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Biomedical subjects

R L Neve

Publications and source records attributed to R L Neve.

At least 91 records · Page 5Linked to original sources
PubMed1990

Transfection of PC12 cells with the human GAP-43 gene: effects on neurite outgrowth and regeneration.

The neuronal growth associated protein GAP-43 is expressed at high levels during axonal growth and regeneration. In this report, we describe the transfection of the nerve growth factor (NGF)-responsive pheochromocytoma cell line PC12 with the human GAP-43 cDNA under the control of the Moloney murine leukemia virus long terminal repeat (MoMuLV LTR). Two PC12 subclones were isolated that constitutively expressed GAP-43 from the transfected cDNA and showed increased responsiveness to NGF. Of the two transfected PC12 subclones, the subclone expressing the most human GAP-43 RNA showed an accelerated initial neurite outgrowth response and a 10-fold increased sensitivity to NGF. Neurite regeneration was significantly enhanced in both transfected subclones and, in contrast to untreated PC12 cells, could occur transiently in the absence of added NGF. These results suggest that GAP-43 may potentiate the action of NGF on neurite initiation and regeneration.

Cell Differentiation↗
PubMed1990

The Alzheimer amyloid precursor-related transcript lacking the beta/A4 sequence is specifically increased in Alzheimer's disease brain.

The deposition of cerebrovascular and plaque amyloid in the CNS is a primary feature of Alzheimer's disease and aged Down's syndrome pathology. The localization of the Alzheimer amyloid protein precursor (APP) gene on chromosome 21, along with its overexpression in Down's syndrome brain compared with normal brain, suggests that alterations in APP gene expression may play a role in the development of the neuropathology common to the two diseases. In the present report, we demonstrate that a specific spliced form of mRNA that is transcribed from the APP gene and that lacks the beta/A4 sequence is elevated in the nucleus basalis, occipitotemporal cortex, and parahippocampal gyrus in Alzheimer's disease brain relative to controls. These results are based on combined data from RNA slot blot analysis, in situ hybridization, and polymerase chain reaction quantification of specific mRNAs taken directly from tissue sections.

Aged↗
PubMed1990

A dorso-ventral asymmetry in the embryonic retina defined by protein conformation.

In a search for determinants of retinotopic specification we previously identified an antigen in the dorsal embryonic retina as a protein called the 68-kDa laminin receptor. A dorso-ventral asymmetry in a laminin receptor seemed consistent with the known responsiveness of embryonic optic axons to laminin, but there were three peculiar points. (i) The molecular mass of this presumed laminin receptor in immunoblots is not 68 kDa but 43 kDa, and the molecular mass of the protein deduced from the mRNA is only 33 kDa. (ii) The antigen does not have the localization expected of a receptor for the extracellular matrix: the antibodies label mainly a granular cytoplasmic antigen in dorsal retina; an additional sparse cell-surface antigen present on a few cells does not show a dorso-ventral asymmetry. (iii) Despite the pronounced dorso-ventral difference seen immunohistochemically, in immunoblots the 43-kDa protein (p40) is evenly distributed throughout the retina. Here we show that (i) native p40 and in vitro-translated gene product are indistinguishable and their anomalous migration in denaturing gels probably is due to low pI; (ii) p40 is bound in a Mg2(+)-dependent manner to large cytoplasmic complexes that appear to include ribosomes; and (iii) there is a labile conformational difference in p40 between dorsal and ventral retina: dorsally it is more accessible to proteolysis, suggesting a more open conformation. In conjunction with the recent hypothesis that p40 constitutes a translation initiation factor (D. Auth and G. Brawerman, personal communication), these observations point to a dorso-ventral asymmetry in some aspect of protein translation, which in turn may set up differences in recognition factors on retinal growth cones.

Animals↗
PubMed1990

Altered levels of amyloid protein precursor transcripts in the basal forebrain of behaviorally impaired aged rats.

The beta/A4 protein is a constituent of plaque and vascular amyloid deposits in Alzheimer disease. Previous studies have shown increased levels of amyloid protein precursor (APP) mRNA in basal forebrain neurons in the disease. Morphological and neurochemical changes occur within the forebrain in Alzheimer disease and are also correlated with behavioral impairments in aged rats. Recent studies suggest that decreased nerve growth factor responsiveness of basal forebrain neurons is a feature of normal aging and of Alzheimer disease. We have used in situ hybridization to show that the abundance of specific forms of APP mRNA, which contain an inserted Kunitz-type serine protease inhibitor motif (APP-751, APP-770, and APP-related 563), are increased relative to the noninserted form (APP-695) of APP mRNA in the basal forebrain of aged rats. This increase appears to be specific to animals who exhibit spatial memory deficits but not aged rats without behavioral impairments.

Aging↗
PubMed1990

A positional marker for the dorsal embryonic retina is homologous to the high-affinity laminin receptor.

In a search for determinants of positional information in the embryonic eye, we isolated two monoclonal antibodies that label strongly the dorsal part of the undifferentiated embryonic retina in mammals, bird and cold-blooded vertebrates. In the chick, the optic tectum is labeled in a corresponding fashion, the ventral tectum more heavily than the dorsal tectum. Through biochemical and molecular analysis both antibodies were found to recognize a protein that has been cloned repeatedly, first in a screen with antibodies to the '68K-laminin receptor' (Wewer et al. (1986) Cancer Res. 47, 5691-5698), a name that may not exhaustively describe its function. Western blots show the protein to be present in most or all tissues, and Western and Southern blots reveal a high degree of conservation in the detected signals up to invertebrates and bacteria. Despite the very strong and selective labeling of the dorsal retina in conventional immunohistochemical preparations, the protein and its mRNA are present in even amounts throughout the embryonic retina, as demonstrated by Western and Northern blots of bisected retinas, and immunohistochemically in retinas fixed with ethylene glycole bissuccinimide (EGS), an NH2-group crosslinker with very long spacer arm. This indicates that the dorsoventral asymmetry in the embryonic retina is not in the amount but in the configuration of this protein; whether this difference relates to laminin binding is not known.

Animals↗
PubMed1989

Neurotoxicity of a fragment of the amyloid precursor associated with Alzheimer's disease.

Amyloid deposition in senile plaques and the cerebral vasculature is a marker of Alzheimer's disease. Whether amyloid itself contributes to the neurodegenerative process or is simply a by-product of that process is unknown. Pheochromocytoma (PC12) and fibroblast (NIH 3T3) cell lines were transfected with portions of the gene for the human amyloid precursor protein. Stable PC12 cell transfectants expressing a specific amyloid-containing fragment of the precursor protein gradually degenerated when induced to differentiate into neuronal cells with nerve growth factor. Conditioned medium from these cells was toxic to neurons in primary hippocampal cultures, and the toxic agent could be removed by immunoabsorption with an antibody directed against the amyloid polypeptide. Thus, a peptide derived from the amyloid precursor may be neurotoxic.

Alzheimer Disease↗
PubMed1989

Quantitative calibration and use of DNA probes for investigating chromosome abnormalities in the Prader-Willi syndrome.

Ten genomic DNA probes, subcloned from inserts derived from a phage library constructed from the DNA of flow-sorted chromosomes, have now been mapped to locations within 15q11-15q13. By dosage blotting and densitometry, 5 of these probes map to the 15q11.2-15q12 segment missing in one 15 chromosome of a Prader-Willi syndrome (PWS) patient with a prominent cytological deletion. A sixth probe most likely maps to the same region. The other 4 probes map outside of this segment but within 15q11-15q13. Several of the 15q11.2-15q12 probes, and a cDNA probe homologous to one, have been used to test the DNA from 8 patients exhibiting a wide range of the clinical manifestations expected for PWS patients. DNA deletion was observed in all 3 patients with cytological 15q1 deletions as well as in a patient with an unbalanced (Y;15) translocation. DNA from 1 PWS patient with an unbalanced (5;15) translocation and an inverted duplication of the short arm and proximal long arm of 15 showed at least 1 and possibly 2 extra copies of each genomic probe tested. In the other 3 patients with no cytological deletions, no DNA deletions were found. Thus, the molecular probes described can be used in most PWS patients to analyze the region of proximal 15q implicated in this syndrome.

Adolescent↗
PubMed1989

Characterization of an unusual and complex chromosome 21 rearrangement using somatic cell genetics and cloned DNA probes.

In a previous case of a newborn infant with typical Down syndrome, chromosome analysis indicated the presence of an unusual and complex translocation of chromosome 21. The patient's cells contained one normal chromosome 21 and a rearranged, F group-sized submetacentric chromosome. This abnormal chromosome appeared to involve duplication of the distal portion of 21q with translocation to the short arm, and a deletion of C-band-positive centromeric heterochromatin. Using linearly ordered cloned DNA probes, we report the detailed molecular examination of this abnormal chromosome, which has been isolated on a hamster background in a hybrid cell line. Both short arm and pericentromeric sequences are present on this chromosome, as well as distal 21q sequences. However, a substantial portion of proximal 21q is deleted. The distal boundary of this deleted section can be pinpointed within the region between two loci (D21S8 and D21S54), a distance of about 5,000 kb. This study illustrates the power of using precisely mapped, linearly ordered DNA probes to characterize this type of rearrangement. In addition, this hybrid cell line can also be used as a member of a mapping panel to map DNA sequences regionally on chromosome 21.

Animals↗
PubMed1989

Tau in situ hybridization in normal and Alzheimer brain: localization in the somatodendritic compartment.

Tau messenger RNA in situ hybridization in human postmortem brain revealed that neurons are the predominant cell type labeled. The probe used includes the nucleotide sequence coding for the amino acids recognized by the well-characterized tau monoclonal antibodies 5E2 and tau 1. The distribution of the tau RNA is abundant throughout the neuronal somata and into the proximal parts of dendrites of pyramidal cells in the cerebral cortex and the hippocampus. The distal extent to which silver grains could be visualized in the pyramidal cell dendrite was comparable to that seen with a probe to ribosomal RNA. In contrast to the tau probe the ribosomal probe also labeled glial cells. Sections hybridized with the tau probe and then double-labeled with thioflavine S revealed that neurons containing neurofibrillary tangles continue to synthesize tau protein.

Alzheimer Disease↗
PubMed1989

The amyloid precursor protein is concentrated in neuronal lysosomes in normal and Alzheimer disease subjects.

The 4.2-kilodalton (kDa) polypeptide associated with the cerebral amyloid deposits of Alzheimer's disease (AD) derives from a much larger protein that is encoded by a gene on chromosome 21. In the present study, we have used antibodies raised against portions of the amyloid protein precursor (APP) to map its normal distribution and to gain further insights into the events that lead to amyloid deposition. Antibodies raised against several different portions of APP reacted with proteins having apparent molecular sizes of 65, 67, and 132 kDa on Western blots. In sections through the normal human brain, immunocytochemistry revealed punctate concentrations of the protein in pyramidal cells of the neocortex, particularly in associative regions, and intense staining in the CA1 pyramidal cells of the hippocampus. By electron microscopy, this punctate distribution coincided with dense concentrations of the protein in secondary lysosomes. In the hippocampus of several AD cases examined, abnormally dense immunostaining in enlarged intracellular domains accompanied a severe atrophy of the CA1 neurons. These data suggest that accumulations of APP in lysosomes of particular neurons may, in AD, lead to proteolytic events that form the insoluble 4.2-kDa amyloid peptide.

Aged↗
PubMed1989

The Alzheimer amyloid precursor protein maps to human chromosome 21 bands q21.105-q21.05.

The Alzheimer amyloid protein precursor (APP) has previously been localized to human chromosome 21q11.2-q21. We have refined the regional localization to a small region including chromosome bands 21q21.105-q21.05 by using quantitative Southern blot analysis of cell lines aneuploid for parts of chromosome 21. Our findings exclude the APP gene from the minimal region producing the classical phenotypic features of Down syndrome. This further narrowing of the APP location will help in identifying the physical location of the gene causing familial Alzheimer disease.

Amyloid↗
PubMed1989

The microtubule binding domain of tau protein.

Tau protein is a microtubule-associated protein implicated in the spatial and temporal specification of microtubules and has been found in the neurofibrillary tangles of Alzheimer's disease. Determination of tau protein structure has revealed three 18 amino acid repeated sequences hypothesized to be tubulin binding sites. Using tau cDNA clones from human fetal brain, we employed E. coli expression systems to synthesize tau protein and fragments of tau protein in order to identify the microtubule binding site. A fragment containing the three repeated sequences binds microtubules, while the amino-terminal half of the protein does not bind. Fragments containing two or one repeat are also capable of binding, indicating that the basic tubulin interacting unit is one repeat.

Amino Acid Sequence↗
PubMed1989

Developmentally regulated expression of specific tau sequences.

Tau protein undergoes a shift in its molecular mass and its electrophoretic complexity during early postnatal development. We have sequenced a tau cDNA from an adult rat brain expression library and have found two inserted sequences. One of these inserts predicts a fourth repeated sequence homologous to the other three in the carboxyl end of tau that have the property of microtubule binding. Oligonucleotide probes directed against the insert hybridized only to tau mRNA at postnatal time points, even though tau is first expressed as early as embryonic day 13. A probe directed against the junction revealed expression of non-insert-containing tau mRNA from embryonic day 14 until postnatal day 8, after which time there was an abrupt decline in the expression of this immature form. Comparison of the developmentally expressed tau sequences with those sequences obtained directly from Alzheimer paired helical filaments revealed the presence of both the mature and the immature tau mRNA sequences.

Alzheimer Disease↗
PubMed1989

Visual experience regulates gene expression in the developing striate cortex.

We have examined the regulation of expression of the genes for the neuronal growth-associated protein GAP43, the type II calcium/calmodulin-dependent protein kinase, and glutamic acid decarboxylase in the kitten visual cortex during normal postnatal development and after a period of visual deprivation. We find that the mRNA transcripts of these genes display very different patterns of normal development but are all increased in the visual cortex of animals reared in the dark. Upon exposure to light, the transcript of the GAP43 gene drops to near-normal levels within 12 hr.

Aging↗