SWR - AN INBRED STRAIN SUITABLE FOR GENERATING TRANSGENIC MICE

Production of fertilized oocytes and generation of transgenic mice is generally more efficient using F2 hybrid embryos than embryos from inb red mice, Most P2 hybrids are of the C57BL/6 background because of its genetic and embryologic features, However, our goal of developing a t ransgenic mouse model for rheumatoid arthritis necessitated using a su sceptible mouse strain such as DBA/1. We prepared alpha and beta T-cel l receptor (TCR) chain gene constructs and microinjected them into emb ryos from DBA/1, SWR, (DBA/1xSWR)F1, and (SWRxDBA/1)F1 strains, We fou nd SWR female mice to be prolific ovulators in response to exogenous h ormones, with oocyte numbers comparable to those produced by (C57BL/6x C3H)F1 female mice, Embryos from the (SWRxDBA/1)F1 or SWR strain were large and had prominent pronuclei, whereas (DBA/1xSWR)F1 embryos were smaller and had less visible pronuclei, similar to those of DBA/1 embr yos, Therefore, the pronuclear size and visibility are features of the SWR female mice and are independent of the genotype of the fertilizin g spermatozoa. Resistance to lysis after co-injection of ap TCR constr ucts and the efficiency of generating DNA-positive founders were compa rable in SWR, (SWRxDBA/1)F1, and (C57BL6xC3H)F2 embryos, Thus, the SWR mouse is another inbred strain, in addition to the FVB inbred strain, found to be highly suitable for propagation of transgenes, Furthermor e, the SWR mouse is well defined genetically, and SWR females have a h igh ovulation rate, comparable to that of F1 hybrid mice.