Genetic regulation of murine pituitary development

Comprehensive transcriptomic analysis revealing the regulatory dynamics and networks of the pituitary-testis axis in sheep across developmental stages

Spermatogenesis is a complex process intricately regulated by the hypothalamic-pituitary-testis (HPT) axis. However, research on the regulatory factors governing the HPT axis remains limited. This study addresses this gap by conducting a comprehensive analysis of transcriptomes from the pituitary and testis tissues across various developmental stages, encompassing embryonic day (E120), neonatal period (P0), pre-puberty (P90), and post-puberty day (P270). Utilizing edgeR and WGCNA, we identified stage-specific genes in both the pituitary and testis throughout the four developmental stages. Notably, 380, 242, 34, and 479 stage-specific genes were identified in the pituitary, while 886, 297, 201, and 3,678 genes were identified in the testis. Subsequent analyses unveiled associations between these stage-specific genes and crucial pathways such as the cAMP signaling pathway, GnRH secretion, and male gamete generation. Furthermore, leveraging single-cell data from the pituitary and testis, we identified some signaling pathways involving BMP, HGF, IGF, and TGF-β, highlighting mutual regulation between the pituitary and testis at different developmental stages. This study sheds light on the pivotal role of the pituitary-testis axis in the reproductive process of sheep across four distinct developmental stages. Additionally, it delves into the intricate regulatory networks governing reproduction, offering novel insights into the dynamics of the pituitary-testis axis within the reproductive system.

In vitro modeling of cranial placode differentiation: Recent advances, challenges, and perspectives

Cranial placodes are transient ectodermal thickenings that contribute to a diverse array of organs in the vertebrate head. They develop from a common territory, the pre-placodal region that over time segregates along the antero-posterior axis into individual placodal domains: the adenohypophyseal, olfactory, lens, trigeminal, otic, and epibranchial placodes. These placodes terminally differentiate into the anterior pituitary, the lens, and contribute to sensory organs including the olfactory epithelium, and inner ear, as well as several cranial ganglia. To study cranial placodes and their derivatives and generate cells for therapeutic purposes, several groups have turned to in vitro derivation of placodal cells from human embryonic stem cells (hESCs) or induced pluripotent stem cells (hiPSCs). In this review, we summarize the signaling cues and mechanisms involved in cranial placode induction, specification, and differentiation in vivo, and discuss how this knowledge has informed protocols to derive cranial placodes in vitro. We also discuss the benefits and limitations of these protocols, and the potential of in vitro cranial placode modeling in regenerative medicine to treat cranial placode-related pathologies.

Neural plate progenitors give rise to both anterior and posterior pituitary cells

The pituitary is the master neuroendocrine gland, which regulates body homeostasis. It consists of the anterior pituitary/adenohypophysis harboring hormones producing cells and the posterior pituitary/neurohypophysis, which relays the passage of hormones from the brain to the periphery. It is accepted that the adenohypophysis originates from the oral ectoderm (Rathke's pouch), whereas the neural ectoderm contributes to the neurohypophysis. Single-cell transcriptomics of the zebrafish pituitary showed that cyp26b1-positive astroglial pituicytes of the neurohypophysis and prop1-positive adenohypophyseal progenitors expressed common markers implying lineage relatedness. Genetic tracing identifies that, in contrast to the prevailing dogma, neural plate precursors of zebrafish (her4.3+) and mouse (Sox1+) contribute to both neurohypophyseal and a subset of adenohypophyseal cells. Pituicyte-derived retinoic-acid-degrading enzyme Cyp26b1 fine-tunes differentiation of prop1+ progenitors into hormone-producing cells. These results challenge the notion that adenohypophyseal cells are exclusively derived from non-neural ectoderm and demonstrate that crosstalk between neuro- and adeno-hypophyseal cells affects differentiation of pituitary cells.

Missing pieces of the pituitary puzzle: participation of extra-adenohypophyseal placode-lineage cells in the adult pituitary gland

The pituitary gland is a major endocrine tissue composing of two distinct entities, the adenohypophysis (anterior pituitary, cranial placode origin) and the neurohypophysis (posterior pituitary, neural ectoderm origin), and plays important roles in maintaining vital homeostasis. This tissue is maintained by a slow, consistent cell-renewal system of adult stem/progenitor cells. Recent accumulating evidence shows that neural crest-, head mesenchyme-, and endoderm lineage cells invade during pituitary development and contribute to the maintenance of the adult pituitary gland. Based on these novel observations, this article discusses whether these lineage cells are involved in pituitary organogenesis, maintenance, regeneration, dysplasia, or tumors.

Organoid models of the pituitary gland in health and disease

The pituitary gland represents the hub of our endocrine system. Its cells produce specific hormones that direct multiple vital physiological processes such as body growth, fertility, and stress. The gland also contains a population of stem cells which are still enigmatic in phenotype and function. Appropriate research models are needed to advance our knowledge on pituitary (stem cell) biology. Over the last decade, 3D organoid models have been established, either derived from the pituitary stem cells or from pluripotent stem cells, covering both healthy and diseased conditions. Here, we summarize the state-of-the-art of pituitary-allied organoid models and discuss applications of these powerful in vitro research and translational tools to study pituitary development, biology, and disease.

Sex-Linked Growth Disorder and Aberrant Pituitary Gene Expression in Nestin-Cre-Mediated Egr1 Conditional Knockout Mice

Genes that regulate hormone release are essential for maintaining metabolism and energy balance. Egr1 encodes a transcription factor that regulates hormone production and release, and a decreased in growth hormones has been reported in Egr1 knockout mice. A reduction in growth hormones has also been observed in Nestin-Cre mice, a model frequently used to study the nervous system. Currently, it is unknown how Egr1 loss or the Nestin-Cre driver disrupt pituitary gene expression. Here, we compared the growth curves and pituitary gene expression profiles of Nestin-Cre-mediated Egr1 conditional knockout (Egr1cKO) mice with those of their controls. Reduced body weight was observed in both the Nestin-Cre and Egr1cKO mice, and the loss of Egr1 had a slightly more severe impact on female mice than on male mice. RNA-seq data analyses revealed that the sex-related differences were amplified in the Nestin-Cre-mediated Egr1 conditional knockout mice. Additionally, in the male mice, the influence of Egr1cKO on pituitary gene expression may be overridden by the Nestin-Cre driver. Differentially expressed genes associated with the Nestin-Cre driver were significantly enriched for genes related to growth factor activity and binding. Altogether, our results demonstrate that Nestin-Cre and the loss of Egr1 in the neuronal cell lineage have distinct impacts on pituitary gene expression in a sex-specific manner.

An expression and function analysis of the CXCR4/SDF-1 signalling axis during pituitary gland development

The chemokine SDF-1 (CXCL12) and its receptor CXCR4 control several processes during embryonic development such as the regulation of stem cell proliferation, differentiation, and migration. However, the role of this pathway in the formation of the pituitary gland is not understood. We sought to characterise the expression patterns of CXCR4, SDF-1 and CXCR7 at different stages of pituitary gland development. Our expression profiling revealed that SDF-1 is expressed in progenitor-rich regions of the pituitary anterior lobe, that CXCR4 and CXCR7 have opposite expression domains and that CXCR4 expression is conserved between mice and human embryos. We then assessed the importance of this signalling pathway in the development and function of the murine pituitary gland through conditional deletion of CXCR4 in embryonic pituitary progenitors. Successful and specific ablation of CXCR4 expression in embryonic pituitary progenitors did not lead to observable embryonic nor postnatal defects but allowed the identification of stromal CXCR4+ cells not derived from HESX1+ progenitors. Further analysis of constitutive SDF-1, CXCR7 and CXCR4 mutants of the pathway indicates that CXCR4 expression in HESX1+ cells and their descendants is not essential for normal pituitary development in mice.

Pituitary Stem Cell Regulation by Zeb2 and BMP Signaling

Epithelial to mesenchymal transition (EMT) is important for many developing organs, and for wound healing, fibrosis, and cancer. Pituitary stem cells undergo an EMT-like process as they migrate and initiate differentiation, but little is known about the input of signaling pathways or the genetic hierarchy of the transcriptional cascade. Prop1 mutant stem cells fail to undergo changes in cellular morphology, migration, and transition to the Pou1f1 lineage. We used Prop1 mutant mice to identify the changes in gene expression that are affiliated with EMT-like processes. BMP and TGF-β family gene expression was reduced in Prop1 mutants and Elf5, a transcription factor that characteristically suppresses EMT, had elevated expression. Genes involved in cell-cell contact such as cadherins and claudins were elevated in Prop1 mutants. To establish the genetic hierarchy of control, we manipulated gene expression in pituitary stem cell colonies. We determined that the EMT inducer, Zeb2, is necessary for robust BMP signaling and repression of Elf5. We demonstrated that inhibition of BMP signaling affects expression of target genes in the Id family, but it does not affect expression of other EMT genes. Zeb2 is necessary for expression of the SHH effector gene Gli2. However, knock down of Gli2 has little effect on the EMT-related genes, suggesting that it acts through a separate pathway. Thus, we have established the genetic hierarchy involved in the transition of pituitary stem cells to differentiation.

Generation of Lens Progenitor Cells and Lentoid Bodies from Pluripotent Stem Cells: Novel Tools for Human Lens Development and Ocular Disease Etiology

In vitro differentiation of human pluripotent stem cells (hPSCs) into specialized tissues and organs represents a powerful approach to gain insight into those cellular and molecular mechanisms regulating human development. Although normal embryonic eye development is a complex process, generation of ocular organoids and specific ocular tissues from pluripotent stem cells has provided invaluable insights into the formation of lineage-committed progenitor cell populations, signal transduction pathways, and self-organization principles. This review provides a comprehensive summary of recent advances in generation of adenohypophyseal, olfactory, and lens placodes, lens progenitor cells and three-dimensional (3D) primitive lenses, "lentoid bodies", and "micro-lenses". These cells are produced alone or "community-grown" with other ocular tissues. Lentoid bodies/micro-lenses generated from human patients carrying mutations in crystallin genes demonstrate proof-of-principle that these cells are suitable for mechanistic studies of cataractogenesis. Taken together, current and emerging advanced in vitro differentiation methods pave the road to understand molecular mechanisms of cataract formation caused by the entire spectrum of mutations in DNA-binding regulatory genes, such as PAX6, SOX2, FOXE3, MAF, PITX3, and HSF4, individual crystallins, and other genes such as BFSP1, BFSP2, EPHA2, GJA3, GJA8, LIM2, MIP, and TDRD7 represented in human cataract patients.

Heterozygous variants in SIX3 and POU1F1 cause pituitary hormone deficiency in mouse and man

Congenital hypopituitarism is a genetically heterogeneous condition that is part of a spectrum disorder that can include holoprosencephaly. Heterozygous mutations in SIX3 cause variable holoprosencephaly in humans and mice. We identified two children with neonatal hypopituitarism and thin pituitary stalk who were doubly heterozygous for rare, likely deleterious variants in the transcription factors SIX3 and POU1F1. We used genetically engineered mice to understand the disease pathophysiology. Pou1f1 loss-of-function heterozygotes are unaffected; Six3 heterozygotes have pituitary gland dysmorphology and incompletely ossified palate; and the Six3+/-; Pou1f1+/dw double heterozygote mice have a pronounced phenotype, including pituitary growth through the palate. The interaction of Pou1f1 and Six3 in mice supports the possibility of digenic pituitary disease in children. Disruption of Six3 expression in the oral ectoderm completely ablated anterior pituitary development, and deletion of Six3 in the neural ectoderm blocked the development of the pituitary stalk and both anterior and posterior pituitary lobes. Six3 is required in both oral and neural ectodermal tissues for the activation of signaling pathways and transcription factors necessary for pituitary cell fate. These studies clarify the mechanism of SIX3 action in pituitary development and provide support for a digenic basis for hypopituitarism.

MicroRNA-7a2 is required for the development of pituitary stem cells

The pituitary gland is inhabited by a subpopulation of SOX2+ stem cells. However, the regulatory mechanisms underlying pituitary stem cell development remain poorly understood. Here, we demonstrate that microRNA-7a (miR-7a) is enriched in the developing pituitary and is spatiotemporally expressed in the pituitary stem cells. Constitutive deletion of miR-7a2 in mice results in pituitary dysplasia emerging during birth, which is primarily manifested as malformed anterior lobes. Using immunofluorescence, immunohistochemistry or in situ hybridization, we observe that the specification of hormone-expressing cells is not impeded post miR-7a2 deletion at birth, although the terminal differentiation of gonadotropes is inhibited. Further investigation of neonatal and adult pituitaries in miR-7a2 knockout mice reveals an expansion of the SOX2+ pituitary stem cell compartment. The inhibition of epithelial-mesenchymal like transition seems to be responsible for this phenotype, rather than abnormal proliferation or apoptosis. Furthermore, our data suggest that Gli3 and Ckap4 are potential targets of miR-7a in pituitary stem cells. In summary, our results identify miR-7a2 as a crucial factor involved in pituitary stem cell development.

Key pituitary miRNAs mediate the expression of pig GHRHR splice variants by regulating splice factors

The growth hormone releasing hormone receptor (GHRHR) is well documented in organism growth and its alternative splicing may generate multiple functional GHRHR splice variants (SVs). Our previous study has demonstrated the key pituitary miRNAs (let-7e and miR-328-5p) in pig regulated the expression of GHRHR SVs by directly targeting to them. And according to recent reports, the interplay between miRNA-based silencing of mRNAs and alternative splicing of pre-mRNAs is a crucial post-transcriptional mechanism. In this study, SF3B3 and CPSF4 were firstly excavated as the splice factors that involved in the formation of GHRHR SVs mediated by let-7e and miR-328-5p through the comparation of the expression relations of GHRHR SVs, let-7e/miR-328-5p and SF3B3/CPSF4 in pituitary tissues between Landrace pigs and BaMa pigs, as well as the prediction of the target relations of let-7e/miR-328-5p with SF3B3 and/or CPSF4. SF3B3 and CPSF4 targeted by let-7e and miR-328-5p were further verified by performing dual-luciferase reporter assays and detecting the expression of target transcripts. Then the RT-PCR, RT-qPCR and Western blot assays were used to confirm SF3B3 and CPSF4 were involved in the formation of the GHRHR SVs, and in this process, let-7e and miR-328-5p mediated GHRHR SVs by regulating SF3B3 and CPSF4. Finally, the target site of SF3B3 on pre-GHRHR was on the Exon 12 to Exon14, while CPSF4 acted on the other fragments of the pre-GHRHR, which were explored by dual-luciferase reporter system preliminarily. To the best of our knowledge, this paper is the first to report the miRNAs regulate GHRHR SVs indirectly by splice factors.

The imprinted Zdbf2 gene finely tunes control of feeding and growth in neonates

Genomic imprinting refers to the mono-allelic and parent-specific expression of a subset of genes. While long recognized for their role in embryonic development, imprinted genes have recently emerged as important modulators of postnatal physiology, notably through hypothalamus-driven functions. Here, using mouse models of loss, gain and parental inversion of expression, we report that the paternally expressed Zdbf2 gene controls neonatal growth in mice, in a dose-sensitive but parent-of-origin-independent manner. We further found that Zdbf2-KO neonates failed to fully activate hypothalamic circuits that stimulate appetite, and suffered milk deprivation and diminished circulating Insulin Growth Factor 1 (IGF-1). Consequently, only half of Zdbf2-KO pups survived the first days after birth and those surviving were smaller. This study demonstrates that precise imprinted gene dosage is essential for vital physiological functions at the transition from intra- to extra-uterine life, here the adaptation to oral feeding and optimized body weight gain.

New insights into the role and origin of pituitary S100β-positive cells

In the anterior pituitary, S100β protein (S100β) has been assumed to be a marker of folliculo-stellate cells, which are one of the non-hormone-producing cells existing in the parenchyma of the adult anterior lobe and are composed of subpopulations with various functions. However, recent accumulating studies on S100β-positive cells, including non-folliculo-stellate cells lining the marginal cell layer (MCL), have shown the novel aspect that most S100β-positive cells in the MCL and parenchyma of the adult anterior lobe are positive for sex determining region Y-box 2 (SOX2), a marker of pituitary stem/progenitor cells. From the viewpoint of SOX2-positive cells, the majority of these cells in the MCL and in the parenchyma are positive for S100β, suggesting that S100β plays a role in the large population of stem/progenitor cells in the anterior lobe of the adult pituitary. Reportedly, S100β/SOX2-double positive cells are able to differentiate into hormone-producing cells and various types of non-hormone-producing cells. Intriguingly, it has been demonstrated that extra-pituitary lineage cells invade the pituitary gland during prenatal pituitary organogenesis. Among them, two S100β-positive populations have been identified: one is SOX2-positive population which invades at the late embryonic period through the pituitary stalk and another is a SOX2-negative population that invades at the middle embryonic period through Atwell's recess. These two populations are likely the substantive origin of S100β-positive cells in the postnatal anterior pituitary, while S100β-positive cells emerging from oral ectoderm-derived cells remain unclear.

Evidence That the Etiology of Congenital Hypopituitarism Has a Major Genetic Component but Is Infrequently Monogenic

Purpose

Congenital hypopituitarism usually occurs sporadically. In most patients, the etiology remains unknown.

Methods

We studied 13 children with sporadic congenital hypopituitarism. Children with non-endocrine, non-familial idiopathic short stature (NFSS) (n = 19) served as a control group. Exome sequencing was performed in probands and both unaffected parents. A burden testing approach was used to compare the number of candidate variants in the two groups.

Results

First, we assessed the frequency of rare, predicted-pathogenic variants in 42 genes previously reported to be associated with pituitary gland development. The average number of variants per individual was greater in probands with congenital hypopituitarism than those with NFSS (1.1 vs. 0.21, mean variants/proband, P = 0.03). The number of probands with at least 1 variant in a pituitary-associated gene was greater in congenital hypopituitarism than in NFSS (62% vs. 21%, P = 0.03). Second, we assessed the frequency of rare, predicted-pathogenic variants in the exome (to capture undiscovered causes) that were inherited in a fashion that could explain the sporadic occurrence of the proband's condition with a monogenic etiology (de novo mutation, autosomal recessive, or X-linked recessive) with complete penetrance. There were fewer monogenic candidates in the probands with congenital hypopituitarism than those with NFSS (1.3 vs. 2.5 candidate variants/proband, P = 0.024). We did not find any candidate variants (0 of 13 probands) in genes previously reported to explain the phenotype in congenital hypopituitarism, unlike NFSS (8 of 19 probands, P = 0.01).

Conclusion

Our findings provide evidence that the etiology of sporadic congenital hypopituitarism has a major genetic component but may be infrequently monogenic with full penetrance, suggesting a more complex etiology.

Single-Cell RNA Sequencing Analysis of Chicken Anterior Pituitary: A Bird's-Eye View on Vertebrate Pituitary

It is well-established that anterior pituitary contains multiple endocrine cell populations, and each of them can secrete one/two hormone(s) to regulate vital physiological processes of vertebrates. However, the gene expression profiles of each pituitary cell population remains poorly characterized in most vertebrate groups. Here we analyzed the transcriptome of each cell population in adult chicken anterior pituitaries using single-cell RNA sequencing technology. The results showed that: (1) four out of five known endocrine cell clusters have been identified and designated as the lactotrophs, thyrotrophs, corticotrophs, and gonadotrophs, respectively. Somatotrophs were not analyzed in the current study. Each cell cluster can express at least one known endocrine hormone, and novel marker genes (e.g., CD24 and HSPB1 in lactotrophs, NPBWR2 and NDRG1 in corticotrophs; DIO2 and SOUL in thyrotrophs, C5H11ORF96 and HPGDS in gonadotrophs) are identified. Interestingly, gonadotrophs were shown to abundantly express five peptide hormones: FSH, LH, GRP, CART and RLN3; (2) four non-endocrine/secretory cell types, including endothelial cells (expressing IGFBP7 and CFD) and folliculo-stellate cells (FS-cells, expressing S100A6 and S100A10), were identified in chicken anterior pituitaries. Among them, FS-cells can express many growth factors, peptides (e.g., WNT5A, HBEGF, Activins, VEGFC, NPY, and BMP4), and progenitor/stem cell-associated genes (e.g., Notch signaling components, CDH1), implying that the FS-cell cluster may act as a paracrine/autocrine signaling center and enrich pituitary progenitor/stem cells; (3) sexually dimorphic expression of many genes were identified in most cell clusters, including gonadotrophs and lactotrophs. Taken together, our data provides a bird's-eye view on the diverse aspects of anterior pituitaries, including cell composition, heterogeneity, cell-to-cell communication, and gene expression profiles, which facilitates our comprehensive understanding of vertebrate pituitary biology.

Dynamic Expression of Imprinted Genes in the Developing and Postnatal Pituitary Gland

In mammals, imprinted genes regulate many critical endocrine processes such as growth, the onset of puberty and maternal reproductive behaviour. Human imprinting disorders (IDs) are caused by genetic and epigenetic mechanisms that alter the expression dosage of imprinted genes. Due to improvements in diagnosis, increasing numbers of patients with IDs are now identified and monitored across their lifetimes. Seminal work has revealed that IDs have a strong endocrine component, yet the contribution of imprinted gene products in the development and function of the hypothalamo-pituitary axis are not well defined. Postnatal endocrine processes are dependent upon the production of hormones from the pituitary gland. While the actions of a few imprinted genes in pituitary development and function have been described, to date there has been no attempt to link the expression of these genes as a class to the formation and function of this essential organ. This is important because IDs show considerable overlap, and imprinted genes are known to define a transcriptional network related to organ growth. This knowledge deficit is partly due to technical difficulties in obtaining useful transcriptomic data from the pituitary gland, namely, its small size during development and cellular complexity in maturity. Here we utilise high-sensitivity RNA sequencing at the embryonic stages, and single-cell RNA sequencing data to describe the imprinted transcriptome of the pituitary gland. In concert, we provide a comprehensive literature review of the current knowledge of the role of imprinted genes in pituitary hormonal pathways and how these relate to IDs. We present new data that implicate imprinted gene networks in the development of the gland and in the stem cell compartment. Furthermore, we suggest novel roles for individual imprinted genes in the aetiology of IDs. Finally, we describe the dynamic regulation of imprinted genes in the pituitary gland of the pregnant mother, with implications for the regulation of maternal metabolic adaptations to pregnancy.

Pituitary stalk interruption syndrome

Pituitary stalk interruption syndrome (PSIS) is a distinct developmental defect of the pituitary gland identified by magnetic resonance imaging and characterized by a thin, interrupted, attenuated or absent pituitary stalk, hypoplasia or aplasia of the adenohypophysis, and an ectopic posterior pituitary. The precise etiology of PSIS still remains elusive or incompletely confirmed in most cases. Adverse perinatal events, including breech delivery and hypoxia, were initially proposed as the underlying mechanism affecting the hypothalamic-pituitary axis. Nevertheless, recent findings have uncovered a wide variety of PSIS-associated molecular defects in genes involved in pituitary development, holoprosencephaly (HPE), neural development, and other important cellular processes such as cilia function. The application of whole exome sequencing (WES) in relatively large cohorts has identified an expanded pool of potential candidate genes, mostly related to the Wnt, Notch, and sonic hedgehog signaling pathways that regulate pituitary growth and development during embryogenesis. Importantly, WES has revealed coexisting pathogenic variants in a significant number of patients; therefore, pointing to a multigenic origin and inheritance pattern of PSIS. The disorder is characterized by inter- and intrafamilial variability and incomplete or variable penetrance. Overall, PSIS is currently viewed as a mild form of an expanded HPE spectrum. The wide and complex clinical manifestations include evolving pituitary hormone deficiencies (with variable timing of onset and progression) and extrapituitary malformations. Severe and life-threatening symptomatology is observed in a subset of patients with complete pituitary hormone deficiency during the neonatal period. Nevertheless, most patients are referred later in childhood for growth retardation. Prompt and appropriate hormone substitution therapy constitutes the cornerstone of treatment. Further studies are needed to uncover the etiopathogenesis of PSIS.

Developmental Genes and Malformations in the Hypothalamus

The hypothalamus is a heterogeneous rostral forebrain region that regulates physiological processes essential for survival, energy metabolism, and reproduction, mainly mediated by the pituitary gland. In the updated prosomeric model, the hypothalamus represents the rostralmost forebrain, composed of two segmental regions (terminal and peduncular hypothalamus), which extend respectively into the non-evaginated preoptic telencephalon and the evaginated pallio-subpallial telencephalon. Complex genetic cascades of transcription factors and signaling molecules rule their development. Alterations of some of these molecular mechanisms acting during forebrain development are associated with more or less severe hypothalamic and pituitary dysfunctions, which may be associated with brain malformations such as holoprosencephaly or septo-optic dysplasia. Studies on transgenic mice with mutated genes encoding critical transcription factors implicated in hypothalamic-pituitary development are contributing to understanding the high clinical complexity of these pathologies. In this review article, we will analyze first the complex molecular genoarchitecture of the hypothalamus resulting from the activity of previous morphogenetic signaling centers and secondly some malformations related to alterations in genes implicated in the development of the hypothalamus.

miR-709 inhibits GHRP6 induced GH synthesis by targeting PRKCA in pituitary

Pituitary growth hormone (GH) plays an essential role in processes of organism growth and metabolism. MicroRNA (miRNA) could also participate in diverse biological processes. However, the role of miRNA in the regulation of pituitary GH during the growth process remains unclear. In this study, we firstly confirmed that the second highly expressed pituitary miRNA (miR-709) significantly inhibited the GH synthesis and suppressed the viability of GH3 cells. The bioinformatics analysis and dual luciferase report system were used to ascertain the PRKCA is the direct target gene of miR-709, which is the coding gene of PKCα. Then the transcription and translation levels of Prkca were obvious reduced by the over-expression of miR-709 in GH3 cells, followed by the inhibition of the transcription factor (CREB1) of Gh1 gene and the ERK1/2 signaling pathway or the possible cross-talk signaling pathway (cAMP/PKA signaling pathway) detected by western blot, suggesting that ERK1/2 maybe an important factor involved in the GH3 cell viability mediated by PKCα. At last, GHRP6 increased PKCα and GH expression but reduced miR-709 expression in vitro and vivo assays, and this conclusion was further confirmed by the result of GHRP6 attenuated the inhibition of miR-709 on GH expression. These findings will provide new molecular mechanism on the regulation of pituitary GH.

Genome-Wide Analysis and Function Prediction of Long Noncoding RNAs in Sheep Pituitary Gland Associated with Sexual Maturation

Long noncoding RNA (lncRNA) plays a crucial role in the hypothalamic-pituitary-testis (HPT) axis associated with sheep reproduction. The pituitary plays a connecting role in the HPT axis. However, little is known of their expression pattern and potential roles in the pituitary gland. To explore the potential lncRNAs that regulate the male sheep pituitary development and sexual maturation, we constructed immature and mature sheep pituitary cDNA libraries (three-month-old, TM, and nine-month-old, NM, respectively, n = 3) for lncRNA and mRNA high-throughput sequencing. Firstly, the expression of lncRNA and mRNA were comparatively analyzed. 2417 known lncRNAs and 1256 new lncRNAs were identified. Then, 193 differentially expressed (DE) lncRNAs and 1407 DE mRNAs were found in the pituitary between the two groups. Moreover, mRNA-lncRNA interaction network was constructed according to the target gene prediction of lncRNA and functional enrichment analysis. Five candidate lncRNAs and their targeted genes HSD17B12, DCBLD2, PDPK1, GPX3 and DLL1 that enriched in growth and reproduction related pathways were further filtered. Lastly, the interaction of candidate lncRNA TCONS_00066406 and its targeted gene HSD17B12 were validated in in vitro of sheep pituitary cells. Our study provided a systematic presentation of lncRNAs and mRNAs in male sheep pituitary, which revealed the potential role of lncRNA in male reproduction.

Liganded T3 receptor β2 inhibits the positive feedback autoregulation of the gene for GATA2, a transcription factor critical for thyrotropin production

The serum concentration of thyrotropin (thyroid stimulating hormone, TSH) is drastically reduced by small increase in the levels of thyroid hormones (T3 and its prohormone, T4); however, the mechanism underlying this relationship is unknown. TSH consists of the chorionic gonadotropin α (CGA) and the β chain (TSHβ). The expression of both peptides is induced by the transcription factor GATA2, a determinant of the thyrotroph and gonadotroph differentiation in the pituitary. We previously reported that the liganded T3 receptor (TR) inhibits transactivation activity of GATA2 via a tethering mechanism and proposed that this mechanism, but not binding of TR with a negative T3-responsive element, is the basis for the T3-dependent inhibition of the TSHβ and CGA genes. Multiple GATA-responsive elements (GATA-REs) also exist within the GATA2 gene itself and mediate the positive feedback autoregulation of this gene. To elucidate the effect of T3 on this non-linear regulation, we fused the GATA-REs at -3.9 kb or +9.5 kb of the GATA2 gene with the chloramphenicol acetyltransferase reporter gene harbored in its 1S-promoter. These constructs were co-transfected with the expression plasmids for GATA2 and the pituitary specific TR, TRβ2, into kidney-derived CV1 cells. We found that liganded TRβ2 represses the GATA2-induced transactivation of these reporter genes. Multi-dimensional input function theory revealed that liganded TRβ2 functions as a classical transcriptional repressor. Then, we investigated the effect of T3 on the endogenous expression of GATA2 protein and mRNA in the gonadotroph-derived LβT2 cells. In this cell line, T3 reduced GATA2 protein independently of the ubiquitin proteasome system. GATA2 mRNA was drastically suppressed by T3, the concentration of which corresponds to moderate hypothyroidism and euthyroidism. These results suggest that liganded TRβ2 inhibits the positive feedback autoregulation of the GATA2 gene; moreover this mechanism plays an important role in the potent reduction of TSH production by T3.

Roles of differential expression of miR-543-5p in GH regulation in rat anterior pituitary cells and GH3 cells

Growth hormone (GH) is an important hormone released by the pituitary gland that plays a key role in the growth and development of organisms. In our study, TargetScan analysis and the dual luciferase reporter assays were used to predict and screen for miRNAs that might act on the rat Gh1 gene, and we identified miR-543-5p. Then, the GH3 cell line and the primary rat pituitary cells were transfected with miRNA mimic, inhibitor, and siRNA. We detected the Gh1 gene expression and the GH secretion by real-time PCR and ELISAs, respectively, to verify the regulatory effect of miR-543-5p on GH secretion. The results showed that miR-543-5p can inhibit Gh1 mRNA expression and reduce GH secretion. MiR-543-5p inhibitor upregulated Gh1 mRNA expression and increased GH secretion compared with the negative control. In summary, miR-543-5p downregulates Gh1 expression, resulting in a decrease in GH synthesis and secretion, which demonstrates the important role of miRNAs in regulating GH and animal growth and development.

Genetic diagnosis of congenital hypopituitarism by a target gene panel: novel pathogenic variants in GLI2, OTX2 and GHRHR

AIM

Congenital hypopituitarism has an incidence of 1:3500-10,000 births and is defined by the impaired production of pituitary hormones. Early diagnosis has an impact on management and genetic counselling. The clinical and genetic heterogeneity of hypopituitarism poses difficulties to select the order of genes to analyse. The objective of our study is to screen hypopituitarism genes (candidate and previously related genes) simultaneously using a target gene panel in patients with congenital hypopituitarism.

METHODS

Screening of 117 subjects with congenital hypopituitarism for pathogenic variants in 26 genes associated with congenital hypopituitarism by massively parallel sequencing using a customized target gene panel.

RESULTS

We found three novel pathogenic variants in OTX2 c.295C>T:p.Gln99*, GLI2 c.1681G>T:p.Glu561* and GHRHR c.820_821insC:p.Asp274Alafs*113, and the previously reported variants in GHRHR c.57+1G>A and PROP1 [c.301_302delAG];[c.109+1G>A].

CONCLUSIONS

Our results indicate that a custom-designed panel is an efficient method to screen simultaneously variants of biological and clinical relevance for congenital GH deficiency. A genetic diagnosis was possible in 5 out of 117 (4%) patients of our cohort. We identified three novel pathogenic variants in GHRHR, OTX2 and GLI2 expanding the spectrum of variants associated with congenital hypopituitarism.

The proneural bHLH genes Mash1, Math3 and NeuroD are required for pituitary development

Multiple signaling molecules and transcription factors are required for pituitary development. Activator-type bHLH genes Mash1, Math, NeuroD (Neurod) and Neurogenin (Neurog) are well known as key molecules in neural development. Although analyses of targeted mouse mutants have demonstrated involvement of these bHLH genes in pituitary development, studies with single-mutant mice could not elucidate their exact functions, because they cooperatively function and compensate each other. The aim of this study was to elucidate the roles of Mash1, Math3 and NeuroD in pituitary development. Mash1;Math3;NeuroD triple-mutant mice were analyzed by immunohistochemistry and quantitative real-time RT-PCR. Misexpression studies with retroviruses in pituisphere cultures were also performed. The triple-mutant adenohypophysis was morphologically normal, though the lumen of the neurohypophysis remained unclosed. However, in triple-mutant pituitaries, somatotropes, gonadotropes and corticotropes were severely decreased, whereas lactotropes were increased. Misexpression of Mash1 alone with retrovirus could not induce generation of hormonal cells, though Mash1 was involved in differentiation of pituitary progenitor cells. These data suggest that Mash1, Math3 and NeuroD cooperatively control the timing of pituitary progenitor cell differentiation and that they are also required for subtype specification of pituitary hormonal cells. Mash1 is necessary for corticotroph and gonadotroph differentiation, and compensated by Math3 and NeuroD. Math3 is necessary for somatotroph differentiation, and compensated by Mash1 and NeuroD. Neurog2 may compensate Mash1, Math3 and NeuroD during pituitary development. Furthermore, Mash1, Math3 and NeuroD are required for neurohypophysis development. Thus, Mash1, Math3 and NeuroD are required for pituitary development, and compensate each other.

Sex-specific changes in postnatal GH and PRL secretion in somatotrope LEPR-null mice

The developing pituitary is a rapidly changing environment that is constantly meeting the physiological demands of the growing organism. During early postnatal development, the anterior pituitary is refining patterns of anterior hormone secretion in response to numerous genetic factors. Our laboratory previously developed a somatotrope leptin receptor (LEPR) deletion mouse model that had decreased lean body mass, disrupted metabolism, decreased GH stores and was GH deficient as an adult. To understand how deletion of LEPR in somatotropes altered GH, we turned our attention to postnatal development. The current study examines GH, PRL, TSH, ACTH, LH and FSH secretion during postnatal days 4, 5, 8, 10 and 15 and compares age and sex differences. The LEPR mutants have dysregulation of GH (P < 0.03) and a reduced developmental prolactin peak in males (P < 0.04) and females (P < 0.002). There were no differences in weight between groups, and the postnatal leptin surge appeared to be normal. Percentages of immunolabeled GH cells were reduced in mutants compared with controls in all age groups by 35-61% in males and 41-44% in females. In addition, we measured pituitary expression of pituitary transcription factors, POU1F1 and PROP1. POU1F1 was reduced in mutant females at PND 10 (P < 0.009) and PND 15 (P < 0.02) but increased in males at PND 10 (P < 0.01). PROP1 was unchanged in female mutants but showed developmental increases at PND 5 (P < 0.02) and PND 15 (P < 0.01). These studies show that the dysfunction caused by LEPR deletion in somatotropes begins as early as neonatal development and involves developing GH and prolactin cells (somatolactotropes).

Premature Expression of FOXO1 in Developing Mouse Pituitary Results in Anterior Lobe Hypoplasia

The process by which the somatotrope lineage emerges in the developing pituitary is regulated by the activity of specific signaling and transcription factors expressed during development. We set out to understand the contribution of FOXO1 to that process by using a mouse model in which FOXO1 is prematurely expressed in the pituitary primordium. Expression of FOXO1 in the oral ectoderm as early as embryonic day (e)9.5 resulted in pituitary gland hypoplasia and reduced expression of anterior lobe hormone transcripts at e18.5. Of note, the relative numbers of somatotropes and thyrotropes were also decreased at e18.5. LHX3 and PITX2, markers of pituitary identity, were present in a reduced number of cells during the formation of the Rathke pouch. Thus, premature expression of FOXO1 may affect adoption of pituitary identity during differentiation. Our results demonstrate that the timing of FOXO1 activation affects its role in pituitary gland organogenesis and somatotrope differentiation.

NOTCH activity differentially affects alternative cell fate acquisition and maintenance

The pituitary is an essential endocrine gland regulating multiple processes. Regeneration of endocrine cells is of therapeutic interest and recent studies are promising, but mechanisms of endocrine cell fate acquisition need to be better characterised. The NOTCH pathway is important during pituitary development. Here, we further characterise its role in the murine pituitary, revealing differential sensitivity within and between lineages. In progenitors, NOTCH activation blocks cell fate acquisition, with time-dependant modulation. In differentiating cells, response to activation is blunted in the POU1F1 lineage, with apparently normal cell fate specification, while POMC cells remain sensitive. Absence of apparent defects in Pou1f1-Cre; Rbpjfl/fl mice further suggests no direct role for NOTCH signalling in POU1F1 cell fate acquisition. In contrast, in the POMC lineage, NICD expression induces a regression towards a progenitor-like state, suggesting that the NOTCH pathway specifically blocks POMC cell differentiation. These results have implications for pituitary development, plasticity and regeneration. Activation of NOTCH signalling in different cell lineages of the embryonic murine pituitary uncovers an unexpected differential sensitivity, and this consequently reveals new aspects of endocrine lineages development and plasticity.

Pioneer factor Pax7 deploys a stable enhancer repertoire for specification of cell fate

Pioneer transcription factors establish new cell-fate competence by triggering chromatin remodeling. However, many features of pioneer action, such as their kinetics and stability, remain poorly defined. Here, we show that Pax7, by opening a unique repertoire of enhancers, is necessary and sufficient for specification of one pituitary lineage. Pax7 binds its targeted enhancers rapidly, but chromatin remodeling and gene activation are slower. Enhancers opened by Pax7 show a loss of DNA methylation and acquire stable epigenetic memory, as evidenced by binding of nonpioneer factors after Pax7 withdrawal. This work shows that transient Pax7 expression is sufficient for stable specification of cell identity.

Fgf10+ progenitors give rise to the chick hypothalamus by rostral and caudal growth and differentiation

Classical descriptions of the hypothalamus divide it into three rostro-caudal domains but little is known about their embryonic origins. To investigate this, we performed targeted fate-mapping, molecular characterisation and cell cycle analyses in the embryonic chick. Presumptive hypothalamic cells derive from the rostral diencephalic ventral midline, lie above the prechordal mesendoderm and express Fgf10Fgf10⁺ progenitors undergo anisotropic growth: those displaced rostrally differentiate into anterior cells, then those displaced caudally differentiate into mammillary cells. A stable population of Fgf10⁺ progenitors is retained within the tuberal domain; a subset of these gives rise to the tuberal infundibulum - the precursor of the posterior pituitary. Pharmacological approaches reveal that Shh signalling promotes the growth and differentiation of anterior progenitors, and also orchestrates the development of the infundibulum and Rathke's pouch - the precursor of the anterior pituitary. Together, our studies identify a hypothalamic progenitor population defined by Fgf10 and highlight a role for Shh signalling in the integrated development of the hypothalamus and pituitary.

Hypothalamic sonic hedgehog is required for cell specification and proliferation of LHX3/LHX4 pituitary embryonic precursors

Sonic hedgehog (SHH) is an essential morphogenetic signal that dictates cell fate decisions in several developing organs in mammals. In vitro data suggest that SHH is required to specify LHX3⁺/LHX4⁺ Rathke's pouch (RP) progenitor identity. However, in vivo studies have failed to reveal such a function, supporting instead a crucial role for SHH in promoting proliferation of these RP progenitors and for differentiation of pituitary cell types. Here, we have used a genetic approach to demonstrate that activation of the SHH pathway is necessary to induce LHX3⁺/LHX4⁺ RP identity in mouse embryos. First, we show that conditional deletion of Shh in the anterior hypothalamus results in a fully penetrant phenotype characterised by a complete arrest of RP development, with lack of Lhx3/Lhx4 expression in RP epithelium at 9.0 days post coitum (dpc) and total loss of pituitary tissue by 12.5 dpc. Conversely, overactivation of the SHH pathway by conditional deletion of Ptch1 in RP progenitors leads to severe hyperplasia and enlargement of the Sox2⁺ stem cell compartment by the end of gestation.

Regulation of pituitary stem cells by epithelial to mesenchymal transition events and signaling pathways

The anterior pituitary gland is comprised of specialized cell-types that produce and secrete polypeptide hormones in response to hypothalamic input and feedback from target organs. These specialized cells arise from stem cells that express SOX2 and the pituitary transcription factor PROP1, which is necessary to establish the stem cell pool and promote an epithelial to mesenchymal-like transition, releasing progenitors from the niche. The adult anterior pituitary responds to physiological challenge by mobilizing the SOX2-expressing progenitor pool and producing additional hormone-producing cells. Knowledge of the role of signaling pathways and extracellular matrix components in these processes may lead to improvements in the efficiency of differentiation of embryonic stem cells or induced pluripotent stem cells into hormone producing cells in vitro. Advances in our basic understanding of pituitary stem cell regulation and differentiation may lead to improved diagnosis and treatment for patients with hypopituitarism.

Foxo1 Is Required for Normal Somatotrope Differentiation

The etiology for half of congenital hypopituitarism cases is unknown. Our long-term goal is to expand the molecular diagnoses for congenital hypopituitarism by identifying genes that contribute to this condition. We have previously shown that the forkhead box transcription factor, FOXO1, is present in approximately half of somatotropes at embryonic day (e) 18.5, suggesting it may have a role in somatotrope differentiation or function. To elucidate the role of FOXO1 in somatotrope differentiation and function, Foxo1 was conditionally deleted from the anterior pituitary (Foxo1^Δpit). Uncommitted progenitor cells are maintained and able to commit to the somatotrope lineage normally based on the expression patterns of Sox2, a marker of uncommitted pituitary progenitors, and Pou1f1 (also known as Pit1), which marks committed progenitors. Interestingly, Foxo1^Δpit embryonic mice exhibit delayed somatotrope differentiation as evidenced by an almost complete absence of GH immunoreactivity at e16.5 and reduced expression of Gh at e18.5 and postnatal day (P) 3. Consistent with this conclusion, expression of GHRH receptor, a marker of terminally differentiated somatotropes, is significantly reduced at e18.5 and P3 in the absence of FOXO1. The mechanism of FOXO1 regulation of somatotrope differentiation may involve the basic helix-loop-helix transcription factor, Neurod4, which has been implicated in somatotrope differentiation and is significantly reduced in Foxo1^Δpit mice. Foxo1^Δpit mice do not exhibit growth defects, and at P21 their pituitary glands exhibit a normal distribution of somatotropes. These studies demonstrate that FOXO1 is important for initial somatotrope specification embryonically but is dispensable for postnatal somatotrope expansion and growth.

Expression Analysis of the Hippo Cascade Indicates a Role in Pituitary Stem Cell Development

The pituitary gland is a primary endocrine organ that controls major physiological processes. Abnormal development or homeostatic disruptions can lead to human disorders such as hypopituitarism or tumors. Multiple signaling pathways, including WNT, BMP, FGF, and SHH regulate pituitary development but the role of the Hippo-YAP1/TAZ cascade is currently unknown. In multiple tissues, the Hippo kinase cascade underlies neoplasias; it influences organ size through the regulation of proliferation and apoptosis, and has roles in determining stem cell potential. We have used a sensitive mRNA in situ hybridization method (RNAscope) to determine the expression patterns of the Hippo pathway components during mouse pituitary development. We have also carried out immunolocalisation studies to determine when YAP1 and TAZ, the transcriptional effectors of the Hippo pathway, are active. We find that YAP1/TAZ are active in the stem/progenitor cell population throughout development and at postnatal stages, consistent with their role in promoting the stem cell state. Our results demonstrate for the first time the collective expression of major components of the Hippo pathway during normal embryonic and postnatal development of the pituitary gland.

The molecular basis of craniofacial placode development

The sensory organs of the vertebrate head originate from simple ectodermal structures known as cranial placodes. All cranial placodes derive from a common domain adjacent to the neural plate, the preplacodal region, which is induced at the border of neural and non-neural ectoderm during gastrulation. Induction and specification of the preplacodal region is regulated by the fibroblast growth factor, bone morphogenetic protein, WNT, and retinoic acid signaling pathways, and characterized by expression of the EYA and SIX family of transcriptional regulators. Once the preplacodal region is specified, different combinations of local signaling molecules and placode-specific transcription factors, including competence factors, promote the induction of individual cranial placodes along the neural axis of the head region. In this review, we summarize the steps of cranial placode development and discuss the roles of the main signaling molecules and transcription factors that regulate these steps during placode induction, specification, and development. For further resources related to this article, please visit the WIREs website.

Functional characterization of a human POU1F1 mutation associated with isolated growth hormone deficiency: a novel etiology for IGHD

POU1F1, a pituitary-specific POU-homeo domain transcription factor, plays an essential role in the specification of the somatotroph, lactotroph and thyrotroph lineages and in the activation of GH1, PRL and TSHβ transcription. Individuals with mutations in POU1F1 present with combined deficiency of GH, PRL and TSH. Here, we identified a heterozygous missense mutation with evidence of pathogenicity, at the POU1F1 locus, in a large family in which an isolated growth hormone deficiency segregates as an autosomal dominant trait. The corresponding p.Pro76Leu mutation maps to a conserved site within the POU1F1 transactivation domain. Bandshift assays revealed that the mutation alters wild-type POU1F1 binding to cognate sites within the hGH-LCR and hGH1 promoter, but not to sites within the PRL promoter, and it selectively increases binding affinity to sites within the hGH-LCR. Co-immunoprecipitation studies reveal that this substitution enhances interactions of POU1F1 with three of its cofactors, PITX1, LHX3a and ELK1, and that residue 76 plays a critical role in these interactions. The insertion of the mutation at the mouse Pou1f1 locus results in a dramatic loss of protein expression despite normal mRNA concentrations. Mice heterozygous for the p.Pro76Leu mutation were phenotypically normal while homozygotes demonstrated a dwarf phenotype. Overall, this study unveils the involvement of POU1F1 in dominantly inherited isolated GH deficiency and demonstrates a significant impact of the Pro76Leu mutation on DNA-binding activities, alterations in transactivating functions and interactions with cofactors. Our data further highlight difficulties in modeling human genetic disorders in the mouse despite apparent conservation of gene expression pathways and physiologic functions.

Hes1 and Hes5 are required for differentiation of pituicytes and formation of the neurohypophysis in pituitary development

The pituitary gland is a critical endocrine organ regulating diverse physiological functions, including homeostasis, metabolism, reproduction, and growth. It is composed of two distinct entities: the adenohypophysis, including the anterior and intermediate lobes, and the neurohypophysis known as the posterior lobe. The neurohypophysis is composed of pituicytes (glial cells) and axons projected from hypothalamic neurons. The adenohypophysis derives from Rathke's pouch, whereas the neurohypophysis derives from the infundibulum, an evagination of the ventral diencephalon. Molecular mechanisms of adenohypophysis development are much better understood, but little is known about mechanisms that regulate neurohypophysis development. Hes genes, known as Notch effectors, play a crucial role in specifying cellular fates during the development of various tissues and organs. Here, we report that the ventral diencephalon fails to evaginate resulting in complete loss of the posterior pituitary lobe in Hes1(-/-); Hes5(+/-) mutant embryos. In these mutant mice, progenitor cells are differentiated into neurons at the expense of pituicytes in the ventral diencephalon. In the developing neurohypophysis, the proliferative zone is located at the base of the infundibulum. Thus, Hes1 and Hes5 modulate not only maintenance of progenitor cells but also pituicyte versus neuron fate specification during neurohypophysis development.