Mice from CD21-cre BAC transgenic line 3a (CD21-cre3a) have Cre recombinase expression directed to mature B cells and follicular dendritic cells. Cre recombinase expression is also observed in forebrain, uterus, ovary, heart, kidney and testes. CD21-cre3a mice are a Cre-lox tool strain useful for studying B lymphocyte development.
Klaus Rajewsky, Max Delbruck Centre for Molecular Medicine
Genetic Background | Generation |
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Allele Type |
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Transgenic (Recombinase-expressing) |
Mice homozygous for the CD21-cre BAC transgene are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. These transgenic mice have nuclear-localized Cre recombinase expression under control of the mouse CD21/35 (Cr2) promoter/enhancer regions within the BAC transgene. CD21-cre BAC transgenic mice from founder line 3a (CD21-cre3a) exhibit cre expression in mature B cells and follicular dendritic cells. In addition to these expected targets, further studies show Cre recombinase expression in forebrain, uterus, ovary (both somatic and germ cell), heart, kidney and testes (both somatic and germ cell).
When bred with mice containing a loxP-flanked sequence of interest, Cre-mediated recombination will result in deletion of the floxed sequences in the offspring. For example, when CD21-cre3a mice are crossed to a lacZ-expressing Cre reporter strain, Cre recombinase activity is detected in 65-90% of mature B cells (as determined by FACS analysis of bone marrow cells).
The CD21-cre BAC transgene was designed in the laboratory of Dr. Klaus Rajewsky. A bacterial artificial chromosome (BAC) clone containing ~100 kbp of the mouse CD21/35 locus (Cr2; complement receptor 2) was obtained. A targeting sequence having a Cre recombinase (with nuclear localization signal), bovine growth hormone polyadenylation site, and a frt-flanked kanamycin resistance gene was inserted downstream of the ATG start site of the Cr2 locus on the BAC via homologous recombination/BAC recombineering. This also replaced the ATG start site of Cr2 with a mutant site.The frt-flanked selection cassette was removed via transient transfection of an FLP-expressing vector during BAC recombineering. The resulting CD21-cre BAC transgene was injected into donor eggs of unknown genetic background to produce independent founder lines. Founder line 3a (CD21-cre3a) transmitted two copies of the transgene. CD21-cre3a mice were subsequently backcrossed to C57BL/6 mice for ten generations prior to sending to The Jackson Laboratory Repository in 2006. Upon arrival, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish our colony.
Expressed Gene | cre, cre recombinase, bacteriophage P1 |
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Site of Expression | mature transitional B cells |
Allele Name | transgene insertion 3, University of Cologne |
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Allele Type | Transgenic (Recombinase-expressing) |
Allele Synonym(s) | CD21-cre; CD21-cre3a; Cr2tm1(cre)Cgn |
Gene Symbol and Name | Tg(Cr2-cre)3Cgn, transgene insertion 3, University of Cologne |
Gene Synonym(s) | |
Promoter | Cr2, complement receptor 2, mouse, laboratory |
Expressed Gene | cre, cre recombinase, bacteriophage P1 |
Site of Expression | mature transitional B cells |
Strain of Origin | Not Specified |
Chromosome | UN |
Molecular Note | This transgene consists of a cre expression cassette including a Kozak sequence, nuclear localization signal, and bovine growth hormone polyadenylation signal inserted into a BAC containing the Cr2 locus. The ATG in the first exon of Cr2 is also mutated in this allele. Cre mediated recombination is detected in 60% - 80% of mature B cells and is undetectable in pro/pre-B and immature B cells. |
Mutations Made By | Marat Alimzhanov, CBR Institute for Biomedical Research |
When maintaining a live colony, hemizygous mice may be bred to wildtype (noncarrier) mice from the colony or to C57BL/6J inbred mice (Stock No. 000664).
When using the CD21-cre mouse strain in a publication, please cite the originating article(s) and include JAX stock #006368 in your Materials and Methods section.
Facility Barrier Level Descriptions
Service/Product | Description | Price |
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Hemizygous or Non carrier for Tg(Cr2-cre)3Cgn |
Frozen Mouse Embryo | B6.Cg-Tg(Cr2-cre)3Cgn/J Frozen Embryo | $2595.00 |
Frozen Mouse Embryo | B6.Cg-Tg(Cr2-cre)3Cgn/J Frozen Embryo | $2595.00 |
Frozen Mouse Embryo | B6.Cg-Tg(Cr2-cre)3Cgn/J Frozen Embryo | $3373.50 |
Frozen Mouse Embryo | B6.Cg-Tg(Cr2-cre)3Cgn/J Frozen Embryo | $3373.50 |
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The Jackson Laboratory has rigorous genetic quality control and mutant gene genotyping programs to ensure the genetic background of JAX® Mice strains as well as the genotypes of strains with identified molecular mutations. JAX® Mice strains are only made available to researchers after meeting our standards. However, the phenotype of each strain may not be fully characterized and/or captured in the strain data sheets. Therefore, we cannot guarantee a strain's phenotype will meet all expectations. To ensure that JAX® Mice will meet the needs of individual research projects or when requesting a strain that is new to your research, we suggest ordering and performing tests on a small number of mice to determine suitability for your particular project. We do not guarantee breeding performance and therefore suggest that investigators order more than one breeding pair to avoid delays in their research.
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