Abstracts (complete list) - Wissenschaft Online

Julia Scholten, Alexander Gerbaulet, Giuseppe Testa, Thomas Krieg, Karin Hartmann,
Axel Roers
Mast cell-specific Cre/loxP-mediated mutagenesis in vivo
Mast cells are important effector cells in type I allergy, but were recently also shown to
play key roles in host defence against pathogens. In addition, mast cells were
implicated in tissue remodeling, wound healing and transplant tolerance. Investigation
of this important cell type, however, was severely hampered by the scarcity of mast
cells in the various tissues and the lack of protocols for ex vivo culture of mast cells.
Until today, in vivo analysis of mast cell-specific functions of individual genes relied on
the reconstitution of genetically mast cell-deficient mice with mast cells differentiated in
vitro from bone marrow of mice deficient for the gene of interest. This system yielded
important information in the past, but suffers severe limitations. Herein, we use the Cre/
loxP recombination system for conditional mast cell-specific mutagenesis in vivo. In a
bacterial artificial chromosome (BAC) containing the entire mouse mast cell protease 5
(Mcpt5) locus, the coding region of exon 1 was replaced by a Cre cassette. The BAC
insert was purified and micro-injected into pronuclei of fertilized C57BL/6 oocytes to
obtain transgenic mice. In order to demonstrate mast cell-specific Cre-mediated
recombination, six Mcpt5-Cre founder lines were crossed to a Rosa26-EYFP Cre-excision
reporter line and cell suspensions of various tissues were analysed by flow cytometry.
Two of the transgenic lines showed highly efficient Cre-mediated induction of the
fluorescent reporter protein in mast cells, but not in other cell types. The new Cretransgenic
mouse lines will be useful tools in the elucidation of mast cell biology.