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

In order to study the mechanism of neural patterning in Xenopus, we used subtractive cloning to isolate genes activated early during this process. One gene isolated was opl, (odd-paired-like) that resembles the Drosophila pair-rule gene odd-paired and encodes a zinc finger protein that is a member of the Zic gene family. At the onset of gastrulation, opl is expressed throughout the presumptive neural plate, indicating that neural determination has begun at this stage while, by neurula, opl expression is restricted to the dorsal neural tube and neural crest. opl encodes a transcriptional activator, with a carboxy terminal regulatory domain, which when removed increases opl activity. opl both sensitizes animal cap ectoderm to the neural inducer noggin and alters the spectrum of genes induced by noggin, allowing activation of the midbrain marker engrailed. Consistent with the later dorsal neural expression of opl, the activated form of opl is able to induce neural crest and dorsal neural tube markers both in animal caps and whole embryos. In ventral ectoderm, opl induces formation of loose cell aggregates that may indicate neural crest precursor cells. Aggregates do not express an epidermal marker, indicating that opl suppresses ventral fates. Together, these data suggest that opl may mediate neural competence and may be involved in activation of midbrain, dorsal neural and neural crest fates.
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PMID:Opl: a zinc finger protein that regulates neural determination and patterning in Xenopus. 965 9

Tbx6 is a member of the T-box gene family. Studies of knockout mice indicate that Tbx6 is involved in somite differentiation. In the present study, we cloned Tbx6 from another vertebrate species, namely Xenopus laevis, and studied its roles in development. The expression of Tbx6 in Xenopus started from the early gastrula stage, reached a peak during the late gastrula to neurula stages and then declined. Initial expression of Tbx6 was observed in the paraxial mesoderm during the gastrula stage. The Tbx6-expressing region spread anteriorly and ventrally in the neurula stage. In the tailbud stage, the area of expression shrank caudally and was finally restricted to the tip of the tailbud. Overexpression of Tbx6 mRNA in dorsal blastomeres caused atrophy of the neural tube and inhibited differentiation of the notochord. Animal cap explants overexpressing Tbx6 or Tbx6VP16 mRNA, but not Tbx6EnR mRNA, differentiated mainly into ventral mesodermal tissues. This suggests that Tbx6 is a transcriptional activator. Higher doses of Tbx6 or Tbx6VP16 mRNA caused hardly any muscular differentiation. However, coinjection of Tbx6 mRNA with noggin mRNA elicited marked muscle differentiation. These results suggest that Tbx6 is implicated in ventral mesoderm specification but is involved in muscle differentiation when acting together with the dorsalizing factor noggin.
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PMID:Cloning and characterization of the T-box gene Tbx6 in Xenopus laevis. 1173 46