The construction of AlbFv or Pf4Fv BACs. (A) The transgene cassette used for homologous recombination into the Alb or Pf4 BACs. The locations of PCR and RT-PCR primers A to D are illustrated by arrows. The cassette contains the murine Fv cDNA with a chimeric 5′ intron and a 3′ UTR deletion tag, followed by an internal ribosome entry site sequence (IRES) preceding the enhanced green fluorescent protein (EGFP) coding sequence and a bacterial kanamycin resistant gene (KAN). (B) Homologous recombination between the flanking sequences of the constructs and corresponding BACs. Exons 1-12 of the murine Alb gene and exons 1-3 of murine Pf4 gene were replaced with an FV cDNA minigene.