Estrogen-related receptor γ (ERRγ) regulates oxygen-dependent expression of voltage-gated potassium (K+) channels and tissue kallikrein during human trophoblast differentiation

Preeclampsia and transport of ions and small molecules: A literature review

Preeclampsia (PE) is a prevalent obstetric complication affecting approximately 3-5% of pregnancies worldwide and is a major cause of maternal and perinatal morbidity and mortality. Preeclampsia is considered a disease of the endothelial system that can progress to eclampsia, characterized by seizures. Early diagnosis and appropriate management are crucial to improving maternal and fetal outcomes, as preeclampsia can lead to severe complications such as placental abruption, fetal growth restriction, and stroke. The pathophysiology of PE is complex, involving a combination of genetic, acquired, and immunological factors. A central feature of the condition is inadequate placentation and impaired uteroplacental perfusion, leading to local hypoxia, endothelial dysfunction, vasoconstriction, and immunological dysregulation. Recent evidence suggests that dysregulation of ion transporters may play a significant role in the adaptation of uterine circulation during placentation. These transporters are essential for maintaining maternal-fetal homeostasis, influencing processes such as nutrient exchange, hormone synthesis, trophoblast cell migration, and the function of smooth muscle cells in blood vessels. In preeclampsia, adverse conditions like hypoxia and oxidative stress result in the downregulation of ion, solute, and water transporters, impairing their function. This review focuses on membrane transporters involved in PE, discussing functional alterations and their physiological implications. The goal of this investigation is to enhance understanding of how dysregulation of ion and small molecule transporters contributes to the development and progression of preeclampsia, underscoring the importance of exploring these signaling pathways for potential therapeutic interventions.

Sex-biased regulatory changes in the placenta of native highlanders contribute to adaptive fetal development

Compared with lowlander migrants, native Tibetans have a higher reproductive success at high altitude though the underlying mechanism remains unclear. Here, we compared the transcriptome and histology of full-term placentas between native Tibetans and Han migrants. We found that the placental trophoblast shows the largest expression divergence between Tibetans and Han, and Tibetans show decreased immune response and endoplasmic reticulum stress. Remarkably, we detected a sex-biased expression divergence, where the male-infant placentas show a greater between-population difference than the female-infant placentas. The umbilical cord plays a key role in the sex-biased expression divergence, which is associated with the higher birth weight of the male newborns of Tibetans. We also identified adaptive histological changes in the male-infant placentas of Tibetans, including larger umbilical artery wall and umbilical artery intima and media, and fewer syncytial knots. These findings provide valuable insights into the sex-biased adaptation of human populations, with significant implications for medical and genetic studies of human reproduction.

Altered placental ion channel gene expression in preeclamptic high-altitude pregnancies

High-altitude (>2,500 m) residence increases the risk of pregnancy vascular disorders such as fetal growth restriction and preeclampsia, each characterized by impaired placental function. Genetic attributes of highland ancestry confer relative protection against vascular disorders of pregnancy at high altitudes. Although ion channels have been implicated in placental function regulation, neither their expression in high-altitude placentas nor their relationship to high-altitude preeclampsia has been determined. Here, we measured the expression of 26 ion-channel genes in placentas from preeclampsia cases and normotensive controls in La Paz, Bolivia (3,850 m). In addition, we correlated gene transcription to maternal and infant ancestry proportions. Gene expression was assessed by PCR, genetic ancestry evaluated by ADMIXTURE, and ion channel proteins localized by immunofluorescence. In preeclamptic placentas, 11 genes were downregulated (ABCC9, ATP2A2, CACNA1C, KCNE1, KCNJ8, KCNK3, KCNMA1, KCNQ1, KCNQ4, PKD2, and TRPV6) and two were upregulated (KCNQ3 and SCNN1G). KCNE1 expression was positively correlated with high-altitude Amerindian ancestry and negatively correlated with non-high altitude. SCNN1G was negatively correlated with African ancestry, despite minimal African admixture. Most ion channels were localized in syncytiotrophoblasts (Cav1.2, TRPP2, TRPV6, and Kv7.1), whereas expression of Kv7.4 was primarily in microvillous membranes, Kir6.1 in chorionic plate and fetal vessels, and MinK in stromal cells. Our findings suggest a role for differential placental ion channel expression in the development of preeclampsia. Functional studies are needed to determine processes affected by these ion channels in the placenta and whether therapies directed at modulating their activity could influence the onset or severity of preeclampsia.

Regulation of human trophoblast gene expression by endogenous retroviruses

The placenta is a fast-evolving organ with large morphological and histological differences across eutherians, but the genetic changes driving placental evolution have not been fully elucidated. Transposable elements, through their capacity to quickly generate genetic variation and affect host gene regulation, may have helped to define species-specific trophoblast gene expression programs. Here we assess the contribution of transposable elements to human trophoblast gene expression as enhancers or promoters. Using epigenomic data from primary human trophoblast and trophoblast stem-cell lines, we identified multiple endogenous retrovirus families with regulatory potential that lie close to genes with preferential expression in trophoblast. These largely primate-specific elements are associated with inter-species gene expression differences and are bound by transcription factors with key roles in placental development. Using genetic editing, we demonstrate that several elements act as transcriptional enhancers of important placental genes, such as CSF1R and PSG5. We also identify an LTR10A element that regulates ENG expression, affecting secretion of soluble endoglin, with potential implications for preeclampsia. Our data show that transposons have made important contributions to human trophoblast gene regulation, and suggest that their activity may affect pregnancy outcomes.

Beckwith-Wiedemann syndrome with long QT caused by a deletion involving KCNQ1 but not KCNQ1OT1:TSS-DMR

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with characteristic features, such as overgrowth, macroglossia, and exomphalos. Hypomethylation of the KCNQ1OT1:TSS-differentially methylated region (DMR) on the 11p15.5 imprinted region is the most common etiology of BWS. KCNQ1 on 11p15.5 is expressed from the maternally inherited allele in most tissues, but is biparentally expressed in the heart, and maternal KCNQ1 transcription is required to establish the maternal DNA imprint in the KCNQ1OT1:TSS-DMR. Loss of function variants in KCNQ1 result in long QT syndrome type 1 (LQT1). To date, eight patients with BWS due to KCNQ1 splice variants or structural abnormalities involving KCNQ1 but not the KCNQ1OT1:TSS-DMR have been reported (KCNQ1-BWS), and four of them had LQT1. We report a Japanese boy with BWS and LQT1 presenting with extreme hypomethylation of the KCNQ1OT1:TSS-DMR caused by a de novo 215-kb deletion including KCNQ1 but not the KCNQ1OT1:TSS-DMR on the maternal allele. He was born by emergency cesarean section due to suspicion of placental abruption at 30 weeks of gestation. His birth weight and length were +1.6 SD and +1.0 SD, respectively. His placental weight was +3.9 SD, and histological examination of his placenta was consistent with mesenchymal dysplasia. He had BWS clinical features, including macroglossia, ear creases and pits, body asymmetry, and rectus abdominis muscle dehiscence, and BWS was therefore diagnosed. LQT1 was first noticed at three months in a preoperative examination for lingual frenectomy. The summarized data of our patient and the previously reported eight patients in KCNQ1-BWS showed more frequent and earlier preterm births and smaller sized birth weight in KCNQ1-BWS cases than those with BWS caused by epimutation of the KCNQ1OT1:TSS-DMR. In addition, in five of nine patients with KCNQ1-BWS, LQT1 was detected, and two of them were identified at school age. In our patient and in another single case with LQT1, the LQT1 was not detected early despite neonatal ECG monitoring. For BWS patients with extreme hypomethylation of the KCNQ1OT1:TSS-DMR, searching for CNVs involving KCNQ1 and mutation screening for KCNQ1 should be considered together with periodic ECG monitoring. (338/500 words).

Placental ion channels: potential target of chemical exposure

The placenta is an important organ for the exchange of substances between the fetus and the mother, hormone secretion, and fetoplacental immunological defense. Placenta has an organ-specific distribution of ion channels and trophoblasts, and placental vessels express a large number of ion channels. Several placental housekeeping activities and pregnancy complications are at least partly controlled by ion channels, which are playing an important role in regulating hormone secretion, trophoblastic homeostasis, ion transport, and vasomotor activity. The function of several placental ion channels (Na, Ca, and Cl ion channels, cation channel, nicotinic acetylcholine receptors, and aquaporin-1) is known to be influenced by chemical exposure, i.e., their responses to different chemicals have been tested and confirmed in experimental models. Here, we review the possibility that placental ion channels are targets of toxicological concern in terms of placental function, fetal growth, and development.

Placental expression of Estrogen related receptor gamma (ESRRG) is reduced in FGR pregnancies and is mediated by hypoxia

Fetal growth restriction (FGR) describes a fetus which has not achieved its genetic growth potential; it is closely linked to placental dysfunction and uteroplacental hypoxia. Estrogen-related receptor gamma (ESRRG) is regulated by hypoxia and is highly expressed in the placenta. We hypothesized ESRRG is a regulator of hypoxia-mediated placental dysfunction in FGR pregnancies. Placentas were collected from women delivering appropriate for gestational age (AGA; n = 14) or FGR (n = 14) infants. Placental explants (n = 15) from uncomplicated pregnancies were cultured for up to 4 days in 21% or 1% O₂, or with 200 μM cobalt chloride (CoCl₂), or treated with the ESRRG agonists DY131 under different oxygen concentrations. RT-PCR, Western blotting, and immunochemistry were used to assess mRNA and protein levels of ESRRG and its localization in placental tissue from FGR or AGA pregnancies, and in cultured placental explants. ESRRG mRNA and protein expression were significantly reduced in FGR placentas, as was mRNA expression of the downstream targets of ESRRG, hydroxysteroid 11-beta dehydrogenase 2 (HSD11B2), and cytochrome P-450 (CYP19A1.1). Hypoxia-inducible factor 1-alpha protein localized to the nuclei of the cytotrophoblasts and stromal cells in the explants exposed to CoCl₂ or 1% O₂. Both hypoxia and CoCl₂ treatment decreased ESRRG and its downstream genes’ mRNA expression, but not ESRRG protein expression. DY131 increased the expression of ESRRG signaling pathways and prevented abnormal cell turnover induced by hypoxia. These data show that placental ESRRG is hypoxia-sensitive and altered ESRRG-mediated signaling may contribute to hypoxia-induced placental dysfunction in FGR. Furthermore, DY131 could be used as a novel therapeutic approach for the treatment of placental dysfunction.

Sex-specific effects of Bisphenol a on the signalling pathway of ESRRG in the human placenta

Bisphenol A (BPA) exposure during pregnancy is associated with low fetal weight, particularly in male fetuses. The expression of estrogen-related receptor gamma (ESRRG), a receptor for BPA in the human placenta, is reduced in fetal growth restriction. This study sought to explore whether ESRRG signaling mediates BPA-induced placental dysfunction and determine whether changes in the ESRRG signaling pathway are sex-specific. Placental villous explants from 18 normal term pregnancies were cultured with a range of BPA concentrations (1 nM–1 μM). Baseline BPA concentrations in the placental tissue used for explant culture ranged from 0.04 to 5.1 nM (average 2.3 ±1.9 nM; n = 6). Expression of ESRRG signaling pathway constituents and cell turnover were quantified. BPA (1 μM) increased ESRRG mRNA expression after 24 h in both sexes. ESRRG mRNA and protein expression was increased in female placentas treated with 1 μM BPA for 24 h but was decreased in male placentas treated with 1 nM or 1 μM for 48 h. Levels of 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) and placenta specific-1 (PLAC1), genes downstream of ESRRG, were also affected. HSD17B1 mRNA expression was increased in female placentas by 1 μM BPA; however, 1 nM BPA reduced HSD17B1 and PLAC1 expression in male placentas at 48 h. BPA treatment did not affect rates of proliferation, apoptosis, or syncytiotrophoblast differentiation in cultured villous explants. This study has demonstrated that BPA affects the ESRRG signaling pathway in a sex-specific manner in human placentas and a possible biological mechanism to explain the differential effects of BPA exposure on male and female fetuses observed in epidemiological studies.

Recurrent Pregnancy Loss and Concealed Long-QT Syndrome

Background

Recurrent pregnancy loss affects 1% to 2% of couples attempting childbirth. A large fraction of all cases remains idiopathic, which warrants research into monogenic causes of this distressing disorder.

Methods and Results

We investigated a nonconsanguineous Estonian family who had experienced 5 live births, intersected by 3 early pregnancy losses, and 6 fetal deaths, 3 of which occurred during the second trimester. No fetal malformations were described at the autopsies performed in 3 of 6 cases of fetal death. Parental and fetal chromosomal abnormalities (including submicroscopic) and maternal risk factors were excluded. Material for genetic testing was available from 4 miscarried cases (gestational weeks 11, 14, 17, and 18). Exome sequencing in 3 pregnancy losses and the mother identified no rare variants explicitly shared by the miscarried conceptuses. However, the mother and 2 pregnancy losses carried a heterozygous nonsynonymous variant, resulting in p.Val173Asp (rs199472695) in the ion channel gene KCNQ1. It is expressed not only in heart, where mutations cause type 1 long‐QT syndrome, but also in other tissues, including uterus. The p.Val173Asp variant has been previously identified in a patient with type 1 long‐QT syndrome, but not reported in the Genome Aggregation Database. With heterologous expression in CHO cells, our in vitro electrophysiologic studies indicated that the mutant slowly activating voltage‐gated K+ channel (I_Ks) is dysfunctional. It showed reduced total activating and deactivating currents (P<0.01), with dramatically positive shift of voltage dependence of activation by ≈10 mV (P<0.05).

Conclusions

The current study uncovered concealed maternal type 1 long‐QT syndrome as a potential novel cause behind recurrent fetal loss.

Clinical Implications and Gender Differences of KCNQ1 p.Gly168Arg Pathogenic Variant in Long QT Syndrome

BACKGROUND

Long QT syndrome (LQTS) is an inheritable arrhythmogenic disorder associated with life-threatening arrhythmic events (LAEs). In general, patients with LQTS2 (KCNH2) and LQTS3 (SCN5A) are considered to be a greater risk of LAEs than LQTS1 (KCNQ1) patients. Gender differences are also important. Series analyzing families with the same pathogenic variants may help in the progress of elaborating strong specific genotype-phenotype management strategies. In this manuscript, we describe the phenotype of seven unrelated families, carriers of the KCNQ1 G168R pathogenic variant.

METHODS

we identified all consecutive index cases referred for genetic testing with LQTS diagnosis carriers of KCNQ1 G168R variant. Genetic and clinical screening for all available relatives was performed.

RESULTS

we evaluated seven unrelated families, with a total 34 KCNQ1 G168R carriers (two obligated carriers died without available EKGs to evaluate the phenotype). All index cases but one were women and three of them presented with aborted sudden cardiac death (SCD) or syncope. The presence of sudden death in these families is notable, with a total of nine unexplained sudden deaths and four aborted SCD. Phenotype penetrance was 100% in women and 37.5% in men.

CONCLUSIONS

KCNQ1 G168R is a pathogenic variant, with a high penetrance among women and mild penetrance among men. Risk for LAEs in this variant seems not negligible, especially among woman, and risk stratification should always be carefully evaluated.

An orally available inverse agonist of estrogen-related receptor gamma showed expanded efficacy for the radioiodine therapy of poorly differentiated thyroid cancer

Estrogen-related receptor gamma (ERRγ) is the NR3B subgroup of associated transcription factors. In this report, a new generation of a potent and selective ERRγ inverse agonist (25) with good biocompatibility was proposed. We also explored the potential of the newly developed compound 25 in the PDTC model to expand the original indications from ATC. In addition, an X-ray crystallographic study of the ligand and ERRγ co-complex showed that 25 completely binds to the target protein (PDB 6KNR). Its medicinal chemistry, including a distinctive structural study to in vivo results, denotes that 25 may be directed towards the development of a pivotal treatment for ERRγ-related cancers.

Placenta-Specific Genes, Their Regulation During Villous Trophoblast Differentiation and Dysregulation in Preterm Preeclampsia

The human placenta maintains pregnancy and supports the developing fetus by providing nutrition, gas-waste exchange, hormonal regulation, and an immunological barrier from the maternal immune system. The villous syncytiotrophoblast carries most of these functions and provides the interface between the maternal and fetal circulatory systems. The syncytiotrophoblast is generated by the biochemical and morphological differentiation of underlying cytotrophoblast progenitor cells. The dysfunction of the villous trophoblast development is implicated in placenta-mediated pregnancy complications. Herein, we describe gene modules and clusters involved in the dynamic differentiation of villous cytotrophoblasts into the syncytiotrophoblast. During this process, the immune defense functions are first established, followed by structural and metabolic changes, and then by peptide hormone synthesis. We describe key transcription regulatory molecules that regulate gene modules involved in placental functions. Based on transcriptomic evidence, we infer how villous trophoblast differentiation and functions are dysregulated in preterm preeclampsia, a life-threatening placenta-mediated obstetrical syndrome for the mother and fetus. In the conclusion, we uncover the blueprint for villous trophoblast development and its impairment in preterm preeclampsia, which may aid in the future development of non-invasive biomarkers for placental functions and early identification of women at risk for preterm preeclampsia as well as other placenta-mediated pregnancy complications.

Insights into the activation mechanism of human estrogen-related receptor γ by environmental endocrine disruptors

The estrogen-related receptor γ (ERRγ, NR3B3) is a constitutively active nuclear receptor which has been proposed to act as a mediator of the low-dose effects of a number of environmental endocrine-disrupting chemicals (EDCs) such as the xenoestrogen bisphenol-A (BPA). To better characterize the ability of exogenous compounds to bind and activate ERRγ, we used a combination of cell-based, biochemical, structural and computational approaches. A purposely created stable cell line allowed for the determination of the EC50s for over 30 environmental ERRγ ligands, including previously unknown ones. Interestingly, affinity constants (Kds) of the most potent compounds measured by isothermal titration calorimetry were in the 50-500 nM range, in agreement with their receptor activation potencies. Crystallographic analysis of the interaction between the ERRγ ligand-binding domain (LBD) and compounds of the bisphenol, alkylphenol and naphthol families revealed a partially shared binding mode and minimal alterations of the receptor conformation upon ligand binding. Further biophysical characterizations coupled to molecular dynamics simulations suggested a mechanism through which ERRγ ligands would exhibit their agonistic properties by preserving the transcriptionally active form of the receptor while rigidifying some loop regions with associated functions. This unique mechanism contrasts with the classical one involving a ligand-induced repositioning and stabilization of the C-terminal activation helix H12.

Expression of endogenous phospholipase D1, localized in mouse submandibular gland, is greater in females and is suppressed by testosterone

To clarify the signal transduction mechanism in the differentiation and secretion of salivary glandular cells, the present study was attempted to examine in the submandibular gland (SMG) of mice, the expression and localization of phospholipase D1 (PLD1), one of the important effector molecules working in response to the activation of intramembranous receptors by first messengers. In immunoblotting analysis, the expression of PLD1 was high at postnatal 4 weeks (P4W) and decreased at P8W, and it was at negligible levels at newborn stage (P0W) and postnatal 2 weeks (P2W). The expression of PLD1 was greater in females, and it was suppressed by administration of testosterone to female mice. In immuno-light microscopy, immunoreactivity for PLD1 at P4W was moderate to intense, in the forms of dots and globules mainly in the apical domains of immature granular convoluted tubule (GCT)-cells localized largely in the proximal portion of the female GCT. By P8W, it decreased in intensity and remained weak to moderate along the apical plasmalemma of cells throughout the course of the female GCT, whereas it was faint throughout the GCT of the male SMG at P4W and negligible at P8W. In immuno-electron microscopy, immature GCT-cells characterized by electron-lucent granules were immunoreactive and the immunoreactive materials were deposited close to, but not within, those granules. Typical GCT cells, characterized by electron-dense granules, were immunonegative. No significant immunoreaction for PLD1 was seen in acini of SMGs of either sex at any time point examined. It is suggested that PLD1 is involved in the signaling for secretion of immature GCT cells and influences differentiation of these cells, probably through their own secretory substances.

Estrogen-related receptor γ regulates expression of 17β-hydroxysteroid dehydrogenase type 1 in fetal growth restriction

INTRODUCTION

Estrogen-related receptor γ (ERRγ) and 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) have important roles in cell invasion and in the proliferation of many types of cancer cells. However, it remains unknown whether ERRγ and HSD17B1 contribute to abnormal placental structure and dysfunction which characterize fetal growth restriction (FGR). Therefore, the aim of this study was to investigate the expression profiles of ERRγ and HSD17B1 in placenta tissues affected by FGR and to examine a possible molecular mechanism by which ERRγ is able to regulate HSD17B1 during development of FGR.

METHODS

Placenta tissues were collected from women affected by FGR (n = 28) and from women with appropriately gestational age (AGA) (n = 30). Relative mRNA and protein levels of ERRγ and HSD17B1 in both groups were assessed by quantitative real-time PCR, immunohistochemistry, and Western blot analyses. The effect of ERRγ on trophoblast function and its associated mechanistic details were studied in the trophoblast cell line, HTR-8/SVneo, which was transfected with small interfering RNA (siRNA) targeting ERRγ.

RESULTS

Both mRNA and protein levels of ERRγ and HSD17B1 were significantly lower in FGR placentae (P < 0.05). When ERRγ expression was knocked down in HTR-8/SVneo cells with siRNA, invasion and proliferation were inhibited. In addition, HSD17B1 expression was significantly decreased. In dual luciferase reporter assays, ERRγ stimulated transcription of HSD17B1 by targeting the ERRγ response element within its 5'-flanking promoter region.

DISCUSSION

Aberrant ERRγ expression may contribute to the pathogenesis of FGR by regulating the transcriptional activity of HSD17B1.

The Role of KCNQ1 Mutations and Maternal Beta Blocker Use During Pregnancy in the Growth of Children With Long QT Syndrome

OBJECTIVE

Two missense mutations in KCNQ1, an imprinted gene that encodes the alpha subunit of the voltage-gated potassium channel Kv7.1, cause autosomal dominant growth hormone deficiency and maternally inherited gingival fibromatosis. We evaluated endocrine features, birth size, and subsequent somatic growth of patients with long QT syndrome 1 (LQT1) due to loss-of-function mutations in KCNQ1.

DESIGN

Medical records of 104 patients with LQT1 in a single tertiary care center between 1995 and 2015 were retrospectively reviewed.

METHODS

Clinical and endocrine data of the LQT1 patients were included in the analyses.

RESULTS

At birth, patients with a maternally inherited mutation (n = 52) were shorter than those with paternal inheritance of the mutation (n = 29) (birth length, -0.70 ± 1.1 SDS vs. -0.2 ± 1.0 SDS, P < 0.05). Further analyses showed, however, that only newborns (n = 19) of mothers who had received beta blockers during pregnancy were shorter and lighter at birth than those with paternal inheritance of the mutation (n = 29) (-0.89 ± 1.0 SDS vs. -0.20 ± 1.0 SDS, P < 0.05; and 3,173 ± 469 vs. 3,515 ± 466 g, P < 0.05). Maternal beta blocker treatment during the pregnancy was also associated with lower cord blood TSH levels (P = 0.011) and significant catch-up growth during the first year of life (Δ0.08 SDS/month, P = 0.004). Later, childhood growth of the patients was unremarkable.

CONCLUSION

Loss-of-function mutations in KCNQ1 are not associated with abnormalities in growth, whereas maternal beta blocker use during pregnancy seems to modify prenatal growth of LQT1 patients-a phenomenon followed by catch-up growth after birth.

ERRγ: a Junior Orphan with a Senior Role in Metabolism

Estrogen-related receptor (ERR)γ is an orphan nuclear hormone receptor that belongs to the ERR subfamily of transcription factors. No endogenous ligand has been identified to date. ERRγ possesses ligand-independent transcriptional activity that is regulated by co-regulator interactions, and post-translational modifications (PTMs). Recent data from animal models have established ERRγ as a crucial mediator of multiple endocrine and metabolic signals. ERRγ plays important roles in pathological conditions such as insulin resistance, alcoholic liver injury, and cardiac hypertrophy, and controls energy metabolism in the heart, skeletal muscle, and pancreatic β cells. These findings corroborate the importance of ERRγ in metabolic homeostasis, and suggest that ERRγ is a good target for the treatment of metabolic diseases.

Complementary Roles of Estrogen-Related Receptors in Brown Adipocyte Thermogenic Function

Brown adipose tissue (BAT) thermogenesis relies on a high abundance of mitochondria and the unique expression of the mitochondrial Uncoupling Protein 1 (UCP1), which uncouples substrate oxidation from ATP synthesis. Adrenergic stimulation of brown adipocytes activates UCP1-mediated thermogenesis; it also induces the expression of Ucp1 and other genes important for thermogenesis, thereby endowing adipocytes with higher oxidative and uncoupling capacities. Adipocyte mitochondrial biogenesis and oxidative capacity are controlled by multiple transcription factors, including the estrogen-related receptor (ERR)α. Whole-body ERRα knockout mice show decreased BAT mitochondrial content and oxidative function but normal induction of Ucp1 in response to cold. In addition to ERRα, brown adipocytes express ERRβ and ERRγ, 2 nuclear receptors that are highly similar to ERRα and whose function in adipocytes is largely unknown. To gain insights into the roles of all 3 ERRs, we assessed mitochondrial function and adrenergic responses in primary brown adipocytes lacking combinations of ERRs. We show that adipocytes lacking just ERRα, the most abundant ERR, show only mild mitochondrial defects. Adipocytes lacking ERRβ and ERRγ also show just mild defects. In contrast, adipocytes lacking all 3 ERRs have severe reductions in mitochondrial content and oxidative capacity. Moreover, adipocytes lacking all 3 ERRs have defects in the transcriptional and metabolic response to adrenergic stimulation, suggesting a wider role of ERRs in BAT function than previously appreciated. Our study shows that ERRs have a great capacity to compensate for each other in protecting mitochondrial function and the metabolic response to adrenergic signaling, processes vital to BAT function.

Asymmetry of parental origin in long QT syndrome: preferential maternal transmission of KCNQ1 variants linked to channel dysfunction

Transmission distortion of disease-causing alleles in long QT syndrome (LQTS) has been reported, suggesting a potential role of KCNQ1 and KCNH2 in reproduction. This study sought to investigate parental transmission in LQTS families according to ethnicity, gene loci (LQT1-3: KCNQ1, KCNH2, and SCN5A) or severity of channel dysfunction. We studied 3782 genotyped members from 679 European and Japanese LQTS families (2748 carriers). We determined grandparental and parental origins of variant alleles in 1903 children and 624 grandchildren, and the grandparental origin of normal alleles in healthy children from 44 three-generation control families. LQTS alleles were more of maternal than paternal origin (61 vs 39%, P<0.001). The ratio of maternally transmitted alleles in LQT1 (66%) was higher than in LQT2 (56%, P<0.001) and LQT3 (57%, P=0.03). Unlike the Mendelian distribution of grandparental alleles seen in control families, variant grandparental LQT1 and LQT2 alleles in grandchildren showed an excess of maternally transmitted grandmother alleles. For LQT1, maternal transmission differs according to the variant level of dysfunction with 68% of maternal transmission for dominant negative or unknown functional consequence variants vs 58% for non-dominant negative and variants leading to haploinsufficiency, P<0.01; however, for LQT2 or LQT3 this association was not significant. An excess of disease-causing alleles of maternal origin, most pronounced in LQT1, was consistently found across ethnic groups. This observation does not seem to be linked to an imbalance in transmission of the LQTS subtype-specific grandparental allele, but to the potential degree of potassium channel dysfunction.

Involvement of Kallikrein-Related Peptidases in Normal and Pathologic Processes

Human kallikrein-related peptidases (KLKs) are a subgroup of serine proteases that participate in proteolytic pathways and control protein levels in normal physiology as well as in several pathological conditions. Their complex network of stimulatory and inhibitory interactions may induce inflammatory and immune responses and contribute to the neoplastic phenotype through the regulation of several cellular processes, such as proliferation, survival, migration, and invasion. This family of proteases, which includes one of the most useful cancer biomarkers, kallikrein-related peptidase 3 or PSA, also has a protective effect against cancer promoting apoptosis or counteracting angiogenesis and cell proliferation. Therefore, they represent attractive therapeutic targets and may have important applications in clinical oncology. Despite being intensively studied, many gaps in our knowledge on several molecular aspects of KLK functions still exist. This review aims to summarize recent data on their involvement in different processes related to health and disease, in particular those directly or indirectly linked to the neoplastic process.

KCNE1 and KCNE3: The yin and yang of voltage-gated K(+) channel regulation

The human KCNE gene family comprises five genes encoding single transmembrane-spanning ion channel regulatory subunits. The primary function of KCNE subunits appears to be regulation of voltage-gated potassium (Kv) channels, and the best-understood KCNE complexes are with the KCNQ1 Kv α subunit. Here, we review the often opposite effects of KCNE1 and KCNE3 on Kv channel biology, with an emphasis on regulation of KCNQ1. Slow-activating IKs channel complexes formed by KCNQ1 and KCNE1 are essential for human ventricular myocyte repolarization, while constitutively active KCNQ1-KCNE3 channels are important in the intestine. Inherited sequence variants in human KCNE1 and KCNE3 cause cardiac arrhythmias but by different mechanisms, and each is important for hearing in unique ways. Because of their contrasting effects on KCNQ1 function, KCNE1 and KCNE3 have proved invaluable tools in the mechanistic understanding of how channel gating can be manipulated, and each may also provide a window into novel insights and new therapeutic opportunities in K(+) channel pharmacology. Finally, findings from studies of Kcne1(-/-) and Kcne3(-/-) mouse lines serve to illustrate the complexity of KCNE biology and KCNE-linked disease states.

The multiple universes of estrogen-related receptor α and γ in metabolic control and related diseases

The identification of the estrogen-related receptors (ERRs) as the first orphan nuclear receptors ignited a new era in molecular endocrinology, which led to the discovery of new ligand-dependent response systems. Although ERR subfamily members have yet to be associated with a natural ligand, the characterization of these orphan receptors has demonstrated that they occupy a strategic node in the transcriptional control of cellular energy metabolism. In particular, ERRs are required for the response to various environmental challenges that require high energy levels by the organism. As central regulators of energy homeostasis, ERRs may also be implicated in the etiology of metabolic disorders, such as type 2 diabetes and metabolic syndrome. Here, we review the recent evidence that further highlights the role of ERRs in metabolic control, particularly in liver and skeletal muscle, and their likely involvement in metabolic diseases. Consequently, we also explore the promises and pitfalls of ERRs as potential therapeutic targets.

Trophoblast syncytialisation necessitates mitochondrial function through estrogen-related receptor-γ activation

Human pregnancy needs a correct placentation which depends on adequate cytotrophoblast proliferation, differentiation and invasion. In this study, using specific mitochondrial respiratory chain inhibitors, we observed a decrease of hormone production (hCG and leptin) and cell fusion of human primary villous cytotrophoblasts (CT). These results demonstrated that mitochondria are involved in the control of CT differentiation process. Moreover, we also observed a decrease of mitochondrial mass associated with an increase of mitochondrial DNA during CT differentiation. Furthermore, lactate production increased during CT differentiation suggesting that anaerobic metabolism was enhanced in differentiated CTs, and that the role of mitochondria in CT fusion is not only related to its energetic function. Otherwise, the orphan nuclear receptor, estrogen-related receptor γ (ERRγ) is known to orchestrate transcriptional control of energy metabolism genes. In this study, using RNA knockdown and transcriptional activation with DY131 (an ERRγ agonist), we clearly demonstrated that ERRγ promotes hormone production and cell fusion indicating that ERRγ is a key positive transcriptional factor involved in CT differentiation. Finally, we showed that ERRγ promotes mitochondrial biogenesis and function during CT differentiation, and that the role of ERRγ during trophoblast differentiation is mainly mediated by the control of mitochondrial functions.

Moderate hypoxia influences potassium outward currents in adipose-derived stem cells

Moderate hypoxic preconditioning of adipose-derived stem cells (ASCs) enhances properties such as proliferation and secretion of growth factors, representing a valuable strategy to increase the efficiency of cell-based therapies. In a wide variety of cells potassium (K⁺) channels are key elements involved in the cellular responses to hypoxia, suggesting that ASCs cultured under low oxygen conditions may display altered electrophysiological properties. Here, the effects of moderate hypoxic culture on proliferation, whole-cell currents, and ion channel expression were investigated using human ASCs cultured at 5% and 20% oxygen. Although cell proliferation was greatly enhanced, the dose-dependent growth inhibition by the K⁺ channel blocker tetraethylammonium (TEA) was not significantly affected by hypoxia. Under both normoxic and hypoxic conditions, ASCs displayed outward K⁺ currents composed by Ca²⁺-activated, delayed rectifier, and transient components. Hypoxic culture reduced the slope of the current-voltage curves and caused a negative shift in the voltage activation threshold of the whole-cell currents. However, the TEA-mediated shift of voltage activation threshold was not affected by hypoxia. Semiquantitative real-time RT-PCR revealed that expression of genes encoding for various ion channels subunits related to oxygen sensing and proliferation remained unchanged after hypoxic culture. In conclusion, outward currents are influenced by moderate hypoxia in ASCs through a mechanism that is not likely the result of modulation of TEA-sensitive K⁺ channels.

Estrogen-related receptor γ serves a role in blood pressure homeostasis during pregnancy

Persistent hypoxia caused by shallow trophoblast invasion and poor placental perfusion may underlie the pathophysiology of preeclampsia, a leading cause of maternal and neonatal morbidity and mortality. Previously, we found that estrogen-related receptor γ (ERRγ) serves a critical and O2-dependent role in differentiation of human trophoblasts in culture and expression of tissue kallikrein and voltage-gated K(+) channels. In this study, we surprisingly observed that ERRγ expression was significantly increased in placentas from preeclamptic women compared with that in gestation-matched normotensive women. To further investigate a functional role for ERRγ during pregnancy, we analyzed ERRγ-deficient mice. Maternal systolic blood pressure was significantly reduced in pregnant ERRγ(+/-) females bred to ERRγ(+/-) males compared with that in wild-type (WT) mice and was markedly up-regulated by treatment of WT pregnant mice with the ERRγ agonist DY131. Placentas of ERRγ(+/-) mice manifested increased vascular endothelial growth factor A expression compared with that in WT mice. Notably, circulating levels of the antiangiogenic factor, soluble fms-like tyrosine kinase-1, were significantly reduced in ERRγ(+/-) pregnant mice as was serum aldosterone. These effects were associated with a decrease in maternal adrenal Cyp11b1 (steroid 11β-hydroxylase) and Cyp11b2 (aldosterone synthase) expression. In contrast, adrenal Cyp11b1 and Cyp11b2 mRNA were increased in pregnant WT mice treated with DY131. Moreover, chromatin immunoprecipitation and luciferase reporter assays identified Cyp11b2 as a transcriptional target of ERRγ. Collectively, these findings reveal a potential role of ERRγ in maternal blood pressure homeostasis during pregnancy and suggest that aberrant ERRγ expression may contribute to the pathogenesis of preeclampsia.

Expression of voltage-dependent potassium channels in first trimester human placentae

Potassium channel α-subunits encoded by KCNQ1-5 genes form voltage-dependent channels (KV7), modulated by KCNE1-5 encoded accessory proteins. The aim was to determine KCNQ and KCNE mRNA expression and assess protein expression/localisation of the KCNQ3 and KCNE5 isoforms in first trimester placental tissue. Placentae were obtained from women undergoing elective surgical termination of pregnancy (TOP) at ≤ 10 weeks' (early TOP) and >10 weeks' (mid TOP) gestations. KCNQ1-5 expression was unchanged during the first trimester. KCNE5 expression increased in mid TOP vs. early TOP samples (P = 0.022). This novel study reports mRNA and protein expression of KV7 channels in first trimester placentae.

The pERK of being a target: Kinase regulation of the orphan nuclear receptor ERRγ

Estrogen-related receptors (ERRs) are orphan members of the nuclear receptor superfamily that are important regulators of mitochondrial metabolism with emerging roles in cancer. In the absence of an endogenous ligand, ERRs are reliant upon other regulatory mechanisms that include protein/protein interactions and post-translational modification, though the cellular and clinical significance of this latter mechanism is unclear. We recently published a study in which we establish estrogen-related receptor gamma (ERRγ) as a target for extracellular signal-regulated kinase (ERK), and show that regulation of ERRγ by ERK has important consequences for the function of this receptor in cellular models of estrogen receptor-positive (ER+) breast cancer. In this Research Highlight, we discuss the implications of these findings from a molecular and clinical perspective.