These Mcm2IRES-CreERT2 mice have Cre-ERT2 knocked into the minichromosome maintenance deficient 2 mitotin gene (Mcm2). Expression of Mcm2 is reduced, but not abolished. This strain may be useful for mediating inducible cre recombination in Mcm2-expressing tissues, as well as for studying the regulation of core DNA replication machinery.
Steven Pruitt, Roswell Park Cancer Institute
Genetic Background | Generation |
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Allele Type | Gene Symbol | Gene Name |
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Targeted (Recombinase-expressing, Inducible) | Mcm2 | minichromosome maintenance complex component 2 |
In this strain a Cre-estrogen receptor (Cre-ERT2) fusion protein is knocked into minichromosome maintenance deficient 2 mitotin (Mcm2) gene downstream of the stop codon. Mcm2 is a component of the DNA replication licensing complex expressed in stem/progenitor cells in a variety of regenerative tissues. Mcm2 plays an essential role in eukaryotic cell division as it marks DNA replication origins during G1 for use in the subsequent S-phase. Mcm2 prevents multiple rounds of replication from a single origin and suppresses endoreduplication. Reduced expression results in highly penetrant early onset cancers and stem cell deficiencies. In these mutant mice, MCM2 expression is reduced to 62% of normal in heterozygotes and 35% in homozygotes. Heterozygotes mice are viable, fertile, and normal in size. Homozygotes do not survive beyond 12 weeks age and exhibit thoracic thymomas. They have a severe stem cell deficiency in the subventricular zone of the brain, skeletal muscle, and the small intestinal crypt. They also display a hunched appearance, rapid shallow respiration, generalized muscle weakness, limited movement, loss of adipose tissue, frailty, and modest hair loss or slight graying. Many homozygous mice also exhibit enlarged spleens, and polyps in both the small intestine and colon. The Cre-ERT2 fusion protein is only active when it binds to the estrogen analog 4-hydroxytamoxifen (OHT). When these mice are bred with mice containing a loxP-flanked sequence, tamoxifen-inducible Cre-mediated recombination is expected to result in deletion of the floxed sequences in the Cre recombinase-expressing highly proliferative stem/progenitor cells of the offspring. For example, when bred to mice carrying the Tg(CAG-Bgeo/GFP)21Lbe transgene, tamoxifen-induced GFP expression is observed in 2% and 10% of stem/progenitor cells in a large number of tissues, including endodermal, mesodermal, and neuroectodermal derivatives. This strain may be useful for studying function and regulation of the core DNA replication machinery.
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.
A targeting vector was designed to insert an internal ribosome entry site (IRES), and a Cre-estrogen receptor (Cre-ERT2) fusion protein (Cre-ERT2; Cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain) followed by a neomycin resistance cassette downstream of the stop codon of the minichromosome maintenance deficient 2 mitotin (Mcm2) gene. The construct was electroporated into 129S6/SvEvTac-derived W4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and the resulting chimeric males were bred to 129/Sv females. These mutant mice were maintained on a 129/Sv background. Upon arrival, mice were bred to 129S1/SvImJ mice (Stock No. 002448) for at least one generation to establish the colony.
Expressed Gene | cre/ERT2, Cre recombinase and estrogen receptor 1 (human) fusion gene, |
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Site of Expression | variety of regenerative tissues. |
Allele Name | targeted mutation 1, Steven C Pruitt |
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Allele Type | Targeted (Recombinase-expressing, Inducible) |
Allele Synonym(s) | Mcm2IRES-CreERT2; Mcm2tm1(cre)Scpr |
Gene Symbol and Name | Mcm2, minichromosome maintenance complex component 2 |
Gene Synonym(s) | |
Expressed Gene | cre/ERT2, Cre recombinase and estrogen receptor 1 (human) fusion gene, |
Site of Expression | variety of regenerative tissues. |
Strain of Origin | 129S6/SvEvTac |
Chromosome | 6 |
Molecular Note | An IRES element, a cre/ESRI fusion gene. and a PGK-neo selection cassette were inserted into exon 16 3' to the stop codon. A cryptic polyA site 3' of the stop codon was deleted in order to permit cre expression. Cre expression was confirmed by EGFP expression after tamoxifen treatment of mice also carrying the Tg(CAG-Bgeo/GFP)21Lbe transgene. MCM2 expression was reduced to 62% of normal in heterozygotes and 35% in homozygotes. |
Mutations Made By | Steven Pruitt, Roswell Park Cancer Institute |
When maintaining a live colony, heterozygotes mice may be bred to wiltype mice or to (Stock No. 002448). Homozygotes do not survive beyond 12 weeks age with a hunched appearance, rapid shallow respiration, generalized muscle weakness, limited movement, loss of adipose tissue, frailty, modest hair loss or slight graying, and thoracic thymomas.
When using the 129-Mcm2tm1(cre/ERT2)Scpr/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #017611 in your Materials and Methods section.
Facility Barrier Level Descriptions
Service/Product | Description | Price |
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Heterozygous or wildtype for Mcm2<tm1(cre/ERT2)Scpr> |
Frozen Mouse Embryo | 129-Mcm2<tm1(cre/ERT2)Scpr>/J | $2595.00 |
Frozen Mouse Embryo | 129-Mcm2<tm1(cre/ERT2)Scpr>/J | $2595.00 |
Frozen Mouse Embryo | 129-Mcm2<tm1(cre/ERT2)Scpr>/J | $3373.50 |
Frozen Mouse Embryo | 129-Mcm2<tm1(cre/ERT2)Scpr>/J | $3373.50 |
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