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General Comment |
Transforming growth factor-beta inhibits the growth of multiple epithelial
cell types, and loss of this negative regulation is thought to contribute to tumor development.
The types I and II TGF-beta receptors (Lin et al., 1992)
belong to the serine-threonine kinase family. The many activities of TGF-beta in regulating cell proliferation and
differentiation and extracellular matrix production are mediated through these receptors. Type II receptors alone can bind ligand, but require association with type I receptors for activation of
their kinase (signaling) function.
Mazerbourg S, et al reported that Growth differentiation factor-9 (GDF-9) signaling is mediated by the type I receptor ALK5.
Growth differentiation factor-9 (GDF-9) is an oocyte-derived growth factor and a member of the transforming growth factor-beta (TGF-beta) superfamily that includes TGF-beta, activin, and bone morphogenetic proteins (BMPs). GDF-9 is indispensable for the development of ovarian follicles from the primary stage, and treatment with GDF-9 enhances the progression of early follicles into small preantral follicles. Similar to other TGF-beta family ligands, GDF-9 likely initiates signaling mediated by type I and type II receptors with serine/threonine kinase activity, followed by the phosphorylation of intracellular transcription factors named Smads. We have shown previously that GDF-9 interacts with the BMP type II receptor (BMPRII) in granulosa cells but the type I receptor involved is unknown. Using P19 cells, we now report that GDF-9 treatment stimulated the CAGA-luciferase reporter known to be responsive to TGF-beta mediated by the type I receptor, activin receptor-like kinase (ALK)5. In contrast, GDF-9 did not stimulate BMP-responsive reporters. In addition, treatment with GDF-9 induced the phosphorylation of Smad2 and Smad3 in P19 cells, and the stimulatory effect of GDF-9 on the CAGA-luciferase reporter was blocked by the inhibitory Smad7, but not Smad6. We further reconstructed the GDF-9 signaling pathway using Cos7 cells that are not responsive to GDF-9. Following overexpression of ALK5, with or without exogenous Smad3, the Cos7 cells gained GDF-9 responsiveness based on the CAGA-luciferase reporter assay. The roles of ALK5 and downstream pathway genes in mediating GDF-9 actions were further tested in ovarian cells. In cultured rat granulosa cells from early antral follicles, treatment with GDF-9 stimulated the CAGA-luciferase reporter activity and induced the phosphorylation of Smad3. Furthermore, transfection with small interfering (si)RNA for ALK5 or overexpression of the inhibitory Smad7 resulted in dose-dependent suppression of GDF-9 actions. In conclusion, although GDF-9 binds to the BMP-activated type II receptor (BMPRII), its downstream actions are mediated by the type I receptor, ALK5, and the Smad2 and Smad3 proteins. Because ALK5 is a known receptor for TGF-beta, diverse members of the TGF-beta family of ligands appear to interact with a limited number of receptors in a combinatorial manner to activate two downstream Smad pathways.
NCBI Summary:
The protein encoded by this gene forms a heteromeric complex with type II TGF-beta receptors when bound to TGF-beta, transducing the TGF-beta signal from the cell surface to the cytoplasm. The encoded protein is a serine/threonine protein kinase. Mutations in this gene have been associated with Loeys-Dietz aortic aneurysm syndrome (LDAS). Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Aug 2008]
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Comment |
Schilling B, et al. reported the expression of transforming growth factor (TGF)-beta1, TGF-beta2, and TGF-beta3 and of type I
and II TGF-beta receptors during the development of the human fetal ovary.
During the first trimester, immunohistochemical analysis for TGF-beta1, TGF-beta2,
and TGF-beta receptor type I revealed homogeneous light staining of the ovary. Staining for TGF-beta3
and TGF-beta receptor type II was predominantly in the oocytes. During the second trimester, staining for
all three TGF-beta isoforms and both receptors was predominantly in the oocytes.
Immunohistochemistry was used by Qu JP et al
to study the expression of insulin-like growth factor (IGF) type I receptor
(IGF-IR) and transforming growth factor-beta (TGF beta) type I (TGF beta R-I)
and type II (T beta R-II) receptors in fresh and frozen ovarian tissues from
14 women. Immunoreactivities for IGF-IR and TGF beta R-I were present
simultaneously in the oocytes of primordial, pre-antral and antral follicles.
Staining for both IGF-IR and TGF beta R-I was also observed in granulosa cells
of primordial, pre-antral and antral follicles. IGF-IR and TGF beta R-I also
stained in thecal cells of pre-antral and antral follicles. Stromal cells in
surrounding ovarian tissue expressed IGF-IR and TGF beta R-I at various
follicular stages. Unlike TGF beta R-I, TGF beta R-II was expressed only in the
oocytes of primordial and primary follicles, and with weak staining intensity
in thecal cells. No significant staining for TGF beta R-II was found in oocytes
and granulosa cells of antral follicles.
Wehrenberg U, et al. reported possible involvement of transforming growth factor-beta 1 and transforming growth factor-beta
receptor type II during luteinization in the marmoset ovary.
Roy SK, et al. reported the expression patterns of transforming growth factor (TGF)-beta receptor type I (TbetaRI) and -II
(TbetaRII) in pre- and post-menopausal human ovaries, using immunohistochemistry and
immunoblotting. Both types of receptor were present in granulosa, theca and interstitial cells; however,
more mural than antral granulosa cells were TbetaRII positive.
Ismail RS, et al. reported that transforming growth factor-beta regulates Kit ligand expression in rat ovarian surface epithelial
cells.
Changes in mouse granulosa cell gene expression during early luteinization. McRae RS et al. Changes in gene expression during granulosa cell luteinization have been measured using serial analysis of gene expression (SAGE). Immature normal mice were treated with pregnant mare serum gonadotropin (PMSG) or PMSG followed, 48 h later, by human chorionic gonadotropin (hCG). Granulosa cells were collected from preovulatory follicles after PMSG injection or PMSG/hCG injection and SAGE libraries generated from the isolated mRNA. The combined libraries contained 105,224 tags representing 40,248 unique transcripts. Overall, 715 transcripts showed a significant difference in abundance between the two libraries of which 216 were significantly down-regulated by hCG and 499 were significantly up-regulated. Among transcripts differentially regulated, there were clear and expected changes in genes involved in steroidogenesis as well as clusters of genes involved in modeling of the extracellular matrix, regulation of the cytoskeleton and intra and intercellular signaling. The SAGE libraries described here provide a base for functional investigation of the regulation of granulosa cell luteinization.
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Mutations |
3 mutations
Species: mouse
Mutation name: None
type: null mutation
fertility: embryonic lethal
Comment: Larsson et al. (2001) used gene targeting to inactivate the Tgfbr1 gene in mice. Mice lacking Tgfbr1 died at midgestation, exhibited severe defects in the vascular development of the yolk sac and placenta, and lacked circulating red blood cells
Species: mouse
Mutation name:
type: targeted overexpression
fertility: subfertile
Comment: A Novel Mouse Model of Testicular Granulosa Cell Tumors. Fang X et al. (2018) What is the role of dysregulated transforming growth factor beta (TGFB) signaling in the development of sex cord-stromal tumors in the testis? Overactivation of TGFB signaling results in the development of testicular tumors resembling granulosa cell tumors (GrCTs). In an earlier study, we demonstrated that constitutively active TGFB receptor 1 (TGFBR1) in ovarian somatic cells promotes the development of ovarian GrCTs. However, the consequence of dysregulation of TGFB signaling in the pathobiology of the testis, remains poorly defined. To identify the impact of dysregulation of TGFB signaling on the testis, we generated mice with constitutive activation of TGFBR1 using anti-Mullerian hormone receptor type 2 (Amhr2)-Cre recombinase. The effect of constitutively active TGFBR1 on testis development and the timeline of testicular tumor formation were examined. We further investigated the molecular features of testicular tumors and determined the expression of beta-catenin (CTNNB1) known to be involved in testicular GrCT development. Male mice with constitutive activation of TGFBR1 were examined at various developmental stages (i.e., from 1 week up to 6 months) along with controls. Testis samples were collected and processed for histological and molecular analyses, including haematoxylin and eosin (H & E) staining, real-time PCR, immunohistochemistry, immunofluorescence, and western blotting. Immunostaining/immunoblotting and real-time PCR experiments were performed using at least three animals per genotype. Data are presented as mean ± SEM. Statistical significance was determined using unpaired two-tail t-test and reported when P value is less than 0.05. Mice harboring constitutively active TGFBR1 in the testes developed tumors resembling testicular GrCTs, a rare type of tumors in the testis. The formation of testicular tumors led to altered cell proliferation, loss of germ cells, and defective spermatogenesis. Immunohistochemically, these tumors were positive for inhibin alpha (INHA), forkhead box O1 (FOXO1), and more importantly, forkhead box L2 (FOXL2), a protein specifically expressed in the ovary and required for normal granulosa cell differentiation and function. Consistent with the immunohistochemical findings, FOXL2 proteins were only detectable in testes of TGFBR1-CAAcre mice but not those of controls by western blotting, suggesting potential alteration of Sertoli cell fate. To explore mechanisms underlying the tumor-promoting effect of TGFBR1 overactivation, we examined the expression of beta-catenin (CTNNB1). The results revealed increased expression of CTNNB1 in testicular tumors in TGFBR1-CAAcre mice. Collectively, this study uncovered tumorigenic function of enhanced TGFB signaling in the testis. N/A. This study was performed using mice, and the direct relevance of the experimental paradigm and findings to human testicular GrCTs awaits further investigation. Of note, constitutive activation of TGFBR1 was employed to enhance TGFB/SMAD signaling activity and may not be interpreted as the genetic cause of the disease. This mouse model may prove to be a useful addition to the mouse genetics toolkit for GrCT research. Our finding that dysregulation of TGFB signaling results in the development of testicular GrCTs supports a common origin between Sertoli cells and granulosa cells, and highlights the paramount importance of balanced TGFB signaling in reproduction and development. This research was supported by the National Institutes of Health grant R03HD082416 from the Eunice Kennedy Shriver National Institute of Child Health & Human Development and the New Faculty Start-up Funds from Texas A&M University awarded to Q.L. The authors declare no competing interest.//////////////////
Constitutively active transforming growth factor β receptor 1 in the mouse ovary promotes tumorigenesis. Gao Y et al. (2016) Despite the well-established tumor suppressive role of TGFβ proteins, depletion of key TGFβ signaling components in the mouse ovary does not induce a growth advantage. To define the role of TGFβ signaling in ovarian tumorigenesis, we created a mouse model expressing a constitutively active TGFβ receptor 1 (TGFBR1) in ovarian somatic cells using conditional gain-of-function approach. Remarkably, these mice developed ovarian sex cord-stromal tumors with complete penetrance, leading to reproductive failure and mortality. The tumors expressed multiple granulosa cell markers and caused elevated serum inhibin and estradiol levels, reminiscent of granulosa cell tumors. Consistent with the tumorigenic effect, overactivation of TGFBR1 altered tumor microenvironment by promoting angiogenesis and enhanced ovarian cell proliferation, accompanied by impaired cell differentiation and dysregulated expression of critical genes in ovarian function. By further exploiting complementary genetic models, we substantiated our finding that constitutively active TGFBR1 is a potent oncogenic switch in mouse granulosa cells. In summary, overactivation of TGFBR1 drives gonadal tumor development. The TGFBR1 constitutively active mouse model phenocopies a number of morphological, hormonal, and molecular features of human granulosa cell tumors and are potentially valuable for preclinical testing of targeted therapies to treat granulosa cell tumors, a class of poorly defined ovarian malignancies.//////////////////
Species: mouse
Mutation name:
type: targeted overexpression
fertility: None
Comment: Disruption of postnatal folliculogenesis and development of ovarian tumor in a mouse model with aberrant transforming growth factor beta signaling. Gao Y et al. (2017) Transforming growth factor beta (TGFB) superfamily signaling is implicated in the development of sex cord-stromal tumors, a category of poorly defined gonadal tumors. The aim of this study was to determine potential effects of dysregulated TGFB signaling in the ovary using Cre recombinase driven by growth differentiation factor 9 (Gdf9) promoter known to be expressed in oocytes. A mouse model containing constitutively active TGFBR1 (TGFBR1CA) using Gdf9-iCre (termed TGFBR1-CAG9Cre) was generated. Hematoxylin and eosin (H & E) staining, follicle counting, and immunohistochemistry and immunofluorescence analyses using antibodies directed to Ki67, forkhead box L2 (FOXL2), forkhead box O1 (FOXO1), inhibin alpha (INHA), and SRY (sex determining region Y)-box 9 were performed to determine the characteristics of the TGFBR1-CAG9Cre ovary. Terminal deoxynucleotidyl transferase (TdT) labeling of 3'-OH ends of DNA fragments, real-time PCR, and western blotting were used to examine apoptosis, select gene expression, and TGFBR1 activation. RNAscope in situ hybridization was used to localize the expression of GLI-Kruppel family member GLI1 (Gli1) in ovarian tumor tissues. TGFBR1-CAG9Cre females were sterile. Sustained activation of TGFBR1 led to altered granulosa cell proliferation evidenced by high expression of Ki67. At an early age, these mice demonstrated follicular defects and development of ovarian granulosa cell tumors, which were immunoreactive for granulosa cell markers including FOXL2, FOXO1, and INHA. Further histochemical and molecular analyses provided evidence of overactivation of TGFBR1 in the granulosa cell compartment during ovarian pathogenesis in TGFBR1-CAG9Cre mice, along with upregulation of Gli1 and Gli2 and downregulation of Tgfbr3 in ovarian tumor tissues. These results reinforce the role of constitutively active TGFBR1 in promoting ovarian tumorigenesis in mice. The mouse model created in this study may be further exploited to define the cellular and molecular mechanisms of TGFB/activin downstream signaling in granulosa cell tumor development. Future studies are needed to test whether activation of TGFB/activin signaling contributes to the development of human granulosa cell tumors.//////////////////
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