Dual roles for Id4 in the regulation of estrogen signaling in the mammary gland and ovary.

The HLH transcriptional regulator Id4 exerts important roles in different organs, including the neural compartment, where Id4 loss usually results in early lethality. To explore the role of this basally restricted transcription factor in the mammary gland, we generated a cre-inducible mouse model. MMTV- or K14-cre-mediated deletion of Id4 led to a delay in ductal morphogenesis, consistent with previous findings using a germ-line knockout mouse model. A striking increase in the expression of ERα (Esr1), PR and FoxA1 was observed in both the basal and luminal cellular subsets of Id4-deficient mammary glands. Together with chromatin immunoprecipitation of Id4 on the Esr1 and Foxa1 promoter regions, these data imply that Id4 is a negative regulator of the ERα signaling axis. Unexpectedly, examination of the ovaries of targeted mice revealed significantly increased numbers of secondary and antral follicles, and reduced Id4 expression in the granulosa cells. Moreover, expression of the cascade of enzymes that are crucial for estrogen biosynthesis in the ovary was decreased in Id4-deficient females and uterine weights were considerably lower, indicating impaired estrogen production. Thus, compromised ovarian function and decreased circulating estrogen likely contribute to the mammary ductal defects evident in Id4-deficient mice. Collectively, these data identify Id4 as a novel regulator of estrogen signaling, where Id4 restrains ERα expression in the basal and luminal cellular compartments of the mammary gland and regulates estrogen biosynthesis in the ovary.

Gata-3 is an essential regulator of mammary-gland morphogenesis and luminal-cell differentiation.

The transcription factor Gata-3 is a defining marker of the 'luminal' subtypes of breast cancer. To gain insight into the role of Gata-3 in breast epithelial development and oncogenesis, we have explored its normal function within the mammary gland by conditionally deleting Gata-3 at different stages of development. We report that Gata-3 has essential roles in the morphogenesis of the mammary gland in both the embryo and adult. Through the discovery of a novel marker (beta3-integrin) of luminal progenitor cells and their purification, we demonstrate that Gata-3 deficiency leads to an expansion of luminal progenitors and a concomitant block in differentiation. Remarkably, introduction of Gata-3 into a stem cell-enriched population induced maturation along the alveolar luminal lineage. These studies provide evidence for the existence of an epithelial hierarchy within the mammary gland and establish Gata-3 as a critical regulator of luminal differentiation.

Neuregulin 1 sustains the gene regulatory network in both trabecular and nontrabecular myocardium.

RATIONALE: The cardiac gene regulatory network (GRN) is controlled by transcription factors and signaling inputs, but network logic in development and it unraveling in disease is poorly understood. In development, the membrane-tethered signaling ligand Neuregulin (Nrg)1, expressed in endocardium, is essential for ventricular morphogenesis. In adults, Nrg1 protects against heart failure and can induce cardiomyocytes to divide. OBJECTIVE: To understand the role of Nrg1 in heart development through analysis of null and hypomorphic Nrg1 mutant mice. METHODS AND RESULTS: Chamber domains were correctly specified in Nrg1 mutants, although chamber-restricted genes Hand1 and Cited1 failed to be activated. The chamber GRN subsequently decayed with individual genes exhibiting decay patterns unrelated to known patterning boundaries. Both trabecular and nontrabecular myocardium were affected. Network demise was spatiotemporally dynamic, the most sensitive region being the central part of the left ventricle, in which the GRN underwent complete collapse. Other regions were partially affected with graded sensitivity. In vitro, Nrg1 promoted phospho-Erk1/2-dependent transcription factor expression, cardiomyocyte maturation and cell cycle inhibition. We monitored cardiac pErk1/2 in embryos and found that expression was Nrg1-dependent and levels correlated with cardiac GRN sensitivity in mutants. CONCLUSIONS: The chamber GRN is fundamentally labile and dependent on signaling from extracardiac sources. Nrg1-ErbB1/4-Erk1/2 signaling critically sustains elements of the GRN in trabecular and nontrabecular myocardium, challenging our understanding of Nrg1 function. Transcriptional decay patterns induced by reduced Nrg1 suggest a novel mechanism for cardiac transcriptional regulation and dysfunction in disease, potentially linking biomechanical feedback to molecular pathways for growth and differentiation.

Reducing pressure damage in the operating theatre.

Pressure sores occurring in surgical patients are often not attributed to time spent in the operating theatre. Initial underlying damage can occur whilst undergoing a surgical procedure but may not become apparent until hours or days later. In carrying out a literature review, the author concluded that such a fundamental aspect of nursing care in the operating theatre is a low priority and that nurses could do more in terms of pressure relief for their patients. The author concludes by identifying implications for practice.

Molecular correlates of platinum response in human high-grade serous ovarian cancer patient-derived xenografts.

INTRODUCTION: Improvement in the ability to target underlying drivers and vulnerabilities of high-grade serous ovarian cancer (HG-SOC) requires the development of molecularly annotated pre-clinical models reflective of clinical responses. METHODS: We generated patient-derived xenografts (PDXs) from consecutive, chemotherapy-naïve, human HG-SOC by transplanting fresh human HG-SOC fragments into subcutaneous and intra-ovarian bursal sites of NOD/SCID IL2Rγ(null) recipient mice, completed molecular annotation and assessed platinum sensitivity. RESULTS: The success rate of xenografting was 83%. Of ten HG-SOC PDXs, all contained mutations in TP53, two were mutated for BRCA1, three for BRCA2, and in two, BRCA1 was methylated. In vivo cisplatin response, determined as platinum sensitive (progression-free interval ≥ 100 d, n = 4), resistant (progression-free interval <100 d, n = 3) or refractory (n = 3), was largely consistent with patient outcome. Three of four platinum sensitive HG-SOC PDXs contained DNA repair gene mutations, and the fourth was methylated for BRCA1. In contrast, all three platinum refractory PDXs overexpressed dominant oncogenes (CCNE1, LIN28B and/or BCL2). CONCLUSIONS: Because PDX platinum response reflected clinical outcome, these annotated PDXs will provide a unique model system for preclinical testing of novel therapies for HG-SOC.

Absence of suppressor of cytokine signalling 3 reduces self-renewal and promotes differentiation in murine embryonic stem cells.

Leukemia inhibitory factor (LIF) is required to maintain pluripotency and permit self-renewal of murine embryonic stem (ES) cells. LIF binds to a receptor complex of LIFR-beta and gp130 and signals via the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway, with signalling attenuated by suppressor of cytokine signalling (SOCS) proteins. Recent in vivo studies have highlighted the role of SOCS-3 in the negative regulation of signalling via gp130. To determine the role of SOCS-3 in ES cell biology, SOCS-3-null ES cell lines were generated. When cultured in LIF levels that sustain self-renewal of wild-type cells, SOCS-3-null ES cell lines exhibited less self-renewal and greater differentiation into primitive endoderm. The absence of SOCS-3 enhanced JAK-STAT and extracellular signal-related kinase 1/2 (ERK-1/2)-mitogen-activated protein kinase (MAPK) signal transduction via gp130, with higher levels of phosphorylated STAT-1, STAT-3, SH-2 domain-containing cytoplasmic protein tyrosine phosphatase 2 (SHP-2), and ERK-1/2 in steady state and in response to LIF stimulation. Attenuation of ERK signalling by the addition of MAPK/ERK kinase (MEK) inhibitors to SOCS-3-null ES cell cultures rescued the differentiation phenotype, but did not restore proliferation to wild-type levels. In summary, SOCS-3 plays a crucial role in the regulation of the LIF signalling pathway in murine ES cells. Its absence perturbs the balance between activation of the JAK-STAT and SHP-2-ERK-1/2-MAPK pathways, resulting in less self-renewal and a greater potential for differentiation into the primitive endoderm lineage.

Genetic reduction of embryonic leukemia-inhibitory factor production rescues placentation in SOCS3-null embryos but does not prevent inflammatory disease.

The suppressor of cytokine-signaling (SOCS) proteins act as negative-feedback inhibitors of cytokine and growth-factor-induced signal transduction. In vivo studies have implicated SOCS3 as a negative regulator of signaling downstream of gp130, the receptor subunit shared by IL-6-like cytokines. Mice lacking SOCS3 die at midgestation because of placental failure, and SOCS3 ablation in a cell-type-specific manner results in changes in the functional outcome of gp130 signaling in response to IL-6. In this study, we show that genetic reduction of leukemia-inhibitory factor (LIF) production by embryo-derived tissues is sufficient to prevent the placental defect. This establishes LIF signaling as a major physiological regulator of trophoblast differentiation in vivo. Mice deficient in both SOCS3 and LIF are born in predicted numbers and appear normal at birth but exhibit failure to thrive and high neonatal mortality. Adult SOCS3-null mice on a LIF-null background succumb to a spontaneous fatal inflammatory disease characterized by neutrophilia and inflammatory-cell tissue infiltrates. The disease spectrum mimics that seen in mice with a conditional deletion of SOCS3 in hematopoietic and endothelial cells, extending the evidence for a major role for SOCS3 in the homeostatic regulation of the inflammatory response and indicates that LIF is not required for this process.

The pluripotency homeobox gene NANOG is expressed in human germ cell tumors.

BACKGROUND: The NANOG gene, a member of the homeobox family of DNA binding transcription factors, was recently identified in a screen for pluripotency-promoting genes. NANOG overexpression in murine embryonic stem cells is sufficient to maintain self-renewal and to block differentiation. The NANOG gene is located on human chromosome 12p13, a region frequently duplicated in human tumors of germ cell origin and in cultured human embryonic stem cells. Here we investigate the expression and gene copy number of NANOG in human germ cells and tumors of germ cell origin. METHODS: Immunohistochemistry and quantitative polymerase chain reaction (QPCR) were used to examine the expression and gene copy number of the human NANOG gene in germ cell tumors. RESULTS: NANOG protein was detected in germline stem cells (gonocytes) within the developing testis. Immunohistochemistry and quantitative real-time PCR analysis were used to demonstrate that NANOG is highly and specifically expressed in carcinoma in situ (CIS), embryonal carcinomas, and seminomas, but not in teratomas and yolk sac tumors. CONCLUSIONS: NANOG expression in germline stem cells (gonocytes), CIS, embryonal carcinoma, and seminoma reveals a molecular and developmental link between germ cell tumors and the embryonic cells from which they arise. Identification of NANOG as a molecular marker of undifferentiated germ cell tumors provides a novel tool for identifying and classifying tumors of germ cell origin.

Identification, cloning and expression analysis of the pluripotency promoting Nanog genes in mouse and human.

The murine Nanog gene, a member of the homeobox family of DNA binding transcription factors, has been shown recently to maintain pluripotency of embryonic stem cells. We have used a sequence homology and expression screen to identify and clone the mouse and human Nanog genes and characterized their phylogenetic context and expression patterns. We report here the gene structure and expression patterns of the mouse Nanog gene, the human Nanog and Nanog2 genes, and six processed human Nanog pseudogenes. Mouse Nanog expression is high in undifferentiated embryonic stem cells and is down-regulated during embryonic stem cell differentiation, concomitant with loss of pluripotency. Murine embryonic Nanog expression is detected in the inner cell mass of the blastocyst. After implantation, Nanog is detectable at embryonic day (E) 6 in proximal epiblast in the region of the presumptive primitive streak. Expression extends distally as the streak elongates during gastrulation and remains restricted to epiblast. Nanog RNA is down-regulated in cells ingressing through the streak to form mesoderm and definitive endoderm. Nanog expression also marks the pluripotent germ cells of the nascent gonad at E11.5-E12.5 and is highly expressed in germ cell tumour and teratoma-derived cell lines. Reverse transcriptase-polymerase chain reaction analysis detected mouse Nanog expression at low levels in several adult tissues. The human Nanog genes are expressed in embryonic stem cells and down-regulated in all adult tissues and differentiated cell lines examined. High levels of human Nanog expression were detected by Northern analysis in the undifferentiated N-Tera embryonal carcinoma cell line. The conservation in gene sequence, structure, and expression of mouse and human Nanog and Nanog2 genes may reflect a common role in the maintenance of pluripotency in both species.

Mixl1 is required for axial mesendoderm morphogenesis and patterning in the murine embryo.

In Xenopus, the Mix/Bix family of homeobox genes has been implicated in mesendoderm development. Mixl1 is the only known murine member of this family. To examine the role of Mixl1 in murine embryogenesis, we used gene targeting to create mice bearing a null mutation of Mixl1. Homozygous Mixl1 mutant embryos can be distinguished from their littermates by a marked thickening of the primitive streak. By the early somite stage, embryonic development is arrested, with the formation of abnormal head folds, foreshortened body axis, absence of heart tube and gut, deficient paraxial mesoderm, and an enlarged midline tissue mass that replaces the notochord. Development of extra-embryonic structures is generally normal except that the allantois is often disproportionately large for the size of the mutant embryo. In chimeras, Mixl1(-/-) mutant cells can contribute to all embryonic structures, with the exception of the hindgut, suggesting that Mixl1 activity is most crucial for endodermal differentiation. Mixl1 is therefore required for the morphogenesis of axial mesoderm, the heart and the gut during embryogenesis.

SOCS3 is a critical physiological negative regulator of G-CSF signaling and emergency granulopoiesis.

To determine the importance of suppressor of cytokine signaling-3 (SOCS3) in the regulation of hematopoietic growth factor signaling generally, and of G-CSF-induced cellular responses specifically, we created mice in which the Socs3 gene was deleted in all hematopoietic cells. Although normal until young adulthood, these mice then developed neutrophilia and a spectrum of inflammatory pathologies. When stimulated with G-CSF in vitro, SOCS3-deficient cells of the neutrophilic granulocyte lineage exhibited prolonged STAT3 activation and enhanced cellular responses to G-CSF, including an increase in cloning frequency, survival, and proliferative capacity. Consistent with the in vitro findings, mutant mice injected with G-CSF displayed enhanced neutrophilia, progenitor cell mobilization, and splenomegaly, but unexpectedly also developed inflammatory neutrophil infiltration into multiple tissues and consequent hind-leg paresis. We conclude that SOCS3 is a key negative regulator of G-CSF signaling in myeloid cells and that this is of particular significance during G-CSF-driven emergency granulopoiesis.