B6.129X1(Cg)-Gt(ROSA)26Sor^{tm3(Runx2)Flng}/J

Stock number: 033970
Product name: R26^Runx2
Research areas: Developmental Biology Research, Research Tools

Description

R26^Runx2 mice have a loxP-flanked STOP cassette followed by a mouse runt related transcription factor 2 cDNA sequence inserted into the Gt(ROSA)26Sor locus. Exposure to Cre recombinase removes the floxed STOP cassette, resulting in Runx2 expression from this allele. This strain is useful in studies of osteoblastogenesis and endochondral skeleton development.

Detailed description

The Runx2 gene encodes a nuclear transcription factor that is important in osteoblastic differentiation and skeletal morphogenesis. These R26^Runx2 mice have Cre recombinase-inducible Runx2 expression from the Gt(ROSA)26Sor locus. Prior to introduction of Cre recombinase, mice heterozygous or homozygous for the R26^Runx2 allele are viable and fertile. These mice also contain an EGFP sequence that is not detectable by immunohistochemistry or direct fluorescence.

When R26^Runx2 are bred to mice that express Cre recombinase, the resulting offspring will have the STOP cassette deleted, resulting in Runx2 expression in cre expressing tissules.

For example, when bred to a strain with Cre recombinase expression in embryonic (E12.5) cartilage, the resulting mice may be useful in studies of endochondral skeleton development.

When crossed with Runx2 knock-out null mice, the Cre recombinase-activated R26^Runx2 allele restores osteoblastogenesis in the double mutant embryos.

Development

The R26^Runx2 allele was created in the laboratory of Dr. Fanxin Long (while at Washington University School of Medicine). First, a targeting vector containing a floxed STOP cassette (PGK-neo-3xpA), mouse Runx2 cDNA (encoding the MASNS isoform), IRES, EGFP and polyadenylation signal sequence was inserted into the Gt(ROSA)26Sor locus. The construct was electroporated into 129X1/SvJ derived RW-4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. The resulting chimeric animals were bred to C57BL/6J mice (Stock No. 000664) to achieve germline transmission. Mice were maintained on a mixture of C57BL/6 and 129 and then sent to Dr. Jennifer H. Jonason (University of Rochester Medical Center). Dr. Jonason backcrossed these mice to C57BL/6J for at least 3 generations (see SNP note below) and subsequently bred them to an Acan-CreERT2 line maintained on the C57BL/6J genetic background. This Acan-CreERT2 allele was removed from the colony by crossing to C57BL/6J again, and mice lacking the creERT2 allele were sent to The Jackson Laboratory. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

In 2021, 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. One of the 43 markers throughout the genome was segregating with 129, on Chromosome 8. One of the 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6N;C57BL/6J genetic background.

Allele

Symbol: Gt(ROSA)26Sor^{tm3(Runx2)Flng}
Name: targeted mutation 3, Fanxin Long
MGI accession ID: MGI:5311032
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Reporter; Inserted expressed sequence
Synonyms: R26^Runx2
Marker symbol: Gt(ROSA)26Sor
Marker name: gene trap ROSA 26, Philippe Soriano
Marker synonyms: beta geo; Gtrgeo26; Gtrosa26; R26; ROSA26; SETD5-AS1; Thumpd3as1
Chromosome: 6
Strain of origin: 129X1/SvJ
Molecular note: The insertional construct contained a floxed neo/STOP cassette, the mouse Runx2 cDNA encoding the MASNS isoform, an IRES, EGFP and polyadenylation sequence.