LT

Inbr (Sv) 121. Colour: Light brown a,B^lt. Origin: MacDowell 1950 from a mutation at the brown locus in strain C58. Outcrossed to BALB/c. To Chase, to Re in 1957 at F28.

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Characteristics

Ovarian teratomas occur spontaneously in about half of the females. Ultrastructurally the stem cells do not differ from those of testicular or embryo-derived teratomas (Damjanov et al., 1975., 1975). Some tumours begin to develop at about 30 days and the incidence rises to 50% at 90 days. These resemble normal embryos until blastocyst stage and then become disorganised. A small percentage of ovulated eggs also develop parthenogenetically, but die at 5-7 days (Stevens and Varnum, 1974). Oocytes arrest at metaphase of meiosis I rather than progressing to metaphase II like other strains. This is a necessary, but not sufficient condition for parthogenetic activation (Eppig et al, 1996). Metaphase I arrest is frequently followed by parthogenetic activation. Oocytes typically contain a single large centrosome with microtubules being shorter than usual (Albertini and Eppig, 1995). Metaphase I arrest is associated with a sustained elevation of p34 (Cdc2) kinase activity, sustained in part by restricted degradation of cyclin B (Hampl and Eppig, 1995). Oocytes ovulated at metaphase I are not capable of undergoing normal fertilisation in-vitro. Only 13% of such oocytes penetrated by sperm formed a diploid female pronucleus and a haploid male pronucleus by 4hr. after insemination (Maleszweski and Yanagimachi, 1995). Spontaneously digynic triploid embryos result from the fertilization of primary oocytes. These embryos develop to the forelimb-bud stage but invariably posess neural tube and cardiac abnormalities (Henery and Kaufman, 1993). Treatment with cisplatin reduced the incidence of ovarian teratomas, and those that did develop were not transplantable (Nishida et al, 1995). A locus on chromosome 6 designated Ots1 (ovarian teratoma susceptibility) is the single major locus that increases the frequency of teratomas in a semidominant manner (Lee et al, 1997)

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Albertini D. F. and Eppig J. J. (1995) Unusual cytoskeletal and chromatin configurations in mouse oocytes that are atypical in meiotic progression. Developmental Genetics 16, 13-19.

Damjanov I., Katic V., and Stevens L. C. (1975) Ultrastructure of ovarian teratomas in LT mice. Z. Krebsforsch. 83, 261-267.

Hampl A. and Eppig J. J. (1995) Analysis of the mechanism(s) of metaphase I arrest in maturing mouse oocytes. Development 121, 925-933.

Henery C. C. and Kaufman M. H. (1993) Cellular and nuclear volume of primitive red blood cells in digynic and diandric triploid and control diploid mouse embryos. European Journal of Morphology 31, 237-249.

Lee G. H., Bugni J. M., Obata M., Nishimori H., Ogawa K., and Drinkwater N. R. (1997) Genetic dissection of susceptibility to murine ovarian teratomas that originate from parthenogenetic oocytes. Cancer Res. 57, 590-593.

Nishida T., Sugiyama T., Kataoka A., Ushijima K., Ueyama T., and Yakushiji M. (1995) Cytotoxic impacts on the tumorigenesis and transplantability of ovarian teratoma in LT/Sv mouse. Oncology Reports 2, 1045-1048.

Stevens L. C. and Varnum D. S. (1974) Development of teratomas from parthenogenetically activated ovarian mouse eggs. Devel. Biol. 37, 369-380.

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INBRED STRAINS OF MICE
Updated 9 Apr. 1998
Michael FW Festing
MRC Toxicology Unit, Hodgkin Building,
University of Leicester, UK