Induction of dorsal mesoderm by soluble, mature Vg1 protein

Development ◽  
1995 ◽  
Vol 121 (7) ◽  
pp. 2155-2164 ◽  
Author(s):  
D.S. Kessler ◽  
D.A. Melton

Mesoderm induction during Xenopus development has been extensively studied, and two members of the transforming growth factor-beta family, activin beta B and Vg1, have emerged as candidates for a natural inducer of dorsal mesoderm. Heretofore, analysis of Vg1 activity has relied on injection of hybrid Vg1 mRNAs, which have not been shown to direct efficient secretion of ligand and, therefore, the mechanism of mesoderm induction by processed Vg1 protein is unclear. This report describes injection of Xenopus oocytes with a chimeric activin-Vg1 mRNA, encoding the pro-region of activin beta B fused to the mature region of Vg1, resulting in the processing and secretion of mature Vg1. Treatment of animal pole explants with mature Vg1 protein resulted in differentiation of dorsal, but not ventral, mesodermal tissues and dose-dependent activation of both dorsal and ventrolateral mesodermal markers. At high doses, mature Vg1 induced formation of ‘embryoids’ with a rudimentary axial pattern, head structures including eyes and a functional neuromuscular system. Furthermore, truncated forms of the activin and FGF receptors, which block mesoderm induction in the intact embryo, fully inhibited mature Vg1 activity. To examine the mechanism of inhibition, we have performed receptor-binding assays with radiolabeled Vg1. Finally, follistatin, a specific inhibitor of activin beta B which is shown not to block endogenous dorsal mesoderm induction, failed to inhibit Vg1. The results support a role for endogenous Vg1 in dorsal mesoderm induction during Xenopus development.

Development ◽  
1990 ◽  
Vol 108 (1) ◽  
pp. 173-183 ◽  
Author(s):  
J.B. Green ◽  
G. Howes ◽  
K. Symes ◽  
J. Cooke ◽  
J.C. Smith

Mesoderm in Xenopus and other amphibian embryos is induced by signals from the vegetal hemisphere acting on equatorial or animal hemisphere cells. These signals are diffusible and two classes of candidate signal molecule have been identified: the fibroblast growth factor (FGF) and transforming growth factor beta (TGF-beta) types. In this paper, we compare the effects of cloned Xenopus basic FGF (XbFGF) and electophoretically homogeneous XTC-MIF (a TGF-beta-like factor obtained from a Xenopus cell line) on animal pole explants. We find that they have a similar minimum active concentration (0.1-0.2 ng ml-1) but that, nonetheless, XTC-MIF is at least 40 times more active in inducing muscle. In general, we find that the two factors cause inductions of significantly different characters in terms of tissue type, morphology, gene expression and timing. At low concentrations (0.1-1.0 ng ml-1) both factors induce the differentiation of ‘mesenchyme’ and ‘mesothelium’ as well as blood-like cells. These latter cells do not, however, react with an antibody to Xenopus globin. This raised the possibility that the identification of red blood cells in other studies on mesoderm induction might have been mistaken, but combinations of animal pole regions with ventral vegetal pole regions confirmed that genuine erythrocytes are formed. The identity of the blood-like cells formed in response to the inducing factors remains unknown. At higher concentrations XTC-MIF induces neural tissue, notochord, pronephros and substantial and often segmented muscle. By contrast, XbFGF only induces significant amounts of muscle above 24 ng ml-1 and even then this is much less than that induced by XTC-MIF. For both factors an exposure of less than 30 min is effective. Competence of animal pole cells to respond to XbFGF is completely lost by the beginning of gastrulation (stage 10) while competence to XTC-MIF is detectable until somewhat later (stage 11). Since animal pole tissue is known to be able to respond to the natural inducer at least until stage 10, and perhaps until stage 10.5, this suggests that bFGF cannot be the sole inducer of mesoderm in vivo. Taken together, these results are consistent with XTC-MIF being a dorsoanterior inducer and XbFGF a ventroposterior inducer, suggesting that body pattern is established by the interaction of two types of inducing signal. This model is discussed in view of the qualitative and quantitative differences between the factors.


Development ◽  
1996 ◽  
Vol 122 (12) ◽  
pp. 3735-3743 ◽  
Author(s):  
A. Renucci ◽  
V. Lemarchandel ◽  
F. Rosa

The role of Transforming Growth Factor beta (TGF-beta)-related molecules in axis formation and mesoderm patterning in vertebrates has been extensively documented, but the identity and mechanisms of action of the endogenous molecules remained uncertain. In this study, we isolate a novel serine/threonine kinase type I receptor, TARAM-A, expressed during early zebrafish embryogenesis first ubiquitously and then restricted to dorsal mesoderm during gastrulation. A constitutive form of the receptor is able to induce the most anterior dorsal mesoderm rapidly and to confer an anterior organizing activity. By contrast, the wild-type form is only able to induce a local expansion of the dorsal mesoderm. Thus an activated form of TARAM-A is sufficient to induce dorsoanterior structures and TARAM-A may be activated by dorsally localized signals. Our data suggest the existence in fish of a specific TGF-beta-related pathway for anterior dorsal mesoderm induction, possibly mediated by TARAM-A and activated at the late blastula stage by localized dorsal determinant.


Development ◽  
1988 ◽  
Vol 104 (4) ◽  
pp. 609-618 ◽  
Author(s):  
K. Symes ◽  
M. Yaqoob ◽  
J.C. Smith

When Xenopus embryos are cultured in calcium- and magnesium-free medium (CMFM), the blastomeres lose adhesion but continue dividing to form a loose heap of cells. If divalent cations are restored at the early gastrula stage the cells re-adhere and eventually form muscle (a mesodermal cell type) as well as epidermis. If, however, the cells are dispersed during culture in CMFM, muscle does not form following reaggregation although epidermis does. This suggests that culturing blastomeres in a heap allows the transmission of mesoderm-induction signals from cell to cell while dispersion effectively dilutes the signal. In this paper, we have attempted to substitute for cell proximity by culturing dispersed blastomeres in XTC mesoderm-inducing factor (MIF). We find that dispersed cells do not respond to XTC-MIF by forming mesodermal cell types after reaggregation, but the factor does inhibit epidermal differentiation. One interpretation of this observation is that an early stage in mesoderm induction is the suppression of epidermal differentiation and that formation of mesoderm may require contact-mediated signals that are produced in response to XTC-MIF. We have gone on to study the suppression of epidermal differentiation in more detail. We find that this is a dose-dependent phenomenon that can occur in single cells in the absence of cell division. Animal pole blastomeres become more difficult to divert from epidermal differentiation at later stages of development and by stage 12 they are ‘determined’ to this fate. Fibroblast growth factor (FGF) also suppresses epidermal differentiation in isolated animal pole blastomeres and transforming growth factor-beta 1 acts synergistically with FGF in doing so.


Development ◽  
2000 ◽  
Vol 127 (13) ◽  
pp. 2917-2931 ◽  
Author(s):  
S. Faure ◽  
M.A. Lee ◽  
T. Keller ◽  
P. ten Dijke ◽  
M. Whitman

Transforming growth factor beta (TGFbeta) superfamily signaling has been implicated in patterning of the early Xenopus embryo. Upon ligand stimulation, TGFbeta receptors phosphorylate Smad proteins at carboxy-terminal SS(V/M)S consensus motifs. Smads 1/5/8, activated by bone morphogenetic protein (BMP) signaling, induce ventral mesoderm whereas Smad2, activated by activin-like ligands, induces dorsal mesoderm. Although ectopic expression studies are consistent with roles for TGFbeta signals in early Xenopus embryogenesis, when and where BMP and activin-like signaling pathways are active endogenously has not been directly examined. In this study, we investigate the temporal and spatial activation of TGFbeta superfamily signaling in early Xenopus development by using antibodies specific for the type I receptor-phosphorylated forms of Smad1/5/8 and Smad2. We find that Smad1/5/8 and two distinct isoforms of Smad2, full-length Smad2 and Smad2(delta)exon3, are phosphorylated in early embryos. Both Smad1/5/8 and Smad2/Smad2(delta)exon3 are activated after, but not before, the mid-blastula transition (MBT). Endogenous activation of Smad2/Smad2(delta)exon3 requires zygotic transcription, while Smad1/5/8 activation at MBT appears to involve transcription-independent regulation. We also find that the competence of embryonic cells to respond to TGF(delta) superfamily ligands is temporally regulated and may be a determinant of early patterning. Levels of phospho-Smad1/5/8 and of phospho-Smad2/Smad2(delta)exon3 are asymmetrically distributed across both the animal-vegetal and dorsoventral axes. The timing of the development of these asymmetries differs for phospho-Smad1/5/8 and for phospho-Smad2/Smad2(delta)exon3, and the spatial distribution of phosphorylation of each Smad changes dramatically as gastrulation begins. We discuss the implications of our results for endogenous functions of BMP and activin-like signals as candidate morphogens regulating primary germ layer formation and dorsoventral patterning of the early Xenopus embryo.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3448-3448
Author(s):  
Amit Verma ◽  
Tony A. Navas ◽  
Jing Ying ◽  
Aaron N. Nguyen ◽  
Perry Pahanish ◽  
...  

Abstract Transforming Growth Factor β (TGF-β) is a myelosuppressive cytokine that has been implicated in the ineffective hematopoiesis seen in myelodysplastic syndromes (MDS). Overactivation of TGF-β signaling in this disease was demonstrated immunohistochemically by significantly higher nuclear SMAD2 phosphorylation observed in 20 MDS bone marrows when compared with 7 non MDS anemic controls (P < 0.0001, 2 Tailed T Test, Image Pro Plus software). This data along with high levels of membrane-bound and plasma TGF-β observed in MDS patients in previous studies support the development of therapeutics targeting the TGF-β signaling pathways in this disease. SD-208 is a novel, potent and specific inhibitor of TGF-β Receptor I (TGFβ-RI) kinase. We demonstrate that SD-208 blocks the phosphorylation of SMAD2 in hematopoietic progenitors which are at the colony forming unit-erythroid (CFU-E) stage of differentiation. SD-208 also abrogates the G0/G1 cell cycle arrest induced by TGF-β in bone marrow progenitors. SD-208 treatment leads to reversal of the myelosuppressive effects of TGF-β on erythroid and myeloid colony formation from primary human CD34+ cells. Selectivity of SD-208 in inhibiting TGF-β-mediated effects on hematopoiesis was supported by similar results observed with siRNAs targeting SMAD2, a major component of the TGF-b signaling pathway. Finally, the efficacy of SD-208 in MDS was evaluated by treating bone marrow mononuclear cells from 15 patients with early low grade MDS. SD-208 treatment led to dose-dependent increases in erythroid and myeloid colonies after 14 days of in vitro culture. The effect was most notable in patients with high levels of activated SMAD-2, as assessed by immunohistochemical staining of bone marrow biopsies. Stimulation of hematopoiesis in MDS-derived marrow culture by SD-208 demonstrates a novel concept and potential therapeutic role for TGFβ-RI inhibition in this disease. Supported by VISN-17 grant, Harris Methodist Foundation Grant and ASCO YIA to AV


1998 ◽  
Vol 95 (16) ◽  
pp. 9378-9383 ◽  
Author(s):  
Michael Weinstein ◽  
Xiao Yang ◽  
Cuiling Li ◽  
Xiaoling Xu ◽  
Jessica Gotay ◽  
...  

smad genes constitute a family of nine members whose products serve as intracellular mediators of transforming growth factor β signals. SMAD2, which is a tumor suppressor involved in colorectal and lung cancer, has been shown to induce dorsal mesoderm in Xenopus laevis in response to transforming growth factor β and activins. The smad2 gene is expressed ubiquitously during murine embryogenesis and in many adult mouse tissues. Animals that lacked smad2 died before 8.5 days of development (E8.5). E6.5 homozygous mutants were smaller than controls, lacked the extraembryonic portion of the egg cylinder, and appeared strikingly similar to E6.5 smad4 mutants. This similarity was no longer evident at E7.5, however, because the smad2 mutants contained embryonic ectoderm within their interiors. Molecular analysis showed that smad2 mutant embryos did not undergo gastrulation or make mesoderm. The results demonstrate that smad2 is required for egg cylinder elongation, gastrulation, and mesoderm induction.


2019 ◽  
Vol 34 (12) ◽  
pp. 2430-2442 ◽  
Author(s):  
Seyedeh-Faezeh Moraveji ◽  
Fereshteh Esfandiari ◽  
Sara Taleahmad ◽  
Saman Nikeghbalian ◽  
Forough-Azam Sayahpour ◽  
...  

Abstract STUDY QUESTION Could small molecules (SM) which target (or modify) signaling pathways lead to increased proliferation of undifferentiated spermatogonia following chemotherapy? SUMMARY ANSWER Inhibition of transforming growth factor-beta (TGFb) signaling by SM can enhance the proliferation of undifferentiated spermatogonia and spermatogenesis recovery following chemotherapy. WHAT IS KNOWN ALREADY Spermatogonial stem cells (SSCs) hold great promise for fertility preservation in prepubertal boys diagnosed with cancer. However, the low number of SSCs limits their clinical applications. SM are chemically synthesized molecules that diffuse across the cell membrane to specifically target proteins involved in signaling pathways, and studies have reported their ability to increase the proliferation or differentiation of germ cells. STUDY DESIGN, SIZE, DURATION In our experimental study, spermatogonia were collected from four brain-dead individuals and used for SM screening in vitro. For in vivo assessments, busulfan-treated mice were treated with the selected SM (or vehicle, the control) and assayed after 2 (three mice per group) and 5 weeks (two mice per group). PARTICIPANTS/MATERIALS, SETTING, METHODS We investigated the effect of six SM on the proliferation of human undifferentiated spermatogonia in vitro using a top–bottom approach for screening. We used histological, hormonal and gene-expression analyses to assess the effect of selected SM on mouse spermatogenesis. All experiments were performed at least in triplicate and were statistically evaluated by Student’s t-test and/or one-way ANOVA followed by Scheffe’s or Tukey’s post-hoc. MAIN RESULTS AND THE ROLE OF CHANCE We found that administration of SB431542, as a specific inhibitor of the TGFb1 receptor (TGFbR1), leads to a two-fold increase in mouse and human undifferentiated spermatogonia proliferation. Furthermore, injection of SB to busulfan-treated mice accelerated spermatogenesis recovery as revealed by increased testicular size, weight and serum level of inhibin B. Moreover, SB administration accelerated both the onset and completion of spermatogenesis. We demonstrated that SB promotes proliferation in testicular tissue by regulating the cyclin-dependent kinase (CDK) inhibitors 4Ebp1 and P57 (proliferation inhibitor genes) and up-regulating Cdc25a and Cdk4 (cell cycle promoting genes). LIMITATIONS, REASONS FOR CAUTION The availability of human testis was the main limitation in this study. WIDER IMPLICATIONS OF THE FINDINGS This is the first study to report acceleration of spermatogenesis recovery following chemotherapy by administration of a single SM. Our findings suggest that SB is a promising SM and should be assessed in future clinical trials for preservation of fertility in men diagnosed with cancer or in certain infertility cases (e.g. oligospermia). STUDY FUNDING/COMPETING INTEREST(S) This study was supported by Royan Institute and National Institute for Medical Research Development (NIMAD, grant no 963337) granted to H.B. The authors have no conflict of interest to report.


2014 ◽  
Vol 35 (3) ◽  
pp. 610-618 ◽  
Author(s):  
Maria Ivshina ◽  
Ilya M. Alexandrov ◽  
Anastassiia Vertii ◽  
Stephen Doxsey ◽  
Joel D. Richter

The cytoplasmic-element-binding (CPEB) protein is a sequence-specific RNA-binding protein that regulates cytoplasmic polyadenylation-induced translation. In mouse embryo fibroblasts (MEFs) lacking CPEB, many mRNAs encoding proteins involved in inflammation are misregulated. Correlated with this aberrant translation in MEFs, a macrophage cell line depleted of CPEB and treated with lipopolysaccharide (LPS) to stimulate the inflammatory immune response expresses high levels of interleukin-6 (IL-6), which is due to prolonged nuclear retention of NF-κB. Two proteins involved in NF-κB nuclear localization and IL-6 expression, IκBα and transforming growth factor beta-activated kinase 1 (TAK1), are present at excessively low and high steady-state levels, respectively, in LPS-treated CPEB-depleted macrophages. However, only TAK1 has an altered synthesis rate that is CPEB dependent and CPEB/TAK1 double depletion alleviates high IL-6 production. Peritoneal macrophages isolated from CPEB knockout (KO) mice treated with LPSin vitroalso have prolonged NF-κB nuclear retention and produce high IL-6 levels. LPS-injected CPEB KO mice secrete prodigious amounts of IL-6 and other proinflammatory cytokines and exhibit hypersensitivity to endotoxic shock; these effects are mitigated when the animals are also injected with (5Z)-7-oxozeaenol, a potent and specific inhibitor of TAK1. These data show that CPEB control of TAK1 mRNA translation mediates the inflammatory immune response.


2021 ◽  
Vol 22 (21) ◽  
pp. 11988
Author(s):  
Zi Zhen (Ginny) Liu ◽  
Aftab Taiyab ◽  
Judith A. West-Mays

Fibrotic cataracts have been attributed to transforming growth factor-beta (TGF-β)-induced epithelial-to-mesenchymal transition (EMT). Using mouse knockout (KO) models, our laboratory has identified MMP9 as a crucial protein in the TGF-β-induced EMT process. In this study, we further revealed an absence of alpha-smooth muscle actin (αSMA) and filamentous-actin (F-actin) stress fibers in MMP9KO mouse lens epithelial cell explants (LECs). Expression analysis using NanoString revealed no marked differences in αSMA (ACTA2) and beta-actin (β-actin) (ACTB) mRNA between the lenses of TGF-β-overexpressing (TGF-βtg) mice and TGF-βtg mice on a MMP9KO background. We subsequently conducted a protein array that revealed differential regulation of proteins known to be involved in actin polymerization and cell migration in TGF-β-treated MMP9KO mouse LECs when compared to untreated controls. Immunofluorescence analyses using rat LECs and the novel MMP9-specific inhibitor, JNJ0966, revealed similar differential regulation of cortactin, FAK, LIMK1 and MLC2 as observed in the array. Finally, a reduction in the nuclear localization of MRTF-A, a master regulator of cytoskeletal remodeling during EMT, was observed in rat LECs co-treated with JNJ0966 and TGF-β. In conclusion, MMP9 deficiency results in differential regulation of proteins involved in actin polymerization and cell migration, and this in turn prevents TGF-β-induced EMT in the lens.


2021 ◽  
pp. 1-11
Author(s):  
Yingbiao Wu ◽  
Jin Can ◽  
Shuwen Hao ◽  
Xun Qiang ◽  
Zhongping Ning

<b><i>Objectives:</i></b> Angiotensin II (Ang II)-induced atrial fibrosis plays a vital role in the development of atrial fibrillation (AF). Lysyl oxidase-like 2 (LOXL2) plays an essential role in matrix remodeling and fibrogenesis, indicating it may involve fibrosis-associated diseases. This study aims to elucidate the role of LOXL2 in AF, and its specific inhibitor can suppress Ang II-induced inflammatory atrial fibrosis and attenuate the enhanced vulnerability to AF. <b><i>Methods:</i></b> Male mice C57BL/6 were subcutaneously infused with either saline or Ang II (2 mg/kg/day) for 4 weeks. DMSO or LOXL2 inhibitor LOXL2-IN-1 hydrochloride (LOXL2-IN-1) at a dose of 100 μg/kg/day were intraperitoneally injected once daily for 4 weeks. Morphological, histological, and biochemical analyses were performed. AF was induced by transesophageal burst pacing in vivo. <b><i>Results:</i></b> Expression of LOXL2 was increased in serum of AF patients and Ang II-treated mice. LOXL2-IN-1 significantly attenuated Ang II-induced AF vulnerability, cardiac hypertrophy, atrial inflammation, and fibrosis. LOXL2-IN-1 suppressed Ang II-induced expression of transforming growth factor beta-1 (TGF-β1) and collagen I and phosphorylation of Smad2/3 in atrial tissue. <b><i>Conclusions:</i></b> LOXL2 is a target of AF, and its inhibitor prevents atrial fibrosis and attenuated enhanced vulnerability to AF potentially through the TGF-β/Smad pathway.


Sign in / Sign up

Export Citation Format

Share Document