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Mouse Mammary Tumor Virus Proviral Integration in the DD/Tbr Mice
1Department of Anatomy, Nara Medical University, 840 Shijo-cho, Kashihara 634, Japan.
Abstract:
The patterns of mouse mammary tumor virus (MMTV) integration in the DNA of spontaneous-mammary tumors, salivary glands and livers of DD/Tbr mice were examined using MMTV env, int -1c and int-2c probes. The MMTV env probe revealed 1 to 7 new proviral insertions in all mammary tumors. MMTV integration into int-1 was observed in 10 of 18 mammary tumors, whereas that into int-2 was seen in only 2 of 18 tumors. Of the 13 salivary glands examined, only 3 showed new MMTV proviral integrations, but rearrangement in int-1 or int-2 loci by MMTV was not observed. Immuno-collidal gold electron microscopy revealed the presence of MMTV particles both in mammary tumors and in salivary glands, but no tumors were found to be developed in salivary glands. Taken together these results suggest that salivary glands support MMTV replication, but the virions thus produced may not lead to salivary gland tumorigenesis. It is suggested that the salivary gland is the source of horizontally transmitted MMTV in DD/Tbr mice.
Insights
Mouse mammary tumor virus (MMTV) replicates in salivary glands of DD/Tbr mice, but does not cause tumors there. Salivary glands may be the source of MMTV transmission in this mouse model.
Area of Science:
- Virology
- Oncology
- Genetics
Background:
- Mouse mammary tumor virus (MMTV) is associated with mammary tumors in mice.
- Understanding MMTV integration patterns is crucial for studying tumorigenesis.
- DD/Tbr mice are a relevant model for MMTV research.
Purpose of the Study:
- To investigate MMTV integration patterns in mammary tumors, salivary glands, and livers of DD/Tbr mice.
- To determine if MMTV replication in salivary glands leads to tumorigenesis.
- To identify the potential source of horizontal MMTV transmission.
Main Methods:
- Analysis of MMTV proviral DNA integration using MMTV env, int-1c, and int-2c probes.
- Examination of MMTV integration sites in mammary tumors, salivary glands, and livers.
- Immuno-collidal gold electron microscopy to detect MMTV particles.
Main Results:
- All examined mammary tumors showed new MMTV proviral insertions.
- MMTV integrated into int-1 in 10/18 mammary tumors and int-2 in 2/18.
- MMTV particles were found in mammary tumors and salivary glands, but salivary glands did not develop tumors.
Conclusions:
- Salivary glands support MMTV replication but do not undergo MMTV-induced tumorigenesis.
- MMTV virions produced in salivary glands may not cause salivary gland tumors.
- Salivary glands are suggested as the source of horizontally transmitted MMTV in DD/Tbr mice.