1,721,091 research outputs found
Expression of the fibroblast growth factor-2 gene during chick development
No full textIn this report, we have carried out mRNA in situ hybridization analysis to study the pattern of expression of the fibroblast growth factor-2 (FGF-2) gene during chick development. The expression pattern of FGF-2 was compared to that of the fibroblast growth factor-1 (FGF-1) gene to further assess a possible role of the FGF-2 during chick embryogenesis. The whole embryos of various stages were examined with S-35-labeled riboprobes transcribed from the coding regions of chick FGF-2 and FGF-1 cDNAs. We show that the distribution pattern of FGF-2 mRNA was highly specific. The FGF-2 transcripts were localized to limb mesenchymes, pharyngeal regions, and embryonic kidneys in day 3 to day 6 chick embryos. However, no FGF-1 mRNA was detected in these structures indicating a unique role of FGF-2 in chick development. These results support the hypothesis that FGF-2 may be a crucial signaling molecule during chick embryogenesis.X114sciescopu
OSCILLATION OF INOSITOL POLYPHOSPHATES IN THE EMBRYONIC CLEAVAGE CYCLE OF THE XENOPUS-LAEVIS
No full textEvidence suggests that a transient increase in intracellular calcium ([Ca2+](i)) is an important modulator during the cell division cycle in early embryos. We have recently shown that inhibition of Ins(1,4,5)P-3-induced Ca2+ release in the cleaving Xenopus embryos greatly lengthens the cell cycle duration. In this report, we have directly measured the changes of Ins(1,4,5)P-3 content during the first two cleavage cycles in the Xenopus embryos. HPLC profiles of cell extracts from dividing embryos show oscillations of inositol polyphosphates throughout the cleavage cycle with a transient production of Ins(1,4,5)P-3 by the time of cleavage furrow completion. In addition, cyclic changes in inositol phospholipids, phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 4-phosphate (PIP) were detected during the cleavage cycle. These data strongly suggest the involvement of PIP2 turnover and periodic increase in Ins(1,4,5)P-3 triggers [Ca2+](i) transients during the early embryonic cell cycle in the Xenopus. (C) 1995 Academic Press, Inc.X116sciescopu
Molecular cloning of chicken embryo fibroblast growth factor 1 cDNA and its expression during early embryogenesis
No full textAccumulating evidance indicates that the products of the FGF gene family function as signaling molecules in diverse processes during vertebrate embryogenesis. In tring to further understand the function of the FGFs during early vertebrate development, we attempted to isolate and clone chicken cognate of the mouse and human FGF1 gene using a polymerase chain reaction (PCR) technique. A single pair of degenerate oligonucleotide primer set was used for amplification of chicken FGF1 gene. About 340 base pairs of expected FGF1 sequences between the primers were amplified. Southern blot hybridization using probes for a mouse FGF1 was performed to confirm that the chicken FGF1 cDNA of interest had been amplified. Sequences upstream and downstream of the amplified products were obtained by means of the rapid amplification of cDNA ends (RACE) method. Sequence analysis revealed that chicken FGF1 is highly homologous to that of its mammalian counterparts. mRNA in situ hybridization analysis studies demonstrate that FGF1 transcripts are highly expressed in developing eyes, suggesting that FGF1 may be an important signaling molecule for vertebrate eye development.X112sci
EMBRYONIC EXPRESSION OF FGF-6 IS RESTRICTED TO THE SKELETAL-MUSCLE LINEAGE
No full textX1151sciescopu
Hydrogen peroxide-induced current in Xenopus oocytes: current characteristics similar to those induced by the removal of extracellular calcium
No full textThe effects of hydrogen peroxide (H2O2) exposure on Xenopus oocytes were examined. An application of I muL of 10% H2O2 to oocytes voltage-clamped in I mL of Modified Barth Saline (MBS: final concentration of 0.01% H2O2) induced a transient ionic current. This H2O2-induced current, however, was not transient but long-lasting in a Ca2+-free medium. The H2O2-induced current was independent of increases in intracellular calcium. Intriguingly, the H2O2-induced current was similar in signature to one stimulated by the removal of extracellular calcium (Ca-o(2+)-inactivated current). Both currents (a) were inactivated by 1.5 mM LaCl3, GdCl3, CdCl2, NiCl2, CaCl2, or MgCl2, but not by LiCl or KCl, (b) exhibited reversal potential shifts to more positive values with increasing external NaCl, (c) showed linear voltage-current (I-VI) relationships, and (d) were reversibly inhibited by two chloride channel blockers, 200 muM 5-nitro-2-(3-phenylpropylamino)-benzoic acid and 250 muM niflumic acid. Additionally, H2O2 was still able to induce current in oocytes loaded with either catalase or N-acetyl-L-cysteine, H2O2 scavengers. These results imply that H2O2 induces this ionic current possibly through the activation of Ca-o(2+)-inactivated channels by an extracellular mechanism. (C) 2002 Elsevier Science Inc. All rights reserved.X112sciescopu
Ephrin-Eph signaling mediates tissue separation between involuting mesoderm and noninvoluting ectoderm, that is critical for Xenopus gastrulaiton movement
No full textX11sciescopu
Rap2 is required for Wnt/beta-catenin signaling pathway in Xenopus early development
No full textThe Wnt/beta-catenin signaling pathway is critical for the establishment of organizer and embryonic body axis in Xenopus development. Here, we present evidence that Xenopus Rap2, a member of Ras GTPase family, is implicated in Wnt/beta-catenin signaling during the dorsoventral axis specification. Ectopic expression of XRap2 can lead to neural induction without mesoderm differentiation. XRap2 dorsalizes ventral tissues, inducing axis duplication, organizer-specific gene expression and convergent extension movements. Knockdown of XRap2 causes ventralized phenotypes including shortened body axis and defective dorsoanterior patterning, which are associated with aberrant Wnt signaling. In line with this, XRap2 depletion inhibits beta-catenin stabilization and the induction of ectopic dorsal axis and Wnt-responsive genes caused by XWnt8, Dsh or beta-catenin, but has no effect on the signaling activities of a stabilized beta-catenin. Its knockdown also disrupts the vesicular localization of Dsh, thereby inhibiting Dsh-mediated beta-catenin stabilization and the membrane recruitment and phosphorylation of Dsh by frizzled signaling. Taking together, we suggest that XRap2 is involved in Wnt/beta-catenin signaling as a modulator of the subcellular localization of Dsh.X112526sciescopu
Cloning and expression of a novel armadillo motif containing gene in Xenopus
No full textWe report an isolation of a cDNA containing armadillo motif (Xamp: Xenopus armadillo motif protein) and its expression during Xenopus development. The open reading frame of Xamp encodes a predicted protein of 275 amino acids including an armadillo motif, and a bipartite nuclear localization signal. Xamp shares significant homology with a putative mouse protein ( GeneBank AK009402) in the database. It is expressed both maternally and zygotically. Xamp is localized to the animal region of an egg and in the ectoderm of a gastrula stage embryo. At the neurula stages, Xamp is expressed in the dorsal region of neural tube from which presumptive sensory neurons arise. In addition to its neural tissue specific expression, Xamp transcripts are found to be localized in the developing gut tube. At the early tadpole stage, Xamp is expressed predominantly in the pharyngeal endoderm. As further development proceeds, its expression domain expands to include the entire foregut region but excludes the midgut and hindgut regions. This polarized pattern of expression persists until stage 46 after which, anterior specific expression of Xamp sharply decreases. These results suggest that Xamp may have a role in the neural tissue specification and gut endoderm patterning during the Xenopus development. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.X11sciescopu
XEPAC, A GUANINE NUCLEOTIDE-EXCHANGE FACTOR FOR RAP GTPASE, IS A NOVEL HATCHING GLAND SPECIFIC MARKER DURING THE XENOPUS EMBRYOGENESIS
No full textcAMP is a second messenger controlling various cellular processes through cAMP-dependent protein kinase (cAPK, PKA) and cyclic nucleotide-gated ion channels. Recently, the PKA-independent-cAMP-mediated signaling pathway by means of exchange protein directly activated by cAMP (Epac) has been demonstrated. Epac is a guanine nucleotide-exchange factor (GEF) for Rap, a Ras-like small GTPase. To investigate this new target for cAMP in development, we have isolated Xepac, the Xenopus laevis homologue of Epac by cDNA library screening. Xepac (Xepac1) encodes 890 amino acids, which have 57% identity with human Epac1 and 59% with that of rat Epac1 in amino acids. Whole-mount in situ hybridization and reverse transcriptase-polymerase chain reaction analysis show that XEpac is expressed both maternally and zygotically and is restricted within the developing hatching gland. Intriguingly, overexpression of XEpac induces the anterior markers XAG-1 and XOtx2 and can convert ectoderm. into cement- and hatching gland-expressing cells. These results suggest that XEpac contains anterior positional information. (c) 2005 Wiley-Liss, Inc.X1144sciescopu
Xenopus Cdc42 regulates convergent extension movements during gastrulation through Wnt/Ca2+ signaling pathway
No full textRho GTPases are molecular switches that regulate many essential cellular processes, including actin dynamics, cell adhesion, cell-cycle progression, and transcription. We have isolated the Xenopus homolog of Rho GTPase Cdc42 and examined its potential role during gastrulation movements in early Xenopus embryos. XCdc42 is expressed in tissues undergoing extensive morphogenetic changes, such as the deep layers of involuting mesoderm and posterior neuroectoderm during gastrulation, and somitic mesoderm at neurula stages. Overexpression of either wild-type (WT) or dominant-negative (DN) XCdc42 interferes with convergent extension movements in intact embryos, activin-stimulated animal caps, and dorsal marginal zone explants. These effects occur without affecting mesodermal specification. Overexpression of WT or DN XCdc42 leads to the decrease and increase of cell adhesiveness of blastomeres, respectively, as demonstrated by the cell adhesion assay. In addition, when overexpressed, PKC-alpha, XWnt-5a, and Mfz-3 inhibit activin-induced convergent extension in animal cap explants. This inhibition can be rescued by coexpression of DN XCdc42, implying that XCdc42 acts downstream of the Wnt/Ca2+ signaling pathway involving PKC activation. XCdc42 also lies downstream of XWnt-5a in the regulation of Ca2+-dependent cell adhesion. Taken together, our results suggest that XCdc42 plays a role in the regulation of convergent extension movements during gastrulation through the protein kinase C-mediated Wnt/Ca2+ pathway. (C) 2002 Elsevier Science (USA).X11111sciescopu
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