ABSTRACT
A common method for generating mice with subtle genetic manipulations uses homologous recombination (HR) in embryonic stem (ES) cells to replace a wild-type gene with a slightly modified one. Generally, a drug resistance gene is inserted with the modified gene to select correctly targeted clones. Often, however, the presence of this drug resistance gene interferes with the normal locus and creates a null or hypomorphic allele. Flanking of the selectable marker by loxP sites followed by Cre-mediated deletion after drug selection can overcome this problem. The simplest method used to remove a loxP-flanked selectable marker is to breed an animal carrying a loxP-flanked drug resistance gene to an animal that expresses Cre recombinase in the germline. To date only outbred transgenic mice are available for this purpose. This can be problematic for phenotypic analysis in many organ systems, including the brain, and for the analysis of behavior. While attempting to make 129S6/SvEvTac inbred background (isogenic to our ES cells) mice that express Cre under the control of several tissue-specific promoters, we serendipitously generated a line that excises loxP-flanked drug resistance genes in all tissues, including the germline. This reagent allows deletion of loxP-flanked sequences while maintaining the mutation on an inbred background.
Subject(s)
Gene Deletion , Integrases/genetics , Viral Proteins/genetics , Animals , Binding Sites/genetics , Drug Resistance/genetics , Female , Genome , Green Fluorescent Proteins , Homozygote , Hypoxanthine Phosphoribosyltransferase/genetics , Integrases/metabolism , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Male , Mice , Mice, Inbred Strains , Mice, Transgenic , Microscopy, Confocal , Mutagenesis, Insertional , Mutation , Recombination, Genetic , Viral Proteins/metabolismABSTRACT
Neuropathy target esterase (NTE) is involved in neural development and is the target for neurodegeneration induced by selected organophosphorus pesticides and chemical warfare agents. We generated mice with disruptions in Nte, the gene encoding NTE. Nte(-/-) mice die after embryonic day 8, and Nte(+/-) mice have lower activity of Nte in the brain and higher mortality when exposed to the Nte-inhibiting compound ethyl octylphosphonofluoridate (EOPF) than do wild-type mice. Nte(+/-) and wild-type mice treated with 1 mg per kg of body weight of EOPF have elevated motor activity, showing that even minor reduction of Nte activity leads to hyperactivity. These studies show that genetic or chemical reduction of Nte activity results in a neurological phenotype of hyperactivity in mammals and indicate that EOPF toxicity occurs directly through inhibition of Nte without the requirement for Nte gain of function or aging.
