These mice carry a floxed/reversible gene trap allele of the mouse Prg4 gene designed to produce membrane-anchored β-galactosidase instead of lubricin in cells where Prg4 is normally expressed. Cre-mediated excision of the genetrap restores lubricin expression.
Matthew Warman, Boston Children's Hospital, Harvard Medical School
Genetic Background | Generation |
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Allele Type | Gene Symbol | Gene Name |
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Targeted (Conditional ready (e.g. floxed), Reporter, Null/Knockout, Inserted expressed sequence, Transactivator) | Prg4 | proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein) |
Congenital deficiency of the principal boundary lubricant in cartilage (lubricin, encoded by the gene Prg4, proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein)) increases joint friction and causes progressive joint failure.
These mice carry a floxed gene trap allele of the mouse Prg4 gene designed to produce membrane-anchored β-galactosidase instead of lubricin in cells where Prg4 is normally expressed. The genetrap allele does not express wildtype Prg4 mRNA, as determined by RT-PCR. Phenotypic features of the genetrap allele recapitulate those of Prg4 knockout alleles (protein deposition on cartilage by 2 months of age, increased articular joint friction, etc. - see Stock No. 025737).
Cre-mediated excision of the genetrap restores lubricin expression and the wildtype condition. Scattered areas of β-galactosidase expression may still be present in the synovium of treated mice, however, suggesting that lubricin expression may not be restored in every type B synoviocyte.
Restoring gene function prior to conception through crosses with germline-specific EIIa-cre (see Stock No. 003724) prevents cartilage damage. Tamoxifen-induced restoration of gene function (through crosses with Gt(ROSA)26SorCreERt2 (see Stock No. 008463)) at 3-weeks-of-age improves, but does not normalize, joint histology or whole joint friction. Restoring gene function in 2-month-old or 6-month-old mice has no beneficial effect.
The gene trap design additionally includes a reverse tet transactivator (rtTA) cassette.
A targeting vector was designed to contain a loxP-flanked artificial exon that contains a strong splice acceptor, an in-frame lacZ coding sequence, an internal ribosome entry site (IRES), a reverse tet transactivator (rtTA) cassette, and a neomycin selection cassette driven by its own promoter. The mutation was introduced to intron 2 of the Prg4 gene via homologous recombination in (129X1/SvJ x 129S1/Sv)F1- Kitl+-derived R1 embryonic stem (ES) cells. The donating laboratory maintained this strain on a mixed C57BL/6J-129 genetic background.
Expressed Gene | Bgeo, fusion of beta-galactosidase and neomycin phosphotransferase genes, E. coli |
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Expressed Gene | rtTA, reverse tetracycline-controlled transactivator, E. coli |
Site of Expression | ß-galactosidase instead of lubricin is expressed in cartilage. |
Allele Name | targeted mutation 2, Matthew Warman |
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Allele Type | Targeted (Conditional ready (e.g. floxed), Reporter, Null/Knockout, Inserted expressed sequence, Transactivator) |
Allele Synonym(s) | Prg4:GT; Prg4GT |
Gene Symbol and Name | Prg4, proteoglycan 4 (megakaryocyte stimulating factor, articular superficial zone protein) |
Gene Synonym(s) | |
Expressed Gene | Bgeo, fusion of beta-galactosidase and neomycin phosphotransferase genes, E. coli |
Expressed Gene | rtTA, reverse tetracycline-controlled transactivator, E. coli |
Site of Expression | ß-galactosidase instead of lubricin is expressed in cartilage. |
Strain of Origin | (129X1/SvJ x 129S1/Sv)F1-Kitl+ |
Chromosome | 1 |
Molecular Note | A targeting vector containing a loxP-flanked artifical exon that contains a strong splice acceptor, an in-frame Bgeo lacZ coding sequence, an internal ribosome entry site (IRES), a reverse tet transactivator (rtTA) cassette with a polyA signal, and a neomycin selection cassette driven by its own promoter was inserted into intron 2 of the gene. The allele does not express wild-type Prg4 mRNA, as determined by RT-PCR. Cre-mediated excision of the targeting vector leaves one loxP in intron 2 and allows expression of Prg4 mRNA. |
Homozygotes and heterozygotes are viable and fertile.
When using the B6;129-Prg4tm2Mawa/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #025740 in your Materials and Methods section.
Facility Barrier Level Descriptions
Service/Product | Description | Price |
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Heterozygous for Prg4<tm2Mawa> |
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