B6.C(Cg)-Cd79a^tm1(cre)Reth/EhobJ

Stock number: 020505
Product name: Mb1-Cre on C57BL/6
Research areas: Research Tools

Description

These mb1-cre knock-in/knock-out mice carry an allele in which exons 2 and 3 of the Cd79a gene have been replaced with a codon optimized Cre recombinase gene and the ATG codon of exon 1 is deleted; both abolishing endogenous Cd79a gene function and placing cre expression under the control of the endogenous Cd79a promoter/enhancer elements. Cre recombinase expression is directed at the earliest stages and throughout B-lymphocyte development and differentiation. Homozygous mice are also useful for studying B cell-deficiency.

Detailed description

The targeted Cd79a (mb1) gene encodes the immunoglobulin-alpha subunit of the B lymphocyte antigen receptor. Mutations in this gene have been associated with agammaglobulinemia-3. This mb1-cre strain expresses cre recombinase from the endogenous Cd79a locus. When crossed with a strain containing loxP site flanked sequence of interest, Cre-mediated recombination results in tissue-specific deletion of the target. Recombination occurs primarily in B cells, with a low level of recombination detected in T cells in the thymus, spleen and lymph nodes. Infrequently, recombined reporter alleles have been detected in progeny mice, indicating Cre recombinase activity in the germ line. Homozygotes are viable and fertile. The Donating Investigator reports that homozygotes are B cell deficient and immunocompromised.

When crossed to a Cre recombinase reporter strain, recombination efficiency in B cells of these mb1-cre mice was 99% compared to the approximately 80% recombination in B cells from the Cd19-cre strain 006785 (Stock No. 006785).

Dr. Michael Reth and Dr. Elias Hobeika would appreciate acknowledgement in publications applying this research model.

Development

A targeting vector containing an FRT site flanked tk-NEO cassette was utilized in the construction of this strain. The construct was used to replace exons 2 and 3 of the Cd79a gene with cDNA encoding hCre (mammalian codon optimized cre recombinase) followed by a SV40 poly(A) signal replaced exons 2 and 3 and to remove the ATG codon by truncatation of exon 1. The construct was electroporated into unspecified BALB/c -derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting chimeric mb1-hCre-neo animals were tested for germline transmission. The mice were then crossed to ACTB::Flpe, Flpe delete, mice on the C57BL/6 background, to excise the FRT flanked NEO cassette. The resulting mb1-hCre mice no longer carrying the FRT site flanked selection cassette were then backcrossed to C57BL/6 for more than 20 generations.

Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Cd79a^tm1(cre)Reth
Name: targeted mutation 1, Michael Reth
MGI accession ID: MGI:3687451
Generation method: Targeted
Attributes: Recombinase-expressing; Null/Knockout
Marker symbol: Cd79a
Marker name: CD79A antigen (immunoglobulin-associated alpha)
Chromosome: 7
Strain of origin: BALB/c
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: Cre-mediated recombination occurs primarily in B cells, with a low level of recombination detected in T cells in the thymus, spleen and lymph nodes.
Molecular note: Exons 2 and 3 of the Cd79a gene were replaced with a cDNA encoding a mammalian codon-optimized cre (hCre) followed by an SV40 poly(A) signal. Exon 1 was truncated to remove the Cd79a ATG start codon, and a tk-neo cassette flanked by FRT sites was introduced 3' to hCre. The neo cassette was deleted in chimeras by crossing to Flpe deleter mice.