordingly, we hypothesized an active mineralocorticoid system to protect from pre-eclampsia.

METHODS

In pregnant women (normotensive n = 44; pre-eclamptic n = 48), blood pressure, urinary tetrahydro-aldosterone excretion and activating polymorphisms (SF-1 site and intron 2) of the aldosterone synthase gene (CYP11B2) were determined; 185 non-pregnant normotensive individuals served as control. Amino acid-changing polymorphisms of the DNA- and agonist-binding regions of the mineralocorticoid receptor were evaluated by RT-PCR, SSCP and sequencing.

RESULTS

Urinary tetrahydro-aldosterone excretion was reduced in pre-eclampsia as compared to normal pregnancy (P < 0.05). It inversely correlated with blood pressure (r = 0.99, P < 0.04). Homozygosity for activating CYP11B2 polymorphisms was preferably present in normotensive as compared to pre-eclamptic pregnancies, identified (intron 2, P = 0.005; SF-1 site, P = 0.016). Two mutant haplotypes decreased the risk of developing pre-eclampsia (RR 0.16; CI 0.05-0.54; P < 0.001). In contrast, intron 2 wild type predisposed to pre-eclampsia (P < 0.0015). No functional mineralocorticoid receptor mutant has been observed.

CONCLUSIONS

High aldosterone availability is associated with lower maternal blood pressure. In line with this observation, gain-of-function variants of the CYP11B2 reduce the risk of developing pre-eclampsia. Mutants of the mineralocorticoid receptor cannot explain the frequent syndrome of pre-eclampsia.

A Novel Missense Mutation, F826Y, in the Mineralocorticoid Receptor Gene in Japanese Hypertensives: Its Implications for Clinical Phenotypes

A gain-of-function mutation resulting in the S810L amino acid substitution in the hormone-binding domain of the mineralocorticoid receptor (MR, locus symbol NR3C2) is responsible for early-onset hypertension that is exacerbated in pregnancy. The objective of this study was to test whether other types of missense mutations in the hormone-binding domain could be implicated in hypertension in Japanese. Here, we screened 942 Japanese patients with hypertension for the S810L mutation in exon 6 in the MR. We did not identify the S810L mutation in our hypertensive population, indicating that S810L does not play a major role in the etiology of essential hypertension in Japanese. However, we identified a novel missense mutation, F826Y, in three patients in a heterozygous state, in addition to four single nucleotide polymorphisms, including one synonymous mutation (L809L). The F826Y mutation is present in the MR hormone-binding domain and might affect the ligand affinity. The F826Y mutation was also identified in 13 individuals (5 hypertensives and 8 normotensives) in a Japanese general population (n=3,655). The allele frequency was 0.00178. The frequencies of the F826Y mutation in the hypertensive population (3/942) and in the hypertensive group (5/ 1,480) and the normotensive group (8/2,175) in the general population were not significantly different, suggesting that this mutation does not greatly affect hypertension. Although it is unclear at present whether or not the F826Y mutation makes a substantial contribution to the mineralocorticoid receptor activity, this missense mutation may contribute, to some extent, to clinical phenotypes through its effects on MR.