Studies of genetic transmission of mammary tumour virus by C3Hf mice

Abstract

By radioimmunoassay (RIA) mammary tumour virus (MTV) antigens were detected in individual milk samples of C3Hf mice, (female BALB/c X male C3Hf)F1 mice and (female C3Hf X male BALB/c)F1 mice; milk samples of BALB/c mice were negative. In the segregating backcross I population, female BALB/c X male (female BALB/c X male C3Hf) viral antigens were found in the milk of 93 out of 169 mice (55%). In the Bc II population (daughters of Bc I mothers and BALB/c fathers) two groups were distinguished. In the first group, derived from positive Bc I mothers, 55 out of 110 mice (50%) had detectable levels of viral antigens in the milk. In the second group, progeny of negative Bc I mothers, 1 mouse out of 47 was positive. These data are consistent with the assumption that one dominant gene is responsible for the presence of viral antigens in the milk of C3Hf mice. This gene (Mtv-1) seems to be linked with the albino locus situated on chromosome 7; the recombination percentage was about 29. In the first experiment with Bc I mice a significant difference was found between the tumour ages of the mice with virus-positive milk and of the mice with virus-negative milk: all mice (18) with viral antigens in the milk developed mammary tumours at an age ranging from 7 to 18 months, whereas in only 7 out of 16 mice with virus-negative milk were mammary tumours found before the age of 21 months. Viral antigens were detectable (by RIA) in the tumours of mice of both subgroups; however, the amounts (mU/mg tumour) were significantly lower in the tumours derived from mice with virus-negative milk. Although MTV-L of C3Hf mothers could be transmitted to BALB/c mice by foster-nursing, viral antigens could not be detected in milk samples collected prior to the third lactation period; thus an influence on the data of extrachromosomally transmitted MTV-L is unlikely.

Suppression of mouse mammary tumor proviral DNA and protooncogene expression: association with nutritional regulation of mammary tumor development.

“…Except for the mouse Mtv-) locus, the endogenous MMTVs (Mtv-6, -8, -11, and -14) are generally silent. Mtv-) is expressed as an infectious virus and is associated with late occurring MTs in C3H mice (23,24). However, transcripts of MMTV provirus at mRNA level have been reported to occur primarily in the lactating mammary gland (25).…”

Molecular Cloning and Functional Analysis of Three Type D Endogenous Retroviruses of Sheep Reveal a Different Cell Tropism from That of the Highly Related Exogenous Jaagsiekte Sheep Retrovirus

“…The expression of some ERV proteins in mice and chickens can prevent infection by related exogenous viruses by receptor interference or postentry mechanisms (5,29,51,56). In terms of deleterious effects, the generation of more pathogenic retroviruses can result from reactivation and/or recombination among different endogenous loci (19,25,60,62,(65)(66)(67) or by recombination with related exogenous viruses (4,17,18,20,40,55). This has been well documented in mice and selected lines of chickens.…”

MuMTV Antigen Expression and Mammary Tumor Incidence in Non-inbred dd Mice

“…However, discrepancies between the rate of MTV antigen expression and incidence of mammary tumors in these mice has still not been clarified. In the three different F1 hybrid mice, MTV antigen expression and the development of mammary tumors was recognized, suggesting that male dd mice from the three different colonies may carry MTV, which is transmitted from the progeny to the offspring by an extrachromoromal route as demonstrated in DD/Tbr strain [19,20], or by a chromosomal route as demonstrated in GRS/A [2, 9,18, 22] SHN and C3Hf [21].…”