Timing of adrenal regression controlled by synergistic interaction between Sf1 SUMOylation and Dax1

An integrated single-cell analysis of human adrenal cortex development

The adrenal glands synthesize and release essential steroid hormones such as cortisol and aldosterone, but many aspects of human adrenal gland development are not well understood. Here, we combined single-cell and bulk RNA sequencing, spatial transcriptomics, IHC, and micro-focus computed tomography to investigate key aspects of adrenal development in the first 20 weeks of gestation. We demonstrate rapid adrenal growth and vascularization, with more cell division in the outer definitive zone (DZ). Steroidogenic pathways favored androgen synthesis in the central fetal zone, but DZ capacity to synthesize cortisol and aldosterone developed with time. Core transcriptional regulators were identified, with localized expression of HOPX (also known as Hop homeobox/homeobox-only protein) in the DZ. Potential ligand-receptor interactions between mesenchyme and adrenal cortex were seen (e.g., RSPO3/LGR4). Growth-promoting imprinted genes were enriched in the developing cortex (e.g., IGF2, PEG3). These findings reveal aspects of human adrenal development and have clinical implications for understanding primary adrenal insufficiency and related postnatal adrenal disorders, such as adrenal tumor development, steroid disorders, and neonatal stress.

Development and function of the fetal adrenal

The adrenal cortex undergoes multiple structural and functional rearrangements to satisfy the systemic needs for steroids during fetal life, postnatal development, and adulthood. A fully functional adrenal cortex relies on the proper subdivision in regions or 'zones' with distinct but interconnected functions, which evolve from the early embryonic stages to adulthood, and rely on a fine-tuned gene network. In particular, the steroidogenic activity of the fetal adrenal is instrumental in maintaining normal fetal development and growth. Here, we review and discuss the most recent advances in our understanding of embryonic and fetal adrenal development, including the known causes for adrenal dys-/agenesis, and the steroidogenic pathways that link the fetal adrenal with the hormone system of the mother through the fetal-placental unit. Finally, we discuss what we think are the major open questions in the field, including, among others, the impact of osteocalcin, thyroid hormone, and other hormone systems on adrenal development and function, and the reliability of rodents as models of adrenal pathophysiology.

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.

[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 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.

Adrenal cortex development and related disorders leading to adrenal insufficiency

The adult human adrenal cortex produces steroid hormones that are crucial for life, supporting immune response, glucose homeostasis, salt balance and sexual maturation. It consists of three histologically distinct and functionally specialized zones. The fetal adrenal forms from mesodermal material and produces predominantly adrenal C₁₉ steroids from its fetal zone, which involutes after birth. Transition to the adult cortex occurs immediately after birth for the formation of the zona glomerulosa and fasciculata for aldosterone and cortisol production and continues through infancy until the zona reticularis for adrenal androgen production is formed with adrenarche. The development of this indispensable organ is complex and not fully understood. This article gives an overview of recent knowledge gained of adrenal biology from two perspectives: one, from basic science studying adrenal development, zonation and homeostasis; and two, from adrenal disorders identified in persons manifesting with various isolated or syndromic forms of primary adrenal insufficiency.

Developmental mechanisms of adrenal cortex formation and their links with adult progenitor populations

The adrenal cortex is the main steroid producing organ of the human body. Studies on adrenal tissue renewal have been neglected for many years, but recent intensified research has seen tremendous progress in our understanding of the formation and homeostasis of this organ. However, cell turnover of the adrenal cortex appears to be complex and several cell populations have been identified that can differentiate into steroidogenic cells and contribute to adrenal cortex renewal. The purpose of this review is to provide an overview of how the adrenal cortex develops and how stem cell populations relate to its developmental progenitors. Finally, we will summarize present and future approaches to harvest the potential of progenitor/stem cells for future cell replacement therapies.

The role of SUMOylation during development

During the development of multicellular organisms, transcriptional regulation plays an important role in the control of cell growth, differentiation and morphogenesis. SUMOylation is a reversible post-translational process involved in transcriptional regulation through the modification of transcription factors and through chromatin remodelling (either modifying chromatin remodelers or acting as a ‘molecular glue’ by promoting recruitment of chromatin regulators). SUMO modification results in changes in the activity, stability, interactions or localization of its substrates, which affects cellular processes such as cell cycle progression, DNA maintenance and repair or nucleocytoplasmic transport. This review focuses on the role of SUMO machinery and the modification of target proteins during embryonic development and organogenesis of animals, from invertebrates to mammals.

RNA-Seq Reveals Sub-Zones in Mouse Adrenal Zona Fasciculata and the Sexually Dimorphic Responses to Thyroid Hormone

The sex-specific prevalence of adrenal diseases has been known for a long time. However, the reason for the high prevalence of these diseases in females is not completely understood. Mouse studies have shown that the adult adrenal gland is sexually dimorphic at different levels such as transcriptome, histology, and cell renewal. Here we used RNA-seq to show that in prepubertal mice, male and female adrenal glands were not only sexually dimorphic but also responded differently to the same external stimulus. We previously reported that thyroid hormone receptor β1 (TRβ1) in the adrenal gland is mainly expressed in the inner cortex and the fate of this TRβ1-expressing cell population can be changed by thyroid hormone (triiodothyronine; T3) treatment. In the present study, we found that adrenal glands in prepubertal mice were sexually dimorphic at the level of the transcriptome. Under T3 treatment, prepubertal females had 1162 genes differentially expressed between the saline and T3 groups, whereas in males of the same age, only 512 genes were T3-responsive. Immunostaining demonstrated that several top sexually dimorphic T3-responsive genes, including Cyp2f2 and Dhcr24, were specifically expressed in the adrenal inner cortex, precisely in an area partially overlapping with the X-zone. Under T3 treatment, a unique cortical layer that surrounds the adrenal X-zone expanded significantly, forming a distinct layer peculiar to females. Our findings identified novel marker genes for the inner adrenal cortex, indicating there are different sub-zones in the zona fasciculata. The results also highlight the sex-specific response to thyroid hormone in the mouse adrenal gland.

Not So Slim Anymore-Evidence for the Role of SUMO in the Regulation of Lipid Metabolism

One of the basic building blocks of all life forms are lipids—biomolecules that dissolve in nonpolar organic solvents but not in water. Lipids have numerous structural, metabolic, and regulative functions in health and disease; thus, complex networks of enzymes coordinate the different compositions and functions of lipids with the physiology of the organism. One type of control on the activity of those enzymes is the conjugation of the Small Ubiquitin-like Modifier (SUMO) that in recent years has been identified as a critical regulator of many biological processes. In this review, I summarize the current knowledge about the role of SUMO in the regulation of lipid metabolism. In particular, I discuss (i) the role of SUMO in lipid metabolism of fungi and invertebrates; (ii) the function of SUMO as a regulator of lipid metabolism in mammals with emphasis on the two most well-characterized cases of SUMO regulation of lipid homeostasis. These include the effect of SUMO on the activity of two groups of master regulators of lipid metabolism—the Sterol Regulatory Element Binding Protein (SERBP) proteins and the family of nuclear receptors—and (iii) the role of SUMO as a regulator of lipid metabolism in arteriosclerosis, nonalcoholic fatty liver, cholestasis, and other lipid-related human diseases.

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.

A ZNRF3-dependent Wnt/β-catenin signaling gradient is required for adrenal homeostasis

The transmembrane E3 ubiquitin ligases ZNRF3 and RNF43 antagonize Wnt signaling by promoting degradation of frizzled receptors. Here, Basham et al. demonstrate that adrenocortical-specific loss of ZNRF3, but not RNF43, results in adrenal hyperplasia that depends on Porcupine-mediated Wnt ligand secretion.

Spatiotemporal control of Wnt signaling is essential for the development and homeostasis of many tissues. The transmembrane E3 ubiquitin ligases ZNRF3 (zinc and ring finger 3) and RNF43 (ring finger protein 43) antagonize Wnt signaling by promoting degradation of frizzled receptors. ZNRF3 and RNF43 are frequently inactivated in human cancer, but the molecular and therapeutic implications remain unclear. Here, we demonstrate that adrenocortical-specific loss of ZNRF3, but not RNF43, results in adrenal hyperplasia that depends on Porcupine-mediated Wnt ligand secretion. Furthermore, we discovered a Wnt/β-catenin signaling gradient in the adrenal cortex that is disrupted upon loss of ZNRF3. Unlike β-catenin gain-of-function models, which induce high Wnt/β-catenin activation and expansion of the peripheral cortex, ZNRF3 loss triggers activation of moderate-level Wnt/β-catenin signaling that drives proliferative expansion of only the histologically and functionally distinct inner cortex. Genetically reducing β-catenin dosage significantly reverses the ZNRF3-deficient phenotype. Thus, homeostatic maintenance of the adrenal cortex is dependent on varying levels of Wnt/β-catenin activation, which is regulated by ZNRF3.

Human fetal adrenal cells retain age-related stem- and endocrine-differentiation potential in culture

The adrenal gland is a multiendocrine organ with a steroidogenic mesenchymal cortex and an inner catecholamine-producing medulla of neuroendocrine origin. After embryonic development, this plastic organ undergoes a functional postnatal remodeling. Elucidating these complex processes is pivotal for understanding the early bases of functional endocrine disorders and tumors affecting the mature gland. We developed an in vitro human adrenal cell model derived from fetal adrenal specimens at different gestational ages, consisting of neuroendocrine and cortical components and expressing the zona and functional markers of the original fetal organ. These cortical and neuroendocrine progenitor cells retain in vitro an intrinsic gestational-age-related differentiation and functional program. In vitro these cells spontaneously form 3-dimensional structure organoids with a structure similar to the fetal gland. The organoids show morphofunctional features and adrenal steroidogenic factor, steroid acute regulatory, cytochrome-P450-17A1, dosage-sensitive, sex-reversal, adrenal hypoplasia-critical region on chromosome X protein , NOTCH1, and nephroblastoma overexpressed/cysteine-rich protein 61/connective tissue growth factor/nephroblastoma overexpressed gene-3; stem (BMI1, nestin); and chromaffin (chromogranin A, tyrosine hydroxylase) markers similar to those of the populations of origin. This in vitro human adrenal system represents a unique but preliminar model for investigating the pathophysiological processes underlying physiologic adrenal remodeling and pathologic alterations involved in organ hypo- and hyperplasia and cancer.-Poli, G., Sarchielli, E., Guasti, D., Benvenuti, S., Ballerini, L., Mazzanti, B., Armignacco, R., Cantini, G., Lulli, M., Chortis, V., Arlt, W., Romagnoli, P., Vannelli, G. B., Mannelli, M., Luconi, M. Human fetal adrenal cells retain age-related stem- and endocrine-differentiation potential in culture.

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.