Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cement gland is a mucus-secreting organ found at the extreme anterior of frog embryos. It attaches the embryo to a solid support before swimming and feeding begin, and also serves a related sensory function that stops the embryo from moving once it is attached. Cement gland is an extremely useful anterior marker, whose study continues to yield fundamental information concerning vertebrate axial patterning. Cement gland arises from the outer layer of the embryonic ectoderm and, in Xenopus, forms a cone of columnar epithelium. It is the first ectodermal organ to differentiate, beginning to do so by late gastrula. A battery of genes expressed in the developing and mature cement gland serve as useful markers. Cement gland development can be influenced by both stimulatory and inhibitory cell interactions. Stimulatory signals arise from the anterior neural plate, head endoderm, and the dorsal mesoderm. Inhibitory signals are present in the posterior dorsal mesoderm and in ventral ectoderm and mesoderm. Further, signalling between the ectodermal layers may restrict cement gland differentiation to the outer ectodermal cells. Several secreted molecules are able to induce or repress cement gland formation: these include noggin, follistatin, hedgehog, chordin, retinoic acid, embryonic fibroblast growth factor (eFGF), Bone Morphogenetic Protein-4 (BMP-4), and Xwnt-8. Several of these factors alter expression of the homeodomain gene Xotx2, which may be a transcriptional activator of cement gland differentiation genes. The significance of the cell interactions and factors described in positioning cement gland at the front of the embryo is explored.
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PMID:A sticky problem: the Xenopus cement gland as a paradigm for anteroposterior patterning. 885 May 63

The POU domain gene, XlPOU 2, acts as a transcriptional activator during mid-gastrulation in Xenopus. Overexpression or misexpression of VP16-POU-GR, a fusion protein consisting of the strong activator domain of VP16 and the POU domain of XlPOU 2, results in ectopic expression of the neural-specific genes, nrp-1, en-2, and beta-tubulin. In contrast, overexpressing a dominant-inhibitory form of XlPOU 2 inhibits the chordin-induced neuralization of uncommitted ectoderm, and results in a loss of nrp-1 and en-2 expression in embryos. Furthermore, in uncommitted ectoderm, XlPOU 2 regulates the developmental neural program that includes a number of pre-pattern genes and at least one proneural gene, X-ngnr-1, thus playing a key role during neural determination.
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PMID:The POU domain gene, XlPOU 2 is an essential downstream determinant of neural induction. 1055 82

Early embryonic development in many organisms relies upon maternal molecules deposited into the egg prior to fertilization. We have cloned and characterized a maternal T-box gene in the zebrafish, eomesodermin (eomes). During oogenesis, the eomes transcript becomes localized to the cortex of the oocyte. After fertilization during early cleavage stages, eomes is expressed in a vegetal to animal gradient in the embryo, whereas Eomesodermin protein (Eom) is distributed cytoplasmically throughout the blastoderm. Strikingly, following midblastula transition, nuclear-localized Eomesodermin is detected on the dorsal side of the embryo only. Overexpression of eomes results in Nodal-dependent and nieuwkoid/dharma (nwk/dhm) independent ectopic expression of the organizer markers goosecoid (gsc), chordin (chd) and floating head (flh) and in the formation of secondary axes. The same phenotypes are observed when a VP16-activator construct is injected into early embryos, indicating that eomes acts as a transcriptional activator. In addition, a dominant-negative construct and antisense morpholino oligonucleotides led to a reduction in gsc and flh expression. Together these data indicate that eomes plays a role in specifying the organizer.
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PMID:The maternally expressed zebrafish T-box gene eomesodermin regulates organizer formation. 1453 Feb 96

Sox proteins are DNA-binding proteins belonging to the HMG box superfamily and they play key roles in animal embryonic development. Zebrafish Sox21a is part of group B Sox proteins and its chicken and mouse orthologs have been described as transcriptional repressor and activator, respectively, in two different target gene contexts. Zebrafish sox21a is present as a maternal transcript in the oocyte and is mainly expressed at the developing midbrain-hindbrain boundary from the onset of neurulation. In order to understand its role in vivo, we ectopically expressed sox21a by microinjection. Ectopic expression of full length sox21a leads to dorsalization of the embryos. A subset of the dorsalized embryos shows a partial axis splitting, and hence an ectopic neural tube, as an additional phenotype. At gastrulation, injected embryos show expansion of the expression domains of organizer-specific genes, such as chordin and goosecoid. Molecular markers used in somitogenesis highlight that sox21a-injected embryos have shortened AP axis, undulating axial structures, enlarged or even radialized paraxial territory. The developmental abnormalities caused by ectopic expression of sox21a are suggestive of defects in convergence-extension morphogenetic movements. Antisense morpholino oligonucleotides, designed to functionally knockdown sox21a, cause ventralization of the embryos. Moreover, gain-of-function experiments with chimeric constructs, where Sox21a DNA-binding domain is fused to a transcriptional activator (VP16) or repressor (EnR) domain, suggests that zebrafish Sox21a acts as a repressor in dorso-ventral patterning.
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PMID:Ectopic expression and knockdown of a zebrafish sox21 reveal its role as a transcriptional repressor in early development. 1503 15

Frodo is a novel conserved regulator of Wnt signaling that has been identified by its association with Dishevelled, an intracellular component of Wnt signal transduction. To understand further how Frodo functions, we have analyzed its role in neural development using specific morpholino antisense oligonucleotides. We show that Frodo and the closely related Dapper synergistically regulate head development and morphogenesis. Both genes were cell-autonomously required for neural tissue formation, as defined by the pan-neural markers sox2 and nrp1. By contrast, beta-catenin was not required for pan-neural marker expression, but was involved in the control of the anteroposterior patterning. In the mesoderm, Frodo and Dapper were essential for the expression of the organizer genes chordin, cerberus and Xnr3, but they were not necessary for the expression of siamois and goosecoid, established targets of beta-catenin signaling. Embryos depleted of either gene showed a decreased transcriptional response to TCF3-VP16, a beta-catenin-independent transcriptional activator. Whereas the C terminus of Frodo binds Dishevelled, we demonstrate that the conserved N-terminal domain associates with TCF3. Based on these observations, we propose that Frodo and Dapper link Dsh and TCF to regulate Wnt target genes in a pathway parallel to that of beta-catenin.
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PMID:The involvement of Frodo in TCF-dependent signaling and neural tissue development. 1532 48