| First Author | Sarkar NH | Year | 2004 |
| Journal | J Virol | Volume | 78 |
| Issue | 2 | Pages | 1055-62 |
| PubMed ID | 14694140 | Mgi Jnum | J:87504 |
| Mgi Id | MGI:3026802 | Doi | 10.1128/JVI.78.2.1055-1062.2004 |
| Citation | Sarkar NH, et al. (2004) RIII/Sa Mice with a High Incidence of Mammary Tumors Express Two Exogenous Strains and One Potential Endogenous Strain of Mouse Mammary Tumor Virus. (Erratum v 78(7):3803). J Virol 78(2):1055-62 |
| abstractText | The inbred mouse strain RIII has long been known for shedding large amounts of mouse mammary tumor virus (MMTV) particles in milk and for the development of hormone-dependent early mammary tumors at a very high incidence (>90%). We have established one RIII subline (RIII/Sa) that shows a pattern of virus expression and tumor incidence similar to that in RIII mice. In the present study, we analyzed the milk and mammary tumors of RIII/Sa mice for virus characterization by reverse transcriptase PCR (RT-PCR) cloning and sequencing of the open reading frame (ORF) of the MMTV long terminal repeats (LTRs). Our results show that these mice express a mixture of at least three different MMTV strains, two of which, designated here as RIII/Sa MMTV-1 and RIII/Sa MMTV-2, are exogenous. The third virus, RIII/Sa MMTV-3, appears to carry the signature of an endogenous provirus, Mtv-17. Similar studies done with the milk and mammary glands of another subline, RIIIS/J, revealed that they do not express MMTV in their milk. The RIII/Sa and RIIIS/J mice also exhibited differences in their endogenous proviral contents. Twelve spontaneously developed mammary tumors of RIII/Sa mice were examined for possible Wnt-1 and/or int-2/Fgf3 mutations that are usually found to occur in most mouse mammary tumors as a consequence of MMTV proviral integration. This work led to the isolation of one MMTV-Wnt-1 junction fragment and one MMTV-int-2/Fgf3 junction fragment from 2 of the 12 tumors. Further analyses showed that both junction fragments contained the RIII/Sa MMTV-2-specific LTR ORF, indicating that this virus was involved in the development of both tumors. Whether RIII/Sa MMTV-1 and/or RIII/Sa MMTV-3 plays any role in mammary tumor development in RIII/Sa mice remains to be established. Overall, the present study demonstrates, to our surprise, that (i) RIII/Sa mice express, unlike other native mouse strains, three strains of MMTVs; and (ii) the virions are completely different from the virus expressed by another subline of RIII mice, the BR6 mice. |
