Pituitary stem cells produce paracrine WNT signals to control the expansion of their descendant progenitor cells

In response to physiological demand, the pituitary gland generates new hormonesecreting cells from committed progenitor cells throughout life. It remains unclear to what extent pituitary stem cells (PSCs), which uniquely express SOX2, contribute to pituitary growth and renewal. Moreover, neither the signals that drive proliferation nor their sources have been elucidated. We have used genetic approaches in the mouse, showing that the WNT pathway is essential for proliferation of all lineages in the gland. We reveal that SOX2+ stem cells are a key source of WNT ligands. By blocking secretion of WNTs from SOX2+ PSCs in vivo, we demonstrate that proliferation of neighbouring committed progenitor cells declines, demonstrating that progenitor multiplication depends on the paracrine WNT secretion from SOX2+ PSCs. Our results indicate that stem cells can hold additional roles in tissue expansion and homeostasis, acting as paracrine signalling centres to coordinate the proliferation of neighbouring cells

The Development of Linguistic Competences for Employability: A Training Project for Teachers

AbstractEmployability is a new concept that has just appeared in the Spanish educational system. Its rising importance is due to European Union educational policies which aim to provide young people with training that enables them to take part successfully in the present and future working world.This paper argues for the need to develop employability from the very start of formal education, and within this, we highlight the importance of developing linguistic competence among pre-school and primary pupils as a key element for favouring employability.To be able to do so, the teaching staff must be trained using quality education to enable them to work effectively on this competence. In this paper we present how a training program, with a specific European dimension, has been designed by a state school from the Valencian Community, to serve as a model for other schools concerned about the development of a linguistic competence that helps to improve both teachers’ and pupils’ employability

Tumour compartment transcriptomics demonstrates the activation of inflammatory and odontogenic programmes in human adamantinomatous craniopharyngioma and identifies the MAPK/ERK pathway as a novel therapeutic target

Adamantinomatous craniopharyngiomas (ACPs) are clinically challenging tumours, the majority of which have activating mutations in CTNNB1. They are histologically complex, showing cystic and solid components, the latter comprised of different morphological cell types (e.g. β-catenin-accumulating cluster cells and palisading epithelium), surrounded by a florid glial reaction with immune cells. Here, we have carried out RNA sequencing on 18 ACP samples and integrated these data with an existing ACP transcriptomic dataset. No studies so far have examined the patterns of gene expression within the different cellular compartments of the tumour. To achieve this goal, we have combined laser capture microdissection with computational analyses to reveal groups of genes that are associated with either epithelial tumour cells (clusters and palisading epithelium), glial tissue or immune infiltrate. We use these human ACP molecular signatures and RNA-Seq data from two ACP mouse models to reveal that cell clusters are molecularly analogous to the enamel knot, a critical signalling centre controlling normal tooth morphogenesis. Supporting this finding, we show that human cluster cells express high levels of several members of the FGF, TGFB and BMP families of secreted factors, which signal to neighbouring cells as evidenced by immunostaining against the phosphorylated proteins pERK1/2, pSMAD3 and pSMAD1/5/9 in both human and mouse ACP. We reveal that inhibiting the MAPK/ERK pathway with trametinib, a clinically approved MEK inhibitor, results in reduced proliferation and increased apoptosis in explant cultures of human and mouse ACP. Finally, we analyse a prominent molecular signature in the glial reactive tissue to characterise the inflammatory microenvironment and uncover the activation of inflammasomes in human ACP. We validate these results by immunostaining against immune cell markers, cytokine ELISA and proteome analysis in both solid tumour and cystic fluid from ACP patients. Our data support a new molecular paradigm for understanding ACP tumorigenesis as an aberrant mimic of natural tooth development and opens new therapeutic opportunities by revealing the activation of the MAPK/ERK and inflammasome pathways in human ACP. KEYWORDS: Craniopharyngioma; IL1-β; Inflammasome; MAPK/ERK pathway; Odontogenesis; Paracrine signalling; Trametini

Identification of novel pathways involved in the pathogenesis of human adamantinomatous craniopharyngioma

Activating mutations in the gene encoding β-catenin have been identified in the paediatric form of human craniopharyngioma (adamantinomatous craniopharyngioma, ACP), a histologically benign but aggressive pituitary tumour accounting for up to 10% of paediatric intracranial tumours. Recently, we generated an ACP mouse model and revealed that, as in human ACP, nucleocytoplasmic accumulation of β-catenin (β-catnc) and over-activation of the Wnt/β-catenin pathway occurs only in a very small proportion of cells, which form clusters. Here, combining mouse genetics, fluorescence labelling and flow-sorting techniques, we have isolated these cells from tumorigenic mouse pituitaries and shown that the β-catnc cells are enriched for colony-forming cells when cultured in stem cell-promoting media, and have longer telomeres, indicating shared properties with normal pituitary progenitors/stem cells (PSCs). Global gene profiling analysis has revealed that these β-catnc cells express high levels of secreted mitogenic signals, such as members of the SHH, BMP and FGF family, in addition to several chemokines and their receptors, suggesting an important autocrine/paracrine role of these cells in the pathogenesis of ACP and a reciprocal communication with their environment. Finally, we highlight the clinical relevance of these findings by showing that these pathways are also up-regulated in the β-catnc cell clusters identified in human ACP. As well as providing further support to the concept that pituitary stem cells may play an important role in the oncogenesis of human ACP, our data reveal novel disease biomarkers and potential pharmacological targets for the treatment of these devastating childhood tumours.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-012-0957-9) contains supplementary material, which is available to authorized users

Adrenal cortical and chromaffin stem cells: Is there a common progeny related to stress adaptation?

The adrenal gland is a highly plastic organ with the capacity to adapt the body homeostasis to different physiological needs. The existence of stem-like cells in the adrenal cortex has been revealed in many studies. Recently, we identified and characterized in mice a pool of glia-like multipotent Nestin-expressing progenitor cells, which contributes to the plasticity of the adrenal medulla. In addition, we found that these Nestin progenitors are actively involved in the stress response by giving rise to chromaffin cells. Interestingly, we also observed a Nestin-GFP-positive cell population located under the adrenal capsule and scattered through the cortex. In this article, we discuss the possibility of a common progenitor giving rise to subpopulations of cells both in the adrenal cortex and medulla, the isolation and characterization of this progenitor as well as its clinical potential in transplantation therapies and in pathophysiology

Concise Review:Paracrine Role of Stem Cells in Pituitary Tumors: A Focus on Adamantinomatous Craniopharyngioma

The existence of tissue‐specific progenitor/stem cells in the adult pituitary gland of the mouse has been demonstrated recently using genetic tracing experiments. These cells have the capacity to differentiate into all of the different cell lineages of the anterior pituitary and self‐propagate in vitro and can therefore contribute to normal homeostasis of the gland. In addition, they play a critical role in tumor formation, specifically in the etiology of human adamantinomatous craniopharyngioma, a clinically relevant tumor that is associated with mutations in CTNNB1 (gene encoding β‐catenin). Mouse studies have shown that only pituitary embryonic precursors or adult stem cells are able to generate tumors when targeted with oncogenic β‐catenin, suggesting that the cell context is critical for mutant β‐catenin to exert its oncogenic effect. Surprisingly, the bulk of the tumor cells are not derived from the mutant progenitor/stem cells, suggesting that tumors are induced in a paracrine manner. Therefore, the cell sustaining the mutation in β‐catenin and the cell‐of‐origin of the tumors are different. In this review, we will discuss the in vitro and in vivo evidence demonstrating the presence of stem cells in the adult pituitary and analyze the evidence showing a potential role of these stem cells in pituitary tumors. Stem Cells 2016;34:268–27

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 tumours. Multiple signalling 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 hybridisation 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

Establishment of the neurogenic boundary of the mouse retina requires cooperation of SOX2 and WNT signaling

BackgroundEye development in vertebrates relies on the critical regulation of SOX2 expression. Humans with mutations in SOX2 often suffer from eye defects including anophthalmia (no eye) and microphthalmia (small eye). In mice, deletion of Sox2 in optic cup progenitor cells results in loss of neural competence and cell fate conversion of the neural retina to a non-neurogenic fate, specifically the acquisition of fate associated with progenitors of the ciliary epithelium. This fate is also promoted with constitutive expression of stabilized β-Catenin in the optic cup, where the WNT pathway is up-regulated. We addressed whether SOX2 co-ordinates the neurogenic boundary of the retina through modulating the WNT/β-Catenin pathway by using a genetic approach in the mouse.ResultsUpon deletion of Sox2 in the optic cup, response to WNT signaling was expanded, correlating with loss of neural competence, cell fate conversion of the neural retina to ciliary epithelium primordium and, in addition, increased cell cycle time of optic cup progenitors. Removal of Ctnnb1 rescued the cell fate conversion; however, the loss of neural competence and the proliferation defect resulting from lack of SOX2 were not overcome. Lastly, central Sox2-deficient optic cup progenitor cells exhibited WNT-independent up-regulation of D-type Cyclins.ConclusionWe propose two distinct roles for SOX2 in the developing retina. Our findings suggest that SOX2 antagonizes the WNT pathway to maintain a neurogenic fate and, in contrast, regulates cycling of optic cup progenitors in a WNT-independent manner. Given that WNT signaling acting upstream of SOX2 has been implicated in the tumorigenicity of embryonic stem cell-derived retinal progenitor cells, our results distinguish the endogenous role of WNT signaling in early optic cup patterning and support a WNT-independent role for SOX2 in maintaining retinal progenitor cell proliferation.Electronic supplementary materialThe online version of this article (doi:10.1186/1749-8104-9-27) contains supplementary material, which is available to authorized users