B6(129)-Jchain^{em1(icre/ERT2)Deep}/J

Stock number: 035764
Product name: Jchain-IRES-CreERT2
Research areas: Cancer Research, Research Tools

Description

Jchain-CreERT2 knock-in mice have the endogenous immunoglobulin joining chain promoter/enhancer sequences directing expression of tamoxifen-inducible Cre recombinase, and are on a congenic C57BL/6N background. These mice are a Cre-lox tool allowing inducible Cre recombination with high specificity for B cells, and may be useful in studying immunology and infectious disease.

Detailed description

The Jchain gene encodes the joining chain polypeptide component of IgM and IgA antibodies secreted by B cells.

The Jchain-IRES-CreERT2 knock-in allele (also called JchainCreERT2) has an IRES sequence and a tamoxifen-inducible improved Cre recombinase (iCreER^T2) inserted into the 3' UTR of the Jchain locus. This is designed to have the endogenous Jchain promoter/enhancer elements directing icre/ERT2 expression primarily in B cells (see below), as well as to retain endogenous Jchain expression. Specific details are below.

CreER^T2 fusion gene activity is inducible - observed following tamoxifen administration. As such, when Jchain-IRES-CreERT2 mice are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination will result in deletion of floxed sequences in Jchain-expressing cells of the double mutant offspring.

The donating investigator reports that Jchain-IRES-CreERT2 mice have tamoxifen-inducible Cre recombinase activity that recapitulates the endogenous Jchain expression pattern - observed mainly in germinal center B cells and bone marrow plasma cells, with only negligible labeling of non-B cell lineages (Wong et al., 2020). The donating investigator reports no CreERT2 activity (no reporter gene expression) is observed prior to tamoxifen exposure. This knock-in allele is designed to avoid disrupting expression of the endogenous protein; although Jchain expression from the Jchain-IRES-CreERT2 allele has not been evaluated to date (December, 2020).

Mice heterozygous or homozygous for the Jchain-IRES-CreERT2 allele are viable and fertile with no reported gross physical or behavioral abnormalities.

The Cre-ERT2 fusion protein consists of iCre recombinase fused to a triple mutant form of the human estrogen receptor which does not bind its natural ligand (17β-estradiol) at physiological concentrations but will bind the synthetic estrogen receptor ligands 4-hydroxytamoxifen (OHT or tamoxifen) and, with lesser sensitivity, ICI 182780. Restricted to the cytoplasm, Cre-ERT2 can only gain access to the nuclear compartment after exposure to tamoxifen. To counteract the mixed estrogen agonist effects of tamoxifen injections, which can result in late fetal abortions in pregnant mice, progesterone may be coadministered.

Development

The Jchain-CreERT2 knock-in allele (also called Jchain-IRES-CreERT2) was created in the of laboratory Dr. Deepta Bhattacharya (University of Arizona) to have an IRES sequence and a CreER^T2 fusion gene inserted into the 3' UTR of the immunoglobulin joining chain locus (Jchain) on chromosome 5.

Jchain-Cre/ERT2 mice were generated using CRISPR/Cas9 technology by microinjecting Cas9-gRNA ribonucleoparticles into C57BL6/J zygotes alongside an IRES-iCreERT2 donor cassette targeting the 3'UTR of the Jchain locus. Correctly targeted mice were crossed to C57BL6/NCrl mice for 6 generations prior to sending males to The Jackson Laboratory Repository. At some point duing development, this line was crossed to Rosa26-LSL-Cas9 knock-in mice (Stock No. 026175). Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304). The Rosa26-LSL-Cas9 allele was bred out of this colony before distribution.

In 2022, a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 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 males sent to The Jackson Laboratory Repository. Three of the 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating, including the rd8 recessive mutation associated with retinal degeneration on Chromosome 1 within the Crb1 locus. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6N;C57BL/6J genetic background.

Allele

Symbol: Jchain^{em1(icre/ERT2)Deep}
Name: endonuclease-mediated mutation 1, Deepta Bhattacharya
MGI accession ID: MGI:6478203
Generation method: Endonuclease-mediated
Attributes: Recombinase-expressing; Inducible
Synonyms: JchainCreERT2
Marker symbol: Jchain
Marker name: immunoglobulin joining chain
Marker synonyms: 9530090F24Rik; IGCJ; IGJ; J chain; Jch
Chromosome: 5
Strain of origin: C57BL/6J
Molecular note: Using CRISPR/Cas9 technology, the allele was generated to insert an IRES sequence and a CreER(T2) fusion gene into the 3' UTR of the immunoglobulin joining chain locus (Jchain) on chromosome 5.