B6.129S2-Alb^{tm1(cre/ERT2)Mtz}/J

Stock number: 039060
Product name: SA^CreERT2
Strain synonyms: Albumin-Cre-ERT2
Research areas: Developmental Biology Research, Research Tools

Description

SA^CreERT2 knock-in mice (also called Albumin-Cre-ERT2) express an inducible IRES-cre/ERT2 fusion gene under the control of the endogenous Alb (albumin) promoter. Following administration of tamoxifen, mice express Cre recombinase in hepatocytes. These mice can be used to specifically target liver tissue.

Detailed description

SA^CreERT2 knock-in mice use the endogenous Alb (albumin, serum albumin [SA]) promoter to drive expression of a bicistronic IRES-cre/ERT2 fusion gene in hepatocytes. RT-PCR analysis confirms that no Cre recombinase expression is observed in other tissues. Administration of tamoxifen results in Cre expression in most if not all hepatocytes as determined by immunohistochemical analysis. The donating investigator did not determine if the expression of albumin is affected by the insertion of cre/ERT2. Mice that are heterozygous for this knock-in allele are viable and fertile. It was not determined if homozygous mice are viable and fertile but they are expected to be.

The Cre-ERT2 fusion protein consists of Cre 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 SA^CreERT2 targeting vector contains an IRES-cre/ERT2, a polyA sequence, and an FRT-flanked neomycin/kanamycin resistance gene. The vector was inserted in the 3' untranslated region the Alb (albumin) stop codon on chromosome 5 using homologous recombination. The construct was electroporated into 129S2/SvPas-derived embryonic stem (ES) cells with a transient Flp expression plasmid (pCAGGS-Flpe) to remove the neo cassette. Correctly targeted ES cells were injected into blastocysts. The chimeric animals were crossed with C57BL/6J females for germline transmission. The donating investigator reports the resulting SA^CreERT2 mice were backcrossed to C57BL/6J for at least 10 generations and then frozen as sperm in 2019. In 2024, the donating investigator sent frozen sperm to The Jackson Laboratory. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Alb^{tm1(cre/ERT2)Mtz}
Name: targeted mutation 1, Daniel Metzger
MGI accession ID: MGI:3052812
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible
Synonyms: Alb^ICE; Alb^{tm1(cre/ESR1)Mtz}; Alb-CreERT2; AlbCre-ERT2^ki; Albumin-CreER; SA^Cre-ERT2; SA-CRE-ER^T2
Marker symbol: Alb
Marker name: albumin
Marker synonyms: Alb1; Alb-1; Albza; FDAHT; HSA; PRO0883; PRO0903; PRO1341
Chromosome: 5
Strain of origin: 129S2/SvPas
Molecular note: A vector was used to insert IRES-Cre-ER^T2 downstream of the stop codon in exon 14. Transient FLP-recombinase excised a FRT-floxed neo 3' to the Cre. ES cell clone XF136.64 was injected into blastocysts to generated mice. Southern blot confirmed recombination. RT-PCR indicated bicistronic expression was only present in the liver of mutants. Immunohistochemical analysis of liver using an anti-Cre antibody showed that Cre is expressed in most, if not all, hepatocytes.