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D Westaway

Publications and source records attributed to D Westaway.

68 records · Page 4Linked to original sources
PubMed1986

Conservation of the cellular gene encoding the scrapie prion protein.

The major protein, PrP 27-30, in purified preparations of hamster scrapie prions is encoded within the genome of the experimental host. DNA sequences related to a PrP cDNA clone can be detected in a wide variety of organisms under relatively stringent conditions where the only signal generated by hamster or mouse DNA corresponds to the PrP gene. Three hosts for scrapie, goat, sheep and rat gave strong hybridization signals. In addition, three invertebrate DNAs reacted with the PrP probe, in the order nematode-Drosophila much greater than yeast. Thus, the sequences detected in goat, sheep, rat, nematode, Drosophila and possibly yeast DNA may arise from authentic PrP genes. This evolutionary conservation is consistent with the notion that PrP proteins participate in essential cellular processes.

Animals↗
PubMed1986

Identification of a provirally activated c-Ha-ras oncogene in an avian nephroblastoma via a novel procedure: cDNA cloning of a chimaeric viral-host transcript.

Retrovirus without oncogenes often exert their neoplastic potential as insertional mutagens of cellular proto-oncogenes. This may be associated with the production of chimaeric viral-host transcripts; in these cases; activated cellular genes can be identified by obtaining cDNA clones of bipartite RNAs. This approach was used in the analysis of chicken nephroblastomas induced by myeloblastosis-associated virus (MAV). One tumor contained a novel mRNA species initiated within a MAV LTR. cDNA cloning revealed that this mRNA encodes a protein of 189 amino acids, identical to that of normal human Ha-ras-1 at 185 positions, including positions implicated in oncogenic activation of ras proto-oncogenes; there are no differences between the coding sequences of presumably normal Ha-ras cDNA clones from chicken lymphoma RNA and the tumor-derived cDNAs. The chimaeric mRNA in the nephroblastoma is at least 25-fold more abundant than c-Ha-ras mRNA in normal kidney tissue, and a 21-kd ras-related protein is present in relatively large amounts in the tumor. We conclude that a quantitative change in c-Ha-ras gene expression results from an upstream insertion mutation and presumably contributes to tumorigenesis in this single case. Little or no increase in c-Ha-ras RNA or protein was observed in other nephroblastomas.

Animals↗
PubMed1986

Molecular cloning of a human prion protein cDNA.

Creutzfeldt-Jakob disease (CJD) of humans and scrapie of animals are degenerative, transmissible neurologic diseases caused by prions. The only known macromolecules within prions are prion proteins (PrP). The cDNA encoding the hamster prion protein (PrP 27-30) has been cloned and sequenced (Oesch et al., 1985). Using that hamster PrP cDNA, we screened a human retina cDNA library and sequenced the cDNA clone with the longest hybridizing insert. This insert was found to contain a long open reading frame (ORF) encoding the human prion protein. Northern transfer analysis showed that a related poly(A)+RNA measuring approximately 2.5 kb is expressed in a variety of human neuroectodermal cell lines. Human PrP differed from hamster PrP at 27 of 253 amino acids and at 98 of 759 ORF nucleotides. Conservation of PrP amino acid sequence between hamster and human is nearly 90%, reflecting similar structural features and shared antigenicity of the two proteins (Bockman et al., 1985). The human PrP sequence contained a presumptive amino-terminal signal peptide of 22 amino acids, two hydrophobic segments of sufficient length to span membranes, and two possible sites for N-glycosylation. The conservation between the hamster and human prion proteins suggests that they may have an important role in cellular metabolism and may explain the similarities between scrapie and CJD.

Amino Acid Sequence↗
PubMed1985

A cellular gene encodes scrapie PrP 27-30 protein.

A clone encoding PrP 27-30, the major protein in purified preparations of scrapie agent, was selected from a scrapie-infected hamster brain cDNA library by oligonucleotide probes corresponding to the N terminus of the protein. Southern blotting with PrP cDNA revealed a single gene with the same restriction patterns in normal and scrapie-infected brain DNA. A single PrP-related gene was also detected in murine and human DNA. PrP-related mRNA was found at similar levels in normal and scrapie-infected hamster brain, as well as in many other normal tissues. Using antisera against PrP 27-30, a PrP-related protein was detected in crude extracts of infected brain and to a lesser extent in extracts of normal brain. Proteinase K digestion yielded PrP 27-30 in infected brain extract, but completely degraded the PrP-related protein in normal brain extract. No PrP-related nucleic acids were found in purified preparations of scrapie prions, indicating that PrP 27-30 is not encoded by a nucleic acid carried within the infectious particles.

Amino Acid Sequence↗
PubMed1985

Augmented expression of normal c-myc is sufficient for cotransformation of rat embryo cells with a mutant ras gene.

We studied the effect of altered c-myc structure and expression upon the ability of c-myc to promote the transformation of normal rat embryo cells when it was supplemented by EJras (the mutant c-H-ras1 gene from EJ/T24 bladder carcinoma cells). We tested several c-myc alleles cloned from normal and tumor tissues of chicken and human origin and found that only LL4myc (derived from a bursal lymphoma in which an avian leukosis virus long terminal repeat resides within the first c-myc intron in the same transcriptional orientation) had cotransforming activity. No activity was observed with normal chicken and human c-myc alleles, two other bursal lymphoma c-myc alleles (LL3myc and LL6myc), and two human c-myc genes (HSRmyc and DMmyc) from human neuroectodermal tumor cell line COLO320, in which c-myc is amplified. Some of these inactive alleles had the following alterations that are frequently found in tumor-derived c-myc: point mutations affecting the encoded protein (LL3myc); a truncated structure with loss of the first, noncoding exon (LL3myc and DMmyc); and proviral integration within or near the myc locus (LL3myc and LL6myc). The following two experimental approaches indicated that cotransforming activity was directly related to the transcriptional activity of the alleles in cultured rat cells: when cotransfected into Rat-2 cells, LL4myc was more highly expressed than the other (inactive) alleles; and augmented expression of HSRmyc, DMmyc, or normal human or normal chicken c-myc placed under the transcriptional control of retroviral long terminal repeats or increased expression of normal human c-myc under the influence of a retroviral enhancer element was accompanied by cotransformation activity. We concluded that augmented expression of even a normal c-myc gene is sufficient for cotransforming activity and that additional structural alterations frequently found in tumor-derived alleles are neither necessary nor sufficient for the gene to acquire rat embryo cell cotransforming properties.

Alleles↗
PubMed1984

Proviral deletions and oncogene base-substitutions in insertionally mutagenized c-myc alleles may contribute to the progression of avian bursal tumors.

Bursal lymphomas induced in chickens by avian leukosis viruses (ALVs) harbor proviral insertions that augment expression of an adjacent cellular oncogene, c-myc. To analyze such insertionally mutagenized c-myc genes in greater detail, we isolated molecular clones from two independent tumors. Precise proviral integration has occurred within the transcribed region of the c-myc gene in both mutant alleles. The proviruses bear different internal deletions that preclude the expression of the gag, pol, and env genes. The c-myc gene from bursal lymphoma LL4 contains a single copy of an ALV long terminal repeat (LTR), presumably the product of homologous recombination between LTRs at the ends of a normal provirus; the "solo" LTR is positioned in the correct orientation to act as a promoter for the c-myc gene. Bursal lymphoma LL3 contains an ALV provirus positioned upstream in the opposite transcriptional orientation to the coding exons of c-myc and deleted from a site within the leader region into the gag gene. In addition, the nucleotide sequence of the c-myc gene from tumor LL3 differs from the published sequence of the normal c-myc coding region at 3 positions of 180 determined. One of these changes, a silent nucleotide transition, is documented as a somatic mutation by restriction endonuclease mapping. It is flanked by two other candidate tumor-specific point mutations, one of which predicts an amino acid replacement, Pro----Thr at position 63. Thus, additional lesions that may affect the expression of viral genes and the quantity and nature of the putative c-myc gene product occur in provirally mutated c-myc alleles and may contribute to tumor progression.

Alleles↗
PubMed1981

An intron nucleotide sequence variant in a cloned beta +-thalassaemia globin gene.

A 7.5 kb Hsu I restriction fragment of genomic DNA containing a beta-globin gene has been isolated from a patient doubly heterozygous for beta + thalassaemia and a delta beta (Lepore globin fusion gene. This fragment must be derived from the chromosome carrying the beta +-thalassaemia determinant. The gross structure of the cloned gene plus flanking sequences is indistinguishable from that of a normal beta-globin gene. Within in 1606 base-pair transcribed region of the gene there is only one nucleotide difference from the normal beta-globin gene sequence. This is a G leads to A replacement 21 nucleotides upstream from the 3' terminus of the small intron. This nucleotide lies within a 10 base-pair sequence repeated in an inverted configuration near the 5' terminus of the small intron. The nucleotide replacement may result in a precursor mRNA less amenable to RNA splicing than its normal counterpart.

Adult↗
PubMedDate not supplied

Spatial learning in transgenic mice expressing human presenilin 1 (PS1) transgenes.

Dominant mutations in the Presenilin 1 gene are linked to an aggressive, early-onset form of familial Alzheimer's Disease (FAD). Spatial memory of transgenic (Tg) mice expressing either mutant (lines Tg(M146L)1, Tg(M146L)76, Tg(L286V)198) or wild type (line Tg(PS1wt)195) human PS1 transgenes was investigated in the Morris water maze (WM) test at 6 and 9 months of age. The results showed that the mutated Tg mice had increased swim speed when compared to non-Tg littermates or Tg PS1 wild type mice. The swim speed difference did not, however, significantly affect the spatial learning in the WM test and all groups showed comparable search paths during training and similar spatial bias during probe trials. When re-tested at 9 months, all mice showed significantly improved learning acquisition of spatial information. The lack of progressive spatial learning impairment in mice expressing the mutated human PS1 transgene in the WM does not preclude impairments in other cognitive tasks but suggests that full phenotypic expression of mutant PS1 alleles may require co-expression of human versions of other AD-associated genes.

Alzheimer Disease↗
PubMedDate not supplied

Normal brain development in PS1 hypomorphic mice with markedly reduced gamma-secretase cleavage of betaAPP.

Presenilin 1-null mice die at birth from brain and skeletal developmental deformities due to disrupted Notch signaling. Presenilin 1-null mice also have severely reduced gamma-secretase cleavage of betaAPP. The assumption has been that facilitation of Notch signaling and betaAPP processing by presenilin 1 are analogous functions. Here we describe a presenilin 1-targetted mouse model that expresses extremely low levels ( approximately 1% of normal) of mutant PS1-M146L. Homozygous mice have significantly reduced viability due to a Notch-like phenotype. The animals that survive have severe axial skeletal deformities and markedly diminished gamma-secretase activity and accumulation of betaAPP-C100, but no obvious abnormalities in brain development. These results suggest that, in mice, a marked reduction of PS1-facilitated gamma-secretase activity is not detrimental to normal brain development.

Amyloid Precursor Protein Secretases↗
PubMedDate not supplied

A beta peptide immunization reduces behavioural impairment and plaques in a model of Alzheimer's disease.

Much evidence indicates that abnormal processing and extracellular deposition of amyloid-beta peptide (A beta), a proteolytic derivative of the beta-amyloid precursor protein (betaAPP), is central to the pathogenesis of Alzheimer's disease (reviewed in ref. 1). In the PDAPP transgenic mouse model of Alzheimer's disease, immunization with A beta causes a marked reduction in burden of the brain amyloid. Evidence that A beta immunization also reduces cognitive dysfunction in murine models of Alzheimer's disease would support the hypothesis that abnormal A beta processing is essential to the pathogenesis of Alzheimer's disease, and would encourage the development of other strategies directed at the 'amyloid cascade'. Here we show that A beta immunization reduces both deposition of cerebral fibrillar A beta and cognitive dysfunction in the TgCRND8 murine model of Alzheimer's disease without, however, altering total levels of A beta in the brain. This implies that either a approximately 50% reduction in dense-cored A beta plaques is sufficient to affect cognition, or that vaccination may modulate the activity/abundance of a small subpopulation of especially toxic A beta species.

Alzheimer Disease↗
PubMedDate not supplied

The cellular prion protein binds copper in vivo.

The normal cellular form of prion protein (PrPC) is a precursor to the pathogenic protease-resistant forms (PrPSc) believed to cause scrapie, bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease. Its amino terminus contains the octapeptide PHGGGWGQ, which is repeated four times and is among the best-preserved regions of mammalian PrPC. Here we show that the amino-terminal domain of PrPC exhibits five to six sites that bind copper (Cu(II)) presented as a glycine chelate. At neutral pH, binding occurs with positive cooperativity, with binding affinity compatible with estimates for extracellular, labile copper. Two lines of independently derived PrPC gene-ablated (Prnp0/0) mice exhibit severe reductions in the copper content of membrane-enriched brain extracts and similar reductions in synaptosomal and endosome-enriched subcellular fractions. Prnp0/0 mice also have altered cellular phenotypes, including a reduction in the activity of copper/zinc superoxide dismutase and altered electrophysiological responses in the presence of excess copper. These findings indicate that PrPC can exist in a Cu-metalloprotein form in vivo.

Animals↗
PubMedDate not supplied

[Prions and their biology].

Prion diseases or transmissible spongiform encephalopathies are fatal neurodegenerative disorders featured by an aberrant metabolism of a cellular membrane glycoprotein, the prion protein (PrP-C). PrP-C is being related to Cu (II) homeostasis and postulated as candidate for cell signaling and cell adhesion functions. Under pathological conditions PrP-C converts into a conformational isomer (PrP*, PrP-res, PrP-Sc, PrP-Creutzfeldt-Jakob disease, etc.). In addition to divergent biochemical characteristics, the latter form displays the property of recognizing the normal protein and transforming it into its homologue. Conversion process is ill tangled and participation of yet unidentified partners has been postulated.

Humans↗