title: Modification of the apolipoprotein B gene in HepG2 cells by gene targeting.
abstract: The HepG2 cell line has been used extensively to study the synthesis and secretion of apolipoprotein (apo) B. In this study, we tested whether gene-targeting techniques can be used to inactivate one of the apo B alleles in HepG2 cells by homologous recombination using a transfected gene-targeting vector. Our vector contained exons 1-7 of the apo B gene, in which exon 2 was interrupted by a promoterless neomycin resistance (neo(r)) gene. The recombination of this vector with the cognate gene would inactivate an apo B allele and enable the apo B promoter to activate the transcription of the neo(r) gene. To detect the rare homologous recombinant clone, we developed a novel solid phase RIA that uses the apo B-specific monoclonal antibody MB19 to analyze the apo B secreted by G418-resistant (G418r) clones. Antibody MB19 detects a two-allele genetic polymorphism in apo B by binding to the apo B allotypes MB19(1) and MB19(2) with high and low affinity, respectively. HepG2 cells normally secrete both the apo B MB19 allotypes. Using the MB19 immunoassay, we identified a G418r HepG2 clone that had lost the ability to secrete the MB19(1) allotype. The inactivation of an apo B allele of this clone was confirmed by the polymerase chain reaction amplification of an 865-bp fragment unique to the targeted apo B allele and by Southern blotting of genomic DNA. This study demonstrates that gene-targeting techniques can be used to modify the apo B gene in HepG2 cells and demonstrates the usefulness of a novel solid phase RIA system for detecting apo B gene targeting events in this cell line.
authors.affiliation: Gladstone Institute of Cardiovascular Disease, Department of Medicine, University of California, San Francisco 94141-9100.
authors.forename: R V
authors.initials: RV
authors.lastname: Farese
authors.forename: L M
authors.initials: LM
authors.lastname: Flynn
authors.forename: S G
authors.initials: SG
authors.lastname: Young
mesh_terms: D000483:Alleles; D000911:Antibodies, Monoclonal / Q000276:immunology; D001055:Apolipoproteins B / Q000235:genetics*; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics; D005822:Genetic Vectors; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D011863:Radioimmunoassay; D011995:Recombination, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D001055:Apolipoproteins B