Generation of GPV-deficient mice. (A) Gene-targeting strategy. A replacement vector69 was used to substitute a neomycin phosphotransferase expression cassette (Neo) for the entireGpV gene. The wavy line represents plasmid backbone; TK, HSV thymidine kinase expression cassette. X1 and X2 represent exons 1 and 2 of the GpV gene, with the coding region shown as a white box and the 5′ and 3′ untranslated regions shown as shaded boxes. (Sal1) indicates a Sal I restriction endonuclease site found in the P1 bacteriophage vector containing the GpV gene that was used to construct the targeting vector. (B) Southern blot analysis of Bgl2-digested genomic DNA from the tails of pups derived from GpV+/− matings using 5′ flanking probe (A). Targeting removed an endogenous Bgl2 site and introduced a new Bgl2 site. The 4.2- and 5.5-kb bands correspond to wild-type and targeted alleles, respectively. (C) RT-PCR analysis of GpV+/+ andGpV−/− mouse spleen total RNA using GpV (right panel) and Par3g (left panel) primers.