Target Discovery and Validation Reviews and Protocols

11
Keratin Transgenic and Knockout Mice
Functional Analysis and Validation
of Disease-Causing Mutations
Preethi Vijayaraj, Goran Söhl, and Thomas M. Magin
Summary
The intermediate filament (IF) cytoskeleton of mammalian epithelia is generated from pairs
of type I and type II keratins that are encoded by two large gene families, made up of 54 genes
in humans and the mouse. These genes are expressed in a spatiotemporal and tissue-specific
manner from the blastocyst stage onward. Since the discovery of keratin mutations leading to
epidermolysis bullosa simplex, mutations in at least 18 keratin genes have been identified that
result in keratinopathies of the epidermis and its appendages. Recently, noncanonical mutations
in simple epithelial keratins were associated with pancreatic, liver, and intestinal disorders,
demonstrating that keratins protect epithelia against mechanical and other forms of
stress. In recent years, animal models provided novel insight and significantly improved understanding
of IF function in tissue homeostasis and its role in disease. Pathological phenotypes
detected in mutant mice generated so far range from embryonic lethality to tissue fragility to
subtlety, which often depends on their genetic background. This range implies at least a partial
influence of yet unidentified modifier genes on the phenotype after the ablation of the respective
keratin. To date, nearly all available keratin mouse models were generated by taking advantage
of conventional gene-targeting strategies. To reveal their cell type-specific functions and the
mechanisms by which mutations lead to disease, it will be necessary to use conditional genetargeting
strategies and the introduction of point-mutated gene copies. Furthermore, conditional
strategies offer the possibility to overcome embryonic or neonatal lethality in some of
the keratin-deficient mice.
Key Words: Blastocysts injection; Cre/LoxP system; epidermolysis bullosa simplex (EBS); epidermolytic
hyperkeratosis (EHK); pachyonychia congenita; embryonic stem (ES) cell culture;
Flp/FRT system; genomic cluster knockout; intermediate filaments; knockout mice; tetraploids;
transgenic mice.
From: Methods in Molecular Biology, vol. 360, Target Discovery and Validation Reviews and Protocols
Volume I, Emerging Strategies for Targets and Biomarker Discovery
Edited by: M. Sioud © Humana Press Inc., Totowa, NJ
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