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C Kintner

Publications and source records attributed to C Kintner.

47 records · Page 3Linked to original sources
PubMed1992

Regulation of embryonic cell adhesion by the cadherin cytoplasmic domain.

Differential adhesion between embryonic cells has been proposed to be mediated by a family of closely related glycoproteins called the cadherins. The cadherins mediate adhesion in part through an interaction between the cadherin cytoplasmic domain and intracellular proteins, called the catenins. To determine whether these interactions could regulate cadherin function in embryos, a form of N-cadherin was generated that lacks an extracellular domain. Expression of this mutant in Xenopus embryos causes a dramatic inhibition of cell adhesion. Analysis of the mutant phenotype shows that at least two regions of the N-cadherin cytoplasmic domain can inhibit adhesion and that the mutant cadherin can inhibit catenin binding to E-cadherin. These results suggest that cadherin-mediated adhesion can be regulated by cytoplasmic interactions and that this regulation may contribute to morphogenesis when emerging tissues coexpress several cadherin types.

Animals↗
PubMed1992

Molecular bases of early neural development in Xenopus embryos.

Genes that are differentially expressed in the ectoderm as it diverts along the neural and epidermal pathways of differentiation can be used to study the inducing signals underlying induction as well as how ectoderm responds to these signals by forming neural tissue. Although these genes have provided, and will continue to provide, new information about the induction process, they are not likely to provide the whole story. For example, Notch is a gene required for neurogenesis in Drosophila embryos. When the Notch gene product is absent, the embryo forms far too many neuroblasts at the expense of the hypodermal cell layer (Artavanis-Tsakonis 1988, Campos-Ortega 1988). Even though Notch appears to play a role in deciding the fate of neural/hypodermal cells, the Notch gene product is expressed ubiquitously in early embryos in the neurogenic region (Hartley et al 1987, Kidd et al 1989). Thus, one possibility is that Notch function does not necessarily depend on differential expression of the Notch gene product within cells in the neurogenic regions [although an alternative view has been suggested by Greenspan (1990)]. Thus, some of the molecules controlling early neural development may not be expressed differentially when the ectoderm forms the neural plate. Obviously, other approaches will have to be taken to isolate and characterize these molecules. In this light, it is noteworthy that a molecule has been identified in Xenopus that is remarkably similar to Drosophila Notch in both structure and developmental expression (Coffman et al 1990). One hope is that the analysis of this molecule in combination with the molecules that are differentially expressed during neural induction will eventually lead to a molecular understanding of early neural development in vertebrate embryos.

Animals↗
PubMed1990

Xotch, the Xenopus homolog of Drosophila notch.

During the development of a vertebrate embryo, cell fate is determined by inductive signals passing between neighboring tissues. Such determinative interactions have been difficult to characterize fully without knowledge of the molecular mechanisms involved. Mutations of Drosophila and the nematode Caenorhabditis elegans have been isolated that define a family of related gene products involved in similar types of cellular inductions. One of these genes, the Notch gene from Drosophila, is involved with cell fate choices in the neurogenic region of the blastoderm, in the developing nervous system, and in the eye-antennal imaginal disc. Complementary DNA clones were isolated from Xenopus embryos with Notch DNA in order to investigate whether cell-cell interactions in vertebrate embryos also depend on Notch-like molecules. This approach identified a Xenopus molecule, Xotch, which is remarkably similar to Drosophila Notch in both structure and developmental expression.

Amino Acid Sequence↗
PubMed1988

Effects of altered expression of the neural cell adhesion molecule, N-CAM, on early neural development in Xenopus embryos.

The neural cell adhesion molecule, N-CAM, is known to be expressed very early in the development of the vertebrate nervous system. In frog embryos, N-CAM expression increases dramatically in ectoderm coincident with the formation of the neural plate and tube, suggesting that morphogenesis of the early nervous system is controlled in part by differential expression of N-CAM. This model was tested by introducing synthetic N-CAM transcripts into Xenopus embryos so that N-CAM was indiscriminately expressed at high levels on the surface of both induced and noninduced ectodermal cells throughout gastrulation and neurulation. Analysis of these embryos shows that high levels of N-CAM misexpression do not effect neural tube formation even though ectopic expression of N-CAM in epidermis and somitic mesoderm caused specific defects in the structure of these tissues. By showing that the properly regulated expression of N-CAM is not essential for neural tube formation, these results provide compelling evidence that N-CAM on its own does not act as a regulatory molecule during early neural development.

Animals↗
PubMed1981

Conservation and progressive methylation of Epstein-Barr viral DNA sequences in transformed cells.

The structure of intracellular viral DNA from a number of cell lines arising by clonal transformation of human lymphocytes in vitro with Epstein-Barr virus was analyzed. Intracellular viral DNAs were partially purified and digested with several restriction endonucleases, and the products of digestion were separated by electrophoresis in agarose gels. The viral fragments were detected by transferring the DNA from the gel to nitrocellulose sheets, hybridizing radiolabeled recombinant vectors carrying fragments of viral DNA to those transfers, and visualizing the hybrids by autoradiography. These analyses indicated that: (i) regions of repetitious viral DNA do undergo expansion and contraction although one size predominates; (ii) novel sequence arrangements appear in the intracellular viral DNA of different clones but are not found in clones analyzed serially and propagated extensively; (iii) the viral DNA is increasingly methylated upon cell propagation. We have not identified a transformed cell phenotype or a viral phenotype that segregates with the observed progressive methylation. We have not detected in Epstein-Barr viral plasmids analogs of the gross rearrangements of viral DNAs observed after lytic infections with high multiplicities of papova-, adeno-, or herpes simplex viruses.

Base Sequence↗
PubMed1981

Cloning overlapping DNA fragments from the B95-8 strain of Epstein-Barr virus reveals a site of homology to the internal repetition.

Overlapping, sheared DNA fragments from the B95-8 strain of Epstein-Barr virus were cloned in Charon 4A. Eleven recombinant phages plus one recombinant plasmid contained all of the sequences found in B95-8 virion DNA. Analysis of recombinant DNA molecules revealed a previously undetected site of homology to the internal repetition found in Epstein-Barr virus DNA. This site was adjacent to or at a site which was unstable when the recombinant DNA was propagated as phage DNA in procaryotic hosts.

Cloning, Molecular↗
PubMed1978

Specific binding of tRNAMet to 23S rRNA of Escherichia coli.

tRNAMetf binds to 23S rRNA of Escherichia coli, forming a complex with a melting temperature of 75 degrees (in 0.6 M NaCl). The regions within the RNAs that bind to each other have been isolated and their nucleotide sequences have been determined. The interacting region in tRNAMetf is 17 nucleotides long, extending from G5 in the acceptor stem to D21 (D = 5.6-dihydrouridine) in the D loop. The sequence in 23S rRNA is complementary to that sequence except for an extra Up in the middle and allowing a Gp.D base pair. We propose that association of these two sequences may play a role in initiation of protein synthesis by tRNAMetf. In addition, part of this sequence in 23S rRNA may also stabilize tRNA binding to the ribosome during elongation of nascent polypeptides.

Base Sequence↗
PubMedDate not supplied

Activation of Xenopus genes required for lateral inhibition and neuronal differentiation during primary neurogenesis.

XNGN-1, a member of the neurogenin family of basic helix-loop-helix proteins, plays a critical role in promoting neuronal differentiation in Xenopus embryos. When ectopically expressed, XNGN-1 induces the expression of a set of genes required for neuronal differentiation such as XMyT1 and NeuroD. At the same time, however, XNGN-1 induces the expression of genes that antagonize neuronal differentiation by a process called lateral inhibition. Here, we present evidence that XNGN-1 activates the expression of genes required for differentiation and lateral inhibition by recruiting transcriptional coactivators p300/CBP (CREB-binding protein) or PCAF (p3OO/CBP-associated protein), both of which contain histone acetyltransferase (HAT) activity. Significantly, transcriptional activation of the genes in the lateral inhibitory pathway is less dependent on the HAT activity than is the activation of the genes that mediate differentiation. We propose that this difference enables the genes in the lateral inhibition pathway to be induced prior to the genes that promote differentiation, thus enabling lateral inhibition to establish a negative feedback loop and restrict the number of cells undergoing neuronal differentiation.

Adenovirus E1A Proteins↗