Targeted mutant Trp53tm2Glo (also referred to as Trp53515C) homozygous mice do not develop the early onset thymic lymphomas found in Trp53null mice.
Dr. Guillermina Lozano, MD Anderson Cancer Center
Trp53 (transformation related protein 53) functions as a tumor suppressor as well an inducer of apoptosis, cell cycle arrest and senescence. A rare mutant form of TRP53 (identified as an amino acid substitution, R175P) found in human tumors is defective in inducing apoptosis, but still functions to induce cell cycle arrest.
In mice the equivalent mutation is R172P or 515C (change to C at nucleotide 515). Mice homozygous for Trp53515C, do not develop the early onset thymic lymphomas found in Trp53null mice. At 7 months of age, 85% of Trp53515C mice are alive and tumor free. Lymphomas (38%) and sarcomas (43%) develop between 7 and 13 months of age. In Trp53515C/515C mice lymphomas occur in the spleen and lymph nodes rather than the thymus and are either diploid or tetraploid in contrast to the anueuploidy found in null mice. Analysis of mutant p53-R172C embryonic fibroblasts (MEFs) indicates that they are resistant to p53-dependent apoptosis. This strain may be useful for studying tumorigenesis.
The targeting vector was designed (by site-directed mutagenesis) to substitute an arginine to proline (R172P) at nucleotide 515 of exon 5. A loxP-flanked neo cassette was inserted into intron 4.
The construct was electroporated into unspecified embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. The resulting chimeric mice were bred to Tg(hCMV-cre)140Sau transgenic mice on a mixed C57BL/6:DBA/2 background to delete the neo cassette leaving a single loxP site. The resulting progeny were backcrossed to C57BL/6 mice for at least 5 generations. The strain was cryopreserved in 2012.
|Allele Name||targeted mutation 2, Guillermina Lozano|
|Allele Type||Targeted (Humanized sequence)|
|Allele Synonym(s)||p53C; p53P; pP53-R172P; Trp53515C|
|Gene Symbol and Name||Trp53, transformation related protein 53|
|Promoter||Trp53, transformation related protein 53, mouse, laboratory|
|Strain of Origin||Not Specified|
|Molecular Note||An arginine to proline substitution was generated at codon 172 by an engineered transversion point mutation was introduced at nucleotide 515. R172P, equivalent to R175P in humans, is associated with human tumors defective in apoptosis. A single loxP site was left in intron 4 after the excision of a floxed neo cassette via cre-mediated recombination. Western blot analysis of homozygous MEFs detected full length protein at levels that exceded those of full length protein in wild-type MEFs.|