Homozygous and Heterozygous p53 Knockout Rats Develop Metastasizing Sarcomas with High Frequency

Abstract

The TP53 tumor suppressor gene is mutated in the majority of human cancers. Inactivation of p53 in a variety of animal models results in early-onset tumorigenesis, reflecting the importance of p53 as a gatekeeper tumor suppressor. We generated a mutant Tp53 allele in the rat using a target-selected mutagenesis approach. Here, we report that homozygosity for this allele results in complete loss of p53 function. Homozygous mutant rats predominantly develop sarcomas with an onset of 4 months of age with a high occurrence of pulmonary metastases. Heterozygous rats develop sarcomas starting at 8 months of age. Molecular analysis revealed that these tumors exhibit a loss-of-heterozygosity of the wild-type Tp53 allele. These unique features make this rat highly complementary to other rodent p53 knockout models and a versatile tool for investigating tumorigenesis processes as well as genotoxic studies.

Fischer 344-Tp53 knockout rats exhibit a high rate of bone and brain neoplasia with frequent metastasis

“…Likewise, it has been noted that fewer homozygous females were recovered in two previously published Tp53 rat models (McCoy et al, 2013; van Boxtel et al, 2011). It was shown in Tp53 -null rats that the lack of live-born female homozygotes is due, at least in part, to neural tube defects that lead to embryonic lethality (Kawamata and Ochiya, 2012).…”

“…Previously reported Tp53 -mutant mice and rats have a decreased lifespan compared to their wild-type counterparts owing to early tumor development (Donehower et al, 1995; McCoy et al, 2013; van Boxtel et al, 2011; Yan et al, 2012). We aged our animals until signs of tumor or illness were noted during daily evaluation, at which time we performed CO 2 euthanasia and complete necropsy.…”

The onset of p53 loss of heterozygosity is differentially induced in various stem cell types and may involve the loss of either allele

“…8 Sarcomas, which are of mesenchymal origin, are prevalent tumors in LFS patients and murine models. [6][7][8]37 The possibility of a link between cancer development and deregulation of SCs [11][12][13] challenged us to study the significance of p53LOH in SCs and tumorigenesis. The availability of the reprogramming process that enables to recapitulate a transition from adult somatic cells into embryonic-like cells and HZp53 mice allowed us to address the above question, both in vitro and in vivo, as a function of age.…”

Spontaneous testicular atrophy occurs despite normal spermatogonial proliferation in a Tp53 knockout rat

“…Notably, as in the mouse, genetic background is likely to influence the effects of p53 loss in the rat testis. Therefore, additional comparisons between this model and the models generated by different methods of mutagenesis on Wistar or Dark Agouti/F344/Sprague Dawley backgrounds (Tong et al 2010; van Boxtel et al 2011) would be appropriate for future studies.…”

“…A germline mutant derived from mouse embryonic stem cell-C57BL/6 chimeras develops a tumor spectrum similar to Li-Fraumeni syndrome, consisting of predominantly sarcomas and lymphomas (Jacks et al 1994). Recently, three p53 knockout rat models have been established using different background strains (Tong et al 2010; van Boxtel et al 2011), including a p53 knockout rat model (SD- Tp53 tm1sage ) developed on a Sprague Dawley background through an 11-nucleotide deletion using pronuclear microinjection of zinc finger nucleases (ZFNs) (McCoy et al 2013). Compared to knockouts established in other strain backgrounds, this Sprague Dawley model has demonstrated a broader tumor spectrum that more closely mirrors that of Li-Fraumeni syndrome.…”