B6;129-Pax7^{tm2.1(cre/ERT2)Fan}/J

Stock number: 012476
Research areas: Research Tools

Description

Tamoxifen-induced, Cre-mediated targeted deletions in tissues such as myogenic progenitor cells and adult myogenic satellite cells can be created upon crossing these Pax7^CE mutant mice with a strain carrying a floxed gene of interest.

Detailed description

Mice that are heterozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Only approximately 10% of homozygotes live to adulthood. Surviving adult homozygotes are approximately half the size of heterozygote animals. The fertility of homozygotes has not been tested. In contrast to B6.129S-Pax7^{tm1(cre/ERT2)Gaka}/J mice, which express a functional PAX7 gene product, no PAX7 protein is detected in 10 day old homozygotes. The Ds-Red is not detectable by immunostaining or FACS. When crossed with a strain containing a loxP site flanked sequence of interest, the offspring are useful for generating tamoxifen-induced, Cre-mediated targeted deletions in tissues such as myogenic progenitor cells and adult myogenic satellite cells.

Development

A targeting vector was used to insert loxP sites flanking exon 2. Exon 2 was excised via transient Cre mediated recombination to generate the Pax7^tm1.1Fan allele. Exon 1 in the Pax7^tm1.1Fan allele was replaced with a targeting vector containing sequence encoding Cre-ERT2, IRES-DsRed and an FRT flanked PGK-neo cassette. The construct was electroporated into (129X1/SvJ x 129S1/Sv)F1-Kitl⁺ derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. The resulting chimeric animals were crossed to mice expressing FLP recombinase under the control of an Actin promoter (on the C57BL/6 background) to remove the neo selection cassette. The mice were then backcrossed to C57BL/6J for 2 generations. Upon arrival at The Jackson Laboratory the mice were crossed to C57BL/6J once to establish the colony.

Allele

Symbol: Pax7^{tm2.1(cre/ERT2)Fan}
Name: targeted mutation 2.1, Chen-Ming Fan
MGI accession ID: MGI:4353154
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible; Null/Knockout
Marker symbol: Pax7
Marker name: paired box 7
Chromosome: 4
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Expressed genes: cre/ERT2,Cre recombinase and estrogen receptor 1 (human) fusion gene,; RFP,Red Fluorescent Protein,coral
Site of expression: When crossed with a strain containing a loxP site flanked sequence of interest, the offspring are useful for generating tamoxifen-induced, Cre-mediated targeted deletions in tissues such as myogenic progenitor cells and adult myogenic satellite cells.
Molecular note: Beginning with the Pax7^tm1.2Sjc allele in which exon 2 was knocked out leaving a single loxP site, part of exon 1 was replaced with a cre/ERT2 (ESR1) fusion followed by an IRES-DsRed and an frt flanked neo cassette. Germ line, flp mediated recombination removed the neo cassette. The absence of full-length Pax7 protein expression was confirmed by western blot analysis on P10 tibialis anterior muscle extracts. Expression of the fusion cre/ERT2 protein was confirmed by a cross with a reporter line. DsRed fluorescence was not detectable by epifluorescence nor was DsRed protein by immunostaining.