Research Techniques Made Simple: Generation of complete or tissue-specific knockout mice Lukas Scharfenberger, Tina Hennerici, Gábor Király, Sophie Kitzmüller, Marigje Vernoij, Julia G. Zielinski

What is a gene knockout? Manipulation of the DNA that results in the nonfunctionality or complete loss of the corresponding protein Whole-body knockout: knockout of a gene in every cell of the organism Conditional knockout: knockout of a gene in specific cell populations or organs

Generation of gene-manipulated mice by gene targeting Isolation of embryonic stem (ES) cells Isolation of blastocyst in vitro cultivation of ES cells Transfection with targeting construct neo 2 targeting construct neo 2 homologous recombination 1 2 3 4 neo gene knockout wildtype gene

Generation of gene-manipulated mice by gene targeting Selection with neomycin Injection of ES cells into mouse embryo Breeding chimeric offspring Implantation into surrogate mother knockout mouse

Conditional knockout Cre mouse floxed mouse created by gene targeting loxP neo 1 2 3 4 tissue-specific promoter crossing

Conditional knockout Cre mouse Cre;;genefl/fl floxed mouse Cre site-specific recombination loxP neo 1 2 3 4 degradation neo 2 3 1 4 Tissue-specific knockout

Confirmation of gene knockout concept of Avcr1b knockout genotyping PCR Tissue-specific knockout in K14-Cre;;Avcr1bflox/flox mouse Qiu et al., 2011

Advantages of a conditional knockout model Overcome embryonic and early postnatal lethality of whole-body knockout mice Tissue or organ autonomous analysis of a gene function The combination of a tissue-specific expressing Cre mouse and floxed gene mouse offers a great variety of mouse models Commercially available mouse lines save time and space

Limitations of a conditional knockout model Not every human disease can be investigated by a mouse gene knockout No temporal control of the gene knockout (inducible KO) Some diseases have an underlying mechanism that results from overactivity of a gene expression (alternative: knockin model) Redundancy of related gene products may compensate and thus not reveal the gene function