PubMed Health⌕ Search

Biomedical subjects

K Shiokawa

Publications and source records attributed to K Shiokawa.

At least 55 records · Page 3Linked to original sources
PubMed1997

Cloning of Xenopus Dr1 (TBP-binding repressor) and its expression in oocytes and early embryos.

With a final goal to study how TBP-binding repressor Dr1 regulates transcription in Xenopus early embryos, we cloned its cDNA from Xenopus liver cDNA library. The cDNA was 1,986 bp long, with the open reading frame coding for 175 amino acids, whose sequence was highly homologous to its human counterpart. Xenopus Dr1 mRNA was expressed from the earliest stage of oogenesis, inherited as maternal mRNA at a high level, but its level became low at and after the neurula stage where RNA synthetic activity is strongly activated. Dr1 mRNA occurred in larger amounts in the animal half than in the vegetal half in 8-cell stage embryos, and in neurula and tailbud stage embryos its distribution was slightly larger in the anterior part than in the posterior part. These data show that Dr1 mRNA is expressed in a temporally and spatially regulated manner, and its occurrence at higher levels in earlier stage embryos may be responsible for their low transcriptional activity.

Amino Acid Sequence↗
PubMed1996

Characterization of the major core structures of the alpha2-->8-linked polysialic acid-containing glycan chains present in neural cell adhesion molecule in embryonic chick brains.

To gain more insight into the possible functional significance of the core glycan chain(s) on which polysialylation takes place in polysialic acid (poly-Sia)-containing glycoproteins, the structure of the core glycans in the embryonic form of chick brain neural cell adhesion molecule (N-CAM) were examined using chemical and instrumental techniques. The following new structural features, which had not been reported by the early pioneering study by Finne (Finne, J. (1982) J. Biol. Chem. 257, 11966-11970), were revealed (Structure I). (i) Two distinct types of multiantennary N-linked glycans, i.e. tri- and tetra-antennary structures, are present; (ii) an alpha1-->6-linked fucosyl residue is attached to the proximal GlcNAc residue of the di-N-acetylchitobiosyl unit; (iii) that the action of GlcNAc-transferase V, which catalyzes the attachment of the beta-(1-->6)-linked GlcNAc residue on the (1-->6)-alpha-linked mannose (Man) arm, appears to be essential for polysialylation to occur on the core glycan chain is suggested by the fact that the Man residue alpha1-->6-linked to the beta-linked Man residue is invariably 2,6-di-O-substituted by the GlcNAc residue; (iv) both type 1 (Galbeta1-->3GlcNAc) and type 2 (Galbeta1-->4 GlcNAc) sequences are present in the peripheral portion of the core glycan structure. An extended form of the type 2 chain, i.e. Galbeta1-->4GlcNAcbeta1-->3Galbeta1-->4GlcNAc, is also expressed on the (1-->3)- and (1-->6)-alpha-linked Man arms; (v) on average about 1.4 mol of sulfate is attached to the type 2 N-acetyllactosamine chain(s), where in the extended form the sulfate group is probably substituted at the O-3 position of the outmost GlcNAc residue, i.e. Galbeta1-->4(HSO3-->3)GlcNAcbeta1-->3Galbeta1--> 4GlcNAcbeta1-->Man. It is possible that the unusual structural features identified in this study might play a role in the initiation of polysialylation and our data should facilitate future research regarding the signals that control polysialylation.

Acetylation↗
PubMed1996

Maternal and zygotic expression of mRNA for S-adenosylmethionine decarboxylase and its relevance to the unique polyamine composition in Xenopus oocytes and embryos.

From Xenopus tailbud cDNA library, we isolated the cDNA for S-adenosylmethionine decarboxylase (SAMDC), an enzyme which provides putrescine and spermidine with the aminopropyl group to form spermidine and spermine, respectively. The cDNA coded for 335 amino acids whose sequence had high homology (ca. 83%) to other vertebrate SAMDCs, preserving the sequences reportedly essential for enzyme activity, proenzyme processing, and putrescine stimulation of the enzyme activity. Northern blot analysis showed one major mRNA signal of ca. 3.5 kb, with a minor signal of ca 2.0 kb which may probably be due to cross-hybridization. In oocytes the SAMDC mRNA occurred from stage I, and its amount peaked at stage II, then gradually decreased from stage III to VI. The decreased level of the mRNA was maintained during oocyte maturation, further decreased from the cleavage to early neurula stage, and then increased greatly due to the zygotic expression during late neurula stages (stage 21-25), reaching a plateau level at the late tailbud stage (stage 28). Enzyme assays showed that the changing level of the SAMDC mRNA was reflected in the level of the functional enzyme, suggesting strongly that the zygotic expression of the mRNA leads to a large increase in the amount of SAMDC, albeit in the pre-neurula embryo the amount of the enzyme is very small. We found that the relative composition of polyamines is the eukaryote-type (high-level spermine) at the beginning of oogenesis, but it changes to the prokaryote-type, or more appropriately Escherichia coli-type (high-level putrescine but background level spermine) during oocyte maturation, and remains E. coli-type throughout embryogenesis. We assume that the E. coli-type polyamine composition is a necessary factor for the normal embryogenic development in Xenopus and its maintenance, especially that in pre-neurula stages, can be explained by the low level of both SAMDC mRNA and SAMDC.

Adenosylmethionine Decarboxylase↗
PubMed1996

Cloning of Xenopus TFIIS and its expression in oocytes and early embryos.

The transcriptional factor TFIIS has been cloned from Xenopus laevis. The length of the cDNA is 1668bp and contains the complete open reading frame of 303 amino acids. Xenopus TFIIS has high homologies to its human and mouse counterparts. In Northern blot analyses, TFIIS mRNAs that consisted of four different sizes were expressed relatively highly from the early stages of Xenopus oogenesis. During oocyte maturation, the pattern of Xenopus TFIIS messages showed a transient peak of expression. TFIIS mRNA occurred maternally and its level increased in later stage embryos. These data suggest that TFIIS mRNA is expressed in a developmentally regulated way in Xenopus laevis.

Amino Acid Sequence↗
PubMed1996

Complementary DNA cloning and sequencing of rat enteropeptidase and tissue distribution of its mRNA.

A cDNA clone encoding enteropeptidase (EC 3.4.21.9), a key enzyme for the conversion of trypsinogen to trypsin, was isolated from a rat duodenal mucosa cDNA library. Sequences of the 3585 base pair clone predicted that enteropeptidase is synthesized as a single-chain precursor form, proenteropeptidase, consisting of 1058 amino acid residues with an internal signal sequence (51 residues) and is then processed into the mature enzyme consisting of three different peptide chains, i.e., mini, light and heavy chains, not the previously reported two-chain enzyme. The structure of enteropeptidase is relatively conserved among different species and the rat enteropeptidase is 24 and 39 amino acids longer than the porcine and human ones, respectively. Northern blot analysis of rNAs from normal rat tissues revealed that the enteropeptidase mRNA of around 4.4 kb in size was expressed only in the duodenal mucosa, and high proteolytic activity of the enzyme was detected in the proximal small intestine. Additional analysis of the RNAs by RT-PCR revealed that a low level of the mRNA was also expressed in the other parts of the small intestine, i.e., jejunum and ileum. These results indicate that the biosynthesis of enteropeptidase takes place mainly in the proximal small intestine, the duodenum, and the importance of the region in the physiology of intestinal protein digestion regulated by the enzyme is suggested. Furthermore a faint signal of the mRNA was also detected in the stomach, colon and brain in which the existence of trypsin-like serine proteases were reported. The significance of the low level expression of the gene is unclear, but the potential peptide-processing function of the enzyme in these tissues is also suggested.

Amino Acid Sequence↗
PubMed1996

Molecular cloning of Xenopus activin type I receptor and the analysis of its expression during embryogenesis.

We cloned cDNAs coding for the Xenopus counterparts of a type I activin receptor. The cDNA clones were predicted to encode 56kd proteins, namely XAR3 and XAR4 proteins. The two proteins are highly homologous to each other, showing 96% identity in the amino acid sequences. The GST-fused kinase domain of XAR3 autophosphorylated itself in vitro on threonine residues. The expression of XAR4 was found throughout embryogenesis, from oocytes to tailbud embryos, and also in adult tissues. By whole mount in situ hybridization, the XAR4 transcripts were detected in the animal half of blastulae and dorsally in gastrulae and neurulae. In tadpoles, the transcript was seen in the brain and around the otic vesicles. These results show that the activin type I receptor is expressed during Xenopus embryogenesis and suggest that the type I and II receptors are expressed together both temporally and spatially, supporting the idea that activin induces mesoderm in the embryo through activation of the two types of receptors.

Activin Receptors↗
PubMed1996

Cloning and expression studies of cDNA for a novel Xenopus cadherin (XmN-cadherin), expressed maternally and later neural-specifically in embryogenesis.

From a Xenopus tailbud cDNA library, we obtained the cDNA for a novel cadherin which was named as XmN-cadherin (Xenopus maternally expressed neural cadherin). The cDNA consisted of 3690 bp and encoded 922 amino acid residues. XmN-cadherin preserved five extracellular cadherin motifs, a single transmembrane domain, and a cytoplasmic domain, and was closely related by its sequence to R- and N-cadherin. In the adult frog, XmN-cadherin mRNA was detected strongly in ovary, testis, brain, eye, and kidney, and weakly in stomach, and intestine. In the egg, the mRNA occurred as a maternal mRNA at a relatively high level, and its level became very low by the neurula stage, then increased steadily thereafter. Dissection experiments with 8-cell stage and neurula stage embryos revealed that the maternally inherited mRNA was relatively uniformly distributed within the embryo. By a sharp contrast, whole mount in situ hybridization revealed that the zygotically expressed mRNA occurred almost exclusively in neural tissues such as brain, the anterior part of spinal cord, and the optic and otic vesicles. Thus, XmN-cadherin appears to have at least triple functions; it probably contributes in early embryos to cell-type non-specific cell adhesion, but in post-neurula embryos may be responsible for the development and/or maintenance of anterior neural tissues, and may be used in adult frog for the development and/or maintenance of neural, endodermal and reproductive organs.

Amino Acid Sequence↗
PubMed1996

Adult moyamoya disease progressing from unilateral to bilateral involvement .

A 30-year-old female and a 38-year-old male developed "definite" moyamoya disease after presenting with "probable" moyamoya disease manifesting as ischemic stroke. Angiography at first presentation demonstrated unilateral involvement with normal contralateral findings. The cases were classified as adult type "probable" moyamoya disease according to the diagnostic criteria. Follow-up angiography demonstrated the occlusive lesions had become bilateral, satisfying the criteria for "definite" cases. Serial angiography is required in adults presenting with "probable" moyamoya disease manifesting as ischemic stroke.

Adult↗
PubMed1995

Developmental and differential regulations in gene expression of Xenopus pleiotrophic factors-alpha and -beta.

Using conserved nucleotide sequences in mammalian osteoblast specific factor-1 (OSF-1) coding regions, we isolated two kinds of cDNA clones from the Xenopus brain library. The encoded proteins, named Xenopus pleiotrophic factors (X-PTFs)-alpha and -beta, were 65 and 87% homologous to human midkine and OSF-1, respectively. In the adult frog, X-ptf-alpha was expressed in the ovary, brain, eye, bone, heart and lung, whereas X-ptf-beta was expressed in the brain, eye and bone. By in situ hybridization of the tailbud embryo, X-ptf-alpha mRNA was detected rather broadly in the head/tail regions including the central nervous system (CNS), whereas X-ptf-beta mRNA was restricted to the CNS, particularly in the hind-brain. During embryogenesis, X-ptf-alpha mRNA was detected in the one-cell stage embryo, whereas only zygotic expression was observed in X-ptf-beta. X-ptf-beta mRNAs contained approximately 79 bp tandem repeats in the 3'-untranslated region, complementary to those found in retinoic acid cellular receptor mRNA and in the sense strand of short interspersed repeat transcripts in X. laevis.

Aging↗
PubMed1995

Differential display analysis of gene expression in developing embryos of Xenopus laevis.

Differential display (DD), an arbitrarily primed RT-PCR fingerprinting technique, is a novel approach for the search of differentially expressed transcripts. Using our improved DD protocol, reproducible cDNA fingerprints were successfully obtained from RNAs of Xenopus laevis embryos at six representative stages. Parallel comparison among the fingerprints revealed a number of bands with differential expression patterns. Analysis with clones of three randomly chosen bands confirmed that their expression patterns were faithfully reflected on fingerprints, thereby proving the reliability and validity of the approach. Nucleotide sequencing of these clones revealed that one is identical with a known transcript (cardiac actin), the second is a novel developmentally regulated gene showing no significant homology with those reported previously, and the last is a close but unique relative of XK endo B gene showing somewhat different spatial expression pattern. These results indicated that the DD analysis provides a rapid and reliable way for the identification of novel differentially expressed genes as well as a unique 'scope' for the survey of the changes in overall gene expression profiles occurring in the early embryonic development of Xenopus as well as of other organisms.

Amino Acid Sequence↗
PubMed1995

mRNA encoding the translation initiation factor eIF-4E is expressed early in Xenopus embryogenesis.

The translation initiation factor eIF-4E plays an important role in regulating the overall rate of translation in eukaryotic cells. To investigate the expression of eIF-4E itself, we characterized the eIF-4E mRNA expressed in Xenopus embryos. 5'-RACE was performed to determine the 5'-end of the mRNA and the result predicts isoforms differing at the amino-terminal end. Expression of the eIF-4E mRNA in Xenopus oocytes and embryos was examined by RT-PCR. Xenopus eIF-4E mRNA is produced during oogenesis and persists during the early stages of embryogenesis as a maternal mRNA.

Activin Receptors↗
PubMed1995

Cloning of cDNA and genomic DNA encoding fibroblast growth factor receptor-4 of Xenopus laevis.

We have isolated and characterized the cDNA and genomic DNA encoding fibroblast growth factor receptor-4 of Xenopus laevis (XFGFR-4). The gene encompassing the total coding sequence spans about 10 kb, consists of 17 exons, and has an organization very similar to those of mammalian genes encoding FGFR-1 and -2, except that the XFGFR-4 gene does not contain an alternative exon for the third immunoglobulin-like domain nor an internal poly(A)-addition site. Thus, XFGFR-4 appears not to generate multiple forms of mRNA, as are identified for the mammalian FGFR-1, -2 and -3 genes. The amino-acid sequence of XFGFR-4 shows high homology to other vertebrate FGFR-4 species, but the similarity was significantly lower than in the cases of FGFR-1 and -2. Northern blot analysis showed the XFGFR-4 mRNA to occur throughout X. laevis early embryogenesis in a profile different from those of X. laevis FGFR-1 and -2.

Amino Acid Sequence↗
PubMed1995

Stimulation of circus movement by activin, bFGF and TGF-beta 2 in isolated animal cap cells of Xenopus laevis.

Lobopodium is a hyaline cytoplasmic protrusion which rotates circumferencially around a cell. This movement is called circus movement, which is seen in dissociated cells of amphibian embryos. Relative abundance of the lobopodia-forming cells changes temporally and spatially within Xenopus embryos, reflecting stage-dependent difference of morphogenetic movements. The lobopodia-forming activity of dissociated animal cap cells was stimulated strongly by activin and bFGF, and weakly by TGF-beta 2. In addition, activin A was found to stimulate cellular attachment to the substratum when the cultivation lasted long. Thus, mesoderm-inducing growth factors stimulate lobopodia formation and cellular movements which may be necessary for gastrulation and neurulation in Xenopus early embryos.

Activins↗
PubMed1995

Molecular cloning of Xenopus HGF cDNA and its expression studies in Xenopus early embryogenesis.

We isolated Xenopus HGF cDNA and examined its expression pattern in Xenopus early embryos and their dissected parts. Xenopus HGF consists of 710 amino acids and contains four kringle domains and serine protease-like structure just like mammalian HGF. Northern blot analysis showed that expression of Xenopus HGF mRNA starts at the late gastrula stage and its level increases during the period of later embryogenesis. Dissection experiments revealed that Xenopus HGF mRNA is expressed in the mesoderm region, especially in the ventral mesoderm, which for the most part gives rise to mesenchymal cells. Furthermore, HGF mRNA was expressed in response to activin A and basic FGF in blastula animal cap cells. Interestingly, a stronger activity was observed with bFGF than with activin and this finding corroborates the preferential expression of HGF mRNA in the ventral mesoderm. Based on these results, we conclude that the Xenopus homologue of HGF gene is transcribed during early embryogenesis preferentially in ventral mesodermal tissues, probably in response to the signals that induce ventral mesoderm.

Amino Acid Sequence↗