B6.129P2(Cg)-Ighg1^tm1(cre)Cgn/J

Stock number: 010611
Product name: Cγ1-cre
Research areas: Immunology, Inflammation and Autoimmunity Research, Research Tools

Description

This strain expresses Cre recombinase from the endogenous Ighg1, immunoglobulin heavy constant gamma 1, locus. This strain represents an effective tool for generating tissue specific-targeted mutants that would be useful in the study of gene function in germinal center, class switched memory and plasma cells.

Detailed description

Homozygous mice are viable, fertile, normal in size, and do not display any gross physical or behavioral abnormalities. Cre recombinase expression is induced by transcription of the immunoglobulin gamma1 heavy chain constant region gene (Cg1) segment and is detected as early as 4 days in 25-50% of germinal center B cells following immunization with T cell dependent antigens. By 12-14 days, 75-85% of germinal center B cells exhibit Cre-mediated recombination. Cre is detected mostly in IgG1, but also in IgG2 and IgA-expressing germinal center B cells as well as a small number of IgM+ germinal center B cells precursors. Homozygotes exhibit a reduction in IgG1+ memory B cells and in IgG1 serum antibody titers. When bred with a mouse carrying a loxP site-flanked DNA sequence, Cre-mediated recombination results in deletion of the flanked genome segment in tissues that express the Cre transgene. This mutant mouse strain may be useful to study gene function in germinal center, class switched memory and plasma cells.

Development

A targeting vector was used to introduce an Internal Ribosome Entry Site (IRES)-Cre-frt-flanked neomycin cassette into the 3' UTR of the immunoglobulin gamma1 constant region gene, between the last membrane coding region and its' polyadenylation site. This strategy allows for the expression of a bicistronic mRNA consisting of the immunoglobulin gamma 1 constant region (Cg1) and Cre recombinase. The construct was electroporated into 129P2/OlaHsd-derived IB10 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. The resulting chimeric animals were tested for germline transmission. Mice were crossed to a FLPe deleter (genetic background unknown) strain to remove the neomycin cassette, leaving a single frt site upstream of the 3' UTR. The donating investigator reported that the resulting mutant mice were backcrossed to C57BL/6J for 10 generations (see SNP note below). Upon arrival, mice were bred to C57BL/6J for at least 1 generation to establish the colony.

A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, 4 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.

Allele

Symbol: Ighg1^tm1(cre)Cgn
Name: targeted mutation 1, University of Cologne
MGI accession ID: MGI:3652526
Generation method: Targeted
Attributes: Recombinase-expressing
Marker symbol: Ighg1
Marker name: immunoglobulin heavy constant gamma 1 (G1m marker)
Chromosome: 12
Strain of origin: 129P2/OlaHsd
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: Cre is detected mostly in IgG1, but also in IgG2 and IgA-expressing germinal center B cells as well as a small number of IgM+ germinal center B cells precursors.
Molecular note: A targeting vector containing an IRES-cre was inserted into the 3' region of the Cgamma1 locus between the last membrane-coding exon and its polyadenylation sites. This targeting design allows for the expression from the locus of a bicistronic mRNA consisting of the Cgamma1 and Cre transcript. An frt-flanked neo was removed via FLP recombinase expression.