Somatic and germline CACNA1D calcium channel mutations in aldosterone-producing adenomas and primary aldosteronism

Deletion of the voltage-gated calcium channel, CaV 1.3, causes deficits in motor performance and associative learning

L-type voltage-gated calcium channels are important regulators of neuronal activity and are widely expressed throughout the brain. One of the major L-type voltage-gated calcium channel isoforms in the brain is Ca_V 1.3. Mice lacking Ca_V 1.3 are reported to have impairments in fear conditioning and depressive-like behaviors, which have been linked to Ca_V 1.3 function in the hippocampus and amygdala. Genetic variation in Ca_V 1.3 has been linked to a variety of psychiatric disorders, including autism and schizophrenia, which are associated with altered motor learning, associative learning and social function. Here, we explored whether Ca_V 1.3 plays a role in these behaviors. We found that Ca_V 1.3 knockout mice have deficits in rotarod learning despite normal locomotor function. Deletion of Ca_V 1.3 is also associated with impaired gait adaptation and associative learning on the Erasmus Ladder. We did not observe any impairments in Ca_V 1.3 knockout mice on assays of anxiety-like, depression-like or social preference behaviors. Our results suggest an important role for Ca_V 1.3 in neural circuits involved in motor learning and concur with previous data showing its involvement in associative learning.

Hypoglycaemia Metabolic Gene Panel Testing

A large number of inborn errors of metabolism present with hypoglycemia. Impairment of glucose homeostasis may arise from different biochemical pathways involving insulin secretion, fatty acid oxidation, ketone bodies formation and degradation, glycogen metabolism, fructose and galactose metabolism, branched chain aminoacids and tyrosine metabolism, mitochondrial function and glycosylation proteins mechanisms. Historically, genetic analysis consisted of highly detailed molecular testing of nominated single genes. However, more recently, the genetic heterogeneity of these conditions imposed to perform extensive molecular testing within a useful timeframe via new generation sequencing technology. Indeed, the establishment of a rapid diagnosis drives specific nutritional and medical therapies. The biochemical and clinical phenotypes are critical to guide the molecular analysis toward those clusters of genes involved in specific pathways, and address data interpretation regarding the finding of possible disease-causing variants at first reported as variants of uncertain significance in known genes or the discovery of new disease genes. Also, the trio's analysis allows genetic counseling for recurrence risk in further pregnancies. Besides, this approach is allowing to expand the phenotypic characterization of a disease when pathogenic variants give raise to unexpected clinical pictures. Multidisciplinary input and collaboration are increasingly key for addressing the analysis and interpreting the significance of the genetic results, allowing rapidly their translation from bench to bedside.

Pathophysiology and histopathology of primary aldosteronism

Primary aldosteronism (PA) can be sporadic or familial and classified into unilateral and bilateral forms. Sporadic PA predominates with excessive aldosterone production usually arising from a unilateral aldosterone-producing adenoma (APA) or bilateral adrenocortical hyperplasia. Familial PA is rare and caused by germline variants, that partly correspond to somatic alterations in APAs. Classification into unilateral and bilateral PA determines the treatment approach but does not accurately mirror disease pathology. Some evidence indicates a disease continuum ranging from balanced aldosterone production from each adrenal to extreme asymmetrical bilateral aldosterone production. Nonetheless, surgical removal of the overactive adrenal in unilateral PA achieves highly successful outcomes and almost all patients are biochemically cured of their aldosteronism.

A Novel Somatic Mutation of CACNA1H p.V1937M in Unilateral Primary Hyperaldosteronism

BACKGROUND

Somatic mutations for excess aldosterone production have been frequently identified as important roles in the pathogenesis of unilateral primary hyperaldosteronism (uPA). Although CACNA1H mutation represents a minor etiology in primary aldosteronism, it plays a significant role in causing uPAs in sporadic cases.

OBJECTIVE

To identify novel somatic CACNA1H mutation in patients with uPA and investigate the pathophysiological, immunohistological, and clinical characteristics of the variant.

METHODS

We applied a customized and targeted gene panel next-generation sequencing approach to detect mutations from the uPA cohort in Taiwan Primary Aldosteronism Investigation study group. Information from pre-diagnostic to postoperative data was collected, including past history, medications, blood pressure readings, biochemical data, and image studies. The functional role of the variant was confirmed by in vitro studies, demonstrating aldosterone production in variant-transfected human adrenal cell lines.

RESULTS

We identified a novel somatic CACNA1H mutation c.5809G>A (p.Val1937Met) in a uPA case. The CACNA1H gene encodes the pore-forming alpha-1H subunit of the voltage-dependent T-type calcium channel Cav3.2. This somatic CACNA1H p.V1937M variant showed excellent clinical and biochemical outcomes after ipsilateral adrenalectomy. The functional effect of somatic CACNA1H p.V1937M variant results in increased CYP11B2 expression and aldosterone biosynthesis in HAC15 cells. A distinct heterogeneous foamy pattern of CYP11B2 and CYP17A1 expression was identified in immunohistological staining, supporting the pathological evidence of aldosterone synthesis.

CONCLUSIONS

The somatic mutation of CACNA1H p.V1937M might be a pathogenic driver in aldosterone overproduction. This study provides new insight into the molecular mechanism and disease outcomes of uPA.

Aldosterone-Regulated Sodium Transport and Blood Pressure

Aldosterone is a major mineralocorticoid steroid hormone secreted by glomerulosa cells in the adrenal cortex. It regulates a variety of physiological responses including those to oxidative stress, inflammation, fluid disruption, and abnormal blood pressure through its actions on various tissues including the kidney, heart, and the central nervous system. Aldosterone synthesis is primarily regulated by angiotensin II, K⁺ concentration, and adrenocorticotrophic hormone. Elevated serum aldosterone levels increase blood pressure largely by increasing Na⁺ re-absorption in the kidney through regulating transcription and activity of the epithelial sodium channel (ENaC). This review focuses on the signaling pathways involved in aldosterone synthesis and its effects on Na⁺ reabsorption through ENaC.

KCNJ5 Somatic Mutation Is Associated With Higher Aortic Wall Thickness and Less Calcification in Patients With Aldosterone-Producing Adenoma

OBJECTIVE

Primary aldosteronism (PA) is the most common type of secondary hypertension, and it is associated with a higher rate of cardiovascular complications. KCNJ5 somatic mutations have recently been identified in aldosterone-producing adenoma (APA), however their influence on vascular remodeling and injury is still unclear. The aim of this study was to investigate the association between KCNJ5 somatic mutation status and vascular status.

METHODS

We enrolled 179 APA patients who had undergone adrenalectomy from a prospectively maintained database, of whom 99 had KCNJ5 somatic mutations. Preoperative clinical, biochemical and imaging data of abdominal CT, including abdominal aortic calcification (AAC) score, aortic diameter and wall thickness at levels of superior (SMA) and inferior (IMA) mesenteric arteries were analyzed.

RESULTS

After propensity score matching for age, sex, body mass index, triglycerides and low-density lipoprotein, there were 48 patients in each KCNJ5 (+) and KCNJ5 (-) group. Mutation carriers had a lower AAC score (217.3 ± 562.2 vs. 605.6 ± 1359.1, P=0.018), higher aortic wall thickness (SMA level: 2.2 ± 0.6 mm vs. 1.8 ± 0.6 mm, P=0.006; IMA level: 2.4 ± 0.6 mm vs. 1.8 ± 0.7 mm, P<0.001) than non-carriers. In multivariate analysis, KCNJ5 mutations were independently associated with AAC score (P=0.014) and aortic wall thickness (SMA level: P<0.001; IMA level: P=0.004). After adrenalectomy, mutation carriers had less aortic wall thickness progression than non-carriers (Δthickness SMA: -0.1 ± 0.8 mm vs. 0.9 ± 0.6 mm, P=0.024; IMA: -0.1 ± 0.6 mm vs. 0.8 ± 0.7 mm, P=0.04).

CONCLUSION

KCNJ5 mutation carriers had less calcification burden of the aorta, thickened aortic wall, and less wall thickness progression than non-carriers.

Disorders of the adrenal cortex: Genetic and molecular aspects

Adrenal cortex produces glucocorticoids, mineralocorticoids and adrenal androgens which are essential for life, supporting balance, immune response and sexual maturation. Adrenocortical tumors and hyperplasias are a heterogenous group of adrenal disorders and they can be either sporadic or familial. Adrenocortical cancer is a rare and aggressive malignancy, and it is associated with poor prognosis. With the advance of next-generation sequencing technologies and improvement of genomic data analysis over the past decade, various genetic defects, either from germline or somatic origin, have been unraveled, improving diagnosis and treatment of numerous genetic disorders, including adrenocortical diseases. This review gives an overview of disorders associated with the adrenal cortex, the genetic factors of these disorders and their molecular implications.

Stabilization of negative activation voltages of Cav1.3 L-Type Ca2+-channels by alternative splicing

-->Low voltage-activated Cav1.3 L-type Ca2+-channels are key regulators of neuronal excitability controlling neuronal development and different types of learning and memory. Their physiological functions are enabled by their negative activation voltage-range, which allows Cav1.3 to be active at subthreshold voltages. Alternative splicing in the C-terminus of their pore-forming α1-subunits gives rise to C-terminal long (Cav1.3L) and short (Cav1.3S) splice variants allowing Cav1.3S to activate at even more negative voltages than Cav1.3L. We discovered that inclusion of exons 8b, 11, and 32 in Cav1.3S further shifts activation (-3 to -4 mV) and inactivation (-4 to -6 mV) to more negative voltages as revealed by functional characterization in tsA-201 cells. We found transcripts of these exons in mouse chromaffin cells, the cochlea, and the brain. Our data further suggest that Cav1.3-containing exons 11 and 32 constitute a significant part of native channels in the brain. We therefore investigated the effect of these splice variants on human disease variants. Splicing did not prevent the gating defects of the previously reported human pathogenic variant S652L, which further shifted the voltage-dependence of activation of exon 11-containing channels by more than -12 mV. In contrast, we found no evidence for gating changes of the CACNA1D missense variant R498L, located in exon 11, which has recently been identified in a patient with an epileptic syndrome. Our data demonstrate that alternative splicing outside the C-terminus involving exons 11 and 32 contributes to channel fine-tuning by stabilizing negative activation and inactivation gating properties of wild-type and mutant Cav1.3 channels.

Diagnosis and treatment of primary aldosteronism

Primary aldosteronism is a common cause of secondary hypertension associated with excess cardiovascular morbidities. Primary aldosteronism is underdiagnosed because it does not have a specific, easily identifiable feature and clinicians can be poorly aware of the disease. The diagnostic investigation is a multistep process of screening, confirmatory testing, and subtype differentiation of unilateral from bilateral forms for therapeutic management. Adrenal venous sampling is key for reliable subtype identification, but can be bypassed in patients with specific characteristics. For unilateral disease, surgery offers the possibility of cure, with total laparoscopic unilateral adrenalectomy being the treatment of choice. Bilateral forms are treated mainly with mineralocorticoid receptor antagonists. The goals of treatment are to normalise both blood pressure and excessive aldosterone production, and the primary aims are to reduce associated comorbidities, improve quality of life, and reduce mortality. Prompt diagnosis of primary aldosteronism and the use of targeted treatment strategies mitigate aldosterone-specific target organ damage and with appropriate patient management outcomes can be excellent. Advances in molecular histopathology challenge the traditional concept of primary aldosteronism as a binary disease, caused by either a unilateral aldosterone-producing adenoma or bilateral adrenal hyperplasia. Somatic mutations drive autonomous aldosterone production in most adenomas. Many of these same mutations have been identified in nodular lesions adjacent to an aldosterone-producing adenoma and in patients with bilateral disease. In addition, germline mutations cause rare familial forms of aldosteronism (familial hyperaldosteronism types 1-4). Genetic testing for inherited forms in suspected cases of familial hyperaldosteronism avoids the burdensome diagnostic investigation in positive patients. In this Review, we discuss advances and future management approaches in the diagnosis of primary aldosteronism.

Progress on Genetic Basis of Primary Aldosteronism

Primary aldosteronism (PA) is a heterogeneous group of disorders caused by the autonomous overproduction of aldosterone with simultaneous suppression of plasma renin activity (PRA). It is considered to be the most common endocrine cause of secondary arterial hypertension (HT) and is associated with a high rate of cardiovascular complications. PA is most often caused by a bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenoma (APA); rarer causes of PA include genetic disorders of steroidogenesis (familial hyperaldosteronism (FA) type I, II, III and IV), aldosterone-producing adrenocortical carcinoma, and ectopic aldosterone-producing tumors. Over the last few years, significant progress has been made towards understanding the genetic basis of PA, classifying it as a channelopathy. Recently, a growing body of clinical evidence suggests that mutations in ion channels appear to be the major cause of aldosterone-producing adenomas, and several mutations within the ion channel encoding genes have been identified. Somatic mutations in four genes (KCNJ5, ATP1A1, ATP2B3 and CACNA1D) have been identified in nearly 60% of the sporadic APAs, while germline mutations in KCNJ5 and CACNA1H have been reported in different subtypes of familial hyperaldosteronism. These new insights into the molecular mechanisms underlying PA may be associated with potential implications for diagnosis and therapy.

Transcriptomics, Epigenetics, and Metabolomics of Primary Aldosteronism

INTRODUCTION

Primary aldosteronism (PA) is the most common cause of endocrine hypertension, mainly caused by aldosterone-producing adenomas or hyperplasia; understanding its pathophysiological background is important in order to provide ameliorative treatment strategies. Over the past several years, significant progress has been documented in this field, in particular in the clarification of the genetic and molecular mechanisms responsible for the pathogenesis of aldosterone-producing adenomas (APAs).

METHODS

Systematic searches of the PubMed and Cochrane databases were performed for all human studies applying transcriptomic, epigenetic or metabolomic analyses to PA subjects. Studies involving serial analysis of gene expression and microarray, epigenetic studies with methylome analyses and micro-RNA expression profiles, and metabolomic studies focused on improving understanding of the regulation of autonomous aldosterone production in PA were all included.

RESULTS

In this review we summarize the main findings in this area and analyze the interplay between primary aldosteronism and several signaling pathways with differential regulation of the RNA and protein expression of several factors involved in, among others, steroidogenesis, calcium signaling, and nuclear, membrane and G-coupled protein receptors. Distinct transcriptomic and metabolomic patterns are also presented herein, depending on the mutational status of APAs. In particular, two partially opposite transcriptional and steroidogenic profiles appear to distinguish APAs carrying a KCNJ5 mutation from all other APAs, which carry different mutations.

CONCLUSIONS

These findings can substantially contribute to the development of personalized treatment in patients with PA.

In Silico Analysis of the Gene Expression Patterns between Aldosterone-Producing Adenoma and Nonfunctional Adrenocortical Adenoma

Primary aldosteronism is the most common form of secondary hypertension, and aldosteronoma makes up a significant proportion of primary aldosteronism cases. Aldosteronoma is also called aldosterone-producing adenoma (APA). Although there have been many studies about APA, the pathogenesis of this disease is not yet fully understood. In this study, we aimed to find out the difference of gene expression patterns between APA and nonfunctional adrenocortical adenoma (NFAA) using a weighted gene coexpression network (WGCNA) and differentially expressed gene (DEG) analysis; only the genes that meet the corresponding standards of both methods were defined as real hub genes and then used for further analysis. Twenty-nine real hub genes were found out, most of which were enriched in the phospholipid metabolic process. WISP2, S100A10, SSTR5-AS1, SLC29A1, APOC1, and SLITRK4 are six real hub genes with the same gene expression pattern between the combined and validation datasets, three of which indirectly or directly participate in lipid metabolism including WISP2, S100A10, and APOC1. According to the gene expression pattern of DEGs, we speculated five candidate drugs with potential therapeutic value for APA, one of which is cycloheximide, an inhibitor for phospholipid biosynthesis. All the evidence suggests that phospholipid metabolism may be an important pathophysiological mechanism for APA. Our study provides a new perspective regarding the pathophysiological mechanism of APA and offers some small molecules that may possibly be effective drugs against APA.

ATP1A1 Mutant in Aldosterone-Producing Adenoma Leads to Cell Proliferation

The molecular mechanisms by which ATP1A1 mutation-mediated cell proliferation or tumorigenesis in aldosterone-producing adenomas (APAs) have not been elucidated. First, we investigated whether the APA-associated ATP1A1 L104R mutation stimulated cell proliferation. Second, we aimed to clarify the molecular mechanisms by which the ATP1A1 mutation-mediated cell proliferated. We performed transcriptome analysis in APAs with ATP1A1 mutation. ATP1A1 L104R mutation were modulated in human adrenocortical carcinoma (HAC15) cells (ATP1A1-mutant cells), and we evaluated cell proliferation and molecular signaling events. Transcriptome and immunohistochemical analysis showed that Na/K-ATPase (NKA) expressions in ATP1A1 mutated APA were more abundant than those in non-functioning adrenocortical adenoma or KCNJ5 mutated APAs. The significant increase of number of cells, amount of DNA and S-phase population were shown in ATP1A1-mutant cells. Fluo-4 in ATP1A1-mutant cells were significantly increased. Low concentration of ouabain stimulated cell proliferation in ATP1A1-mutant cells. ATP1A1-mutant cells induced Src phosphorylation, and low concentration of ouabain supplementation showed further Src phosphorylation. We demonstrated that NKAs were highly expressed in ATP1A1 mutant APA, and the mutant stimulated cell proliferation and Src phosphorylation in ATP1A1-mutant cells. NKA stimulations would be a risk factor for the progression and development to an ATP1A1 mutant APA.

Tuberous Sclerosis Complex (TSC) Inactivation Increases Neuronal Network Activity by Enhancing Ca2+ Influx via L-Type Ca2+ Channels

Tuberous sclerosis complex (TSC) is a multisystem developmental disorder characterized by hamartomas in various organs, such as the brain, lungs, and kidneys. Epilepsy, along with autism and intellectual disability, is one of the neurologic impairments associated with TSC that has an intimate relationship with developmental outcomes and quality of life. Sustained activation of the mammalian target of rapamycin (mTOR) via TSC1 or TSC2 mutations is known to be involved in the onset of epilepsy in TSC. However, the mechanism by which mTOR causes seizures remains unknown. In this study, we showed that, human induced pluripotent stem cell-derived TSC2-deficient (TSC2 ^-/-) neurons exhibited elevated neuronal activity with highly synchronized Ca²⁺ spikes. Notably, TSC2 ^-/- neurons presented enhanced Ca²⁺ influx via L-type Ca²⁺ channels (LTCCs), which contributed to the abnormal neurite extension and sustained activation of cAMP response element binding protein (CREB), a critical mediator of synaptic plasticity. Expression of Cav1.3, a subtype of LTCCs, was increased in TSC2 ^-/- neurons, but long-term rapamycin treatment suppressed this increase and reversed the altered neuronal activity and neurite extensions. Thus, we identified Cav1.3 LTCC as a critical downstream component of TSC-mTOR signaling that would trigger enhanced neuronal network activity of TSC2 ^-/- neurons. We suggest that LTCCs could be potential novel targets for the treatment of epilepsy in TSC.SIGNIFICANCE STATEMENT There is a close relationship between elevated mammalian target of rapamycin (mTOR) activity and epilepsy in tuberous sclerosis complex (TSC). However, the underlying mechanism by which mTOR causes epilepsy remains unknown. In this study, using human TSC2 ^-/- neurons, we identified elevated Ca²⁺ influx via L-type Ca²⁺ channels as a critical downstream component of TSC-mTOR signaling and a potential cause of both elevated neuronal activity and neurite extension in TSC2 ^-/- neurons. Our findings demonstrate a previously unrecognized connection between sustained mTOR activation and elevated Ca²⁺ signaling via L-type Ca²⁺ channels in human TSC neurons, which could cause epilepsy in TSC.

Characteristics of a Novel ATP2B3 K416_F418delinsN Mutation in a Classical Aldosterone-Producing Adenoma

Simple Summary

The ATP2B3 channel mutation is a rare cause of primary aldosteronism (PA). ATP2B3 gene mutation leads to the dysfunction of calcium channel that pumps calcium ion out of the cell and accumulates intracellular calcium signal to stimulate aldosterone synthesis. In the present study, we found a novel somatic ATP2B3 K416_F418delinsN mutation in a PA patient, and proved its functionality by demonstrating aldosterone hyper-function in the mutant-transfected adrenal cell-line. The ATP2B3 K416_F418delinsN mutation resulted from the deletion from nucleotides 1248 to 1253. The translated amino acid sequence from 416 to 418 as lysine-phenylalanine-phenylalanine was deleted and an asparagine was inserted due to the merging of residual nucleotide sequences.

Abstract

In patients with primary aldosteronism (PA), the prevalence of ATP2B3 mutation is rare. The aim of this study is to report a novel ATP2B3 mutation in a PA patient. Based on our tissue bank of aldosterone-producing adenomas (APA), we identified a novel somatic ATP2B3 K416_F418delinsN mutation. The affected individual was a 53 year-old man with a 4 year history of hypertension. Computed tomography (CT) showed bilateral adrenal masses of 1.6 (left) and 0.5 cm (right) in size. An adrenal venous sampling (AVS) showed a lateralization index (LI) of 2.2 and a contralateral suppression index (CLS) of 0.12; indicating left functional predominance. After a left unilateral adrenalectomy, he achieved partial biochemical and hypertension–remission. This classical adenoma harbored a novel ATP2B3 K416_F418delinsN somatic mutation, which is a deletion from nucleotides 1248 to 1253. The translated amino acid sequence from 416 to 418, reading as lysine-phenylalanine-phenylalanine, was deleted; however, an asparagine was inserted due to merging of residual nucleotide sequences. The CYP11B2 immunohistochemistry staining demonstrated strong immunoreactivity in this classical adenoma. The ATP2B3 K416_F418delinsN mutation is a functional mutation in APA, since HAC15 cells, a human adrenal cell line, transfected with the mutant gene showed increased CYP11B2 expression and aldosterone production.

The invention of aldosterone, how the past resurfaces in pediatric endocrinology

Sodium and water homeostasis are drastically modified at birth, in mammals, by the transition from aquatic life to terrestrial life. Accumulating evidence during the past ten years underscores the central role for the mineralocorticoid signaling pathway, in the fine regulation of this equilibrium, at this critical period of development. Interestingly, regarding evolution, while the mineralocorticoid receptor is expressed in fish, the appearance of its related ligand, aldosterone, coincides with terrestrial life, as it is first detected in lungfish and amphibian. Thus, aldosterone is likely one of the main hormones regulating the transition from an aquatic environment to an air environment. This review will focus on the different actors of the mineralocorticoid signaling pathway from aldosterone secretion in the adrenal gland, to mineralocorticoid receptor expression in the kidney, summarizing their regulation and roles throughout fetal and neonatal development, in the light of evolution.

Novel Mutations Detection with Next-Generation Sequencing and Its Association with Clinical Outcome in Unilateral Primary Aldosteronism

Somatic mutations have been identified in adrenal tissues of unilateral primary aldosteronism (uPA). The spectrum of somatic mutations in uPAs was investigated using a customized and targeted next-generation sequencing (cNGS) approach. We also assessed whether cNGS or Sanger sequencing-identified mutations have an association with clinical outcomes in uPA. Adrenal tumoral tissues of uPA patients who underwent adrenalectomy were obtained. Conventional somatic mutation hotspots in 240 extracted DNA samples were initially screened using Sanger sequencing. A total of 75 Sanger-negative samples were further investigated by sequencing the entire coding regions of the known aldosterone-driver genes by our cNGS gene panel. Somatic mutations in aldosterone-driver genes were detected in 21 (28%) of these samples (8.8% of all samples), with 9 samples, including mutations in CACNA1D gene (12%), 5 in CACNA1H (6.6%), 3 in ATP2B3 (4%), 2 in CLCN2 (2.6%), 1 in ATP1A1 (1.3%), and 1 in CTNNB1 (1.3%). Via combined cNGS and Sanger sequencing aldosterone-driver gene mutations were detected in altogether 186 of our 240 (77.5%) uPA samples. The complete clinical success rate of patients containing cNGS-identified mutations was higher than those without mutations (odds ratio (OR) = 10.9; p = 0.012). Identification of somatic mutations with cNGS or Sanger sequencing may facilitate the prediction of complete clinical success after adrenalectomy in uPA patients.

Somatic mutations of GNA11 and GNAQ in CTNNB1-mutant aldosterone-producing adenomas presenting in puberty, pregnancy or menopause

Most aldosterone-producing adenomas (APAs) have gain-of-function somatic mutations of ion channels or transporters. However, their frequency in aldosterone-producing cell clusters of normal adrenal gland suggests a requirement for codriver mutations in APAs. Here we identified gain-of-function mutations in both CTNNB1 and GNA11 by whole-exome sequencing of 3/41 APAs. Further sequencing of known CTNNB1-mutant APAs led to a total of 16 of 27 (59%) with a somatic p.Gln209His, p.Gln209Pro or p.Gln209Leu mutation of GNA11 or GNAQ. Solitary GNA11 mutations were found in hyperplastic zona glomerulosa adjacent to double-mutant APAs. Nine of ten patients in our UK/Irish cohort presented in puberty, pregnancy or menopause. Among multiple transcripts upregulated more than tenfold in double-mutant APAs was LHCGR, the receptor for luteinizing or pregnancy hormone (human chorionic gonadotropin). Transfections of adrenocortical cells demonstrated additive effects of GNA11 and CTNNB1 mutations on aldosterone secretion and expression of genes upregulated in double-mutant APAs. In adrenal cortex, GNA11/Q mutations appear clinically silent without a codriver mutation of CTNNB1.

Analysis of 200,000 Exome-Sequenced UK Biobank Subjects Implicates Genes Involved in Increased and Decreased Risk of Hypertension

BACKGROUND

Previous analyses have identified common variants along with some specific genes and rare variants which are associated with risk of hypertension, but much remains to be discovered.

METHODS AND RESULTS

Exome-sequenced UK Biobank participants were phenotyped based on having a diagnosis of hypertension or taking anti-hypertensive medication to produce a sample of 66,123 cases and 134,504 controls. Variants with minor allele frequency (MAF) <0.01 were subjected to a gene-wise weighted burden analysis, with higher weights assigned to variants which are rarer and/or predicted to have more severe effects. Of 20,384 genes analysed, 2 genes were exome-wide significant, DNMT3A and FES. Also strongly implicated were GUCY1A1 and GUCY1B1, which code for the subunits of soluble guanylate cyclase. There was further support for the previously reported effects of variants in NPR1 and protective effects of variants in DBH. An inframe deletion in CACNA1D with MAF = 0.005, rs72556363, is associated with modestly increased risk of hypertension. Other biologically plausible genes highlighted consist of CSK, AGTR1, ZYX, and PREP. All variants implicated were rare, and cumulatively they are not predicted to make a large contribution to the population risk of hypertension.

CONCLUSIONS

This approach confirms and clarifies previously reported findings and also offers novel insights into biological processes influencing hypertension risk, potentially facilitating the development of improved therapeutic interventions. This research has been conducted using the UK Biobank Resource.

KCNJ5 Somatic Mutations in Aldosterone-Producing Adenoma Are Associated with a Greater Recovery of Arterial Stiffness

Simple Summary

Primary aldosteronism (PA) is the most common form of secondary hypertension and induces various cardiovascular injuries. Aldosterone-producing adenoma (APA) is one of the major forms of PA. The occurrence of APA is closely correlated with somatic mutations, including KCNJ5. We described here the impact of KCNJ5 somatic mutations on arterial stiffness excluding the influence of age, sex, and blood pressure status. We found KCNJ5 mutation carriers had similar arterial stiffness before surgery, but greater improvement of arterial stiffness after adrenalectomy compared with non-carriers. Hence, APA patients with KCNJ5 mutations had a greater improvement in arterial stiffness after adrenalectomy than those without mutations.

Abstract

Primary aldosteronism is the most common form of secondary hypertension and induces various cardiovascular injuries. In aldosterone-producing adenoma (APA), the impact of KCNJ5 somatic mutations on arterial stiffness excluding the influence of confounding factors is uncertain. We enrolled 213 APA patients who were scheduled to undergo adrenalectomy. KCNJ5 gene sequencing of APA was performed. After propensity score matching (PSM) for age, sex, body mass index, blood pressure, number of hypertensive medications, and hypertension duration, there were 66 patients in each group with and without KCNJ5 mutations. The mutation carriers had a higher aldosterone level and lower log transformed brachial–ankle pulse wave velocity (baPWV) than the non-carriers before PSM, but no difference in log baPWV after PSM. One year after adrenalectomy, the mutation carriers had greater decreases in log plasma aldosterone concentration, log aldosterone–renin activity ratio, and log baPWV than the non-carriers after PSM. Only the mutation carriers had a significant decrease in log baPWV after surgery both before and after PSM. KCNJ5 mutations were not correlated with baseline baPWV after PSM but were significantly correlated with ∆baPWV after surgery both before and after PSM. Conclusively, APA patients with KCNJ5 mutations had a greater regression in arterial stiffness after adrenalectomy than those without mutations.

Pathophysiological and Pharmacological Characteristics of KCNJ5 157-159delITE Somatic Mutation in Aldosterone-Producing Adenomas

Mutated channelopathy could play important roles in the pathogenesis of aldosterone-producing adenoma (APA). In this study, we identified a somatic mutation, KCNJ5 157-159delITE, and reported its immunohistological, pathophysiological and pharmacological characteristics. We conducted patch-clamp experiments on HEK293T cells and experiments on expression of aldosterone synthase (CYP11B2) and aldosterone secretion in HAC15 cells to evaluate electrophysiological and functional properties of this mutated KCNJ5. Immunohistochemistry was conducted to identify expressions of several steroidogenic enzymes. Macrolide antibiotics and a calcium channel blocker were administrated to evaluate the functional attenuation of mutated KCNJ5 channel in transfected HAC15 cells. The interaction between macrolides and KCNJ5 protein was evaluated via molecular docking and molecular dynamics simulation analysis. The immunohistochemistry analysis showed strong CYP11B2 immunoreactivity in the APA harboring KCNJ5 157-159delITE mutation. Whole-cell patch-clamp data revealed that mutated KCNJ5 157-159delITE channel exhibited loss of potassium ion selectivity. The mutant-transfected HAC15 cells increased the expression of CYP11B2 and aldosterone secretion, which was partially suppressed by clarithromycin and nifedipine but not roxithromycin treatment. The docking analysis and molecular dynamics simulation disclosed that roxithromycin had strong interaction with KCNJ5 L168R mutant channel but not with this KCNJ5 157-159delITE mutant channel. We showed comprehensive evaluations of the KCNJ5 157-159delITE mutation which revealed that it disrupted potassium channel selectivity and aggravated autonomous aldosterone production. We further demonstrated that macrolide antibiotics, roxithromycin, could not interfere the aberrant electrophysiological properties and gain-of-function aldosterone secretion induced by KCNJ5 157-159delITE mutation.

Molecular Mechanisms of Functional Adrenocortical Adenoma and Carcinoma: Genetic Characterization and Intracellular Signaling Pathway

The adrenal cortex produces steroid hormones as adrenocortical hormones in the body, secreting mineralocorticoids, glucocorticoids, and adrenal androgens, which are all considered essential for life. Adrenocortical tumors harbor divergent hormonal activity, frequently with steroid excess, and disrupt homeostasis of the body. Aldosterone-producing adenomas (APAs) cause primary aldosteronism (PA), and cortisol-producing adenomas (CPAs) are the primary cause of Cushing’s syndrome. In addition, adrenocortical carcinoma (ACC) is a highly malignant cancer harboring poor prognosis. Various genetic abnormalities have been reported, which are associated with possible pathogenesis by the alteration of intracellular signaling and activation of transcription factors. In particular, somatic mutations in APAs have been detected in genes encoding membrane proteins, especially ion channels, resulting in hypersecretion of aldosterone due to activation of intracellular calcium signaling. In addition, somatic mutations have been detected in those encoding cAMP-PKA signaling-related factors, resulting in hypersecretion of cortisol due to its driven status in CPAs. In ACC, mutations in tumor suppressor genes and Wnt-β-catenin signaling-related factors have been implicated in its pathogenesis. In this article, we review recent findings on the genetic characteristics and regulation of intracellular signaling and transcription factors in individual tumors.

Primary Aldosteronism: Metabolic Reprogramming and the Pathogenesis of Aldosterone-Producing Adenomas

Simple Summary

Primary aldosteronism is a common form of endocrine hypertension often caused by a hyper-secreting tumor of the adrenal cortex called an aldosterone-producing adenoma. Metabolic reprogramming plays a role in tumor progression and influences the tumor immune microenvironment by limiting immune-cell infiltration and suppressing its anti-tumor function. We hypothesized that the development of aldosterone-producing adenomas involves metabolic adaptations of its component tumor cells and intrinsically influences tumor pathogenesis. Herein, we use state-of-the-art computational tools for the comprehensive analysis of array-based gene expression profiles to demonstrate metabolic reprogramming and remodeling of the immune microenvironment in aldosterone-producing adenomas compared with paired adjacent adrenal cortical tissue. Our findings suggest metabolic alterations may function in the pathogenesis of aldosterone-producing adenomas by conferring survival advantages to their component tumor cells.

Abstract

Aldosterone-producing adenomas (APAs) are characterized by aldosterone hypersecretion and deregulated adrenocortical cell growth. Increased energy consumption required to maintain cellular tumorigenic properties triggers metabolic alterations that shape the tumor microenvironment to acquire necessary nutrients, yet our knowledge of this adaptation in APAs is limited. Here, we investigated adrenocortical cell-intrinsic metabolism and the tumor immune microenvironment of APAs and their potential roles in mediating aldosterone production and growth of adrenocortical cells. Using multiple advanced bioinformatics methods, we analyzed gene expression datasets to generate distinct metabolic and immune cell profiles of APAs versus paired adjacent cortex. APAs displayed activation of lipid metabolism, especially fatty acid β-oxidation regulated by PPARα, and glycolysis. We identified an immunosuppressive microenvironment in APAs, with reduced infiltration of CD45⁺ immune cells compared with adjacent cortex, validated by CD45 immunohistochemistry (3.45-fold, p < 0.001). APAs also displayed an association of lipid metabolism with ferroptosis and upregulation of antioxidant systems. In conclusion, APAs exhibit metabolic reprogramming towards fatty acid β-oxidation and glycolysis. Increased lipid metabolism via PPARα may serve as a key mechanism to modulate lipid peroxidation, a hallmark of regulated cell death by ferroptosis. These findings highlight survival advantages for APA tumor cells with metabolic reprogramming properties.

A de novo CACNA1D missense mutation in a patient with congenital hyperinsulinism, primary hyperaldosteronism and hypotonia

Congenital hyperinsulinemic hypoglycemia is the most frequent cause of persistent and recurrent hypoglycemia in the first years of life and in many patients rare genetic variants can be identified. Recently a case of congenital hyperinsulinemic hypoglycemia and a severe neurodevelopmental syndrome due to a mutation in the voltage-gated Cav1.3 Ca²⁺ channel CACNA1D gene has been reported which required long-term treatment with diazoxide. This suggested CACNA1D variants as a potential cause for this condition.

Here we support this observation by presenting the case of a female child with congential hyperinsulinemic hypoglycemia and primary hyperaldosteronism, aortic insufficiency, pronounced developmental delay, muscle hypotonia, and facial dysmorphias but without seizures. Sequencing of the exome of the child and its parents identified a novel de novo CACNA1D missense mutation p.L271 H, replacing a highly conserved residue in a functionally relevant region of the voltage-gated Cav1.3 Ca²⁺ channel. The patient was treated with diazoxide and nifedipine with adequate control of glucose metabolism and blood pressure, and with improvement in muscle tone.

Our findings further confirm the pathogenic role of CACNA1D for congentital hyperinsulinemic hypoglycemia and primary aldosteronism. Moreover, we provide evidence that the dihydropyridine Ca²⁺ channel blocker nifedipine, although not considered a first-line treatment for congenital hyperinsulinism, may be beneficial to control blood pressure and neurological symptoms in patients with CACNA1D mutations.

Early delivery and prolonged treatment with nimodipine prevents the development of spasticity after spinal cord injury in mice

Spasticity, one of the most frequent comorbidities of spinal cord injury (SCI), disrupts motor recovery and quality of life. Despite major progress in neurorehabilitative and pharmacological approaches, therapeutic strategies for treating spasticity are lacking. Here, we show in a mouse model of chronic SCI that treatment with nimodipine-an L-type calcium channel blocker already approved from the European Medicine Agency and from the U.S. Food and Drug Administration-starting in the acute phase of SCI completely prevents the development of spasticity measured as increased muscle tone and spontaneous spasms. The aberrant muscle activities associated with spasticity remain inhibited even after termination of the treatment. Constitutive and conditional silencing of the L-type calcium channel Ca_V1.3 in neuronal subtypes demonstrated that this channel mediated the preventive effect of nimodipine on spasticity after SCI. This study identifies a treatment protocol and suggests that targeting Ca_V1.3 could prevent spasticity after SCI.

GENETICS IN ENDOCRINOLOGY: Impact of race and sex on genetic causes of aldosterone-producing adenomas

Primary aldosteronism (PA) is a common cause of secondary hypertension. Recent technological advances in genetic analysis have provided a better understanding of the molecular pathogenesis of this disease. The application of next-generation sequencing has resulted in the identification of somatic mutations in aldosterone-producing adenoma (APA), a major subtype of PA. Based on the recent findings using a sequencing method that selectively targets the tumor region where aldosterone synthase (CYP11B2) is expressed, the vast majority of APAs appear to harbor a somatic mutation in one of the aldosterone-driver genes, including KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, and CLCN2. Mutations in these genes alter intracellular ion homeostasis and enhance aldosterone production. In a small subset of APAs, somatic activating mutations in the CTNNB1 gene, which encodes β-catenin, have also been detected. Accumulating evidence suggests that race and sex impact the somatic mutation spectrum of APA. Specifically, somatic mutations in the KCNJ5 gene, encoding an inwardly rectifying K+ channel, are common in APAs from Asian populations as well as women regardless of race. Associations between APA histology, genotype, and patient clinical characteristics have also been proposed, suggesting a potential need to consider race and sex for the management of PA patients. Herein, we review recent findings regarding somatic mutations in APA and discuss potential roles of race and sex on the pathophysiology of APA as well as possible clinical implications.

X-chromosome variants are associated with aldosterone producing adenomas

Aldosterone-producing adenomas (APAs) are a major cause of primary aldosteronism (PA) and are characterized by constitutively producing aldosterone, which leads to hypertension. Several mutations have been identified in ion channels or ion channel-associated genes that result in APAs. To date, no studies have used a genome-wide association study (GWAS) approach to search for predisposing loci for APAs. Thus, we investigated Scandinavian APA cases (n = 35) and Swedish controls (n = 60) in a GWAS and discovered a susceptibility locus on chromosome Xq13.3 (rs2224095, OR = 7.9, 95% CI = 2.8-22.4, P = 1 × 10^-7) in a 4-Mb region that was significantly associated with APA. Direct genotyping of sentinel SNP rs2224095 in a replication cohort of APAs (n = 83) and a control group (n = 740) revealed persistently strong significance (OR = 6.1, 95% CI = 3.5-10.6, p < 0.0005). We sequenced an adjacent gene, MAGEE1, of the sentinel SNP and identified a rare variant in one APA, p.Gly327Glu, which is complementary to other mutations in our primary cohort. Expression quantitative trait loci (eQTL) were investigated on the X-chromosome, and 24 trans-eQTL were identified. Some of the genes identified by trans-eQTL point towards a novel mechanistic explanation for the association of the SNPs with APAs. In conclusion, our study provides further insights into the genetic basis of APAs.

Taiwan mini-frontier of primary aldosteronism: Updating treatment and comorbidities detection

The aim of this study was to update the information on internationally acceptable standards and clinical practice recommendations for the management of patients with primary aldosteronism (PA). The Taiwan Society of Aldosteronism (TSA) Task Force acknowledged the novel issues of PA and reached a group consensus on PA in Taiwan by collecting the best available evidence and conducting one group meeting, several conference calls, and multiple e-mail communications. Unilateral adrenalectomy is the preferred treatment for patients with aldosterone-producing adenoma (APA). For medical treatment with mineralocorticoid receptor antagonists (MRAs), spironolactone is the first-line treatment, and eplerenone is a reasonable alternative in PA patients intolerant or contraindicated to spironolactone. The dose of MRAs can be titrated according to plasma renin activity (PRA). For screening PA-related comorbidities, we suggest albuminuria to predict a post-treatment decline in renal function, echocardiography as cardiac evaluation, bone mineral density scan for osteoporosis, and obstructive sleep apnea. In tissue and genetic surveys, we suggest immunohistochemical staining and somatic mutation screening for post-operative adrenal specimens in APA patients. With this consensus, we hope to update the information on PA for clinical physicians to facilitate better identification, management and treatment of patients with PA.

Enhanced Ca2+ signaling, mild primary aldosteronism, and hypertension in a familial hyperaldosteronism mouse model (Cacna1h M1560V/+ )

Primary aldosteronism (increased production of the adrenal steroid hormone aldosterone) is the most common cause of secondary hypertension. We here generated a mouse model of familial hyperaldosteronism type IV with a heterozygous gain-of-function mutation in a calcium channel gene (Cacna1h^M1560V/+). Cacna1h^M1560V/+ mice have about twofold elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism) and elevated blood pressure, with an overall mild phenotype. Elevated adrenal aldosterone synthase expression in Cacna1h^M1560V/+ mice is associated with increased intracellular calcium concentrations in glomerulosa cells. This model allows for the ex vivo analysis of calcium signaling in aldosterone-producing glomerulosa cells of the adrenal gland. Cacna1h^−/− mice have normal aldosterone synthase expression, with implications for the evaluation of CACNA1H as a therapeutic target.

Gain-of-function mutations in the CACNA1H gene (encoding the T-type calcium channel Ca_V3.2) cause autosomal-dominant familial hyperaldosteronism type IV (FH-IV) and early-onset hypertension in humans. We used CRISPR/Cas9 to generate Cacna1h^M1560V/+ knockin mice as a model of the most common FH-IV mutation, along with corresponding knockout mice (Cacna1h^−/−). Adrenal morphology of both Cacna1h^M1560V/+ and Cacna1h^−/− mice was normal. Cacna1h^M1560V/+ mice had elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism). Their adrenal Cyp11b2 (aldosterone synthase) expression was increased and remained elevated on a high-salt diet (relative autonomy, characteristic of primary aldosteronism), but plasma aldosterone was only elevated in male animals. The systolic blood pressure of Cacna1h^M1560V/+ mice was 8 mmHg higher than in wild-type littermates and remained elevated on a high-salt diet. Cacna1h^−/− mice had elevated renal Ren1 (renin-1) expression but normal adrenal Cyp11b2 levels, suggesting that in the absence of Ca_V3.2, stimulation of the renin-angiotensin system activates alternative calcium entry pathways to maintain normal aldosterone production. On a cellular level, Cacna1h^M1560V/+ adrenal slices showed increased baseline and peak intracellular calcium concentrations in the zona glomerulosa compared to controls, but the frequency of calcium spikes did not rise. We conclude that FH-IV, on a molecular level, is caused by elevated intracellular Ca²⁺ concentrations as a signal for aldosterone production in adrenal glomerulosa cells. We demonstrate that a germline Cacna1h gain-of-function mutation is sufficient to cause mild primary aldosteronism, whereas loss of Ca_V3.2 channel function can be compensated for in a chronic setting.

Update on Genetics of Primary Aldosteronism

Primary aldosteronism (PA) is the most common form of secondary hypertension, with a prevalence of 5–10% among patients with hypertension. PA is mainly classified into two subtypes: aldosterone-producing adenoma (APA) and bilateral idiopathic hyperaldosteronism. Recent developments in genetic analysis have facilitated the discovery of mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, CLCN2, and CTNNB1 in sporadic or familial forms of PA in the last decade. These findings have greatly advanced our understanding of the mechanism of excess aldosterone synthesis, particularly in APA. Most of the causative genes encode ion channels or pumps, and their mutations lead to depolarization of the cell membrane due to impairment of ion transport. Depolarization activates voltage-gated Ca²⁺ channels and intracellular calcium signaling and promotes the transcription of aldosterone synthase, resulting in overproduction of aldosterone. In this article, we review recent findings on the genetic and molecular mechanisms of PA.

The neurodevelopmental spectrum of synaptic vesicle cycling disorders

In this review, we describe and discuss neurodevelopmental phenotypes arising from rare, high penetrance genomic variants which directly influence synaptic vesicle cycling (SVC disorders). Pathogenic variants in each SVC disorder gene lead to disturbance of at least one SVC subprocess, namely vesicle trafficking (e.g. KIF1A and GDI1), clustering (e.g. TRIO, NRXN1 and SYN1), docking and priming (e.g. STXBP1), fusion (e.g. SYT1 and PRRT2) or re-uptake (e.g. DNM1, AP1S2 and TBC1D24). We observe that SVC disorders share a common set of neurological symptoms (movement disorders, epilepsies), cognitive impairments (developmental delay, intellectual disabilities, cerebral visual impairment) and mental health difficulties (autism, ADHD, psychiatric symptoms). On the other hand, there is notable phenotypic variation between and within disorders, which may reflect selective disruption to SVC subprocesses, spatiotemporal and cell-specific gene expression profiles, mutation-specific effects, or modifying factors. Understanding the common cellular and systems mechanisms underlying neurodevelopmental phenotypes in SVC disorders, and the factors responsible for variation in clinical presentations and outcomes, may translate to personalized clinical management and improved quality of life for patients and families.

BEX1 Is Differentially Expressed in Aldosterone-Producing Adenomas and Protects Human Adrenocortical Cells From Ferroptosis

[Figure: see text].

Molecular Genetic and Genomic Alterations in Cushing's Syndrome and Primary Aldosteronism

The genetic alterations that cause the development of glucocorticoid and/or mineralocorticoid producing benign adrenocortical tumors and hyperplasias have largely been elucidated over the past two decades through advances in genomics. In benign aldosterone-producing adrenocortical tumors and hyperplasias, alteration of intracellular calcium signaling has been found to be significant in aldosterone hypersecretion, with causative defects including those in KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, and CLCN2. In benign cortisol-producing adrenocortical tumors and hyperplasias abnormal cyclic adenosine monophosphate-protein kinase A signaling has been found to play a central role in tumorigenesis, with pathogenic variants in GNAS, PRKAR1A, PRKACA, PRKACB, PDE11A, and PDE8B being implicated. The role of this signaling pathway in the development of Cushing's syndrome and adrenocortical tumors was initially discovered through the study of the underlying genetic defects causing the rare multiple endocrine neoplasia syndromes McCune-Albright syndrome and Carney complex with subsequent identification of defects in genes affecting the cyclic adenosine monophosphate-protein kinase A pathway in sporadic tumors. Additionally, germline pathogenic variants in ARMC5, a putative tumor suppressor, were found to be a cause of cortisol-producing primary bilateral macronodular adrenal hyperplasia. This review describes the genetic causes of benign cortisol- and aldosterone-producing adrenocortical tumors.

Unravelling the Genetic Basis of Primary Aldosteronism

Primary aldosteronism (PA), a condition characterized by autonomous aldosterone hypersecretion, constitutes the most common cause of secondary hypertension. Over the last decade, major breakthroughs have been made in the field of genetics underpinning PA. The advent and wide application of Next Generation Sequencing (NGS) technology led to the identification of several somatic and germline mutations associated with sporadic and familial forms of PA. Somatic mutations in ion-channel genes that participate in aldosterone biosynthesis, including KCNJ5, CACNA1D, ATP1A1, and ATP2B3, have been implicated in the development of aldosterone-producing adenomas (APAs). On the other hand, germline variants in CLCN2, KCNJ5, CACNA1H, and CACNA1D genes have been implicated in the pathogenesis of the familial forms of PA, FH-II, FH-III, and F-IV, as well as PA associated with seizures and neurological abnormalities. However, recent studies have shown that the prevalence of PA is higher than previously thought, indicating the need for an improvement of our diagnostic tools. Further research is required to recognize mild forms of PA and to investigate the underlying molecular mechanisms.

Voltage-Gated Ca2+-Channel α1-Subunit de novo Missense Mutations: Gain or Loss of Function - Implications for Potential Therapies

This review summarizes our current knowledge of human disease-relevant genetic variants within the family of voltage gated Ca2+ channels. Ca2+ channelopathies cover a wide spectrum of diseases including epilepsies, autism spectrum disorders, intellectual disabilities, developmental delay, cerebellar ataxias and degeneration, severe cardiac arrhythmias, sudden cardiac death, eye disease and endocrine disorders such as congential hyperinsulinism and hyperaldosteronism. A special focus will be on the rapidly increasing number of de novo missense mutations identified in the pore-forming α1-subunits with next generation sequencing studies of well-defined patient cohorts. In contrast to likely gene disrupting mutations these can not only cause a channel loss-of-function but can also induce typical functional changes permitting enhanced channel activity and Ca2+ signaling. Such gain-of-function mutations could represent therapeutic targets for mutation-specific therapy of Ca2+-channelopathies with existing or novel Ca2+-channel inhibitors. Moreover, many pathogenic mutations affect positive charges in the voltage sensors with the potential to form gating-pore currents through voltage sensors. If confirmed in functional studies, specific blockers of gating-pore currents could also be of therapeutic interest.

What Did We Learn from the Molecular Biology of Adrenal Cortical Neoplasia? From Histopathology to Translational Genomics

Approximately one-tenth of the general population exhibit adrenal cortical nodules, and the incidence has increased. Afflicted patients display a multifaceted symptomatology-sometimes with rather spectacular features. Given the general infrequency as well as the specific clinical, histological, and molecular considerations characterizing these lesions, adrenal cortical tumors should be investigated by endocrine pathologists in high-volume tertiary centers. Even so, to distinguish specific forms of benign adrenal cortical lesions as well as to pinpoint malignant cases with the highest risk of poor outcome is often challenging using conventional histology alone, and molecular genetics and translational biomarkers are therefore gaining increased attention as a possible discriminator in this context. In general, our understanding of adrenal cortical tumorigenesis has increased tremendously the last decade, not least due to the development of next-generation sequencing techniques. Comprehensive analyses have helped establish the link between benign aldosterone-producing adrenal cortical proliferations and ion channel mutations, as well as mutations in the protein kinase A (PKA) signaling pathway coupled to cortisol-producing adrenal cortical lesions. Moreover, molecular classifications of adrenal cortical tumors have facilitated the distinction of benign from malignant forms, as well as the prognostication of the individual patients with verified adrenal cortical carcinoma, enabling high-resolution diagnostics that is not entirely possible by histology alone. Therefore, combinations of histology, immunohistochemistry, and next-generation multi-omic analyses are all needed in an integrated fashion to properly distinguish malignancy in some cases. Despite significant progress made in the field, current clinical and pathological challenges include the preoperative distinction of non-metastatic low-grade adrenal cortical carcinoma confined to the adrenal gland, adoption of individualized therapeutic algorithms aligned with molecular and histopathologic risk stratification tools, and histological confirmation of functional adrenal cortical disease in the context of multifocal adrenal cortical proliferations. We herein review the histological, genetic, and epigenetic landscapes of benign and malignant adrenal cortical neoplasia from a modern surgical endocrine pathology perspective and highlight key mechanisms of value for diagnostic and prognostic purposes.

[Hyperaldosteronism]

Aldosterone is produced in the adrenal cortex and governs volume and electrolyte homeostasis. Hyperaldosteronism can occur either as primary aldosteronism (renin-independent) or secondary aldosteronism (renin-dependent). As the commonest cause of secondary hypertension, primary aldosteronism is associated with increased cardiovascular risk. Its most prevalent subtypes are aldosterone-producing adenomas as the most frequent unilateral form and bilateral hyperaldosteronism. Unilateral hyperplasia, familial hyperaldosteronism and aldosterone-producing carcinoma are rare. The aldosterone/renin ratio serves as a screening parameter for primary aldosteronism. If this ratio is elevated, confirmatory testing and adrenal imaging are performed. Adrenal venous sampling is considered the gold standard for the distinction of unilateral from bilateral disease. Unilateral disease can potentially be cured by adrenalectomy, whereas patients that are not candidates for surgery or have bilateral disease are treated with mineralocorticoid receptor antagonists. Over the past 10 years, somatic mutations in ion channels or transporters have been identified as causes of aldosterone-producing adenomas and so-called aldosterone-producing cell clusters (potential precursors of adenomas and correlates of bilateral hyperplasia, but also of subclinical hyperaldosteronism). In addition, germline mutations in overlapping genes cause familial hyperaldosteronism. Secondary hyperaldosteronism can occur in patients with hypertension treated with diuretics or in renal artery stenosis.

Zebrafish Larvae Carrying a Splice Variant Mutation in cacna1d: A New Model for Schizophrenia-Like Behaviours?

Persons with certain single nucleotide polymorphisms (SNPs) in the CACNA1D gene (encoding voltage-gated calcium channel subunit alpha 1-D) have increased risk of developing neuropsychiatric disorders such as bipolar, schizophrenia and autism. The molecular consequences of SNPs on gene expression and protein function are not well understood. Thus, the use of animal models to determine genotype-phenotype correlations is critical to understanding disease pathogenesis. Here, we describe the behavioural changes in larval zebrafish carrying an essential splice site mutation (sa17298) in cacna1da. Heterozygous mutation resulted in 50% reduction of splice variants 201 and 202 (haploinsufficiency), while homozygosity increased transcript levels of variant 201 above wild type (WT; gain-of-function, GOF). Due to low homozygote viability, we focused primarily on performing the phenotypic analysis on heterozygotes. Indeed, cacna1dasa17298/WT larvae displayed hyperlocomotion-a behaviour characterised in zebrafish as a surrogate phenotype for epilepsy, anxiety or psychosis-like behaviour. Follow-up tests ruled out anxiety or seizures, however, as neither thigmotaxis defects nor epileptiform-like discharges in larval brains were observed. We therefore focused on testing for potential "psychosis-like" behaviour by assaying cacna1dasa17298/WT larval locomotor activity under constant light, during light-dark transition and in startle response to dark flashes. Furthermore, exposure of larvae to the antipsychotics, risperidone and haloperidol reversed cacna1da-induced hyperactivity to WT levels while valproate decreased but did not reverse hyperactivity. Together, these findings demonstrate that cacna1da haploinsufficiency induces behaviours in larval zebrafish analogous to those observed in rodent models of psychosis. Future studies on homozygous mutants will determine how cacna1d GOF alters behaviour in this context.

The Genotype-Based Morphology of Aldosterone-Producing Adrenocortical Disorders and Their Association with Aging

Primary aldosteronism (PA) is the most common cause of secondary hypertension, and is associated with an increased incidence of cardiovascular events. PA itself is clinically classified into the following two types: unilateral PA, mostly composed of aldosteroneproducing adenoma (APA); and bilateral hyperaldosteronism, consisting of multiple aldosterone-producing micronodules (APMs) and aldosterone-producing diffuse hyperplasia. Histopathologically, those disorders above are all composed of compact and clear cells. The cellular morphology in the above-mentioned aldosterone-producing disorders has been recently reported to be closely correlated with patterns of somatic mutations of ion channels including KCNJ5, CACNA1D, ATP1A1, ATP2B3, and others. In addition, in non-pathological adrenal glands, APMs are frequently detected regardless of the status of the renin-angiotensin-aldosterone system (RAAS). Aldosterone-producing nodules have been also proposed as non-neoplastic nodules that can be identified by hematoxylin and eosin staining. These non-neoplastic CYP11B2-positive nodules could represent possible precursors of APAs possibly due to the presence of somatic mutations. On the other hand, aging itself also plays a pivotal role in the development of aldosterone-producing lesions. For instance, the number of APMs was also reported to increase with aging. Therefore, recent studies indicated the novel classification of PA into normotensive PA (RAAS-independent APM) and clinically overt PA.

A Review of Genetic and Physiological Disease Mechanisms Associated With Cav1 Channels: Implications for Incomplete Congenital Stationary Night Blindness Treatment

Calcium channels are crucial to a number of cellular functions. The high voltage-gated calcium channel family comprise four heteromeric channels (Cav1.1-1.4) that function in a similar manner, but that have distinct expression profiles. Three of the pore-forming α₁ subunits are located on autosomes and the forth on the X chromosome, which has consequences for the type of pathogenic mutation and the disease mechanism associated with each gene. Mutations in this family of channels are associated with malignant hyperthermia (Cav1.1), various QT syndromes (Cav1.2), deafness (Cav1.3), and incomplete congenital stationary night blindness (iCSNB; Cav1.4). In this study we performed a bioinformatic analysis on reported mutations in all four Cav α₁ subunits and correlated these with variant frequency in the general population, phenotype and the effect on channel conductance to produce a comprehensive composite Cav1 mutation analysis. We describe regions of mutation clustering, identify conserved residues that are mutated in multiple family members and regions likely to cause a loss- or gain-of-function in Cav1.4. Our research highlights that therapeutic treatments for each of the Cav1 channels will have to consider channel-specific mechanisms, especially for the treatment of X-linked iCSNB.

KCNJ5 Mutation Contributes to Complete Clinical Success in Aldosterone-Producing Adenoma: A Study From a Single Center

OBJECTIVE

The KCNJ5 mutation is the most frequent mutation in aldosterone-producing adenoma (APA). We aimed to illustrate the relationship between KCNJ5 and prognosis after adrenalectomy as a guide for further treatment.

METHODS

Our study included 458 patients with APA. Tumor tissues were screened for somatic mutations in KCNJ5 hot-spot regions. We performed a retrospective analysis to identify correlations between KCNJ5 and clinical outcomes in 334 patients with adrenal venous sampling lateralization.

RESULTS

Somatic KCNJ5 mutations were identified in 324 of 458 patients with APA (70.7%). Compared with the KCNJ5-wild type patients, patients with KCNJ5 mutations were younger, had a higher proportion of women, and had shorter durations of hypertension, lower body mass indexes (BMIs), and lower systolic blood pressure values (P < .05). During follow-up, among the 334 patients with APA with adrenal venous sampling lateralization, 320 (95.8%) presented complete biochemical success and 187 (56.0%) presented complete clinical success. One hundred eighty-seven patients with primary aldosteronism who achieved complete clinical success presented the following characteristics: age <40 years (78.7%), BMI <24 kg/m² (71.0%), hypertension duration <5 years (78.4%), females (66.9%), and KCNJ5 mutation (65.5%). A multivariate logistic regression analysis identified BMI, hypertension duration, and KCNJ5 mutation as independent predictors of complete clinical success.

CONCLUSION

The prevalence of KCNJ5 mutations was 70.7%. KCNJ5 mutation is a protective factor of complete clinical success, while BMI and hypertension duration were risk factors of incomplete clinical success.

Trigeminal Neuralgia TRPM8 Mutation: Enhanced Activation, Basal [Ca2+]i and Menthol Response

Objective

To assess the functional effects of a variant, c.89 G > A (p.Arg30Gln), in the transient receptor potential melastatin 8 (TRPM8) cold-sensing, nonselective cation channel, which we have previously identified in a patient with familial trigeminal neuralgia.

Methods

We carried out Ca²⁺ imaging and whole-cell patch-clamp recording.

Results

The TRPM8 mutation enhances channel activation, increases basal current amplitude and intracellular [Ca²⁺] in cells carrying the mutant channel, and enhances the response to menthol.

Conclusions

We propose that Arg30Gln confers gain-of-function attributes on TRPM8, which contribute to pathogenesis of trigeminal neuralgia in patients carrying this mutation.

The establishment of a novel high-throughput screening system using RNA-guided genome editing to identify chemicals that suppress aldosterone synthase expression

Aldosterone is synthesized in the adrenal by the aldosterone synthase CYP11B2. Although the control of CYP11B2 expression is important to maintain the mineral homeostasis, its overexpression induced by the depolarization-induced calcium (Ca2+) signaling activation has been reported to increase the synthesis of aldosterone in primary aldosteronism (PA). The drug against PA focused on the suppression of CYP11B2 expression has not yet been developed, since the molecular mechanism of CYP11B2 transcriptional regulation activated via Ca2+ signaling remains unclear. To address the issue, we attempted to reveal the mechanism of the transcriptional regulation of CYP11B2 using chemical screening. We generated a cell line by inserting Nanoluc gene as a reporter into CYP11B2 locus in H295R adrenocortical cells using the CRSPR/Cas9 system, and established the high-throughput screening system using the cell line. We then identified 9 compounds that inhibited the CYP11B2 expression induced by potassium-mediated depolarization from the validated compound library (3399 compounds). Particularly, tacrolimus, an inhibitor of phosphatase calcineurin, strongly suppressed the CYP11B2 expression even at 10 nM. These results suggest that the system is effective in identifying drugs that suppress the depolarization-induced CYP11B2 expression. Our screening system may therefore be a useful tool for the development of novel medicines against PA.

Functional Characteristic and Significance of Aldosterone-Producing Cell Clusters in Primary Aldosteronism and Age-Related Hypertension

Primary aldosteronism (PA) is one of the most frequent curable forms of secondary hypertension. It can be caused by the overproduction of aldosterone in one or both adrenal glands. The most common subtypes of PA are unilateral aldosterone over-production due to aldosterone-producing adenomas (APA) or bilateral aldosterone over-production due to bilateral hyperaldosteronism (BHA). Utilizing the immunohistochemical (IHC) detection of aldosterone synthase (CYP11B2) has allowed the identification of aldosterone-producing cell clusters (APCCs) with unique focal localization positive for CYP11B2 expression in the subcapsular portion of the human adult adrenal cortex. The presence of CYP11B2 supports that synthesis of aldosterone can occur in these cell clusters and therefore might contribute to hyperaldosteronism. However, the significance of the steroidogenic properties of APCCs especially in regards to PA remains unclear. Herein, we review the available evidence on the presence of APCCs in normal adrenals and adrenal tissues adjacent to APAs, their aldosterone-stimulating somatic gene mutations, and their accumulation during the ageing process; raising the possibility that APCCs may play a role in the development of PA and age-related hypertension.

Approaches to Gene Mutation Analysis Using Formalin-Fixed Paraffin-Embedded Adrenal Tumor Tissue From Patients With Primary Aldosteronism

Aldosterone production is physiologically under the control of circulating potassium and angiotensin II as well as adrenocorticotropic hormone and other secretagogues such as serotonin. The adrenal's capacity to produce aldosterone relies heavily on the expression of a single enzyme, aldosterone synthase (CYP11B2). This enzyme carries out the final reactions in the synthesis of aldosterone and is expressed almost solely in the adrenal zona glomerulosa. From a disease standpoint, primary aldosteronism (PA) is the most common of all adrenal disorders. PA results from renin-independent adrenal expression of CYP11B2 and production of aldosterone. The major causes of PA are adrenal aldosterone-producing adenomas (APA) and adrenal idiopathic hyperaldosteronism. Our understanding of the genetic causes of APA has significantly improved through comprehensive genetic profiling with next-generation sequencing. Whole-exome sequencing has led to the discovery of mutations in six genes that cause renin-independent aldosterone production and thus PA. To facilitate broad-based prospective and retrospective studies of APA, recent technologic advancements have allowed the determination of tumor mutation status using formalin-fixed paraffin-embedded (FFPE) tissue sections. This approach has the advantages of providing ready access to archival samples and allowing CYP11B2 immunohistochemistry-guided capture of the exact tissue responsible for inappropriate aldosterone synthesis. Herein we review the methods and approaches that facilitate the use of adrenal FFPE material for DNA capture, sequencing, and mutation determination.

Confirmatory testing of primary aldosteronism with saline infusion test and LC-MS/MS

OBJECTIVE

Saline infusion testing (SIT) for confirmation of primary aldosteronism (PA) is based on impaired aldosterone suppression in PA compared to essential hypertension (EH). In the past, aldosterone was quantified using immunoassays (IA). Liquid chromatography tandem mass spectrometry (LC-MS/MS) is increasingly used in clinical routine. We aimed at a method-specific aldosterone threshold for the diagnosis of PA during SIT and explored the diagnostic utility of steroid panel analysis.

DESIGN

Retrospective cohort study of 187 paired SIT samples (2009-2018). Diagnosis of PA (n = 103) and EH (n = 84) was established based on clinical routine workup without using LC-MS/MS values.

SETTING

Tertiary care center.

METHODS

LC-MS/MS using a commercial steroid panel. Receiver operator characteristics analysis was used to determine method-specific cut-offs using a positive predictive value (PPV) of 90% as criterion.

RESULTS

Aldosterone measured by IA was on average 31 ng/L higher than with LC-MS/MS. The cut-offs for PA confirmation were 54 ng/L for IA (sensitivity: 95%, 95% CI: 89.0-98.4; specificity: 87%, 95% CI: 77.8-93.3; area under the curve (AUC): 0.955, 95% CI: 0.924-0.986; PPV: 90%, 95% CI: 83.7-93.9) and 69 ng/L for LC-MS/MS (79%, 95% CI: 69.5-86.1; 89%, 95% CI: 80.6-95.0; 0.902, 95% CI: 0.857-0.947; 90%, 95% CI: 82.8-94.4). Other steroids did not improve SIT.

CONCLUSIONS

Aldosterone quantification with LC-MS/MS and IA yields comparable SIT-cut-offs. Lower AUC for LC-MS/MS is likely due to the spectrum of disease in PA and previous decision making based on IA results. Until data of a prospective trial with clinical endpoints are available, the suggested cut-off can be used in clinical routine.

Aldosterone is Aberrantly Regulated by Various Stimuli in a High Proportion of Patients with Primary Aldosteronism

CONTEXT

In primary aldosteronism (PA), aldosterone secretion is relatively independent of the renin-angiotensin system, but can be regulated by several other stimuli.

OBJECTIVE

To evaluate aldosterone response to several stimuli in a series of patients with PA secondary either to bilateral adrenal hyperplasia (BAH) or unilateral aldosterone-producing adenoma (APA).

DESIGN AND SETTING

Prospective cohort study conducted in a university teaching hospital research center.

PATIENTS

Forty-three patients with confirmed PA and subtyped by adrenal vein sampling (n = 39) were studied, including 11 with BAH, 28 with APA, and 4 with undefined etiology. We also studied 4 other patients with aldosterone and cortisol cosecretion.

INTERVENTIONS

We systematically explored aberrant regulation of aldosterone using an in vivo protocol that included the following stimulation tests performed over 3 days under dexamethasone suppression: upright posture, mixed meal, adrenocorticotropin (ACTH) 1-24, gonadotropin-releasing hormone (GnRH), vasopressin, and serotonin R4 agonist.

MAIN OUTCOME MEASURES

Positive response was defined as >50% renin or ACTH-independent increase in plasma aldosterone/cortisol concentration following the various stimulation tests.

RESULTS

Renin-independent aldosterone secretion increased in response to several aberrant stimuli (upright posture, GnRH) in up to 83% of patients with APA or BAH in whom ACTH 1-24 and HT4R agonists also produced aldosterone oversecretion in all patients. The mean significant aberrant responses per patient was similar in BAH (4.6) and in APA (4.0).

CONCLUSIONS

Aldosterone secretion in PA is relatively autonomous from the renin-angiotensin system, but is highly regulated by several other stimuli, which contributes to the large variability of aldosterone levels in PA patients.

Phosphodiesterase 2A and 3B variants are associated with primary aldosteronism

Familial primary aldosteronism (PA) is rare and mostly diagnosed in early-onset hypertension (HT). However, 'sporadic' bilateral adrenal hyperplasia (BAH) is the most frequent cause of PA and remains without genetic etiology in most cases. Our aim was to investigate new genetic defects associated with BAH and PA. We performed whole-exome sequencing (paired blood and adrenal tissue) in six patients with PA caused by BAH that underwent unilateral adrenalectomy. Additionally, we conducted functional studies in adrenal hyperplastic tissue and transfected cells to confirm the pathogenicity of the identified genetic variants. Rare germline variants in phosphodiesterase 2A (PDE2A) and 3B (PDE3B) genes were identified in three patients. The PDE2A heterozygous variant (p.Ile629Val) was identified in a patient with BAH and early-onset HT at 13 years of age. Two PDE3B heterozygous variants (p.Arg217Gln and p.Gly392Val) were identified in patients with BAH and HT diagnosed at 18 and 33 years of age, respectively. A strong PDE2A staining was found in all cases of BAH in zona glomerulosa and/or micronodules (that were also positive for CYP11B2). PKA activity in frozen tissue was significantly higher in BAH from patients harboring PDE2A and PDE3B variants. PDE2A and PDE3B variants significantly reduced protein expression in mutant transfected cells compared to WT. Interestingly, PDE2A and PDE3B variants increased SGK1 and SCNN1G/ENaCg at mRNA or protein levels. In conclusion, PDE2A and PDE3B variants were associated with PA caused by BAH. These novel genetic findings expand the spectrum of genetic etiologies of PA.

Aldosterone-Regulating Receptors and Aldosterone-Driver Somatic Mutations

BACKGROUND

Somatic gene mutations that facilitate inappropriate intracellular calcium entrance have been identified in most aldosterone-producing adenomas (APAs). Studies suggest that angiotensin II and adrenocorticotropic hormone (ACTH) augment aldosterone production from APAs. Little is known, however, regarding possible variations in response to hormonal stimuli between APAs with different aldosterone-driver mutations.

OBJECTIVE

To analyze the transcript expression of type 1 angiotensin II receptors (AGTR1), ACTH receptors (MC2R), and melanocortin 2 receptor accessory protein (MRAP) in APAs with known aldosterone-driver somatic mutations.

METHODS

RNA was isolated from APAs with mutations in: KCNJ5 (n = 14), ATP1A1 (n = 14), CACNA1D (n = 14), and ATP2B3 (n = 5), and from normal adjacent adrenal tissue (n = 45). Transcript expression of MC2R, MRAP, AGTR1, aldosterone synthase (CYP11B2), 17α-hydroxylase/17,20-lyase (CYP17A1), and 11β-hydroxylase (CYP11B1) were quantified using quantitative RT-PCR and normalized to β-actin.

RESULTS

Compared to adjacent normal adrenal tissue, APAs had higher transcript levels of CYP11B2 (2,216.4 [1,112.0, 2,813.5]-fold, p < 0.001), MC2R (2.88 [2.00, 4.52]-fold, p < 0.001), and AGTR1 (1.80 [1.02, 2.80]-fold, p < 0.001]), and lower transcript levels of MRAP, CYP17A1, and CYP11B1 (0.28-0.36, p < 0.001 for all). MC2R and CYP11B2 transcripts were lower in APAs with KCNJ5 vs. other mutations (p < 0.01 for both). MC2R expression correlated positively with that of AGTR1 in APAs harboring KCNJ5 and CACNA1D mutations, and with MRAP expression in APAs harboring ATPase mutations.

CONCLUSIONS

While MC2R and AGTR1 are expressed in all APAs, differences were observed based on the underlying aldosterone-driver somatic mutations. In tandem, our findings suggest that APAs with ATPase-mutations are more responsive to ACTH than KCNJ5-mutated APAs.