STOCK Prg4^{tm1(GFP/cre/ERT2)Abl}/J

Stock number: 022757
Research areas: Internal/Organ Research, Research Tools

Description

These Prg4^GFPCreERt2 mice express the inducible GFP/cre/ERT2 fusion gene in a pattern that mimics the expression of the endogenous Prg4 gene: in the chondrocytes of articular cartilage but not in the growth plate chondrocytes.

Detailed description

The Prg4, proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein), gene encodes the lubricin protein, a large proteoglycan that acts as a lubricant at the surface of cartilage of articulating joints. Prg4 also encodes for the superficial zone protein, megakaryocyte stimulating factor, and hemangiopoietin. These mice carry a targeted mutation (knock in) allele in which a GFP/cre/ERT2 fusion gene has been inserted into exon 2 of the Prg4 gene. Mice that are homozygous for the targeted mutation are viable and fertile, but exhibit a loss of the superficial-most layer of articular chondrocytes and displayed synoviocyte hyperplasia in joints. Expression of the GFP/cre/ERT2 fusion gene mimics expression of the endogenous Prg4 gene. When these Prg4^GFPCreERt2 mice are bred with mice containing a loxP flanked sequence of interest, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the flanked sequences in Prg4 expressing cells.

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

A targeting vector designed in the laboratory of Dr. Andrew B. Lassar (Harvard Medical School) containing a GFPCreERt2, Green Fluorescent Protein, Cre recombinase and estrogen receptor 1 (human) fusion gene and an FRT flanked PGK-NEO selection cassette, was inserted into the translation initiation codon of exon 2 of the Prg4, proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein). The construct was electroporated into unspecified 129/SV derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. The resulting chimeric animals were crossed to FLP recombinase expressing mice (ACT-FLPe) mice (on an unknown genetic background) to remove the FRT flanked PGK-NEO selection cassette. The mice were crossed to mice carrying the Gt(ROSA)26Sor^tm1Sor allele (Stock No. 003474). Further breeding of the double mutant male mice to C57BL/6 female mice was completed to remove the Gt(ROSA)26Sor^tm1Sor allele. Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.

Allele

Symbol: Prg4^{tm1(GFP/cre/ERT2)Abl}
Name: targeted mutation 1, Andrew Lassar
MGI accession ID: MGI:5490969
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible
Marker symbol: Prg4
Marker name: proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein)
Chromosome: 1
Strain of origin: 129
Expressed genes: GFP,Green Fluorescent Protein,; cre/ERT2,Cre recombinase and estrogen receptor 1 (human) fusion gene,
Site of expression: GFP/cre/ERT2 fusion protein is expressed in the top layer cells of the articular cartilage (in younger mice) or in the top and deeper layers of articular cartilage (in older mice).
Molecular note: A targeting vector containing a GFP/cre/ERT2 (green fluorescent protein, cre recombinase and estrogen receptor 1 tamoxifen binding domain fusion gene and an FRT flanked PGK-NEO selection cassette), was inserted into the translation initiation codon of exon 2 of the Prg4, proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein). The resulting chimeric animals were crossed to FLP recombinase expressing mice (ACT-FLPe) mice (on an unknown genetic background) to remove the Frt flanked PGK-neo selection cassette.
General note: ES cells = unspecified 129/SV