Chung Expression of the Xenopus homologue of the receptor for activated C-kinase 1 ( RACK 1 ) in the Xenopus embryo (original) (raw)
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Characterization of protein kinase C in early Xenopus embryogenesis
Development (Cambridge, England), 1990
Recently, we presented evidence that protein kinase C (PKC) is involved in mediating the endogenous signals that induced competent Xenopus ectoderm to differentiate to neural tissue. We report here that PKC is already strongly activated in neural-induced ectoderm from midgastrula embryos and that this activation runs parallel with an increase in the level of inositol phosphates. We further identify several proteins that are phosphorylated, both in natural neural-induced ectoderm and in TPA-treated ectoderm, suggesting that they are phosphorylated through the PKC route. We found no major changes in PKC activity among different pregastrula stages, including the unfertilized egg. However, PKC isolated from animal, ectodermal cells is highly sensitive to Ca2+ and can be activated by low concentrations, (6-25 microM) of arachidonic acid, while PKC isolated from vegetal, endodermal cells is more insensitive to Ca2+ and cannot be activated by arachidonic acid. These results suggest that di...
American Journal of Anatomy, 1995
Growth factors and their receptors play an important role in controlling cellular proliferation, migration, and differentiation during vertebrate embryogenesis. We have used the reverse transcription-polymerase chain reaction to survey the repertoire of receptor tyrosine kinases (TK) expressed during early embryogenesis of Xenopus laeuis. Twelve distinct Xenopus TK cDNA classes were identified among a total of 352 cDNAs screened. A single TK cDNA class has been described previously and encodes the fibroblast growth factor receptor FGFR-A1. The remaining 11 TK cDNA classes appear to encode novel genes of the FGFR, platelet-derived growth factor receptor (PDGFR), Eph, Csk, Tyk2, and Klg subfamilies. By RNase protection assays, Xenopus TK mRNAs are rare transcripts (<lo' mRNA molecules/embryo), and are usually found to be expressed also maternally in the embryo. Most Xenopus TK genes examined by whole-mount in situ hybridization were expressed widely in tissues derived from multiple germ layers. Two Eck-related genes, however, were found to be restricted in their expression to neural crest of the second (hyoid) arch. Our findings are consistent with the proposed function of TKs in the regulation of specification and differentiation of embryonic tissues.
Developmental Dynamics, 1995
Growth factors and their receptors play an important role in controlling cellular proliferation, migration, and differentiation during vertebrate embryogenesis. We have used the reverse transcription-polymerase chain reaction to survey the repertoire of receptor tyrosine kinases (TK) expressed during early embryogenesis of Xenopus laeuis. Twelve distinct Xenopus TK cDNA classes were identified among a total of 352 cDNAs screened. A single TK cDNA class has been described previously and encodes the fibroblast growth factor receptor FGFR-A1. The remaining 11 TK cDNA classes appear to encode novel genes of the FGFR, platelet-derived growth factor receptor (PDGFR), Eph, Csk, Tyk2, and Klg subfamilies. By RNase protection assays, Xenopus TK mRNAs are rare transcripts (<lo' mRNA molecules/embryo), and are usually found to be expressed also maternally in the embryo. Most Xenopus TK genes examined by whole-mount in situ hybridization were expressed widely in tissues derived from multiple germ layers. Two Eck-related genes, however, were found to be restricted in their expression to neural crest of the second (hyoid) arch. Our findings are consistent with the proposed function of TKs in the regulation of specification and differentiation of embryonic tissues.
Development Genes and Evolution, 2004
MAK-V/Hunk is a recently identified MARK/ Par-1-related mammalian protein kinase. Although the precise function of this protein kinase is yet to be established, available data suggest its involvement in animals' development and in the physiology of the nervous system. Here we report characterization of a cDNA encoding Xenopus laevis orthologue of MAK-V/ Hunk protein kinase, xMAK-V. The in silico analysis also revealed MAK-V/Hunk orthologues in the fish Fugu rubripes and primitive chordate Ciona intestinalis but not in invertebrate species such as Drosophila melanogaster and Caenorhabditis elegans, suggesting that MAK-V/ Hunk is a chordate-specific protein kinase. The expression of xmak-v in X. laevis embryos was analyzed using whole-mount in situ hybridization. Expression of xmak-v has been detected in all developmental stages studied including maternal expression in unfertilized eggs. The xmak-v mRNA has a predominant occurrence on the animal hemisphere of the egg, and this pattern of expression is sustained throughout cleavage and blastula stages. At the gastrula stage xmak-v expression is restricted to the ectoderm. In the later stage embryos xmak-v is expressed over the entire embryonic surface including the open neural plate at stage 15 and also in neural tube at stage 22. At tadpole stage xmak-v expression is strong in embryonic epidermis, nervous system and sensory organs, and is also obvious in perisomitic mesoderm and brachial arches.
Mitogen-activated protein kinase and neural specification in Xenopus
Proceedings of the National Academy of Sciences, 1998
We have investigated the activity and function of mitogen-activated protein kinase (MAPK) during neural specification in Xenopus . Ectodermal MAPK activity increased between late blastula and midgastrula stages. At midgastrula, MAPK activity in both newly induced neural ectoderm and ectoderm overexpressing the anterior neural inducer noggin was 5-fold higher than in uninduced ectoderm. Overexpression of MAPK phosphatase-1 (MKP-1) in ectoderm inhibited MAPK activity and prevented neurectoderm-specific gene expression when the ectoderm was recombined with dorsal mesoderm or treated with fibroblast growth factor (FGF). Neurectoderm-specific gene expression was observed, however, in ectoderm overexpressing both noggin and MKP-1. To evaluate the role of MAPK in posterior regionalization, ectodermal isolates were treated with increasing concentrations of FGF and assayed for MAPK activity and neurectoderm-specific gene expression. Although induction of posterior neural ectoderm by FGF was ...
Expression of Xkl-1, a Xenopus gene related to mammalian c-kit, in dorsal embryonic tissue
Mechanisms of Development, 1995
In mice, the Kit receptor tyrosine kinase and its ligand, Steel factor, are required for melanogenesis, hematopoesis and gametogenesis We have identified a Xenopus gene, Xkl-I (Xenopus Kit-like-l) whose predicted protein has striking sequence identity in the catalytic domain and kinase insert to that of c-kit. Xkl-I is expressed only in dorsal tissues such as the nervous system, notochord and somites of neurulae. Ultraviolet irradiated embryos and animal caps treated with basic FGF unexpectedly express Xkl-1, since they are considered to develop only ventral type tissues. These observations raise. the hypothesis that Xkl-I is involved in Xenopus dorsal development and that dorsal tissues inhibit the expression of Xkl-I in ventral structures.
Protein kinase CK2 is required for dorsal axis formation in Xenopus embryos
Developmental Biology, 2004
Dorsal axis formation in Xenopus embryos is dependent upon asymmetrical localization of h-catenin, a transducer of the canonical Wnt signaling pathway. Recent biochemical experiments have implicated protein kinase CK2 as a regulator of members of the Wnt pathway including h-catenin. Here, we have examined the role of CK2 in dorsal axis formation. CK2 was present in the developing embryo at an appropriate time and place to participate in dorsal axis formation. Overexpression of mRNA encoding CK2 in ventral blastomeres was sufficient to induce a complete ectopic axis, mimicking Wnt signaling. A kinase-inactive mutant of CK2a was able to block ectopic axis formation induced by XWnt8 and h-catenin and was capable of suppressing endogenous axis formation when overexpressed dorsally. Taken together, these studies demonstrate that CK2 is a bona fide member of the Wnt pathway and has a critical role in the establishment of the dorsal embryonic axis.
MAP Kinase Converts MyoD into an Instructive Muscle Differentiation Factor in Xenopus
Developmental Biology, 2001
In amphibian development, muscle is specified in the dorsal lateral marginal zone (DLMZ) of the gastrula embryo. Two critical events specify the formation of skeletal muscle: the expression of the myogenic transcription factor, XMyoD, and the secretion of bone morphogenetic protein (BMP) antagonists by the adjacent Spemann organizer. Inhibition of BMP signaling during early gastrula stages converts XMyoD protein into an instructive differentiation factor in the DLMZ. Yet, the intracellular signaling factors connecting BMP antagonism and activation of XMyoD remain unknown. Our data show that BMP antagonism induces the activity of mitogen-activated protein kinase (MAPK), and that the activity of MAPK is necessary for muscle-specific differentiation. Treatment of gastrula-stage DLMZ explants with MAPK pathway inhibitors ventralized mesoderm and prevented muscle differentiation. Expression of XMyoD in ventral mesoderm weakly induced muscle formation; however, the coexpression of a constitutively active MEK1 with XMyoD efficiently induced muscle differentiation. Activation of the MAPK pathway did not induce the transcription of XMyoD, but increased its protein levels and transcriptional activity. Thus, MAPK activation is subsequent to BMP antagonism, and participates in the dorsalization of mesoderm by converting the XMyoD protein into a potent differentiation factor.