Molecular Endocrinology Current Issue

Minireview: Pref-1: Role in Adipogenesis and Mesenchymal Cell Fate

Sul, H. S. — Tue, 27 Oct 2009 10:02:17 PDT

Preadipocyte factor-1 [Pref-1; also called Dlk1 (Delta-like protein 1)] is made as an epidermal growth factor-repeat containing transmembrane protein that produces a biologically active soluble form by TNF--converting enzyme (TACE)-mediated cleavage. Soluble Pref-1 activates the MAPK kinase/ERK pathway. In adipose tissue, Pref-1 is specifically expressed in preadipocytes but not in adipocytes and thus is used as a preadipocyte marker. Inhibition of adipogenesis by Pref-1 has been well established in vitro as well as in vivo by ablation and overexpression of Pref-1. SRY (sex determining region Y)-box 9 (Sox9), a transcription factor expressed in preadipocytes to suppress CCAAT enhancer binding protein β and (C/EBP) expression, is required to be down-regulated before adipocyte differentiation can proceed. By activating MAPK kinase/ERK, Pref-1 prevents down-regulation of Sox9, resulting in inhibition of adipogenesis. Furthermore, by inducing Sox9, Pref-1 promotes chondrogenic induction of mesenchymal cells but prevents chondrocyte maturation as well as osteoblast differentiation. Thus, Pref-1 directs multipotent mesenchymal cells toward the chondrogenic lineage but inhibits differentiation into adipocytes as well as osteoblasts and chondrocytes. Pref-1, encoded by an imprinted gene, has also been detected in progenitor cells in various tissues during regeneration and therefore may have a more general role in maintaining cells in an undifferentiated state.

Genomic and Nongenomic Cross Talk between the Gonadotropin-Releasing Hormone Receptor and Glucocorticoid Receptor Signaling Pathways

Kotitschke, A., Sadie-Van Gijsen, H., Avenant, C., Fernandes, S., Hapgood, J. P. — Tue, 27 Oct 2009 10:02:17 PDT

The GnRH receptor (GnRHR), a member of the G protein-coupled receptor family, is a central regulator of reproductive function in all vertebrates. The peptide hormone GnRH exerts its effects via binding to the GnRHR in pituitary gonadotropes. We investigated the mechanisms of regulation of transcription of the mGnRHR gene in the mouse pituitary gonadotrope LβT2 cell line by GnRH and dexamethasone (dex). Reporter assays with transfected mGnRHR promoter show that both dex and GnRH increase transcription of the mGnRHR gene via an activating protein-1 (AP-1) site. Real-time PCR confirmed this on the endogenous mGnRHR gene, and small interfering RNA experiments revealed a requirement for the glucocorticoid receptor (GR) for both the dex and GnRH response. Chromatin immunoprecipitation (ChIP) and immunofluorescence assays provide evidence that both GnRH and dex up-regulate the GnRHR gene via nuclear translocation and interaction of the GR with the AP-1 region on the mGnRHR promoter. We show that GnRH activates the unliganded GR by rapid phosphorylation of the GR at Ser-234 in a GnRHR-dependent fashion to transactivate a GRE reporter gene in LβT2 and COS-1 cells. Using kinase inhibitors, we established a direct link between GnRH-induced protein kinase C and MAPK activation, leading to unliganded GR phosphorylation at Ser-234 and transactivation of the glucocorticoid response element. Furthermore, we show that GnRH and dex synergistically activate the endogenous GnRHR promoter in LβT2 cells, via a mechanism involving steroid receptor coactivator-1 recruitment to the GnRHR AP-1 region. Our results suggest a novel mechanism of rapid nongenomic cross talk between the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes via GnRHR-dependent phosphorylation and activation of the unliganded GR in response to GnRH.

A Novel Isoform of Human LZIP Negatively Regulates the Transactivation of the Glucocorticoid Receptor

Kang, H., Kim, Y. S., Ko, J. — Tue, 27 Oct 2009 10:02:17 PDT

The human leucine zipper protein (LZIP) is a basic leucine zipper transcription factor that is involved in leukocyte migration, tumor suppression, and endoplasmic reticulum stress-associated protein degradation. Although evidence suggests a diversity of roles for LZIP, its function is not fully understood, and the subcellular localization of LZIP is still controversial. We identified a novel isoform of LZIP and characterized its function in ligand-induced transactivation of the glucocorticoid receptor (GR) in COS-7 and HeLa cells. A novel isoform of human LZIP designated as "sLZIP" contains a deleted putative transmembrane domain (amino acids 229–245) of LZIP and consists of 345 amino acids. LZIP and sLZIP were ubiquitously expressed in a variety of cell lines and tissues, with LZIP being much more common. sLZIP was mainly localized in the nucleus, whereas LZIP was located in the cytoplasm. Unlike LZIP, sLZIP was not involved in the chemokine-mediated signal pathway. sLZIP recruited histone deacetylases (HDACs) to the promoter region of the mouse mammary tumor virus luciferase reporter gene and enhanced the activities of HDACs, resulting in suppression of expression of the GR target genes. Our findings suggest that sLZIP functions as a negative regulator in glucocorticoid-induced transcriptional activation of GR by recruitment and activation of HDACs.

Isoform-Specific Transcriptional Activity of Overlapping Target Genes that Respond to Thyroid Hormone Receptors {alpha}1 and {beta}1

Chan, I. H., Privalsky, M. L. — Tue, 27 Oct 2009 10:02:17 PDT

Thyroid hormone receptors (TRs) are hormone-regulated transcription factors that control multiple aspects of physiology and development. TRs are expressed in vertebrates as a series of distinct isoforms that exert distinct biological roles. We wished to determine whether the two most widely expressed isoforms, TR1 and TRβ1, exert their different biological effects by regulating different sets of target genes. Using stably transformed HepG2 cells and a microarray analysis, we were able to demonstrate that TR1 and TRβ1 regulate a largely overlapping repertoire of target genes in response to T₃ hormone. However, these two isoforms display very different transcriptional properties on each individual target gene, ranging from a much greater T₃-mediated regulation by TR1 than by TRβ1, to near equal regulation by both isoforms. We also identified TR1 and TRβ1 target genes that were regulated by these receptors in a hormone-independent fashion. We suggest that it is this gene-specific, isoform-specific amplitude of transcriptional regulation that is the likely basis for the appearance and maintenance of TR1 and TRβ1 over evolutionary time. In essence, TR1 and TRβ1 adjust the magnitude of the transcriptional response at different target genes to different levels; by altering the ratio of these isoforms in different tissues or at different developmental times, the intensity of T₃ response can be individually tailored to different physiological and developmental requirements.

Functional Screening of FxxLF-Like Peptide Motifs Identifies SMARCD1/BAF60a as an Androgen Receptor Cofactor that Modulates TMPRSS2 Expression

Tue, 27 Oct 2009 10:02:17 PDT

Androgen receptor (AR) transcriptional activity is tightly regulated by interacting cofactors and cofactor complexes. The best described cofactor interaction site in the AR is the hormone-induced coactivator binding groove in the ligand-binding domain, which serves as a high-affinity docking site for FxxLF-like motifs. This study aimed at identifying novel AR cofactors by in silico selection and functional screening of FxxLF-like peptide motifs. Candidate interacting motifs were selected from a proteome-wide screening and from a supervised screening focusing on components of protein complexes involved in transcriptional regulation. Of the 104 peptides tested, 12 displayed moderate to strong in vivo hormone-dependent interactions with AR. For three of these, ZBTB16/PLZF, SMARCA4/BRG1, and SMARCD1/BAF60a, the full-length protein was tested for interaction with AR. Of these, BAF60a, a subunit of the SWI/SNF chromatin remodeling complex, displayed hormone-dependent interactions with AR through its FxxFF motif. Vice versa, recruitment of BAF60a by the AR required an intact coactivator groove. BAF60a depletion by small interfering RNA in LNCaP cells demonstrated differential effects on expression of endogenous AR target genes. AR-driven expression of TMPRSS2 was almost completely blocked by BAF60a small interfering RNA. In summary, our data demonstrate that BAF60a directly interacts with the coactivator groove in the AR ligand-binding domain via its FxxFF motif, thereby selectively activating specific AR-driven promoters.

Decreased PPAR{gamma} Expression Compromises Perigonadal-Specific Fat Deposition and Insulin Sensitivity

Tue, 27 Oct 2009 10:02:17 PDT

Mutations and polymorphisms in PPARG have been linked to adiposity and partial lipodystrophy in humans. However, how disturbances in PPARG lead to depot-specific effects on adipose tissue, as shown by the characteristic aberrant fat distribution in patients, remains unclear. By manipulating the 3'-untranslated region of the Pparg gene, we have generated mice with peroxisome proliferator-activated receptor (PPAR) gene expression ranging from 25% to 100% normal. Basal levels of PPAR transcripts between 50% and approximately 100% had no significant effect on body weight, fat mass, and insulin sensitivity. In contrast, mice with 25% normal PPAR expression exhibited reduced body weight and total fat mass, insulin resistance, and dyslipidemia. Interestingly, fat mass was selectively reduced in perigonadal depot without significant changes in inguinal and other depots. Expression of adipogenic factor CCAAT enhancer binding protein- and some other metabolic genes containing peroxisome proliferator response element were reduced in a perigonadal depot-specific fashion. This was further associated with depot-specific reduction in the expression of adipokines, increased expression of TNF, and increased ectopic lipid deposition in muscles. Together, these results underscore the differential sensitivity of the individual fat depots on PPAR availability as an underlying mechanism of partial lipodystrophy.

Proteomic Analysis of Phosphorylated Nuclear Proteins Underscores Novel Roles for Rapid Actions of Retinoic Acid in the Regulation of mRNA Splicing and Translation

Tue, 27 Oct 2009 10:02:17 PDT

Retinoic acid (RA) signaling is mediated by the retinoic acid receptor (RAR), belonging to the nuclear hormone receptor superfamily. In addition to its classical transcriptional actions, RAR also mediates rapid transcription-independent (nongenomic) actions, consisting in the activation of signal transduction pathways, as the phosphatidyl-inositol-3-kinase or the ERK MAPK-signaling pathways. RA-induced rapid transcription-independent actions play a role in different physiological contexts. As an effort toward understanding the functions of those rapid actions on signaling elicited by RA, we have identified nuclear proteins the phosphorylation state of which is rapidly modified by RA treatment in neuroblastoma cells, using a proteomic approach. Our results show that RA treatment led to changes in the phosphorylation patterns in two families of proteins: 1) those related to chromatin dynamics in relation to transcriptional activation, and 2) those related to mRNA processing and, in particular, mRNA splicing. We show that treatment of neuroblastoma cells with RA leads to alteration of the regulation of pre-mRNA splicing and mRNA translation. Thus, our results underscore novel functions for the rapid signaling elicited by RAR in the regulation of mRNA processing. We conclude that RA activation of signaling pathways can indeed regulate mRNA processing as part of a cellular response orchestrated by the nuclear receptor RAR.

G Protein-Coupled Receptor 30 Expression Is Up-Regulated by EGF and TGF{alpha} in Estrogen Receptor {alpha}-Positive Cancer Cells

Tue, 27 Oct 2009 10:02:17 PDT

In the present study, we evaluated the regulation of G protein-coupled receptor (GPR)30 expression in estrogen receptor (ER)-positive endometrial, ovarian, and estrogen-sensitive, as well as tamoxifen-resistant breast cancer cells. We demonstrate that epidermal growth factor (EGF) and TGF transactivate the GPR30 promoter and accordingly up-regulate GPR30 mRNA and protein levels only in endometrial and tamoxifen-resistant breast cancer cells. These effects exerted by EGF and TGF were dependent on EGF receptor (EGFR) expression and activation and involved phosphorylation of the Tyr¹⁰⁴⁵ and Tyr¹¹⁷³ EGFR sites. Using gene-silencing experiments and specific pharmacological inhibitors, we have ascertained that EGF and TGF induce GPR30 expression through the EGFR/ERK transduction pathway, and the recruitment of c-fos to the activator protein-1 site located within GPR30 promoter sequence. Interestingly, we show that functional cross talk of GPR30 with both activated EGFR and ER relies on a physical interaction among these receptors, further extending the potential of estrogen to trigger a complex stimulatory signaling network in hormone-sensitive tumors. Given that EGFR/HER2 overexpression is associated with tamoxifen resistance, our data may suggest that ligand-activated EGFR could contribute to the failure of tamoxifen therapy also by up-regulating GPR30, which in turn could facilitates the action of estrogen. In addition, important for resistance is the ability of tamoxifen to bind to and activate GPR30, the expression of which is up-regulated by EGFR activation. Our results emphasize the need for new endocrine agents able to block widespread actions of estrogen without exerting any stimulatory activity on transduction pathways shared by the steroid and growth factor-signaling networks.

BMP-4 Induction of Arrest and Differentiation of Osteoblast-Like Cells via p21CIP1 and p27KIP1 Regulation

Tue, 27 Oct 2009 10:02:17 PDT

Cell cycle regulation by differentiation signals is critical for eukaryote development. We investigated the roles of bone morphogenetic protein (BMP)-4, an important stimulator of osteoblast differentiation and bone formation, in regulating cell cycle distribution in four osteoblast-like cell lines and mouse primary osteoblasts, and the underlying mechanisms. In all cells used, BMP-4 induced G₀/G₁ arrest. The molecular basis of the BMP-4 effect was analyzed, and the presentation on molecular mechanism is focused on human MG63 cells. BMP-4 induced p21^CIP1 and p27^KIP1 expressions and hence cell differentiation but had no effects on the expressions of cyclins A, B1, D1, and E, cyclin-dependent protein kinase-2, -4, and -6. Using specific small interfering RNA (siRNA), we found that BMP-4-induced G₀/G₁ arrest, and p21^CIP1 and p27^KIP1 expressions were mediated by BMP receptor type IA (BMPRIA)-specific Sma- and Mad-related protein (Smad)1/5. BMP-4 induced transient phosphorylations of ERK; transfection of MG63 cells with ERK2, but not ERK1, -specific siRNA inhibited the BMP-4-induced responses in MG63 cells. Pretreatment of MG63 cells with Arg-Gly-Asp-Ser, which blocks the cell-extracellular matrix interaction, or transfection with β₃ integrin-specific siRNA inhibited BMP-4-induced ERK and Smad1/5 phosphorylations. BMP-4 induced transient increases in associations of β₃-integrin with focal adhesion kinase and Shc, the dominant-negative mutants of which inhibited BMP-4-induced ERK and Smad1/5 phosphorylations. Our results indicate that BMP-4 induces G₀/G₁ arrest and hence differentiation in osteoblast-like cells through increased expressions of p21^CIP1 and p27^KIP1, which are mediated by BMPRIA-specific Smad1/5. The extracellular matrix/β₃ integrin/ focal adhesion kinase/Shc/ERK2 signaling pathway is involved in these BMP-4-induced responses in osteoblast-like cells.

Paradoxical Stimulation of Cyclooxygenase-2 Expression by Glucocorticoids via a Cyclic AMP Response Element in Human Amnion Fibroblasts

Tue, 27 Oct 2009 10:02:17 PDT

Human amnion fibroblasts produce abundant prostaglandins toward the end of gestation, which is one of the major events leading to parturition. In marked contrast to its well-described antiinflammatory effect, glucocorticoids have been shown to up-regulate cyclooxygenase-2 (COX-2) expression in human amnion fibroblasts. The mechanisms underlying this paradoxical induction of COX-2 by glucocorticoids have not been resolved. Using cultured human amnion fibroblasts, we found that the induction of COX-2 mRNA expression by cortisol was a glucocorticoid receptor (GR)-dependent process requiring ongoing transcription. Upon transfection of a COX-2 promoter-driven reporter gene into the amnion fibroblasts, cortisol stimulated the COX-2 promoter activity. This was abolished by mutagenesis of a cAMP response element (CRE) at –53 to approximately –59bp as well as by cotransfection of a plasmid expressing dominant-negative CRE-binding protein (CREB). The phosphorylation level of CREB-1 was significantly increased by cortisol treatment of the amnion fibroblasts, whereas the effect was attenuated either by the protein kinase A inhibitor H89 or the p38 -MAPK inhibitor SB203580. The induction of the COX-2 promoter activity and the phosphorylation of CREB-1 were also blocked by the GR antagonist RU486. Chromatin immunoprecipitation (ChIP) assay revealed that the binding of CREB-1 to the CRE of the COX-2 promoter was increased by cortisol treatment of the amnion fibroblasts. In conclusion, cortisol, via binding to GR, stimulated COX-2 expression by increasing phosphorylated CREB-1 binding to the CRE of the COX-2 gene. Cortisol may phosphorylate CREB-1 by activating either protein kinase A or p38-MAPK in the amnion fibroblasts.

A Preformed Signaling Complex Mediates GnRH-Activated ERK Phosphorylation of Paxillin and FAK at Focal Adhesions in L{beta}T2 Gonadotrope Cells

Tue, 27 Oct 2009 10:02:18 PDT

Most receptor tyrosine kinases and G protein-coupled receptors (GPCRs) operate via a limited number of MAPK cascades but still exert diverse functions, and therefore signal specificity remains an enigma. Also, most GPCR ligands utilize families of receptors for mediation of diverse biological actions; however, the mammalian type I GnRH receptor (GnRHR) seems to be the sole receptor mediating GnRH-induced gonadotropin synthesis and release. Signaling complexes associated with GPCRs may thus provide the means for signal specificity. Here we describe a signaling complex associated with the GnRHR, which is a unique GPCR lacking a C-terminal tail. Unlike other GPCRs, this signaling complex is preformed, and exposure of LβT2 gonadotropes to GnRH induces its dynamic rearrangement. The signaling complex includes c-Src, protein kinase C, -, and -, Ras, MAPK kinase 1/2, ERK1/2, tubulin, focal adhesion kinase (FAK), paxillin, vinculin, caveolin-1, kinase suppressor of Ras-1, and the GnRHR. Exposure to GnRH (5 min) causes MAPK kinase 1/2, ERK1/2, tubulin, vinculin, and the GnRHR to detach from c-Src, but they reassociate within 30 min. On the other hand, FAK, paxillin, the protein kinase Cs, and caveolin-1 stay bound to c-Src, whereas kinase suppressor of Ras-1 appears in the complex only 30 min after GnRH stimulation. GnRH was found to activate ERK1/2 in the complex in a c-Src-dependent manner, and the activated ERK1/2 subsequently phosphorylates FAK and paxillin. In parallel, caveolin-1, FAK, vinculin, and paxillin are phosphorylated on Tyr residues apparently by GnRH-activated c-Src. Receptor tyrosine kinases and GPCRs translocate ERK1/2 to the nucleus to phosphorylate and activate transcription factors. We therefore propose that the role of the multiprotein signaling complex is to sequester a cytosolic pool of activated ERK1/2 to phosphorylate FAK and paxillin at focal adhesions.

Cyclin D2 Protein Stability Is Regulated in Pancreatic {beta}-Cells

Tue, 27 Oct 2009 10:02:18 PDT

The molecular determinants of β-cell mass expansion remain poorly understood. Cyclin D2 is the major D-type cyclin expressed in β-cells, essential for adult β-cell growth. We hypothesized that cyclin D2 could be actively regulated in β-cells, which could allow mitogenic stimuli to influence β-cell expansion. Cyclin D2 protein was sharply increased after partial pancreatectomy, but cyclin D2 mRNA was unchanged, suggesting posttranscriptional regulatory mechanisms influence cyclin D2 expression in β-cells. Consistent with this hypothesis, cyclin D2 protein stability is powerfully regulated in fibroblasts. Threonine 280 of cyclin D2 is phosphorylated, and this residue critically limits D2 stability. We derived transgenic (tg) mice with threonine 280 of cyclin D2 mutated to alanine (T280A) or wild-type cyclin D2 under the control of the insulin promoter. Cyclin D2 T280A protein was expressed at much higher levels than wild-type cyclin D2 protein in β-cells, despite equivalent expression of tg mRNAs. Cyclin D2 T280A tg mice exhibited a constitutively nuclear cyclin D2 localization in β-cells, and increased cyclin D2 stability in islets. Interestingly, threonine 280-mutant cyclin D2 tg mice had greatly reduced β-cell apoptosis, with suppressed expression of proapoptotic genes. Suppressed β-cell apoptosis in threonine 280-mutant cyclin D2 tg mice resulted in greatly increased β-cell area in aged mice. Taken together, these data indicate that cyclin D2 is regulated by protein stability in pancreatic β-cells, that signals that act upon threonine 280 limit cyclin D2 stability in β-cells, and that threonine 280-mutant cyclin D2 overexpression prolongs β-cell survival and augments β-cell mass expansion.

MicroRNA 132 Regulates Nutritional Stress-Induced Chemokine Production through Repression of SirT1

Tue, 27 Oct 2009 10:02:18 PDT

Human adipose tissue secretes a number of proinflammatory mediators that may contribute to the pathophysiology of obesity-related disorders. Understanding the regulatory pathways that control their production is paramount to developing effective therapeutics to treat these diseases. Using primary human adipose-derived stem cells as a source of preadipocytes and in vitro differentiated adipocytes, we found IL-8 and monocyte chemoattractant protein-1 (MCP-1) are constitutively secreted by both cell types and induced in response to serum deprivation. MicroRNA profiling revealed the rapid induction of microRNA 132 (miR-132) in these cells when switched to serum-free medium. Furthermore, miR-132 overexpression was sufficient to induce nuclear factor-B translocation, acetylation of p65, and production of IL-8 and MCP-1. Inhibitors of miR-132 decreased acetylated p65 and partially inhibited the production of IL-8 and MCP-1 induced by serum deprivation. MiR-132 was shown to inhibit silent information regulator 1 (SirT1) expression through a miR-132 binding site in the 3'-untranslated region of SirT1. Thus, in response to nutritional availability, induction of miR-132 decreases SirT1-mediated deacetylation of p65 leading to activation of nuclear factor-B and transcription of IL-8 and MCP-1 in primary human preadipocytes and in vitro differentiated adipocytes.

Genomic Priming of the Antisecretory Response to Estrogen in Rat Distal Colon throughout the Estrous Cycle

O'Mahony, F., Alzamora, R., Chung, H.-L., Thomas, W., Harvey, B. J. — Tue, 27 Oct 2009 10:02:18 PDT

The secretion of Cl^– across distal colonic crypt cells provides the driving force for the movement of fluid into the luminal space. 17β-Estradiol (E2) produces a rapid and sustained reduction in secretion in females, which is dependent on the novel protein kinase C (PKC) isozyme and PKA isoform I targeting of KCNQ1 channels. This sexual dimorphism in the E2 response is associated with a higher expression level of PKC in female compared with the male tissue. The present study revealed the antisecretory response is regulated throughout the female reproductive (estrous) cycle and is primed by genomic regulation of the kinases. E2 (1–10 nm) decreased cAMP-dependent secretion in colonic epithelia during the estrus, metestrus, and diestrus stages. A weak inhibition of secretion was demonstrated in the proestrus stage. The expression levels of PKC and PKA fluctuated throughout the estrous cycle and correlated with the potency of the antisecretory effect of E2. The expression of PKC and PKA were up-regulated by estrogen at a transcriptional level via a PKC-MAPK-cAMP response element-binding protein-regulated pathway indicating a genomic priming of the antisecretory response. PKC was activated by the membrane-impermeant E2-BSA, and this response was inhibited by the estrogen receptor antagonist ICI 182,780. The 66-kDa estrogen receptor- isoform was present at the plasma membrane of female colonic crypt cells with a lower abundance found in male colonic crypts. The study demonstrates estrogen regulation of intestinal secretion both at a rapid and transcriptional level, demonstrating an interdependent relationship between both nongenomic and genomic hormone responses.

NIDDK Workshop on Circadian Rhythms and Metabolic Disease

Tue, 27 Oct 2009 10:02:18 PDT

Retinoblastoma Protein Plays Multiple Essential Roles in the Terminal Differentiation of Sertoli Cells

Nalam, R. L., Andreu-Vieyra, C., Braun, R. E., Akiyama, H., Matzuk, M. M. — Tue, 27 Oct 2009 10:02:18 PDT

Retinoblastoma protein (RB) plays crucial roles in cell cycle control and cellular differentiation. Specifically, RB impairs the G₁ to S phase transition by acting as a repressor of the E2F family of transcriptional activators while also contributing towards terminal differentiation by modulating the activity of tissue-specific transcription factors. To examine the role of RB in Sertoli cells, the androgen-dependant somatic support cell of the testis, we created a Sertoli cell-specific conditional knockout of Rb. Initially, loss of RB has no gross effect on Sertoli cell function because the mice are fertile with normal testis weights at 6 wk of age. However, by 10–14 wk of age, mutant mice demonstrate severe Sertoli cell dysfunction and infertility. We show that mutant mature Sertoli cells continue cycling with defective regulation of multiple E2F1- and androgen-regulated genes and concurrent activation of apoptotic and p53-regulated genes. The most striking defects in mature Sertoli cell function are increased permeability of the blood-testis barrier, impaired tissue remodeling, and defective germ cell-Sertoli cell interactions. Our results demonstrate that RB is essential for proper terminal differentiation of Sertoli cells.

Male-Specific Hepatic Bcl6: Growth Hormone-Induced Block of Transcription Elongation in Females and Binding to Target Genes Inversely Coordinated with STAT5

Meyer, R. D., Laz, E. V., Su, T., Waxman, D. J. — Tue, 27 Oct 2009 10:02:18 PDT

The transcriptional repressor Bcl6 is a male-specific rat liver gene product and one of 24 early GH-response genes encoding DNA-binding proteins. Presently, the sex specificity of Bcl6 was shown to emerge at puberty, when hepatic Bcl6 mRNA was induced in males and repressed in females by the female plasma GH profile. Hepatic Bcl6 mRNA was increased to near-normal male levels in hypophysectomized females and was extinguished in intact males given a continuous GH infusion (female-like GH pattern). Bcl6 was also repressed in adult male somatostatin-deficient mice, where plasma GH profiles are female like. Hepatic Bcl6 RNA was rapidly down-regulated by GH pulse treatment, both in hypophysectomized male rats and in primary rat hepatocytes. Bcl6 was substantially induced in female mice deficient in hepatic signal transducer and activator of transcription (STAT)5a/STAT5b, suggesting that these STAT transcriptional mediators of GH signaling repress Bcl6. Indeed, STAT5 was bound to Bcl6 STAT5-binding region-B, previously associated with Bcl6 repression, in both male and female liver chromatin. STAT5 also bound to Bcl6 region-A in male chromatin but only during a plasma GH pulse. Analysis of primary transcripts (heterogenous nuclear RNA) across the Bcl6 gene revealed a novel mechanism of GH-dependent sex specificity, with two apparent blocks in Bcl6 transcription elongation seen in female liver and in continuous GH-treated male liver, one early in intron 4 and one in exon 5, which together reduced transcription beyond exon 5 more than 300-fold. Finally, Bcl6 was bound to a subset of STAT5-binding sites in male liver chromatin, including a Socs2 STAT5-binding site where Bcl6 binding increased substantially between plasma GH pulses, i.e. when STAT5 binding was low. Bcl6 and STAT5 binding are thus inversely coordinated by the endogenous pulses of pituitary GH release, suggesting this male-specific transcriptional repressor modulates hepatic GH signaling to select STAT5 target genes.

Androgen-Responsive Gene Database: Integrated Knowledge on Androgen-Responsive Genes

Tue, 27 Oct 2009 10:02:18 PDT

Androgen signaling plays an important role in many biological processes. Androgen Responsive Gene Database (ARGDB) is devoted to providing integrated knowledge on androgen-controlled genes. Gene records were collected on the basis of PubMed literature collections. More than 6000 abstracts and 950 original publications were manually screened, leading to 1785 human genes, 993 mouse genes, and 583 rat genes finally included in the database. All the collected genes were experimentally proved to be regulated by androgen at the expression level or to contain androgen-responsive regions. For each gene important details of the androgen regulation experiments were collected from references, such as expression change, androgen-responsive sequence, response time, tissue/cell type, experimental method, ligand identity, and androgen amount, which will facilitate further evaluation by researchers. Furthermore, the database was integrated with multiple annotation resources, including National Center for Biotechnology Information, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway, to reveal the biological characteristics and significance of androgen-regulated genes. The ARGDB web site is mainly composed of the Browse, Search, Element Scan, and Submission modules. It is user friendly and freely accessible at http://argdb.fudan.edu.cn. Preliminary analysis of the collected data was performed. Many disease pathways, such as prostate carcinogenesis, were found to be enriched in androgen-regulated genes. The discovered androgen-response motifs were similar to those in previous reports. The analysis results are displayed in the web site. In conclusion, ARGDB provides a unified gateway to storage, retrieval, and update of information on androgen-regulated genes.

Expression of Progesterone Receptor A form and Its Role in the Interaction of Progesterone with Cortisol on Cyclooxygenase-2 Expression in Amnionic Fibroblasts

Guo, C. M., Zhu, X. O., Ni, X. T., Yang, Z., Myatt, L., Sun, K. — Tue, 27 Oct 2009 10:02:18 PDT

11{beta}-Hydroxysteroid Dehydrogenase Type 1 and Its Role in the Hypothalamus-Pituitary-Adrenal Axis, Metabolic Syndrome, and Inflammation

Cooper, M. S., Stewart, P. M. — Tue, 27 Oct 2009 10:02:18 PDT

Correlation of Telomere Length and Telomerase Activity with Occult Ovarian Insufficiency

Tue, 27 Oct 2009 10:02:18 PDT

Programmed Death Ligand 1 (PD-L1) Gene Variants Contribute to Autoimmune Addison's Disease and Graves' Disease Susceptibility

Tue, 27 Oct 2009 10:02:18 PDT

Partial Primary Deficiency of Insulin-Like Growth Factor (IGF)-I Activity Associated with IGF1 Mutation Demonstrates Its Critical Role in Growth and Brain Development

Tue, 27 Oct 2009 10:02:18 PDT

Effects of Endogenous Growth Differentiation Factor 9 on Activin A-Induced Inhibin B Production in Human Granulosa-Lutein Cells

Shi, F.-T., Cheung, A. P., Huang, H.-F., Leung, P. C. K. — Tue, 27 Oct 2009 10:02:18 PDT

Dual Inhibition of Mitogen-Activated Protein Kinase Kinase and Mammalian Target of Rapamycin in Differentiated and Anaplastic Thyroid Cancer

Jin, N., Jiang, T., Rosen, D. M., Nelkin, B. D., Ball, D. W. — Tue, 27 Oct 2009 10:02:18 PDT