Introduction 2002 1997 2005a b 2004 2007 1996 1996 2006 2000 2006 2006 1992 2002 2000 2007 1978 1985 2002 2000) kit W/W-v kit W-sh/W-sh kit 2005b 2005 kit W/W-v 2005b kit W-sh kit W/W-v 2005 in vitro 2005 2005 loxP 1996 loxP 1994 Cre Material and methods Construction of the transgene and generation of transgenic mice Mcpt5 2000 E. coli 1998 1 1 Cre i 2002 Mcpt5 Cre loxm2 neo Mcpt5 Cre Cre Mcpt5 1 Cre Mcpt5 Cre-Neo Not Mcpt5 neo 2004 Not Mcpt5-Cre 2001 Table 1 Primers used for transgene construction by homologous recombination  Oligonucleotides used for transgene construction by homologous recombination. The respective 50 bp homology regions (HR) were included into the primers used for the amplification of selection markers or the minimal vector Fig. 1 Not Mcpt5 Cre loxm2 neo E. coli Not EcoR  Flow cytometric analysis Total splenocyte suspensions were separated into lymphocyte and non-lymphocyte fractions by magnetic cell sorting (MACS, Miltenyi Biotec, Bergisch Gladbach, Germany) using anti-CD3-Biotin (clone 145-2C11, BD Pharmingen), anti-Biotin MicroBeads, anti-CD19 MicroBeads and LS MACS columns (Miltenyi Biotec). Skin cell suspensions were prepared from shaved abdominal skin plus one ear pinna by mincing followed by an incubation with 2 mg/ml collagenase IV (Worthington Biochem. Corporation, Lakewood, NJ, USA) at 37°C. Cells in peritoneal lavage as well as single cell suspensions from skin and spleen were stained with phycoerythrin (PE)-conjugated anti-CD3 (clone 145-2C11), anti-CD19 (clone 1D3); anti-CD11c (clone HL3), anti-CD45 (clone 30-F11) and anti-Siglec-F (clone E50-2440) (all from BD Pharmingen) or anti-FcεRIα-PE (clone MAR-1), allophycocyanin (APC)-conjugated anti-CD117 (clone 2B8) and anti-CD49b (clone D×5), F4/80-Biotin (clone BM8) and streptavidin-PE (all from eBiosciences, SanDiego, CA) or anti-Gr-1-PE (clone RB6-8C5) (Miltenyi Biotech). The cells were analyzed on a FACSCalibur (BD Biosciences). Results Transgene construction and screening of transgenic mice for Cre expression Mcpt5 1 Mcpt5 Cre 1 Not 1 Mcpt5-Cre 2001 ROSA26 loxP Mcpt5-Cre ROSA26 EYFP 2 Fig. 2 Mcpt5-Cre ROSA26-EYFP Mcpt5-Cre ROSA26-EYFP Cre- ROSA26-EYFP  Efficient and mast cell-specific Cre-mediated recombination in the lines A-Mcpt5-Cre and X-Mcpt5-Cre + +  A-Mcpt5-Cre ROSA26-EYFP 2 + +  + +  2 3 Mcpt5-Cre Mcpt5 Fig. 3 Mcpt5-Cre ROSA26-EYFP Mcpt5-Cre ROSA26-EYFP Cre- ROSA26-EYFP  Absence of significant Cre-mediated genotoxicity in mast cells of Mcpt5-Cre animals Mcpt5-Cre Mcpt5-Cre ROSA26-EYFP 4 4 Mcpt5-Cre ROSA26-EYFP Mcpt5-Cre Fig. 4 Mcpt5-Cre a Mcpt5-Cre + + b A-Mcpt5Cre ROSA26-EYFP 2007  Discussion Cre Mcpt5 2005b 2005 1978 2005 2005 Cre Cre Mcpt5 Cre a Mcpt5 X Cre Cre 2007 Mcpt5-Cre ex vivo 2005