Paul Leibowitz

Bio: Paul Leibowitz is an academic researcher. The author has contributed to research in topics: Transgene & Amyloid precursor protein. The author has an hindex of 6, co-authored 9 publications receiving 2763 citations.

Alzheimer-type neuropathology in transgenic mice overexpressing V717F beta-amyloid precursor protein.

Abstract: Alzheimer's disease (AD) is the most common cause of progressive intellectual failure in aged humans. AD brains contain numerous amyloid plaques surrounded by dystrophic neurites, and show profound synaptic loss, neurofibrillary tangle formation and gliosis. The amyloid plaques are composed of amyloid beta-peptide (A beta), a 40-42-amino-acid fragment of the beta-amyloid precursor protein (APP). A primary pathogenic role for APP/A beta is suggested by missense mutations in APP that are tightly linked to autosomal dominant forms of AD. A major obstacle to elucidating and treating AD has been the lack of an animal model. Animals transgenic for APP have previously failed to show extensive AD-type neuropathology, but we now report the production of transgenic mice that express high levels of human mutant APP (with valine at residue 717 substituted by phenylalanine) and which progressively develop many of the pathological hallmarks of AD, including numerous extracellular thioflavin S-positive A beta deposits, neuritic plaques, synaptic loss, astrocytosis and microgliosis. These mice support a primary role for APP/A beta in the genesis of AD and could provide a preclinical model for testing therapeutic drugs.

Transgenic mouse assay for compounds affecting amyloid protein processing

Abstract: The construction of transgenic animal models for testing potential treatments for Alzheimer's disease are described. The models are characterized by a greater similarity to the conditions existing in naturally occurring Alzheimer's disease, based on expression of all three forms of the β-amyloid precursor protein (APP), APP 695 , APP 751 , and APP 770 ), as well as various point mutations based on naturally occurring mutations, such as the London and Indiana familial Alzheimer's disease (FAD) mutations at amino acid 717, and predicted mutations in the APP gene. The APP gene constructs are prepared using the naturally occurring promoter, as well as inducible promoters such as the mouse metallothionine promoter, which can be regulated by addition of heavy metals such as zinc to the animal's water or diet, and promoters such as the rat neuron specific enolase promoter, human β actin gene promoter, human platelet derived growth factor B (PDGF-B) chain gene promoter, rat sodium channel gene promoter, mouse myelin basic protein gene promoter, human copper-zinc superoxide dismutase gene promoter, and mammalian POU-domain regulatory gene promoter. The constructs are introduced into animal embryos using standard techniques such as microinjection. Animal cells can be isolated from the transgenic animals or prepared using the same constructs with standard techniques such as lipofection or electroporation. The transgenic animals, or animal cells, are used to screen for compounds altering the pathological course of Alzheimer's Disease as measured by their effect on the amount and histopathology of APP and β-amyloid peptide in the animals, as well as by behavioral alterations.

Developmental and tissue-specific expression of human CD4 in transgenic rabbits.

Abstract: A major obstacle to understanding AIDS is the lack of a suitable small animal model for studying HIV-1 infection and the subsequent development of AIDS, and for testing diagnostic, therapeutic, and preventive modalities. Our goal is to produce a rabbit model for the study of AIDS. Here we report on the generation of transgenic rabbits that express the human CD4 (hCD4) gene. The transgene, which contains the coding region for hCD4 and approximately 23 kb of sequence upstream of the translation start site, was used previously to direct hcD4 expression on the surface of CD4+ T cells of transgenic mice (Gillespie et al., 1993: Mol Cell Biol 13:2952-2958). The hCD4 transgene was detected in five males and two females derived from the microinjection in five males and two females derived from the microinjection of 271 rabbit embryos. Both hCD4 RNA and protein were expressed in peripheral blood lymphocytes (PBLs) from all five males but neither of the females. Human CD4 was expressed on PBLs from F1 offspring of all founder males. T-cell subset analysis revealed that hCD4 expression was restricted to rabbit CD4 (rCD4) expressing lymphocytes; mature rCD4- rCD8+ lymphocytes did not express hCD4. In preliminary studies, PBLs from hCD4 transgenic rabbits produced greater amounts of HIV-1 p24 core protein following HIV-1 infection in vitro than HIV-1 p24 antigen in nontransgenic rabbit infected cultures. These results extend to rabbits our previous observation that this transgene contains the sequence elements required for high-level expression in the appropriate cells of transgenic mice. Furthermore, these and previous studies demonstrating that expression of hCD4 protein enhances HIV-1 infection of rabbit T cells in vitro, coupled with reports that normal, nontransgenic rabbits are susceptible to HIV-1 infection, suggests that the hCD4 transgenic rabbits described herein will have an increased susceptibility to HIV-1 infection. In vivo HIV-1 infection studies with these rabbits are under way.

Transgenic mouse expressing APP770

Abstract: The construction of transgenic mouse models for testing potential treatments for Alzheimer's disease are described. The models are characterized by a greater similarity to the conditions existing in naturally occurring Alzheimer's disease, based on expression of all three forms of the β-amyloid precursor protein (APP), APP 695 , APP 751 , and APP 770 ), as well as various point mutations based on naturally occurring mutations, such as the London and Indiana familial Alzheimer's disease (FAD) mutations at amino acid 717, and predicted mutations in the APP gene. The APP gene constructs are prepared using the naturally occurring promoter, as well as inducible promoters such as the mouse metallothionine promoter, which can be regulated by addition of heavy metals such as zinc to the mouse's water or diet, and promoters such as the rat neuron specific enolase promoter, human β actin gene promoter, human platelet derived growth factor B (PDGF-B) chain gene promoter, rat sodium channel gene promoter, mouse myelin basic protein gene promoter, human copper-zinc superoxide dismutase gene promoter, and mammalian POU-domain regulatory gene promoter. The constructs are introduced into mouse embryos using standard techniques such as microinjection. Mouse cells can be isolated from the transgenic mice or prepared using the same constructs with standard techniques such as lipofection or electroporation. The transgenic mice, or mouse cells, are used to screen for compounds altering the pathological course of Alzheimer's Disease as measured by their effect on the amount and histopathology of APP and β-amyloid peptide in the mice, as well as by behavioral alterations.

Producing cells for transplantation to reduce host rejection and resulting cells

Abstract: A method for treating cells with E19 protein in order to alter the presentation of MHC class I cell surface antigens on these cells and thereby allow introduction of these cells into a recipient organism while reducing transplant rejection by the recipient organism's immune system is described. The cells may be contacted with E19 protein by the presence in the cells of a vector which carries and expresses the E19 coding sequence or by the presence in the cells of a transgene with expresses the E19 coding sequence. The method may be used for treating a genetic disorder, a wound, a burn, or a disease, or for effecting gene therapy in a recipient organism. Transgenic and chimeric organisms, and cells are also provided.

Alzheimer's Disease: Genes, Proteins, and Therapy

Abstract: Rapid progress in deciphering the biological mechanism of Alzheimer's disease (AD) has arisen from the application of molecular and cell biology to this complex disorder of the limbic and association cortices. In turn, new insights into fundamental aspects of protein biology have resulted from research on the disease. This beneficial interplay between basic and applied cell biology is well illustrated by advances in understanding the genotype-to-phenotype relationships of familial Alzheimer's disease. All four genes definitively linked to inherited forms of the disease to date have been shown to increase the production and/or deposition of amyloid β-protein in the brain. In particular, evidence that the presenilin proteins, mutations in which cause the most aggressive form of inherited AD, lead to altered intramembranous cleavage of the β-amyloid precursor protein by the protease called γ-secretase has spurred progress toward novel therapeutics. The finding that presenilin itself may be the long-sought γ-...

Correlative Memory Deficits, Aβ Elevation, and Amyloid Plaques in Transgenic Mice

Abstract: Transgenic mice overexpressing the 695-amino acid isoform of human Alzheimer beta-amyloid (Abeta) precursor protein containing a Lys670 --> Asn, Met671 --> Leu mutation had normal learning and memory in spatial reference and alternation tasks at 3 months of age but showed impairment by 9 to 10 months of age. A fivefold increase in Abeta(1-40) and a 14-fold increase in Abeta(1-42/43) accompanied the appearance of these behavioral deficits. Numerous Abeta plaques that stained with Congo red dye were present in cortical and limbic structures of mice with elevated amounts of Abeta. The correlative appearance of behavioral, biochemical, and pathological abnormalities reminiscent of Alzheimer's disease in these transgenic mice suggests new opportunities for exploring the pathophysiology and neurobiology of this disease.

HIV-1 Entry Cofactor: Functional cDNA Cloning of a Seven-Transmembrane, G Protein-Coupled Receptor

Abstract: A cofactor for HIV-1 (human immunodeficiency virus-type 1) fusion and entry was identified with the use of a novel functional complementary DNA (cDNA) cloning strategy. This protein, designated “fusin,” is a putative G protein-coupled receptor with seven transmembrane segments. Recombinant fusin enabled CD4-expressing nonhuman cell types to support HIV-1 Env-mediated cell fusion and HIV-1 infection. Antibodies to fusin blocked cell fusion and infection with normal CD4-positive human target cells. Fusin messenger RNA levels correlated with HIV-1 permissiveness in diverse human cell types. Fusin acted preferentially for T cell line-tropic isolates, in comparison to its activity with macrophage-tropic HIV-1 isolates.

HIV-1 Entry Cofactor: Functional cDNA Cloning of a Seven-Transmembrane, G Protein–Coupled Receptor

Abstract: A cofactor for HIV-1 (human immunodeficiency virus-type 1) fusion and entry was identified with the use of a novel functional complementary DNA (cDNA) cloning strategy. This protein, designated "fusin," is a putative G protein-coupled receptor with seven transmembrane segments. Recombinant fusin enabled CD4-expressing nonhuman cell types to support HIV-1 Env-mediated cell fusion and HIV-1 infection. Antibodies to fusin blocked cell fusion and infection with normal CD4-positive human target cells. Fusin messenger RNA levels correlated with HIV-1 permissiveness in diverse human cell types. Fusin acted preferentially for T cell line-tropic isolates, in comparison to its activity with macrophage-tropic HIV-1 isolates.

Beta-secretase cleavage of Alzheimer's amyloid precursor protein by the transmembrane aspartic protease BACE.

Abstract: Cerebral deposition of amyloid beta peptide (Abeta) is an early and critical feature of Alzheimer's disease. Abeta generation depends on proteolytic cleavage of the amyloid precursor protein (APP) by two unknown proteases: beta-secretase and gamma-secretase. These proteases are prime therapeutic targets. A transmembrane aspartic protease with all the known characteristics of beta-secretase was cloned and characterized. Overexpression of this protease, termed BACE (for beta-site APP-cleaving enzyme) increased the amount of beta-secretase cleavage products, and these were cleaved exactly and only at known beta-secretase positions. Antisense inhibition of endogenous BACE messenger RNA decreased the amount of beta-secretase cleavage products, and purified BACE protein cleaved APP-derived substrates with the same sequence specificity as beta-secretase. Finally, the expression pattern and subcellular localization of BACE were consistent with that expected for beta-secretase. Future development of BACE inhibitors may prove beneficial for the treatment of Alzheimer's disease.