B6.Cg-Tg(Cr2-cre)3Cgn/J

Stock number: 006368
Product name: CD21-cre
Research areas: Research Tools

Description

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.

Detailed description

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).

Development

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.

Allele

Symbol: Tg(Cr2-cre)3Cgn
Name: transgene insertion 3, University of Cologne
MGI accession ID: MGI:3047571
Generation method: Transgenic
Attributes: Recombinase-expressing
Synonyms: CD21-cre; CD21-cre3a; Cr2^tm1(cre)Cgn
Marker symbol: Tg(Cr2-cre)3Cgn
Marker name: transgene insertion 3, University of Cologne
Marker synonyms: CD21-cre; CD21-cre3a; Cr2^tm1(cre)Cgn
Chromosome: UN
Strain of origin: Not Specified
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: mature transitional B cells
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.