The homeobox gene Siamois is a target of the Wnt dorsalisation pathway and triggers organiser activity in the absence of mesoderm

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3055-3065 ◽  
Author(s):  
G. Carnac ◽  
L. Kodjabachian ◽  
J.B. Gurdon ◽  
P. Lemaire
Keyword(s):  
Gene Expression ◽  
Target Genes ◽  
Homeobox Gene ◽  
Neural Tissue ◽  
Wnt Signalling ◽  
Cement Gland ◽  
Signalling Pathway ◽  
Mesoderm Induction ◽  
Embryonic Cells ◽  
Dorsal Mesoderm

Siamois, a Xenopus zygotic homeobox gene with strong dorsalising activity, is expressed in the dorsal-vegetal organiser known as the Nieuwkoop centre. We show that, in contrast to Spemann organiser genes such as goosecoid, chordin and noggin, Siamois gene expression is not induced following overexpression of mesoderm inducers in ectodermal (animal cap) cells. However, Siamois is induced by overexpressing a dorsalising Wnt molecule. Furthermore, like Wnt, Siamois can dorsalise ventral mesoderm and cooperate with Xbrachyury to generate dorsal mesoderm. These results suggest that Siamois is a mediator of the Wnt-signalling pathway and that the synergy between the Wnt and mesoderm induction pathways occurs downstream of the early target genes of these two pathways. Overexpression of Siamois in animal cap cells reveals that this gene can act in a non vegetal or mesodermal context. We show the following. (1) Animal cap cells overexpressing Siamois secrete a factor able to dorsalise ventral gastrula mesoderm in tissue combination experiments. (2) The Spemann organiser-specific genes goosecoid, Xnr-3 and chordin, but not Xlim.1, are activated in these caps while the ventralising gene Bmp-4 is repressed. However, the dorsalising activity of Siamois-expressing animal caps is significantly different from that of noggin- or chordin-expressing animal caps, suggesting the existence of other dorsalising signals in the embryo. (3) Ectodermal cells overexpressing Siamois secrete a neuralising signal and can differentiate into cement gland and, to a lesser extent, into neural tissue. Hence, in the absence of mesoderm induction, overexpression of Siamois is sufficient to confer organiser properties on embryonic cells.

scholarly journals FgHtf1 Regulates Global Gene Expression towards Aerial Mycelium and Conidiophore Formation in the Cereal Fungal Pathogen Fusarium graminearum

2020 ◽  
Vol 86 (9) ◽  
Author(s):  
Gaili Fan ◽  
Huawei Zheng ◽  
Kai Zhang ◽  
Veena Devi Ganeshan ◽  
Stephen Obol Opiyo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Gene Family ◽  
Fusarium Graminearum ◽  
Target Genes ◽  
Homeobox Gene ◽  
Global Gene Expression ◽  
Binding Motifs ◽  
Content Type ◽  
Aerial Growth

ABSTRACT The homeobox gene family of transcription factors (HTF) controls many developmental pathways and physiological processes in eukaryotes. We previously showed that a conserved HTF in the plant-pathogenic fungus Fusarium graminearum, Htf1 (FgHtf1), regulates conidium morphology in that organism. This study investigated the mechanism of FgHtf1-mediated regulation and identified putative FgHtf1 target genes by a chromatin immunoprecipitation assay combined with parallel DNA sequencing (ChIP-seq) and RNA sequencing. A total of 186 potential binding peaks, including 142 genes directly regulated by FgHtf1, were identified. Subsequent motif prediction analysis identified two DNA-binding motifs, TAAT and CTTGT. Among the FgHtf1 target genes were FgHTF1 itself and several important conidiation-related genes (e.g., FgCON7), the chitin synthase pathway genes, and the aurofusarin biosynthetic pathway genes. In addition, FgHtf1 may regulate the cAMP-protein kinase A (PKA)-Msn2/4 and Ca2+-calcineurin-Crz1 pathways. Taken together, these results suggest that, in addition to autoregulation, FgHtf1 also controls global gene expression and promotes a shift to aerial growth and conidiation in F. graminearum by activation of FgCON7 or other conidiation-related genes. IMPORTANCE The homeobox gene family of transcription factors is known to be involved in the development and conidiation of filamentous fungi. However, the regulatory mechanisms and downstream targets of homeobox genes remain unclear. FgHtf1 is a homeobox transcription factor that is required for phialide development and conidiogenesis in the plant pathogen F. graminearum. In this study, we identified FgHtf1-controlled target genes and binding motifs. We found that, besides autoregulation, FgHtf1 also controls global gene expression and promotes conidiation in F. graminearum by activation of genes necessary for aerial growth, FgCON7, and other conidiation-related genes.

Identification of otx2 target genes and restrictions in ectodermal competence during Xenopus cement gland formation

Development ◽  
1997 ◽  
Vol 124 (2) ◽  
pp. 471-481 ◽  
Author(s):  
L.S. Gammill ◽  
H. Sive
Keyword(s):  
Retinoic Acid ◽  
Target Genes ◽  
Homeobox Gene ◽  
Cement Gland ◽  
Inhibitory Effects ◽  
Temporal Modulation ◽  
Downstream Target ◽  
Positional Identity ◽  
Direct Target ◽  
Differentiation Marker

The homeobox gene otx2 is a key regulator of positional identity in vertebrates, however its downstream target genes and mechanism of action are not known. We have analyzed otx2 function during formation of the Xenopus cement gland, an organ that expresses otx2. The cement gland forms at early neurula from extreme anterior ectoderm and corresponds to the chin primordium of mammals. Previous studies (Blitz, I. and Cho, K. (1995) Development 121, 993–1004; Pannese, M., Polo, C., Andreazzoli, M., Vignali, R., Kablar, B., Barsacchi, G. and Boncinelli, E. (1995) Development 121, 707–720) showed that misexpressed otx2 could activate cement gland formation. However, it was not clear whether this was a direct effect of otx2 or a secondary consequence of other tissues induced by otx2. In this study we ask whether otx2 activity is spatially and temporally restricted in the ectoderm and whether cement gland-specific genes are direct targets of otx2. In order to control the timing of otx2 activity, we constructed a dexamethasone-inducible otx2 protein (otx2-GR) by fusion with the ligand-binding domain of the glucocorticoid receptor. We conclude first, that regionally restricted factors regulate otx2 activity since otx2-GR is able to activate the cement gland markers XCG and XAG only in ventrolateral ectoderm, and never in the neural plate. Second, we show that temporal responsiveness of the ectoderm to otx2-GR is limited, beginning only at mid-gastrula but continuing as late as tailbud stages. Third, we show that otx2-GR activates expression of the cement gland differentiation marker XCG in the absence of protein synthesis, identifying a direct target of otx2. otx2-GR can also activate expression of the endogenous otx2 gene, defining an autoregulatory loop. Fourth, we show that otx2-GR is sufficient to overcome the inhibitory effects of retinoic acid on cement gland formation, indicating that this effect is caused by failure to express otx2. Corroboratively, we show that otx2 autoactivation is prevented by retinoic acid. Together, these findings suggest that otx2 directly controls cement gland differentiation, and that spatial and temporal modulation of otx2 activity limits cement gland formation to the front of the embryo.

Fibroblast growth factor is a direct neural inducer, which combined with noggin generates anterior-posterior neural pattern

Development ◽  
1995 ◽  
Vol 121 (11) ◽  
pp. 3627-3636 ◽  
Author(s):  
T.M. Lamb ◽  
R.M. Harland
Keyword(s):  
Neural Induction ◽  
Neural Tissue ◽  
Mesoderm Induction ◽  
Gastrula Stage ◽  
Neural Patterning ◽  
The Third ◽  
Dorsal Mesoderm ◽  
Early Gastrula ◽  
Anterior Posterior ◽  
Mesodermal Tissue

Neural tissue in developing Xenopus embryos is induced by signals from the dorsal mesoderm. Induction of anterior neural tissue could be mediated by noggin, a secreted polypeptide found in dorsal mesoderm. We show that bFGF, a known mesoderm inducer of blastula staged ectoderm, induces neural tissue from gastrula stage ectoderm. The type of neural tissue induced by bFGF from stage 10.25 ectoderm is posterior, as marked by Hox B9 expression. When bFGF and noggin are combined on early gastrula stage ectoderm, a more complete neural pattern is generated and no mesodermal tissue is detected. Explants treated with noggin and bFGF elongate and display distinct anterior and posterior ends marked by otx2 and Hox B9 expression, respectively. Furthermore, treatment of early gastrula ectoderm with noggin and bFGF results in the induction of En-2, a marker of the midbrain-hindbrain junction and Krox 20, a marker of the third and fifth rhombomeres of the hindbrain. Neither of these genes is induced by noggin alone or bFGF alone at this stage, suggesting a synergy in anterior-posterior neural patterning. The response of later gastrula (stage 11–12) ectoderm to bFGF changes so that Krox 20 and En-2 are induced by bFGF alone, while induction of more posterior tissue marked by Hox B9 is eliminated. The dose of bFGF affects the amount of neural tissue induced, but has little effect on the anterior-posterior character, rather the age of the ectoderm treated is the determinant of the response. Thus, an FGF signal may account for posterior neural induction, and anterior-posterior neural patterning could be partly explained by the actions of noggin and FGF, together with the changing response of the ectoderm to these factors.

scholarly journals Intestinal region-specific Wnt signalling profiles reveal interrelation between cell identity and oncogenic pathway activity in cancer development

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Ronja S. Adam ◽  
Sanne M. van Neerven ◽  
Cayetano Pleguezuelos-Manzano ◽  
Salvatore Simmini ◽  
Nicolas Léveillé ◽  
...  
Keyword(s):  
Gene Expression ◽  
Colorectal Cancer ◽  
Target Genes ◽  
Wnt Signalling ◽  
Cancer Development ◽  
Specific Cell ◽  
Stable Form ◽  
Significant Differential Expression ◽  
Cell Identity ◽  
Left And Right

Abstract Background Cancer results from the accumulation of mutations leading to the acquisition of cancer promoting characteristics such as increased proliferation and resistance to cell death. In colorectal cancer, an early mutation leading to such features usually occurs in the APC or CTNNB1 genes, thereby activating Wnt signalling. However, substantial phenotypic differences between cancers originating within the same organ, such as molecular subtypes, are not fully reflected by differences in mutations. Indeed, the phenotype seems to result from a complex interplay between the cell-intrinsic features and the acquired mutations, which is difficult to disentangle when established tumours are studied. Methods We use a 3D in vitro organoid model to study the early phase of colorectal cancer development. From three different murine intestinal locations we grow organoids. These are transformed to resemble adenomas after Wnt activation through lentiviral transduction with a stable form of β-Catenin. The gene expression before and after Wnt activation is compared within each intestinal origin and across the three locations using RNA sequencing. To validate and generalize our findings, we use gene expression data from patients. Results In reaction to Wnt activation we observe downregulation of location specific genes and differentiation markers. A similar effect is seen in patient data, where genes with significant differential expression between the normal left and right colon are downregulated in the cancer samples. Furthermore, the signature of Wnt target genes differs between the three intestinal locations in the organoids. The location specific Wnt signatures are dominated by genes which have been lowly expressed in the tissue of origin, and are the targets of transcription factors that are activated following enhanced Wnt signalling. Conclusion We observed that the region-specific cell identity has a substantial effect on the reaction to Wnt activation in a simple intestinal adenoma model. These findings provide a way forward in resolving the distinct biology between left- and right-sided human colon cancers with potential clinical relevance.

The Xvent-2 homeobox gene is part of the BMP-4 signalling pathway controlling [correction of controling] dorsoventral patterning of Xenopus mesoderm

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3045-3053 ◽  
Author(s):  
D. Onichtchouk ◽  
V. Gawantka ◽  
R. Dosch ◽  
H. Delius ◽  
K. Hirschfeld ◽  
...  
Keyword(s):  
Feedback Loop ◽  
Homeobox Gene ◽  
Dominant Negative ◽  
Signalling Pathway ◽  
Dependent Manner ◽  
Dorsoventral Patterning ◽  
Spemann Organizer ◽  
Dorsal Mesoderm ◽  
Dose Dependent

We describe a novel Xenopus homeobox gene, Xvent-2, which together with the previously identified homeobox gene Xvent-1, defines a novel class of homeobox genes. vent genes are related by sequence homology, expression pattern and gain-of-function phenotype. Evidence is presented for a role of Xvent-2 in the BMP-4 pathway involved in dorsoventral patterning of mesoderm. (1) Xvent-2 is expressed in regions that also express BMP-4. (2) Xvent-2 and BMP-4 interact in a positive feedback loop. (3) Xvent-2 ventralizes dorsal mesoderm in a dose-dependent manner resulting in phenoytpes ranging from microcephaly to Bauchstuck pieces, as does BMP-4. (4) Like BMP-4 and gsc, Xvent-2 and gsc are able to interact in a crossregulatory loop to suppress each other. (5) Microinjection of Xvent-2 mRNA can rescue dorsalization by a dominant-negative BMP-4 receptor. The results suggest that Xvent-2 functions in the BMP-4 signalling pathway that antagonizes the Spemann organizer.

MAP3K1 functionally interacts with Axin1 in the canonical Wnt signalling pathway

2010 ◽  
Vol 391 (2/3) ◽  
Author(s):  
Ser Sue Ng ◽  
Tokameh Mahmoudi ◽  
Vivian S.W. Li ◽  
Pantelis Hatzis ◽  
Paul J. Boersema ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Target Genes ◽  
Wnt Signalling ◽  
Signalling Pathway ◽  
Negative Regulator ◽  
Mitogen Activated Protein Kinase ◽  
Endogenous Gene ◽  
Wnt Signalling Pathway ◽  
Mitogen Activated Protein ◽  
Canonical Wnt

Abstract A central point of regulation in the Wnt/β-catenin signalling pathway is the formation of the β-catenin destruction complex. Axin1, an essential negative regulator of Wnt signalling, serves as a scaffold within this complex and is critical for rapid turnover of β-catenin. To examine the mechanism by which Wnt signalling disables the destruction complex, we used an immunoprecipitation-coupled proteomics approach to identify novel endogenous binding partners of Axin1. We found mitogen-activated protein kinase kinase kinase 1 (MAP3K1) as an Axin1 interactor in Ls174T colorectal cancer (CRC) cells. Importantly, confirmation of this interaction in HEK293T cells indicated that the Axin1-MAP3K1 interaction is induced and modulated by Wnt stimulation. siRNA depletion of MAP3K1 specifically abrogated TCF/LEF-driven transcription and Wnt3A-driven endogenous gene expression in both HEK293T as well as DLD-1 CRC. Expression of ubiquitin ligase mutants of MAP3K1 abrogated TCF/LEF transcription, whereas kinase mutants had no effect in TCF-driven activity, highlighting the essential role of the MAP3K1 E3 ubiquitin ligase activity in regulation of the Wnt/β-catenin pathway. These results suggest that MAP3K1, previously reported as an Axin1 inter-actor in c-Jun NH2-terminal kinase pathway, is also involved in the canonical Wnt signalling pathway and positively regulates expression of Wnt target genes.

Wingless and its signalling pathway have common and separable functions during tracheal development

Development ◽  
2000 ◽  
Vol 127 (20) ◽  
pp. 4407-4417 ◽  
Author(s):  
M. Llimargas
Keyword(s):  
Gene Product ◽  
Respiratory System ◽  
Wnt Pathway ◽  
Target Genes ◽  
Wnt Signalling ◽  
Canonical Pathway ◽  
Signalling Pathway ◽  
Dorsoventral Axis ◽  
Separable Functions ◽  
Antagonistic Interactions

The Drosophila tracheal tree consists of a tubular network of epithelial branches that constitutes the respiratory system. Groups of tracheal cells migrate towards stereotyped directions while they acquire specific tracheal fates. This work shows that the wingless/WNT signalling pathway is needed within the tracheal cells for the formation of the dorsal trunk and for fusion of the branches. These functions are achieved through the regulation of target genes, such as spalt in the dorsal trunk and escargot in the fusion cells. The pathway also aids tracheal invagination and helps guide the ganglionic branch. Moreover the wingless/WNT pathway displays antagonistic interactions with the DPP (decapentaplegic) pathway, which regulates branching along the dorsoventral axis. Remarkably, the wingless gene itself, acting through its canonical pathway, seems not to be absolutely required for all these tracheal functions. However, the artificial overexpression of wingless in tracheal cells mimics the overexpression of a constitutively activated armadillo protein. The results suggest that another gene product, possibly a WNT, could help to trigger the wingless cascade in the developing tracheae.

Andrographolide activates the canonical Wnt signalling pathway by a mechanism that implicates the non-ATP competitive inhibition of GSK-3β: autoregulation of GSK-3β in vivo

2015 ◽  
Vol 466 (2) ◽  
pp. 415-430 ◽  
Author(s):  
Cheril Tapia-Rojas ◽  
Andreas Schüller ◽  
Carolina B. Lindsay ◽  
Roxana C. Ureta ◽  
Cristóbal Mejías-Reyes ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Wnt Pathway ◽  
Target Genes ◽  
Competitive Inhibition ◽  
Wnt Signalling ◽  
Signalling Pathway ◽  
Canonical Wnt Pathway ◽  
Gsk 3Β ◽  
Canonical Wnt

Andrographolide activates the canonical Wnt pathway and induces the transcription of Wnt target genes through a mechanism independent of Wnt ligand binding to its receptor, by direct substrate-competitive inhibition of GSK-3.

scholarly journals Strong Correlation Between CTLA-4 and LEF1 Gene Expression Levels in CLL: Targeting of the Wnt/β-Catenin Pathway May Adversely Affect CTLA-4 Expression and Function

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5571-5571
Author(s):  
Philip T Murphy ◽  
Gary Lynch ◽  
Stephen Bergin ◽  
John Quinn ◽  
Siobhan Glavey ◽  
...  
Keyword(s):  
Gene Expression ◽  
Peripheral Blood ◽  
Surface Expression ◽  
Wnt Signalling ◽  
Signalling Pathway ◽  
Expression Levels ◽  
Cd38 Expression ◽  
Previously Treated ◽  
And Function ◽  
Gene Expression Levels

Abstract Recently published clinical trials have confirmed the effectiveness of anti-CD38 monoclonal antibody therapy in myeloma. Furthermore, in vitro studies of chronic lymphocytic leukaemia (CLL) cells suggest that CD38 expression can be enhanced by treatment with retinoid derivatives and thus may enhance the cytotoxic effects of anti-CD38 therapy. However, retinoids have been shown to have diverse effects on cellular function and we have previously shown that the retinoid drug acitretin upregulates CD38 expression while also reducing cell homing to the chemokine CXCL12 in primary CLL cells. To investigate possible key mechanisms for these effects, we purified CD20+ B cells from the peripheral blood of 20 CLL patients (9 previously treated, 11 untreated) and, using flow cytometry, measured percentage cell surface expression of CD38 and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4, CD152). We also measured gene expression levels of the key retinoid receptor, stimulated by retinoic acid 6 (STRA6) and it's agonist, retinol-binding protein 4 (RBP4), as well as CTLA-4, cyclin D1 (CCND1) and the transcription factors, lymphoid enhancer factor 1 (LEF1) and signal transducer and activator of transcription 3 (STAT3) using RT-PCR. GAPDH was used as a reference gene. Mean percentage surface expression of CD38 and CTLA-4 was 21.96% and 45.25% respectively. Mean ∆CT gene expression levels of CCND1, CTLA-4, LEF1 and STAT3 were 12.03, 5.57 , 5.99 and 8.98 respectively. RBP4 and STRA6 gene expression levels were undetectable in all 20 patients. Gene expression of LEF1 showed significant correlations with CTLA-4 (rs=0.572, p=0.008), CCND1 (rs=0.61, p=0.004) and STAT3 (rs=0.587, p=0.006). There was also a significant correlation between gene expression of CCND1 and of STAT3 (r =0.499, p=0.025). No significant correlations were found between percentage surface expression of CTLA-4 and gene expression levels of either CTLA-4 or of LEF1. A weak negative correlation between percentage surface expression of CTLA-4 and of CD38 was not statistically significant. Comparing untreated and previously treated patients, there was no significant difference in gene expression levels of CTLA-4 and of LEF1 or in surface expression of CTLA-4. The failure to detect RBP4 and STRA6 gene expression in unstimulated peripheral blood CLL cells is evidence against an autocrine retinoid effect in CLL, although upregulation of STRA6 gene expression following stimulation by retinoids might be anticipated. The Wnt signalling pathway has been shown to be active in CLL, including aggressive disease subtypes, highlighting the potential benefits in targeting this pathway. Intriguingly, CTLA-4 expression, although found to be the most highly induced gene following treatment with recombinant Wnt-3a in melanoma cell lines, is associated with a favourable outcome in CLL, possibly by inhibiting cell proliferation and survival. In contrast, expression of LEF1, which is a direct target of the Wnt signalling pathway, is associated with disease progression in CLL. Our finding that CTLA-4 and LEF1 gene expression levels are strongly correlated suggests that further investigation of the relationship between CTLA-4 and the Wnt/β-Catenin pathway in CLL is required and that targeting of the Wnt/β-catenin pathway may have unwanted consequences on CTLA-4 expression and function. Disclosures Quinn: Celgene: Honoraria; Janssen Cilag: Honoraria.

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