Localization of the mouse mammary tumor provirus, Mtv44, on chromosome 11

• Published in: Mammalian genome 1995-07, Vol.6 (7), p.472-473
• Main Authors: Fairchild, S P, Rosenwasser, O A, Tomonari, K
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Viral - genetics; Chromosome Mapping; Chromosomes; Haplotypes; Mammalia; Mammary Tumor Virus, Mouse - genetics; Mice - genetics; Mice - virology; Mice, Inbred Strains; Mus spretus; Proviruses - genetics; Superantigens - genetics; Viral Envelope Proteins - genetics
• ISSN: 0938-8990; 1432-1777
• DOI: 10.1007/BF00360657

The mouse mammary tumor virus, a type B retrovirus, is transmitted to the offspring, either as an infectious agent through milk (MMTV) or as a proviral integrate in germline DNA (Mtv). Transfection and transgenic studies have demonstrated that the open reading frame (Orf) in the 3' long terminal repeats of mouse mammary tumor viruses encode superantigens. These superantigens associate with major histocompatibility complex class II molecules and mediate the deletion of T cells bearing particular V beta chains of the T cell receptor. We previously identified a new Mtv, Mtv44, which appears to be present in only the NZW/Ola/Hsd strain of mouse. Analysis of peripheral T cells and Mtv44 integration in backcross mice revealed that Mtv44 encodes a superantigen that partially deletes V beta 3 super(+), V beta 6 super(+), V beta 8.1 super(+), and V beta 9 super(+) T cells. In this study, we mapped the chromosomal location of Mtv44 in the NZW/Ola/Hsd strain by producing an interspecific backcross, [(NZW/Ola/Hsd x Czech II)F sub(1) x Czech II]. NZW/Ola/Hsd mice were purchased from Olac (Bicester, England), whereas Mus musculus musculus feral mice Czech II were obtained from the National Cancer Institute (Bethesda, Md., USA). This cross was generated because (i) unlike common laboratory inbred strains, Czech II mice are free of genomic Mtv provirus and (ii) like Mus spretus, Czech II is a wild-derived strain, which we have found to have highly polymorphic Mit microsatellites compared with laboratory strains. Seventy-eight offspring were examined for their levels of peripheral V beta 6 super(+) T cells and the presence or absence of Mtv44. Forty-one offspring (F sub(1) type progeny: 53%) showed partial deletion of these T cells. The percentages of V beta 6 super(+) T cells in these mice ranged from 1.2% to 5.5%, and the mean plus or minus standard error was calculated to be 2.5% plus or minus 0.2%. These mice were regarded as being Mtv44 super(+). In contrast, the percentage of V beta 6 super(+) T cells in the remaining 37 offspring (Czech II type: 47%) ranged from 5.7% to 11.0%, giving a mean and standard error of 8.8% plus or minus 0.2%. These mice were regarded as being nondeletors of V beta 6 super(+) T cells and hence Mtv44 super(-). The presence or absence of Mtv44 in these two groups, including borderline cases (5.5% and 5.7%), was confirmed with an Mtv44 Orf-specific primer. PCR analysis on the genomic DNA from individual backcross progeny showed complete conco