Targeted Disruption of YAP and TAZ Impairs the Maintenance of the Adrenal Cortex

Transgenic Mouse Models to Study the Development and Maintenance of the Adrenal Cortex

The cortex of the adrenal gland is organized into concentric zones that produce distinct steroid hormones essential for body homeostasis in mammals. Mechanisms leading to the development, zonation and maintenance of the adrenal cortex are complex and have been studied since the 1800s. However, the advent of genetic manipulation and transgenic mouse models over the past 30 years has revolutionized our understanding of these mechanisms. This review lists and details the distinct Cre recombinase mouse strains available to study the adrenal cortex, and the remarkable progress total and conditional knockout mouse models have enabled us to make in our understanding of the molecular mechanisms regulating the development and maintenance of the adrenal cortex.

Genetic determinants of chromatin reveal prostate cancer risk mediated by context-dependent gene regulation

Many genetic variants affect disease risk by altering context-dependent gene regulation. Such variants are difficult to study mechanistically using current methods that link genetic variation to steady-state gene expression levels, such as expression quantitative trait loci (eQTLs). To address this challenge, we developed the cistrome-wide association study (CWAS), a framework for identifying genotypic and allele-specific effects on chromatin that are also associated with disease. In prostate cancer, CWAS identified regulatory elements and androgen receptor-binding sites that explained the association at 52 of 98 known prostate cancer risk loci and discovered 17 additional risk loci. CWAS implicated key developmental transcription factors in prostate cancer risk that are overlooked by eQTL-based approaches due to context-dependent gene regulation. We experimentally validated associations and demonstrated the extensibility of CWAS to additional epigenomic datasets and phenotypes, including response to prostate cancer treatment. CWAS is a powerful and biologically interpretable paradigm for studying variants that influence traits by affecting transcriptional regulation.

The YAP/TAZ Signaling Pathway in the Tumor Microenvironment and Carcinogenesis: Current Knowledge and Therapeutic Promises

The yes-associated protein (YAP) and the transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional coactivators, members of the Hippo signaling pathway, which play a critical role in cell growth regulation, embryonic development, regeneration, proliferation, and cancer origin and progression. The mechanism involves the nuclear binding of the un-phosphorylated YAP/TAZ complex to release the transcriptional enhanced associate domain (TEAD) from its repressors. The active ternary complex is responsible for the aforementioned biological effects. Overexpression of YAP/TAZ has been reported in cancer stem cells and tumor resistance. The resistance involves chemotherapy, targeted therapy, and immunotherapy. This review provides an overview of YAP/TAZ pathways’ role in carcinogenesis and tumor microenvironment. Potential therapeutic alternatives are also discussed.

[Adrenal glands stem cells: general signaling pathways]

 Nowadays stem cells of adult type are attractive in case of active development of cell and genome technologies. They are the target of new therapeutic approaches, which are based on correction of mutations or replenishment of organs, that were damaged by autoimmune reactions, aging or other pathological processes. Also stem cells, including patient-specific (induced Pluripotent Stem Cells, iPSCs), and obtained by differentiation from them tissue cultures and organoids are the closest models to in vivo researches on humans, which gives an opportunity to get more relevant data while testing different therapeutic approaches and pharmacological drugs. The main molecular pathways, that are essential for homeostasis of a cortex of a adrenal gland - compound, structurally and functionally heterogeneous organ, is described the presented review. The adrenal cortex is renewing during the organism's ontogenesis at the expense of the pool of stem and progenitors cells, which are in tight junctions with differentiated steroidogenic cells and which are under constant control of endocrine and paracrine signals. The understanding of signaling pathways and interactions of different cell types will give an opportunity to develop the most suitable protocols for obtaining cells of adrenal gland cortex in a different stages of differentiation to use them in scientific and medical purposes.

Adrenal Cortex Development and Maintenance: Knowledge Acquired From Mouse Models

The adrenal cortex is an endocrine organ organized into concentric zones that are specialized to produce specific steroid hormones essential for life. The development and maintenance of the adrenal cortex are complex, as a fetal adrenal is first formed from a common primordium with the gonads, followed by its separation in a distinct primordium, the invasion of the adrenal primordium by neural crest-derived cells to form the medulla, and finally its encapsulation. The fetal cortex is then replaced by a definitive cortex, which will establish zonation and be maintained throughout life by regeneration relying on the proliferation, centripetal migration, and differentiation of several stem/progenitor cell populations whose activities are sex-specific. Here, we highlight the advances made, using transgenic mouse models, to delineate the molecular mechanisms regulating these processes.

Adrenal cortex renewal in health and disease

Resident progenitor and/or stem cell populations in the adult adrenal cortex enable cortical cells to undergo homeostatic renewal and regeneration after injury. Renewal occurs predominantly in the outer layers of the adrenal gland but newly formed cells undergo centripetal migration, differentiation and lineage conversion in the process of forming the different functional steroidogenic zones. Over the past 10 years, advances in the genetic characterization of adrenal diseases and studies of mouse models with altered adrenal phenotypes have helped to elucidate the molecular pathways that regulate adrenal tissue renewal, several of which are fine-tuned via complex paracrine and endocrine influences. Moreover, the adrenal gland is a sexually dimorphic organ, and testicular androgens have inhibitory effects on cell proliferation and progenitor cell recruitment in the adrenal cortex. This Review integrates these advances, including the emerging role of sex hormones, into existing knowledge on adrenocortical cell renewal. An in-depth understanding of these mechanisms is expected to contribute to the development of novel therapies for severe endocrine diseases, for which current treatments are unsatisfactory.

The Sexually Dimorphic Adrenal Cortex: Implications for Adrenal Disease

Many adrenocortical diseases are more prevalent in women than in men, but the reasons underlying this sex bias are still unknown. Recent studies involving gonadectomy and sex hormone replacement experiments in mice have shed some light onto the molecular basis of sexual dimorphism in the adrenal cortex. Indeed, it has been shown that gonadal hormones influence many aspects of adrenal physiology, ranging from stem cell-dependent tissue turnover to steroidogenesis and X-zone dynamics. This article reviews current knowledge on adrenal cortex sexual dimorphism and the potential mechanisms underlying sex hormone influence of adrenal homeostasis. Both topics are expected to contribute to personalized and novel therapeutic approaches in the future.

Targeted Disruption of Lats1 and Lats2 in Mice Impairs Adrenal Cortex Development and Alters Adrenocortical Cell Fate

It has recently been shown that the loss of the Hippo signaling effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in adrenocortical steroidogenic cells impairs the postnatal maintenance of the adrenal gland. To further explore the role of Hippo signaling in mouse adrenocortical cells, we conditionally deleted the key Hippo kinases large tumor suppressor homolog kinases 1 and -2 (Lats1 and Lats2, two kinases that antagonize YAP and TAZ transcriptional co-regulatory activity) in steroidogenic cells using an Nr5a1-cre strain (Lats1flox/flox;Lats2flox/flox;Nr5a1-cre). We report here that developing adrenocortical cells adopt characteristics of myofibroblasts in both male and female Lats1flox/flox;Lats2flox/flox;Nr5a1-cre mice, resulting in a loss of steroidogenic gene expression, adrenal failure and death by 2 to 3 weeks of age. A marked accumulation of YAP and TAZ in the nuclei of the myofibroblast-like cell population with an accompanying increase in the expression of their transcriptional target genes in the adrenal glands of Lats1flox/flox;Lats2flox/flox;Nr5a1-cre animals suggested that the myofibroblastic differentiation could be attributed in part to YAP and TAZ. Taken together, our results suggest that Hippo signaling is required to maintain proper adrenocortical cell differentiation and suppresses their differentiation into myofibroblast-like cells.

Retinoic acid receptor α as a novel contributor to adrenal cortex structure and function through interactions with Wnt and Vegfa signalling

Primary aldosteronism (PA) is the most frequent form of secondary arterial hypertension. Mutations in different genes increase aldosterone production in PA, but additional mechanisms may contribute to increased cell proliferation and aldosterone producing adenoma (APA) development. We performed transcriptome analysis in APA and identified retinoic acid receptor alpha (RARα) signaling as a central molecular network involved in nodule formation. To understand how RARα modulates adrenal structure and function, we explored the adrenal phenotype of male and female Rarα knockout mice. Inactivation of Rarα in mice led to significant structural disorganization of the adrenal cortex in both sexes, with increased adrenal cortex size in female mice and increased cell proliferation in males. Abnormalities of vessel architecture and extracellular matrix were due to decreased Vegfa expression and modifications in extracellular matrix components. On the molecular level, Rarα inactivation leads to inhibition of non-canonical Wnt signaling, without affecting the canonical Wnt pathway nor PKA signaling. Our study suggests that Rarα contributes to the maintenance of normal adrenal cortex structure and cell proliferation, by modulating Wnt signaling. Dysregulation of this interaction may contribute to abnormal cell proliferation, creating a propitious environment for the emergence of specific driver mutations in PA.

Regulation of stem and progenitor cells in the adrenal cortex

The adrenal cortex is an endocrine organ comprised of three histological zones, the outermost zona glomerulosa, the intermediate zona fasciculata, and the innermost zona reticularis. High plasticity of the adrenal gland is supported by pools of stem and progenitor cells that are deployed to sustain physiological and homeostatic demands. In recent decades, exciting new discoveries elucidating the identity, function, and fate of these cell populations have emerged. In this review, we describe paracrine and endocrine signaling loops that are crucial for adrenal biology, focusing on recent studies unpacking the enigmatic nature of adrenal stem and progenitor cell populations.

Immunofluorescence Microscopy to Study Endogenous TAZ in Mammalian Cells

The transcriptional coactivator with PDZ-binding motif (TAZ), which is encoded by the WWTR1 gene, is a key transcriptional effector of the Hippo signaling pathway. TAZ function has been implicated in a variety of developmental processes and diseases, most notably in driving oncogenesis. Given that nuclear-cytoplasmic localization dynamics dictate TAZ activity, techniques for visualizing TAZ localization are critical for its study. Here we describe an immunofluorescence microscopy protocol that allows for the visualization of TAZ subcellular localization in mammalian cells, offering an approach that can aid in the analysis of TAZ regulation and function.

The Adult Adrenal Cortex Undergoes Rapid Tissue Renewal in a Sex-Specific Manner

Evolution has resulted in profound differences between males and females that extend to non-reproductive organs and are reflected in the susceptibility and progression of diseases. However, the cellular and molecular basis for these differences remains largely unknown. Here we report that adrenal gland tissue renewal is highly active and sexually dimorphic, with female mice showing a 3-fold higher turnover than males. Moreover, in males, homeostasis relies on proliferation of cells within the steroidogenic zone, but females employ an additional stem and/or progenitor compartment situated in the adrenal capsule. Using lineage tracing, sex reversal models, gonadectomy, and dihydrotestosterone treatments, we further show that sex-specific stem cell activity is driven by male hormones that repress recruitment of Gli1⁺ stem cells from the capsule and cell proliferation. Taken together, our findings provide a molecular and cellular basis for adrenal sex dimorphism that may contribute to the increased incidence of adrenal diseases in females.

The transient cortical zone in the adrenal gland: the mystery of the adrenal X-zone

The X-zone is a transient cortical region enriched in eosinophilic cells located in the cortical-medullary boundary of the mouse adrenal gland. Similar to the X-zone, the fetal zone in human adrenals is also a transient cortical compartment, comprising the majority of the human fetal adrenal gland. During adrenal development, fetal cortical cells are gradually replaced by newly formed adult cortical cells that develop into outer definitive zones. In mice, the regression of this fetal cell population is sexually dimorphic. Many mouse models with mutations associated with endocrine factors have been reported with X-zone phenotypes. Increasing findings indicate that the cell fate of this aged cell population of the adrenal cortex can be manipulated by many hormonal and nonhormonal factors. This review summarizes the current knowledge of this transient adrenocortical zone with an emphasis on genes and signaling pathways that affect X-zone cells.

The human adrenal cortex: growth control and disorders

This review summarizes key knowledge regarding the development, growth, and growth disorders of the adrenal cortex from a molecular perspective. The adrenal gland consists of two distinct regions: the cortex and the medulla. During embryological development and transition to the adult adrenal gland, the adrenal cortex acquires three different structural and functional zones. Significant progress has been made in understanding the signaling and molecules involved during adrenal cortex zonation. Equally significant is the knowledge obtained regarding the action of peptide factors involved in the maintenance of zonation of the adrenal cortex, such as peptides derived from proopiomelanocortin processing, adrenocorticotropin and N-terminal proopiomelanocortin. Findings regarding the development, maintenance and growth of the adrenal cortex and the molecular factors involved has improved the scientific understanding of disorders that affect adrenal cortex growth. Hypoplasia, hyperplasia and adrenocortical tumors, including adult and pediatric adrenocortical adenomas and carcinomas, are described together with findings regarding molecular and pathway alterations. Comprehensive genomic analyses of adrenocortical tumors have shown gene expression profiles associated with malignancy as well as methylation alterations and the involvement of miRNAs. These findings provide a new perspective on the diagnosis, therapeutic possibilities and prognosis of adrenocortical disorders.